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Costa MD, Rangasamy V, Behera A, Mathur P, Khera T, Goldberger AL, Subramaniam B. Blood pressure fragmentation as a new measure of blood pressure variability: association with predictors of cardiac surgery outcomes. Front Physiol 2024; 15:1277592. [PMID: 38405117 PMCID: PMC10884313 DOI: 10.3389/fphys.2024.1277592] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Accepted: 01/12/2024] [Indexed: 02/27/2024] Open
Abstract
Background: Fluctuations in beat-to-beat blood pressure variability (BPV) encode untapped information of clinical utility. A need exists for developing new methods to quantify the dynamical properties of these fluctuations beyond their mean and variance. Objectives: Introduction of a new beat-to-beat BPV measure, termed blood pressure fragmentation (BPF), and testing of whether increased preoperative BPF is associated with (i) older age; (ii) higher cardiac surgical risk, assessed using the Society of Thoracic Surgeons' (STS) Risk of Morbidity and Mortality index and the European System for Cardiac Operative Risk Evaluation Score (EuroSCORE II); and (iii) longer ICU length of stay (LOS) following cardiac surgery. The secondary objective was to use standard BPV measures, specifically, mean, SD, coefficient of variation (CV), average real variability (ARV), as well a short-term scaling index, the detrended fluctuation analysis (DFA) ⍺1 exponent, in the same type of analyses to compare the results with those obtained using BPF. Methods: Consecutive sample of 497 adult patients (72% male; age, median [inter-quartile range]: 67 [59-75] years) undergoing cardiac surgery with cardiopulmonary bypass. Fragmentation, standard BPV and DFA ⍺1 measures were derived from preoperative systolic blood pressure (SBP) time series obtained from radial artery recordings. Results: Increased preoperative systolic BPF was associated with older age, higher STS Risk of Morbidity and Mortality and EuroSCORE II values, and longer ICU LOS in all models. Specifically, a one-SD increase in systolic BPF (9%) was associated with a 26% (13%-40%) higher likelihood of longer ICU LOS (>2 days). Among the other measures, only ARV and DFA ⍺1 tended to be associated with longer ICU LOS. However, the associations did not reach significance in the most adjusted models. Conclusion: Preoperative BPF was significantly associated with preoperative predictors of cardiac surgical outcomes as well as with ICU LOS. Our findings encourage future studies of preoperative BPF for assessment of health status and risk stratification of surgical and non-surgical patients.
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Affiliation(s)
- Madalena D. Costa
- Margret and H. A. Rey Institute for Nonlinear Dynamics in Medicine, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, United States
| | - Valluvan Rangasamy
- Sadhguru Center for a Conscious Planet, Department of Anesthesia, Critical Care and Pain Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, United States
| | - Alkananda Behera
- Sadhguru Center for a Conscious Planet, Department of Anesthesia, Critical Care and Pain Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, United States
| | - Priyam Mathur
- Sadhguru Center for a Conscious Planet, Department of Anesthesia, Critical Care and Pain Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, United States
| | - Tanvi Khera
- Sadhguru Center for a Conscious Planet, Department of Anesthesia, Critical Care and Pain Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, United States
| | - Ary L. Goldberger
- Margret and H. A. Rey Institute for Nonlinear Dynamics in Medicine, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, United States
| | - Balachundhar Subramaniam
- Sadhguru Center for a Conscious Planet, Department of Anesthesia, Critical Care and Pain Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, United States
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Velez Rueda AJ, Gonano LA, Smith AG, Parisi G, Fornasari MS, Sommese LM. CardIAP: calcium transients confocal image analysis tool. FRONTIERS IN BIOINFORMATICS 2023; 3:1137815. [PMID: 37521316 PMCID: PMC10381969 DOI: 10.3389/fbinf.2023.1137815] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Accepted: 06/23/2023] [Indexed: 08/01/2023] Open
Abstract
One of the main topics of cardiovascular research is the study of calcium (Ca2+) handling, as even small changes in Ca2+ concentration can alter cell functionality (Bers, Annu Rev Physiol, 2014, 76, 107-127). Ionic calcium (Ca2+) plays the role of a second messenger in eukaryotic cells, associated with cellular functions such as cell cycle regulation, transport, motility, gene expression, and regulation. The use of fluorometric techniques in isolated cells loaded with Ca2+-sensitive fluorescent probes allows quantitative measurement of dynamic events occurring in living, functioning cells. The Cardiomyocytes Images Analyzer Python (CardIAP) application addresses the need to analyze and retrieve information from confocal microscopy images systematically, accurately, and rapidly. Here we present CardIAP, an open-source tool developed entirely in Python, freely available and useable in an interactive web application. In addition, CardIAP can be used as a standalone Python library and freely installed via PIP, making it easy to integrate into biomedical imaging pipelines. The images that can be generated in the study of the heart have the particularity of requiring both spatial and temporal analysis. CardIAP aims to open the field of cardiomyocytes and intact hearts image processing. The improvement in the extraction of information from the images will allow optimizing the usage of resources and animals. With CardIAP, users can run the analysis to both, the complete image, and portions of it in an easy way, and replicate it on a series of images. This analysis provides users with information on the spatial and temporal changes in calcium releases and characterizes them. The web application also allows users to extract calcium dynamics data in downloadable tables, simplifying the calculation of alternation and discordance indices and their classification. CardIAP aims to provide a tool that could assist biomedical researchers in studying the underlying mechanisms of anomalous calcium release phenomena.
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Affiliation(s)
- Ana Julia Velez Rueda
- Departamento de Ciencia y Tecnología, CONICET, Universidad Nacional de Quilmes, Bernal, Argentina
| | - Luis Alberto Gonano
- Centro de Investigaciones Cardiovasculares, Facultad de Medicina, CONICET, Universidad Nacional de La Plata, La Plata, Argentina
| | - Agustín García Smith
- Departamento de Ciencia y Tecnología, CONICET, Universidad Nacional de Quilmes, Bernal, Argentina
| | - Gustavo Parisi
- Departamento de Ciencia y Tecnología, CONICET, Universidad Nacional de Quilmes, Bernal, Argentina
| | - María Silvina Fornasari
- Departamento de Ciencia y Tecnología, CONICET, Universidad Nacional de Quilmes, Bernal, Argentina
| | - Leandro Matías Sommese
- Departamento de Ciencia y Tecnología, CONICET, Universidad Nacional de Quilmes, Bernal, Argentina
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Qian Y, Zuo D, Xiong J, Yin Y, Qi R, Ma X, Yan A, Yang Y, Liu P, Zhang J, Tang K, Peng W, Xu Y, Liu Z. Arrhythmogenic mechanism of a novel ryanodine receptor mutation underlying sudden cardiac death. Europace 2023; 25:euad220. [PMID: 37466361 PMCID: PMC10374982 DOI: 10.1093/europace/euad220] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2023] [Accepted: 06/23/2023] [Indexed: 07/20/2023] Open
Abstract
AIMS The ryanodine receptor 2 (RyR2) is essential for cardiac muscle excitation-contraction coupling; dysfunctional RyR2 participates in the development of inherited arrhythmogenic cardiac disease. In this study, a novel RyR2 mutation A690E is identified from a patient with family inheritance of sudden cardiac death, and we aimed to investigate the pathogenic basis of the mutation. METHODS AND RESULTS We generated a mouse model that carried the A690E mutation. Mice were characterized by adrenergic-induced ventricular arrhythmias similar to clinical manifestation of the patient. Optical mapping studies revealed that isolated A690E hearts were prone to arrhythmogenesis and displayed frequency-dependence calcium transient alternans. Upon β-adrenoceptor challenge, the concordant alternans was shifted towards discordant alternans that favour triggering ectopic beats and Ca2+ re-entry; similar phenomenon was also found in the A690E cardiomyocytes. In addition, we found that A690E cardiomyocytes manifested abnormal Ca2+ release and electrophysiological disorders, including an increased sensitivity to cytosolic Ca2+, an elevated diastolic RyR2-mediated Ca2+ leak, and an imbalance between Ca2+ leak and reuptake. Structural analyses reveal that the mutation directly impacts RyR2-FK506 binding protein interaction. CONCLUSION In this study, we have identified a novel mutation in RyR2 that is associated with sudden cardiac death. By characterizing the function defects of mutant RyR2 in animal, whole heat, and cardiomyocytes, we demonstrated the pathogenic basis of the disease-causing mutation and provided a deeper mechanistic understanding of a life-threatening cardiac arrhythmia.
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Affiliation(s)
- Yunyun Qian
- Department of Cardiology, Shanghai Tenth People’s Hospital, Tongji University School of Medicine, 301 Middle Yanchang Road, Jingan District, Shanghai 200072, China
- Pan-Vascular Research Institute, Heart, Lung, and Blood Center, Tongji University School of Medicine, 36 Yunxin Road, Jingan District, Shanghai 200435, China
| | - Dongchuan Zuo
- Key Laboratory of Medical Electrophysiology, Institute of Cardiovascular Research, Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Southwest Medical University, 1 Xianglin Road, Longmatan District, Luzhou 646000, China
- National Traditional Chinese Medicine Clinical Research Base and Department of Cardiovascular Medicine of the Affiliated Traditional Chinese Medicine Hospital of Southwest Medical University, 182 Chunhui Road, Longmatan District, Luzhou 646000, China
| | - Jing Xiong
- Department of Cardiology, Shanghai Tenth People’s Hospital, Tongji University School of Medicine, 301 Middle Yanchang Road, Jingan District, Shanghai 200072, China
- Pan-Vascular Research Institute, Heart, Lung, and Blood Center, Tongji University School of Medicine, 36 Yunxin Road, Jingan District, Shanghai 200435, China
| | - Yihen Yin
- Department of Cardiology, Shanghai Tenth People’s Hospital, Tongji University School of Medicine, 301 Middle Yanchang Road, Jingan District, Shanghai 200072, China
- Pan-Vascular Research Institute, Heart, Lung, and Blood Center, Tongji University School of Medicine, 36 Yunxin Road, Jingan District, Shanghai 200435, China
| | - Ruxi Qi
- Cryo-electron Microscopy Center, Southern University of Science and Technology, 1088 Xueyuan Road, Nanshan District, Shenzhen 518055, China
| | - Xiaomin Ma
- Cryo-electron Microscopy Center, Southern University of Science and Technology, 1088 Xueyuan Road, Nanshan District, Shenzhen 518055, China
| | - An Yan
- Cryo-electron Microscopy Center, Southern University of Science and Technology, 1088 Xueyuan Road, Nanshan District, Shenzhen 518055, China
| | - Yawen Yang
- Key Laboratory of Medical Electrophysiology, Institute of Cardiovascular Research, Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Southwest Medical University, 1 Xianglin Road, Longmatan District, Luzhou 646000, China
| | - Ping Liu
- National Traditional Chinese Medicine Clinical Research Base and Department of Cardiovascular Medicine of the Affiliated Traditional Chinese Medicine Hospital of Southwest Medical University, 182 Chunhui Road, Longmatan District, Luzhou 646000, China
| | - Jingying Zhang
- Department of Cardiology, Shanghai Tenth People’s Hospital, Tongji University School of Medicine, 301 Middle Yanchang Road, Jingan District, Shanghai 200072, China
| | - Kai Tang
- Department of Cardiology, Shanghai Tenth People’s Hospital, Tongji University School of Medicine, 301 Middle Yanchang Road, Jingan District, Shanghai 200072, China
| | - Wenhui Peng
- Department of Cardiology, Shanghai Tenth People’s Hospital, Tongji University School of Medicine, 301 Middle Yanchang Road, Jingan District, Shanghai 200072, China
- Pan-Vascular Research Institute, Heart, Lung, and Blood Center, Tongji University School of Medicine, 36 Yunxin Road, Jingan District, Shanghai 200435, China
| | - Yawei Xu
- Department of Cardiology, Shanghai Tenth People’s Hospital, Tongji University School of Medicine, 301 Middle Yanchang Road, Jingan District, Shanghai 200072, China
- Pan-Vascular Research Institute, Heart, Lung, and Blood Center, Tongji University School of Medicine, 36 Yunxin Road, Jingan District, Shanghai 200435, China
| | - Zheng Liu
- Department of Cardiology, Shanghai Tenth People’s Hospital, Tongji University School of Medicine, 301 Middle Yanchang Road, Jingan District, Shanghai 200072, China
- Pan-Vascular Research Institute, Heart, Lung, and Blood Center, Tongji University School of Medicine, 36 Yunxin Road, Jingan District, Shanghai 200435, China
- Cryo-electron Microscopy Center, Southern University of Science and Technology, 1088 Xueyuan Road, Nanshan District, Shenzhen 518055, China
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Grandi E, Navedo MF, Saucerman JJ, Bers DM, Chiamvimonvat N, Dixon RE, Dobrev D, Gomez AM, Harraz OF, Hegyi B, Jones DK, Krogh-Madsen T, Murfee WL, Nystoriak MA, Posnack NG, Ripplinger CM, Veeraraghavan R, Weinberg S. Diversity of cells and signals in the cardiovascular system. J Physiol 2023; 601:2547-2592. [PMID: 36744541 PMCID: PMC10313794 DOI: 10.1113/jp284011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2022] [Accepted: 01/19/2023] [Indexed: 02/07/2023] Open
Abstract
This white paper is the outcome of the seventh UC Davis Cardiovascular Research Symposium on Systems Approach to Understanding Cardiovascular Disease and Arrhythmia. This biannual meeting aims to bring together leading experts in subfields of cardiovascular biomedicine to focus on topics of importance to the field. The theme of the 2022 Symposium was 'Cell Diversity in the Cardiovascular System, cell-autonomous and cell-cell signalling'. Experts in the field contributed their experimental and mathematical modelling perspectives and discussed emerging questions, controversies, and challenges in examining cell and signal diversity, co-ordination and interrelationships involved in cardiovascular function. This paper originates from the topics of formal presentations and informal discussions from the Symposium, which aimed to develop a holistic view of how the multiple cell types in the cardiovascular system integrate to influence cardiovascular function, disease progression and therapeutic strategies. The first section describes the major cell types (e.g. cardiomyocytes, vascular smooth muscle and endothelial cells, fibroblasts, neurons, immune cells, etc.) and the signals involved in cardiovascular function. The second section emphasizes the complexity at the subcellular, cellular and system levels in the context of cardiovascular development, ageing and disease. Finally, the third section surveys the technological innovations that allow the interrogation of this diversity and advancing our understanding of the integrated cardiovascular function and dysfunction.
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Affiliation(s)
- Eleonora Grandi
- Department of Pharmacology, University of California Davis, Davis, CA, USA
| | - Manuel F. Navedo
- Department of Pharmacology, University of California Davis, Davis, CA, USA
| | - Jeffrey J. Saucerman
- Department of Biomedical Engineering, University of Virginia, Charlottesville, VA, USA
| | - Donald M. Bers
- Department of Pharmacology, University of California Davis, Davis, CA, USA
| | - Nipavan Chiamvimonvat
- Department of Pharmacology, University of California Davis, Davis, CA, USA
- Department of Internal Medicine, University of California Davis, Davis, CA, USA
| | - Rose E. Dixon
- Department of Physiology and Membrane Biology, University of California Davis, Davis, CA, USA
| | - Dobromir Dobrev
- Institute of Pharmacology, West German Heart and Vascular Center, University Duisburg-Essen, Essen, Germany
- Department of Medicine, Montreal Heart Institute and Université de Montréal, Montréal, Canada
- Department of Molecular Physiology & Biophysics, Baylor College of Medicine, Houston, TX, USA
| | - Ana M. Gomez
- Signaling and Cardiovascular Pathophysiology-UMR-S 1180, INSERM, Université Paris-Saclay, Orsay, France
| | - Osama F. Harraz
- Department of Pharmacology, Larner College of Medicine, and Vermont Center for Cardiovascular and Brain Health, University of Vermont, Burlington, VT, USA
| | - Bence Hegyi
- Department of Pharmacology, University of California Davis, Davis, CA, USA
| | - David K. Jones
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI, USA
- Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Trine Krogh-Madsen
- Department of Physiology & Biophysics, Weill Cornell Medicine, New York, New York, USA
| | - Walter Lee Murfee
- J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, FL, USA
| | - Matthew A. Nystoriak
- Department of Medicine, Division of Environmental Medicine, Center for Cardiometabolic Science, University of Louisville, Louisville, KY, 40202, USA
| | - Nikki G. Posnack
- Department of Pediatrics, Department of Pharmacology and Physiology, The George Washington University, Washington, DC, USA
- Sheikh Zayed Institute for Pediatric and Surgical Innovation, Children’s National Heart Institute, Children’s National Hospital, Washington, DC, USA
| | | | - Rengasayee Veeraraghavan
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA
- Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University – Wexner Medical Center, Columbus, OH, USA
| | - Seth Weinberg
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA
- Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University – Wexner Medical Center, Columbus, OH, USA
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Kanaporis G, Martinez‐Hernandez E, Blatter LA. Calcium- and voltage-driven atrial alternans: Insight from [Ca] i and V m asynchrony. Physiol Rep 2023; 11:e15703. [PMID: 37226365 PMCID: PMC10209431 DOI: 10.14814/phy2.15703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Revised: 04/21/2023] [Accepted: 04/23/2023] [Indexed: 05/26/2023] Open
Abstract
Cardiac alternans is defined as beat-to-beat alternations in contraction strength, action potential duration (APD), and Ca transient (CaT) amplitude. Cardiac excitation-contraction coupling relies on the activity of two bidirectionally coupled excitable systems, membrane voltage (Vm ) and Ca release. Alternans has been classified as Vm - or Ca-driven, depending whether a disturbance of Vm or [Ca]i regulation drives the alternans. We determined the primary driver of pacing induced alternans in rabbit atrial myocytes, using combined patch clamp and fluorescence [Ca]i and Vm measurements. APD and CaT alternans are typically synchronized; however, uncoupling between APD and CaT regulation can lead to CaT alternans in the absence of APD alternans, and APD alternans can fail to precipitate CaT alternans, suggesting a considerable degree of independence of CaT and APD alternans. Using alternans AP voltage clamp protocols with extra APs showed that most frequently the pre-existing CaT alternans pattern prevailed after the extra-beat, indicating that alternans is Ca-driven. In electrically coupled cell pairs, dyssynchrony of APD and CaT alternans points to autonomous regulation of CaT alternans. Thus, with three novel experimental protocols, we collected evidence for Ca-driven alternans; however, the intimately intertwined regulation of Vm and [Ca]i precludes entirely independent development of CaT and APD alternans.
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Affiliation(s)
- G. Kanaporis
- Department of Physiology & BiophysicsRush University Medical CenterChicagoIllinoisUSA
| | - E. Martinez‐Hernandez
- Department of Physiology & BiophysicsRush University Medical CenterChicagoIllinoisUSA
| | - L. A. Blatter
- Department of Physiology & BiophysicsRush University Medical CenterChicagoIllinoisUSA
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Sun H, Song J, Li K, Li Y, Shang L, Zhou Q, Lu Y, Zong Y, He X, Kari M, Yang H, Zhou X, Zhang L, Tang B. Increased β1-adrenergic receptor antibody confers a vulnerable substrate for atrial fibrillation via mediating Ca2+ mishandling and atrial fibrosis in active immunization rabbit models. Clin Sci (Lond) 2023; 137:195-217. [PMID: 36597894 PMCID: PMC9885845 DOI: 10.1042/cs20220654] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2022] [Revised: 12/19/2022] [Accepted: 01/03/2023] [Indexed: 01/05/2023]
Abstract
BACKGROUND Autoimmune disorder is the emerging mechanism of atrial fibrillation (AF). The β1-adrenergic receptor antibody (β1-AAb) is associated with AF progress. Our study aims to investigate whether β1-AAbs involves in atrial vulnerable substrate by mediating Ca2+ mishandling and atrial fibrosis in autoimmune associated AF. METHODS Active immunization models were established via subcutaneous injection of the second extracellular loop (ECL2) peptide for β1 adrenergic receptor (β1AR). Invasive electrophysiologic study and ex vivo optical mapping were used to evaluate the changed electrophysiology parameters and calcium handling properties. Phospho-proteomics combined with molecular biology assay were performed to identify the potential mechanisms of remodeled atrial substrate elicited by β1-AAbs. Exogenous β1-AAbs were used to induce the cellular phenotypes of HL-1 cells and atrial fibroblasts to AF propensity. RESULTS β1-AAbs aggravated the atrial electrical instability and atrial fibrosis. Bisoprolol alleviated the alterations of action potential duration (APD), Ca2+ transient duration (CaD), and conduction heterogeneity challenged by β1-AAbs. β1-AAbs prolonged calcium transient refractoriness and promoted arrhythmogenic atrial alternans and spatially discordant alternans, which were partly counteracted through blocking β1AR. Its underlying mechanisms are related to β1AR-drived CaMKII/RyR2 activation of atrial cardiomyocytes and the myofibroblasts phenotype formation of fibroblasts. CONCLUSION Suppressing β1-AAbs effectively protects the atrial vulnerable substrate by ameliorating intracellular Ca2+ mishandling and atrial fibrosis, preventing the process of the autoimmune associated AF.
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Affiliation(s)
- Huaxin Sun
- Xinjiang Key Laboratory of Cardiac Electrophysiology and Remodeling, The First Affiliated Hospital of Xinjiang Medical University, Urumqi 830011, China
- Department of Pacing and Electrophysiology, The First Affiliated Hospital of Xinjiang Medical University, Urumqi 830011, China
| | - Jie Song
- Xinjiang Key Laboratory of Cardiac Electrophysiology and Remodeling, The First Affiliated Hospital of Xinjiang Medical University, Urumqi 830011, China
- Department of Pacing and Electrophysiology, The First Affiliated Hospital of Xinjiang Medical University, Urumqi 830011, China
| | - Kai Li
- Xinjiang Key Laboratory of Cardiac Electrophysiology and Remodeling, The First Affiliated Hospital of Xinjiang Medical University, Urumqi 830011, China
- Department of Pacing and Electrophysiology, The First Affiliated Hospital of Xinjiang Medical University, Urumqi 830011, China
| | - Yao Li
- Psychosomatic Medical Center, The Fourth People’s Hospital of Chengdu, Chengdu, China
| | - Luxiang Shang
- Department of Cardiology, The First Affiliated Hospital of Shandong First Medical University and Shandong Provincial Qianfoshan Hospital, Shandong Medicine and Health Key Laboratory of Cardiac Electrophysiology and Arrhythmia, Jinan, China
| | - Qina Zhou
- School of Nursing, Midwifery and Social Work, University of Queensland, Brisbane, Queensland, Australia
| | - Yanmei Lu
- Xinjiang Key Laboratory of Cardiac Electrophysiology and Remodeling, The First Affiliated Hospital of Xinjiang Medical University, Urumqi 830011, China
- Department of Pacing and Electrophysiology, The First Affiliated Hospital of Xinjiang Medical University, Urumqi 830011, China
| | - Yazhen Zong
- Xinjiang Key Laboratory of Cardiac Electrophysiology and Remodeling, The First Affiliated Hospital of Xinjiang Medical University, Urumqi 830011, China
- Department of Pacing and Electrophysiology, The First Affiliated Hospital of Xinjiang Medical University, Urumqi 830011, China
| | - Xiuyuan He
- Xinjiang Key Laboratory of Cardiac Electrophysiology and Remodeling, The First Affiliated Hospital of Xinjiang Medical University, Urumqi 830011, China
- Department of Pacing and Electrophysiology, The First Affiliated Hospital of Xinjiang Medical University, Urumqi 830011, China
| | - Muzappar Kari
- Xinjiang Key Laboratory of Cardiac Electrophysiology and Remodeling, The First Affiliated Hospital of Xinjiang Medical University, Urumqi 830011, China
- Department of Pacing and Electrophysiology, The First Affiliated Hospital of Xinjiang Medical University, Urumqi 830011, China
| | - Hang Yang
- Xinjiang Key Laboratory of Cardiac Electrophysiology and Remodeling, The First Affiliated Hospital of Xinjiang Medical University, Urumqi 830011, China
- Department of Pacing and Electrophysiology, The First Affiliated Hospital of Xinjiang Medical University, Urumqi 830011, China
| | - Xianhui Zhou
- Xinjiang Key Laboratory of Cardiac Electrophysiology and Remodeling, The First Affiliated Hospital of Xinjiang Medical University, Urumqi 830011, China
- Department of Pacing and Electrophysiology, The First Affiliated Hospital of Xinjiang Medical University, Urumqi 830011, China
- Correspondence: Baopeng Tang () or Ling Zhang () or Xianhui Zhou ()
| | - Ling Zhang
- Xinjiang Key Laboratory of Cardiac Electrophysiology and Remodeling, The First Affiliated Hospital of Xinjiang Medical University, Urumqi 830011, China
- Correspondence: Baopeng Tang () or Ling Zhang () or Xianhui Zhou ()
| | - Baopeng Tang
- Xinjiang Key Laboratory of Cardiac Electrophysiology and Remodeling, The First Affiliated Hospital of Xinjiang Medical University, Urumqi 830011, China
- Department of Pacing and Electrophysiology, The First Affiliated Hospital of Xinjiang Medical University, Urumqi 830011, China
- Correspondence: Baopeng Tang () or Ling Zhang () or Xianhui Zhou ()
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7
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Banach K, Blatter LA. The 'Reverse FDUF' Mechanism of Atrial Excitation-Contraction Coupling Sustains Calcium Alternans-A Hypothesis. Biomolecules 2022; 13:biom13010007. [PMID: 36671392 PMCID: PMC9855423 DOI: 10.3390/biom13010007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Revised: 12/07/2022] [Accepted: 12/15/2022] [Indexed: 12/24/2022] Open
Abstract
Cardiac calcium alternans is defined as beat-to-beat alternations of Ca transient (CaT) amplitude and has been linked to cardiac arrhythmia, including atrial fibrillation. We investigated the mechanism of atrial alternans in isolated rabbit atrial myocytes using high-resolution line scan confocal Ca imaging. Alternans was induced by increasing the pacing frequency until stable alternans was observed (1.6-2.5 Hz at room temperature). In atrial myocytes, action potential-induced Ca release is initiated in the cell periphery and subsequently propagates towards the cell center by Ca-induced Ca release (CICR) in a Ca wave-like fashion, driven by the newly identified 'fire-diffuse-uptake-fire' (FDUF) mechanism. The development of CaT alternans was accompanied by characteristic changes of the spatio-temporal organization of the CaT. During the later phase of the CaT, central [Ca]i exceeded peripheral [Ca]i that was indicative of a reversal of the subcellular [Ca]i gradient from centripetal to centrifugal. This gradient reversal resulted in a reversal of CICR propagation, causing a secondary Ca release during the large-amplitude alternans CaT, thereby prolonging the CaT, enhancing Ca-release refractoriness and reducing Ca release on the subsequent beat, thus enhancing the degree of CaT alternans. Here, we propose the 'reverse FDUF' mechanism as a novel cellular mechanism of atrial CaT alternans, which explains how the uncoupling of central from peripheral Ca release leads to the reversal of propagating CICR and to alternans.
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Affiliation(s)
- Kathrin Banach
- Department of Internal Medicine/Cardiology, Rush University Medical Center, Chicago, IL 60612, USA
| | - Lothar A. Blatter
- Department of Physiology & Biophysics, Rush University Medical Center, Chicago, IL 60612, USA
- Correspondence:
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8
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Martinez-Hernandez E, Kanaporis G, Blatter LA. Mechanism of carvedilol induced action potential and calcium alternans. Channels (Austin) 2022; 16:97-112. [PMID: 35501948 PMCID: PMC9067505 DOI: 10.1080/19336950.2022.2055521] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Carvedilol is a nonspecific β-blocker clinically used for the treatment of cardiovascular diseases but has also been shown to have profound effects on excitation-contraction coupling and Ca signaling at the cellular level. We investigate the mechanism by which carvedilol facilitates Ca transient (CaT) and action potential duration (APD) alternans in rabbit atrial myocytes. Carvedilol lowered the frequency threshold for pacing-induced CaT alternans and facilitated alternans in a concentration-dependent manner. Carvedilol prolonged the sarcoplasmic reticulum (SR) Ca release refractoriness by significantly increasing the time constant τ of recovery of SR Ca release; however, no changes in L-type calcium current recovery from inactivation or SR Ca load were found after carvedilol treatment. Carvedilol enhanced the degree of APD alternans nearly two-fold. Carvedilol slowed the APD restitution kinetics and steepened the APD restitution curve at the pacing frequency (2 Hz) where alternans were elicited. No effect on the CaT or APD alternans ratios was observed in experiments with a different β-blocker (metoprolol), excluding the possibility that the carvedilol effect on CaT and APD alternans was determined by its β-blocking properties. These data suggest that carvedilol contributes to the generation of CaT and APD alternans in atrial myocytes by modulating the restitution of CaT and APD.
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Affiliation(s)
| | - Giedrius Kanaporis
- Department of Physiology & Biophysics, Rush University Medical Center, Chicago, Illinois, USA
| | - Lothar A. Blatter
- Department of Physiology & Biophysics, Rush University Medical Center, Chicago, Illinois, USA,CONTACT Lothar A. Blatter Department of Physiology & Biophysics, Rush University Medical Center, 1750 W. Harrison Street, Chicago, IL60612, USA
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9
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Abstract
The global burden caused by cardiovascular disease is substantial, with heart disease representing the most common cause of death around the world. There remains a need to develop better mechanistic models of cardiac function in order to combat this health concern. Heart rhythm disorders, or arrhythmias, are one particular type of disease which has been amenable to quantitative investigation. Here we review the application of quantitative methodologies to explore dynamical questions pertaining to arrhythmias. We begin by describing single-cell models of cardiac myocytes, from which two and three dimensional models can be constructed. Special focus is placed on results relating to pattern formation across these spatially-distributed systems, especially the formation of spiral waves of activation. Next, we discuss mechanisms which can lead to the initiation of arrhythmias, focusing on the dynamical state of spatially discordant alternans, and outline proposed mechanisms perpetuating arrhythmias such as fibrillation. We then review experimental and clinical results related to the spatio-temporal mapping of heart rhythm disorders. Finally, we describe treatment options for heart rhythm disorders and demonstrate how statistical physics tools can provide insights into the dynamics of heart rhythm disorders.
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Affiliation(s)
- Wouter-Jan Rappel
- Department of Physics, University of California San Diego, La Jolla, CA 92037
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10
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Huang C, Song Z, Qu Z. Synchronization of spatially discordant voltage and calcium alternans in cardiac tissue. Phys Rev E 2022; 106:024406. [PMID: 36109882 DOI: 10.1103/physreve.106.024406] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2022] [Accepted: 07/18/2022] [Indexed: 06/01/2023]
Abstract
The heart is an excitable medium which is excited by membrane potential depolarization and propagation. Membrane potential depolarization brings in calcium (Ca) through the Ca channels to trigger intracellular Ca release for contraction of the heart. Ca also affects voltage via Ca-dependent ionic currents, and thus, voltage and Ca are bidirectionally coupled. It has been shown that the voltage subsystem or the Ca subsystem can generate its own dynamical instabilities which are affected by their bidirectional couplings, leading to complex dynamics of action potential and Ca cycling. Moreover, the dynamics become spatiotemporal in tissue in which cells are diffusively coupled through voltage. A widely investigated spatiotemporal dynamics is spatially discordant alternans (SDA) in which action potential duration (APD) or Ca amplitude exhibits temporally period-2 and spatially out-of-phase patterns, i.e., APD-SDA and Ca-SDA patterns, respectively. However, the mechanisms of formation, stability, and synchronization of APD-SDA and Ca-SDA patterns remain incompletely understood. In this paper, we use cardiac tissue models described by an amplitude equation, coupled iterated maps, and reaction-diffusion equations with detailed physiology (the ionic model) to perform analytical and computational investigations. We show that, when the Ca subsystem is stable, the Ca-SDA pattern always follows the APD-SDA pattern, and thus, they are always synchronized. When the Ca subsystem is unstable, synchronization of APD-SDA and Ca-SDA patterns depends on the stabilities of both subsystems, their coupling strengths, and the spatial scales of the initial Ca-SDA patterns. Spontaneous (initial condition-independent) synchronization is promoted by enhancing APD instability and reducing Ca instability as well as stronger Ca-to-APD and APD-to-Ca coupling, a pattern formation caused by dynamical instabilities. When Ca is more unstable and APD is less unstable or APD-to-Ca coupling is weak, synchronization of APD-SDA and Ca-SDA patterns is promoted by larger initially synchronized Ca-SDA clusters, i.e., initial condition-dependent synchronization. The synchronized APD-SDA and Ca-SDA patterns can be locked in-phase, antiphase, or quasiperiodic depending on the coupling relationship between APD and Ca. These theoretical and simulation results provide mechanistic insights into the APD-SDA and Ca-SDA dynamics observed in experimental studies.
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Affiliation(s)
- Chunli Huang
- School of Mathematics and Statistics, Guangdong University of Foreign Studies, Guangzhou 510420, China
- Department of Medicine, University of California, Los Angeles, California 90095, USA
| | - Zhen Song
- Peng Cheng Laboratory, Shenzhen, Guangdong, China
| | - Zhilin Qu
- Department of Medicine, University of California, Los Angeles, California 90095, USA
- Department of Computational Medicine, University of California, Los Angeles, California 90095, USA
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11
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Discordant Ca 2+ release in cardiac myocytes: characterization and susceptibility to pharmacological RyR2 modulation. Pflugers Arch 2022; 474:625-636. [PMID: 35235009 DOI: 10.1007/s00424-022-02678-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2021] [Revised: 01/26/2022] [Accepted: 02/14/2022] [Indexed: 10/19/2022]
Abstract
Systolic Ca2+ transients are shaped by the concerted summation of Ca2+ sparks across cardiomyocytes. At high pacing rates, alterations of excitation-contraction coupling manifest as pro-arrhythmic Ca2+ alternans that can be classified as concordant or discordant. Discordance is ascribed to out-of-phase alternation of local Ca2+ release across the cell, although the triggers and consequences of this phenomenon remain unclear. Rat ventricular cardiomyocytes were paced at increasing rates. A discordance index (SD of local alternans ratios) was developed to quantify discordance in confocal recordings of Ca2+ transients. Index values were significantly increased by rapid pacing, and negatively correlated with Ca2+ transient amplitude change, indicating that discordance is an important contributor to the negative Ca2+ transient-frequency relationship. In addition, the largest local calcium transient in two consecutive transients was measured to build a potential "best release" profile, which quantitatively confirmed discordance-induced Ca2+ release impairment (DICRI). Diastolic Ca2+ homeostasis was also observed to be disrupted by discordance, as late Ca2+ release events elicited instability of resting Ca2+ levels. Finally, the effects of two RyR2 inhibitors (VK-II-86 and dantrolene) were tested. While both compounds inhibited Ca2+ wave generation, only VK-II-86 augmented subcellular discordance. Discordant Ca2+ release is a quantifiable phenomenon, sensitive to pacing frequency, and impairs both systolic and diastolic Ca2+ homeostasis. Interestingly, RyR2 inhibition can induce discordance, which should be considered when evaluating pharmacological RyR2 modulators for clinical use.
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12
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Trongtorsak A, Thangjui S, Chaisidhivej N, Sharma A, Ariyachaipanich A. A Premature Ventricular Contraction Associated With Transient Worsening Pulsus Alternans: A Case Report. Cureus 2021; 13:e20284. [PMID: 35018271 PMCID: PMC8742136 DOI: 10.7759/cureus.20284] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/08/2021] [Indexed: 12/01/2022] Open
Abstract
Pulsus alternans is a rare condition characterized by alternation between strong and weak pulses during regular heart rhythm. Although pulsus alternans occurs mostly in severe heart failure, it can also be seen in other conditions that alternate ventricular contraction such as rapid tachycardia and extrasystole. Here, we report the case of a patient with peripartum cardiomyopathy who developed worsening pulsus alternans after a premature ventricular contraction.
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13
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Cely-Ortiz A, Felice JI, Díaz-Zegarra LA, Valverde CA, Federico M, Palomeque J, Wehrens XHT, Kranias EG, Aiello EA, Lascano EC, Negroni JA, Mattiazzi A. Determinants of Ca2+ release restitution: Insights from genetically altered animals and mathematical modeling. J Gen Physiol 2021; 152:152125. [PMID: 32986800 PMCID: PMC7594441 DOI: 10.1085/jgp.201912512] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Revised: 07/27/2020] [Accepted: 08/21/2020] [Indexed: 01/07/2023] Open
Abstract
Each heartbeat is followed by a refractory period. Recovery from refractoriness is known as Ca2+ release restitution (CRR), and its alterations are potential triggers of Ca2+ arrhythmias. Although the control of CRR has been associated with SR Ca2+ load and RYR2 Ca2+ sensitivity, the relative role of some of the determinants of CRR remains largely undefined. An intriguing point, difficult to dissect and previously neglected, is the possible independent effect of SR Ca2+ content versus the velocity of SR Ca2+ refilling on CRR. To assess these interrogations, we used isolated myocytes with phospholamban (PLN) ablation (PLNKO), knock-in mice with pseudoconstitutive CaMKII phosphorylation of RYR2 S2814 (S2814D), S2814D crossed with PLNKO mice (SDKO), and a previously validated human cardiac myocyte model. Restitution of cytosolic Ca2+ (Fura-2 AM) and L-type calcium current (ICaL; patch-clamp) was evaluated with a two-pulse (S1/S2) protocol. CRR and ICaL restitution increased as a function of the (S2-S1) coupling interval, following an exponential curve. When SR Ca2+ load was increased by increasing extracellular [Ca2+] from 2.0 to 4.0 mM, CRR and ICaL restitution were enhanced, suggesting that ICaL restitution may contribute to the faster CRR observed at 4.0 mM [Ca2+]. In contrast, ICaL restitution did not differ among the different mouse models. For a given SR Ca2+ load, CRR was accelerated in S2814D myocytes versus WT, but not in PLNKO and SDKO myocytes versus WT and S2814D, respectively. The model mimics all experimental data. Moreover, when the PLN ablation-induced decrease in RYR2 expression was corrected, the model revealed that CRR was accelerated in PLNKO and SDKO versus WT and S2814D myocytes, consistent with the enhanced velocity of refilling, SR [Ca2+] recovery, and CRR. We speculate that refilling rate might enhance CRR independently of SR Ca2+ load.
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Affiliation(s)
- Alejandra Cely-Ortiz
- Centro de Investigaciones Cardiovasculares, Centro Científico Tecnológico-La Plata, Consejo Nacional de Investigaciones Científicas y Técnicas, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Juan I Felice
- Centro de Investigaciones Cardiovasculares, Centro Científico Tecnológico-La Plata, Consejo Nacional de Investigaciones Científicas y Técnicas, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Leandro A Díaz-Zegarra
- Centro de Investigaciones Cardiovasculares, Centro Científico Tecnológico-La Plata, Consejo Nacional de Investigaciones Científicas y Técnicas, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Carlos A Valverde
- Centro de Investigaciones Cardiovasculares, Centro Científico Tecnológico-La Plata, Consejo Nacional de Investigaciones Científicas y Técnicas, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Marilén Federico
- Centro de Investigaciones Cardiovasculares, Centro Científico Tecnológico-La Plata, Consejo Nacional de Investigaciones Científicas y Técnicas, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Julieta Palomeque
- Centro de Investigaciones Cardiovasculares, Centro Científico Tecnológico-La Plata, Consejo Nacional de Investigaciones Científicas y Técnicas, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Xander H T Wehrens
- Departments of Molecular Physiology and Biophysics, Medicine (in Cardiology), Neuroscience, Pediatrics, Center for Space Medicine, Baylor College of Medicine, Cardiovascular Research Institute, Houston, TX
| | - Evangelia G Kranias
- Department of Pharmacology, University of Cincinnati College of Medicine, Cincinnati, OH
| | - Ernesto A Aiello
- Centro de Investigaciones Cardiovasculares, Centro Científico Tecnológico-La Plata, Consejo Nacional de Investigaciones Científicas y Técnicas, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Elena C Lascano
- Instituto de Medicina Traslacional, Trasplante y Bioingeniería, Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad Favaloro, Ciudad Autónoma de Buenos Aires, Buenos Aires, Argentina
| | - Jorge A Negroni
- Instituto de Medicina Traslacional, Trasplante y Bioingeniería, Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad Favaloro, Ciudad Autónoma de Buenos Aires, Buenos Aires, Argentina
| | - Alicia Mattiazzi
- Centro de Investigaciones Cardiovasculares, Centro Científico Tecnológico-La Plata, Consejo Nacional de Investigaciones Científicas y Técnicas, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina
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14
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Tóth N, Szlovák J, Kohajda Z, Bitay G, Veress R, Horváth B, Papp JG, Varró A, Nagy N. The development of L-type Ca 2+ current mediated alternans does not depend on the restitution slope in canine ventricular myocardium. Sci Rep 2021; 11:16652. [PMID: 34404848 PMCID: PMC8371021 DOI: 10.1038/s41598-021-95299-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Accepted: 07/23/2021] [Indexed: 11/25/2022] Open
Abstract
Cardiac alternans have crucial importance in the onset of ventricular fibrillation. The early explanation for alternans development was the voltage-driven mechanism, where the action potential (AP) restitution steepness was considered as crucial determining factor. Recent results suggest that restitution slope is an inadequate predictor for alternans development, but several studies still claim the role of membrane potential as underlying mechanism of alternans. These controversial data indicate that the relationship of restitution and alternans development is not completely understood. APs were measured by conventional microelectrode technique from canine right ventricular papillary muscles. Ionic currents combined with fluorescent measurements were recorded by patch-clamp technique. APs combined with fluorescent measurements were monitored by sharp microelectrodes. Rapid pacing evoked restitution-independent AP duration (APD) alternans. When non-alternating AP voltage command was used, Ca2+i-transient (CaT) alternans were not observed. When alternating rectangular voltage pulses were applied, CaT alternans were proportional to ICaL amplitude alternans. Selective ICaL inhibition did not influence the fast phase of APD restitution. In this study we found that ICaL has minor contribution in shaping the fast phase of restitution curve suggesting that ICaL—if it plays important role in the alternans mechanism—could be an additional factor that attenuates the reliability of APD restitution slope to predict alternans.
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Affiliation(s)
- Noémi Tóth
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Dóm tér 12, P.O. Box 427, 6720, Szeged, Hungary
| | - Jozefina Szlovák
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Dóm tér 12, P.O. Box 427, 6720, Szeged, Hungary
| | - Zsófia Kohajda
- ELKH-SZTE Research Group of Cardiovascular Pharmacology, Szeged, Hungary
| | - Gergő Bitay
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Dóm tér 12, P.O. Box 427, 6720, Szeged, Hungary
| | - Roland Veress
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Balázs Horváth
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.,Faculty of Pharmacy, University of Debrecen, Debrecen, Hungary
| | - Julius Gy Papp
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Dóm tér 12, P.O. Box 427, 6720, Szeged, Hungary.,ELKH-SZTE Research Group of Cardiovascular Pharmacology, Szeged, Hungary
| | - András Varró
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Dóm tér 12, P.O. Box 427, 6720, Szeged, Hungary.,ELKH-SZTE Research Group of Cardiovascular Pharmacology, Szeged, Hungary.,Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of Szeged, Szeged, Hungary
| | - Norbert Nagy
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Dóm tér 12, P.O. Box 427, 6720, Szeged, Hungary. .,ELKH-SZTE Research Group of Cardiovascular Pharmacology, Szeged, Hungary.
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15
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Sadredini M, Haugsten Hansen M, Frisk M, Louch WE, Lehnart SE, Sjaastad I, Stokke MK. CaMKII inhibition has dual effects on spontaneous Ca 2+ release and Ca 2+ alternans in ventricular cardiomyocytes from mice with a gain-of-function RyR2 mutation. Am J Physiol Heart Circ Physiol 2021; 321:H446-H460. [PMID: 34270372 DOI: 10.1152/ajpheart.00011.2021] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
In conditions with abnormally increased activity of the cardiac ryanodine receptor (RyR2), Ca2+/calmodulin-dependent protein kinase II (CaMKII) can contribute to a further destabilization of RyR2 that results in triggered arrhythmias. Therefore, inhibition of CaMKII in such conditions has been suggested as a strategy to suppress RyR2 activity and arrhythmias. However, suppression of RyR2 activity can lead to the development of arrhythmogenic Ca2+ alternans. The aim of this study was to test whether the suppression of RyR2 activity caused by inhibition of CaMKII increases propensity for Ca2+ alternans. We studied spontaneous Ca2+ release events and Ca2+ alternans in isolated left ventricular cardiomyocytes from mice carrying the gain-of-function RyR2 mutation RyR2-R2474S and from wild-type mice. CaMKII inhibition by KN-93 effectively decreased the frequency of spontaneous Ca2+ release events in RyR2-R2474S cardiomyocytes exposed to the β-adrenoceptor agonist isoprenaline. However, KN-93-treated RyR2-R2474S cardiomyocytes also showed increased propensity for Ca2+ alternans and increased Ca2+ alternans ratio compared with both an inactive analog of KN-93 and with vehicle-treated controls. This increased propensity for Ca2+ alternans was explained by prolongation of Ca2+ release refractoriness. Importantly, the increased propensity for Ca2+ alternans in KN-93-treated RyR2-R2474S cardiomyocytes did not surpass that of wild type. In conclusion, inhibition of CaMKII efficiently reduces spontaneous Ca2+ release but promotes Ca2+ alternans in RyR2-R2474S cardiomyocytes with a gain-of-function RyR2 mutation. The dominant effect in RyR2-R2474S is to reduce spontaneous Ca2+ release, which supports this intervention as a therapeutic strategy in this specific condition. However, future studies on CaMKII inhibition in conditions with increased propensity for Ca2+ alternans should include investigation of both phenomena.NEW & NOTEWORTHY Genetically increased RyR2 activity promotes arrhythmogenic Ca2+ release. Inhibition of CaMKII suppresses RyR2 activity and arrhythmogenic Ca2+ release. Suppression of RyR2 activity prolongs refractoriness of Ca2+ release. Prolonged refractoriness of Ca2+ release leads to arrhythmogenic Ca2+ alternans. CaMKII inhibition promotes Ca2+ alternans by prolonging Ca2+ release refractoriness.
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Affiliation(s)
- Mani Sadredini
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,KG Jebsen Cardiac Research Centre, University of Oslo, Oslo, Norway
| | - Marie Haugsten Hansen
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,KG Jebsen Cardiac Research Centre, University of Oslo, Oslo, Norway
| | - Michael Frisk
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,KG Jebsen Cardiac Research Centre, University of Oslo, Oslo, Norway
| | - William E Louch
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,KG Jebsen Cardiac Research Centre, University of Oslo, Oslo, Norway
| | - Stephan E Lehnart
- Department of Cardiology and Pulmonology, Heart Research Center Göttingen, University Medical Center Göttingen, Göttingen, Germany.,Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, Göttingen, Germany.,DZHK (German Centre for Cardiovascular Research), Göttingen, Germany
| | - Ivar Sjaastad
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,KG Jebsen Cardiac Research Centre, University of Oslo, Oslo, Norway
| | - Mathis Korseberg Stokke
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,KG Jebsen Cardiac Research Centre, University of Oslo, Oslo, Norway.,Department of Cardiology, Oslo University Hospital, Rikshospitalet, Oslo, Norway
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16
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Floras JS. The 2021 Carl Ludwig Lecture. Unsympathetic autonomic regulation in heart failure: patient-inspired insights. Am J Physiol Regul Integr Comp Physiol 2021; 321:R338-R351. [PMID: 34259047 DOI: 10.1152/ajpregu.00143.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Defined as a structural or functional cardiac abnormality accompanied by symptoms, signs, or biomarkers of altered ventricular pressures or volumes, heart failure also is a state of autonomic disequilibrium. A large body of evidence affirms that autonomic disturbances are intrinsic to heart failure; basal or stimulated sympathetic nerve firing or neural norepinephrine (NE) release more often than not exceed homeostatic need, such that an initially adaptive adrenergic or vagal reflex response becomes maladaptive. The magnitude of such maladaptation predicts prognosis. This Ludwig lecture develops two theses: the elucidation and judiciously targeted amelioration of maladaptive autonomic disturbances offers opportunities to complement contemporary guideline-based heart failure therapy, and serendipitous single-participant insights, acquired in the course of experimental protocols with entirely different intent, can generate novel insight, inform mechanisms, and launch entirely new research directions. I précis six elements of our current synthesis of the causes and consequences of maladaptive sympathetic disequilibrium in heart failure, shaped by patient-inspired epiphanies: arterial baroreceptor reflex modulation, excitation stimulated by increased cardiac filling pressure, paradoxical muscle sympathetic activation as a peripheral neurogenic constraint on exercise capacity, renal sympathetic restraint of natriuresis, coexisting sleep apnea, and augmented chemoreceptor reflex sensitivity and then conclude by envisaging translational therapeutic opportunities.
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Affiliation(s)
- John S Floras
- University Health Network and Sinai Health Division of Cardiology, Toronto General Hospital Research Institute and Department of Medicine, University of Toronto, Toronto, Ontario, Canada
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17
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Wang L, Myles RC, Lee IJ, Bers DM, Ripplinger CM. Role of Reduced Sarco-Endoplasmic Reticulum Ca 2+-ATPase Function on Sarcoplasmic Reticulum Ca 2+ Alternans in the Intact Rabbit Heart. Front Physiol 2021; 12:656516. [PMID: 34045974 PMCID: PMC8144333 DOI: 10.3389/fphys.2021.656516] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Accepted: 03/29/2021] [Indexed: 01/16/2023] Open
Abstract
Sarcoplasmic reticulum (SR) Ca2+ cycling is tightly regulated by ryanodine receptor (RyR) Ca2+ release and sarco-endoplasmic reticulum Ca2+-ATPase (SERCA) Ca2+ uptake during each excitation–contraction coupling cycle. We previously showed that RyR refractoriness plays a key role in the onset of SR Ca2+ alternans in the intact rabbit heart, which contributes to arrhythmogenic action potential duration (APD) alternans. Recent studies have also implicated impaired SERCA function, a key feature of heart failure, in cardiac alternans and arrhythmias. However, the relationship between reduced SERCA function and SR Ca2+ alternans is not well understood. Simultaneous optical mapping of transmembrane potential (Vm) and SR Ca2+ was performed in isolated rabbit hearts (n = 10) using the voltage-sensitive dye RH237 and the low-affinity Ca2+ indicator Fluo-5N-AM. Alternans was induced by rapid ventricular pacing. SERCA was inhibited with cyclopiazonic acid (CPA; 1–10 μM). SERCA inhibition (1, 5, and 10 μM of CPA) resulted in dose-dependent slowing of SR Ca2+ reuptake, with the time constant (tau) increasing from 70.8 ± 3.5 ms at baseline to 85.5 ± 6.6, 129.9 ± 20.7, and 271.3 ± 37.6 ms, respectively (p < 0.05 vs. baseline for all doses). At fast pacing frequencies, CPA significantly increased the magnitude of SR Ca2+ and APD alternans, most strongly at 10 μM (pacing cycle length = 220 ms: SR Ca2+ alternans magnitude: 57.1 ± 4.7 vs. 13.4 ± 8.9 AU; APD alternans magnitude 3.8 ± 1.9 vs. 0.2 ± 0.19 AU; p < 0.05 10 μM of CPA vs. baseline for both). SERCA inhibition also promoted the emergence of spatially discordant alternans. Notably, at all CPA doses, alternation of SR Ca2+ release occurred prior to alternation of diastolic SR Ca2+ load as pacing frequency increased. Simultaneous optical mapping of SR Ca2+ and Vm in the intact rabbit heart revealed that SERCA inhibition exacerbates pacing-induced SR Ca2+ and APD alternans magnitude, particularly at fast pacing frequencies. Importantly, SR Ca2+ release alternans always occurred before the onset of SR Ca2+ load alternans. These findings suggest that even in settings of diminished SERCA function, relative refractoriness of RyR Ca2+ release governs the onset of intracellular Ca2+ alternans.
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Affiliation(s)
- Lianguo Wang
- Department of Pharmacology, School of Medicine, University of California, Davis, Davis, CA, United States
| | - Rachel C Myles
- Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom
| | - I-Ju Lee
- Department of Pharmacology, School of Medicine, University of California, Davis, Davis, CA, United States
| | - Donald M Bers
- Department of Pharmacology, School of Medicine, University of California, Davis, Davis, CA, United States
| | - Crystal M Ripplinger
- Department of Pharmacology, School of Medicine, University of California, Davis, Davis, CA, United States
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18
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Ware WA, Cheney AB, Murphy S. Biventricular Pulsus Alternans in a Dog with Pulmonic Stenosis and Sepsis. CASE 2021; 5:105-109. [PMID: 33937597 PMCID: PMC8071959 DOI: 10.1016/j.case.2020.12.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Pulsus alternans is characterized by beat-to-beat variability in cardiac contractile strength. Besides severe LV failure, hypovolemia and tachycardia can provoke pulsus alternans. Right ventricular or biventricular alternans is reported only sporadically in people. The first biventricular pulsus alternans in the veterinary clinical literature is presented.
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19
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You T, Luo C, Zhang K, Zhang H. Electrophysiological Mechanisms Underlying T-Wave Alternans and Their Role in Arrhythmogenesis. Front Physiol 2021; 12:614946. [PMID: 33746768 PMCID: PMC7969788 DOI: 10.3389/fphys.2021.614946] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Accepted: 02/10/2021] [Indexed: 12/18/2022] Open
Abstract
T-wave alternans (TWA) reflects every-other-beat alterations in the morphology of the electrocardiogram ST segment or T wave in the setting of a constant heart rate, hence, in the absence of heart rate variability. It is believed to be associated with the dispersion of repolarization and has been used as a non-invasive marker for predicting the risk of malignant cardiac arrhythmias and sudden cardiac death as numerous studies have shown. This review aims to provide up-to-date review on both experimental and simulation studies in elucidating possible mechanisms underlying the genesis of TWA at the cellular level, as well as the genesis of spatially concordant/discordant alternans at the tissue level, and their transition to cardiac arrhythmia. Recent progress and future perspectives in antiarrhythmic therapies associated with TWA are also discussed.
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Affiliation(s)
- Tingting You
- Key Lab of Medical Electrophysiology, Ministry of Education, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, China
| | - Cunjin Luo
- School of Computer Science and Electronic Engineering, University of Essex, Colchester, United Kingdom
| | - Kevin Zhang
- School of Medicine, Imperial College of London, London, United Kingdom
| | - Henggui Zhang
- Key Lab of Medical Electrophysiology, Ministry of Education, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, China.,Department of Physics and Astronomy, University of Manchester, Manchester, United Kingdom
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20
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Blatter LA, Kanaporis G, Martinez-Hernandez E, Oropeza-Almazan Y, Banach K. Excitation-contraction coupling and calcium release in atrial muscle. Pflugers Arch 2021; 473:317-329. [PMID: 33398498 DOI: 10.1007/s00424-020-02506-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Revised: 12/03/2020] [Accepted: 12/16/2020] [Indexed: 01/02/2023]
Abstract
In cardiac muscle, the process of excitation-contraction coupling (ECC) describes the chain of events that links action potential induced myocyte membrane depolarization, surface membrane ion channel activation, triggering of Ca2+ induced Ca2+ release from the sarcoplasmic reticulum (SR) Ca2+ store to activation of the contractile machinery that is ultimately responsible for the pump function of the heart. Here we review similarities and differences of structural and functional attributes of ECC between atrial and ventricular tissue. We explore a novel "fire-diffuse-uptake-fire" paradigm of atrial ECC and Ca2+ release that assigns a novel role to the SR SERCA pump and involves a concerted "tandem" activation of the ryanodine receptor Ca2+ release channel by cytosolic and luminal Ca2+. We discuss the contribution of the inositol 1,4,5-trisphosphate (IP3) receptor Ca2+ release channel as an auxiliary pathway to Ca2+ signaling, and we review IP3 receptor-induced Ca2+ release involvement in beat-to-beat ECC, nuclear Ca2+ signaling, and arrhythmogenesis. Finally, we explore the topic of electromechanical and Ca2+ alternans and its ramifications for atrial arrhythmia.
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Affiliation(s)
- L A Blatter
- Department of Physiology & Biophysics, Rush University Medical Center, 1750 W. Harrison Street, Chicago, IL, 60612, USA.
| | - G Kanaporis
- Department of Physiology & Biophysics, Rush University Medical Center, 1750 W. Harrison Street, Chicago, IL, 60612, USA
| | - E Martinez-Hernandez
- Department of Physiology & Biophysics, Rush University Medical Center, 1750 W. Harrison Street, Chicago, IL, 60612, USA
| | - Y Oropeza-Almazan
- Department of Physiology & Biophysics, Rush University Medical Center, 1750 W. Harrison Street, Chicago, IL, 60612, USA
| | - K Banach
- Department of Internal Medicine/Cardiology, Rush University Medical Center, Chicago, IL, 60612, USA
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21
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Pandey V, Xie LH, Qu Z, Song Z. Mitochondrial depolarization promotes calcium alternans: Mechanistic insights from a ventricular myocyte model. PLoS Comput Biol 2021; 17:e1008624. [PMID: 33493168 PMCID: PMC7861552 DOI: 10.1371/journal.pcbi.1008624] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Revised: 02/04/2021] [Accepted: 12/10/2020] [Indexed: 01/08/2023] Open
Abstract
Mitochondria are vital organelles inside the cell and contribute to intracellular calcium (Ca2+) dynamics directly and indirectly via calcium exchange, ATP generation, and production of reactive oxygen species (ROS). Arrhythmogenic Ca2+ alternans in cardiac myocytes has been observed in experiments under abnormal mitochondrial depolarization. However, complex signaling pathways and Ca2+ cycling between mitochondria and cytosol make it difficult in experiments to reveal the underlying mechanisms of Ca2+ alternans under abnormal mitochondrial depolarization. In this study, we use a newly developed spatiotemporal ventricular myocyte computer model that integrates mitochondrial Ca2+ cycling and complex signaling pathways to investigate the mechanisms of Ca2+ alternans during mitochondrial depolarization. We find that elevation of ROS in response to mitochondrial depolarization plays a critical role in promoting Ca2+ alternans. Further examination reveals that the redox effect of ROS on ryanodine receptors and sarco/endoplasmic reticulum Ca2+-ATPase synergistically promote alternans. Upregulation of mitochondrial Ca2+ uniporter promotes Ca2+ alternans via Ca2+-dependent mitochondrial permeability transition pore opening. Due to their relatively slow kinetics, oxidized Ca2+/calmodulin-dependent protein kinase II activation and ATP do not play significant roles acutely in the genesis of Ca2+ alternans after mitochondrial depolarization, but their roles can be significant in the long term, mainly through their effects on sarco/endoplasmic reticulum Ca2+-ATPase activity. In conclusion, mitochondrial depolarization promotes Ca2+ alternans acutely via the redox effect of ROS and chronically by ATP reduction. It suppresses Ca2+ alternans chronically through oxidized Ca2+/calmodulin-dependent protein kinase II activation.
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Affiliation(s)
- Vikas Pandey
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California, United States of America
| | - Lai-Hua Xie
- Department of Cell Biology and Molecular Medicine, Rutgers, New Jersey Medical School, Newark, New Jersey, United States of America
| | - Zhilin Qu
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California, United States of America
- Department of Computational Medicine, David Geffen School of Medicine, University of California, Los Angeles, California, United States of America
| | - Zhen Song
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California, United States of America
- Peng Cheng Laboratory, Shenzhen, Guangdong, China
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22
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Orini M, Yanni J, Taggart P, Hanson B, Hayward M, Smith A, Zhang H, Colman M, Jones G, Jie X, Dobrzynski H, Boyett MR, Lambiase PD. Mechanistic insights from targeted molecular profiling of repolarization alternans in the intact human heart. Europace 2020; 21:981-989. [PMID: 30753421 PMCID: PMC6545501 DOI: 10.1093/europace/euz007] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Revised: 10/17/2018] [Accepted: 01/21/2019] [Indexed: 02/05/2023] Open
Abstract
AIMS Action potential duration (APD) alternans is an established precursor or arrhythmia and sudden cardiac death. Important differences in fundamental electrophysiological properties relevant to arrhythmia exist between experimental models and the diseased in vivo human heart. To investigate mechanisms of APD alternans using a novel approach combining intact heart and cellular cardiac electrophysiology in human in vivo. METHODS AND RESULTS We developed a novel approach combining intact heart electrophysiological mapping during cardiac surgery with rapid on-site data analysis to guide myocardial biopsies for laboratory analysis, thereby linking repolarization dynamics observed at the organ level with underlying ion channel expression. Alternans-susceptible and alternans-resistant regions were identified by an incremental pacing protocol. Biopsies from these sites (n = 13) demonstrated greater RNA expression in Calsequestrin (CSQN) and Ryanodine (RyR) and ion channels underlying IK1 and Ito at alternans-susceptible sites. Electrical restitution properties (n = 7) showed no difference between alternans-susceptible and resistant sites, whereas spatial gradients of repolarization were greater in alternans-susceptible than in alternans-resistant sites (P = 0.001). The degree of histological fibrosis between alternans-susceptible and resistant sites was equivalent. Mathematical modelling of these changes indicated that both CSQN and RyR up-regulation are key determinants of APD alternans. CONCLUSION Combined intact heart and cellular electrophysiology show that regions of myocardium in the in vivo human heart exhibiting APD alternans are associated with greater expression of CSQN and RyR and show no difference in restitution properties compared to non-alternans regions. In silico modelling identifies up-regulation and interaction of CSQN with RyR as a major mechanism underlying APD alternans.
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Affiliation(s)
- Michele Orini
- Institute of Cardiovascular Science, University College London, London, UK.,Department of Electrophysiology, Barts Heart Centre at St Bartholomew's Hospital, London, UK
| | - Joseph Yanni
- Division of Cardiovascular Science, University of Manchester, Manchester, UK
| | - Peter Taggart
- Institute of Cardiovascular Science, University College London, London, UK
| | - Ben Hanson
- Department of Mechanical Engineering, University College London, UK
| | - Martin Hayward
- Department of Cardiothoracic Surgery, The Heart Hospital, University College London Hospitals, London, UK
| | - Andrew Smith
- Department of Electrophysiology, Barts Heart Centre at St Bartholomew's Hospital, London, UK
| | - Henggui Zhang
- Division of Cardiovascular Science, University of Manchester, Manchester, UK.,School of Physics and Astronomy, University of Manchester, Manchester, UK
| | | | - Gareth Jones
- School of Physics and Astronomy, University of Manchester, Manchester, UK
| | - Xiao Jie
- Institute of Cardiovascular Science, University College London, London, UK
| | - Halina Dobrzynski
- Division of Cardiovascular Science, University of Manchester, Manchester, UK
| | - Mark R Boyett
- Division of Cardiovascular Science, University of Manchester, Manchester, UK
| | - Pier D Lambiase
- Institute of Cardiovascular Science, University College London, London, UK.,Department of Electrophysiology, Barts Heart Centre at St Bartholomew's Hospital, London, UK
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23
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van Duijvenboden S, Ramírez J, Young WJ, Mifsud B, Orini M, Tinker A, Munroe PB, Lambiase PD. Genetic Basis and Prognostic Value of Exercise QT Dynamics. CIRCULATION-GENOMIC AND PRECISION MEDICINE 2020; 13:e002774. [PMID: 32527199 PMCID: PMC7439940 DOI: 10.1161/circgen.119.002774] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Supplemental Digital Content is available in the text. Background: Abnormal QT interval responses to heart rate (QT dynamics) is an independent risk predictor for cardiovascular disease in patients, but its genetic basis and prognostic value in a population-based cohort have not been investigated. Methods: QT dynamics during exercise and recovery were derived in 56 643 individuals from UK Biobank without a history of cardiovascular events. Genome-wide association studies were conducted to identify genetic variants and bioinformatics analyses were performed to prioritize candidate genes. The prognostic value of QT dynamics was evaluated for cardiovascular events (death or hospitalization) and all-cause mortality. Results: Heritability of QT dynamics during exercise and recovery were 10.7% and 5.4%, respectively. Genome-wide association studies identified 20 loci, of which 4 loci included genes implicated in mendelian long-QT syndrome. Five loci did not overlap with previously reported resting QT interval loci; candidate genes included KCNQ4 and KIAA1755. Genetic risk scores were not associated with cardiovascular events in 357 882 unrelated individuals from UK Biobank. We also did not observe associations of QT dynamics during exercise and recovery with cardiovascular events. Increased QT dynamics during recovery was significantly associated with all-cause mortality in the univariate Cox regression analysis (hazard ratio, 1.09 [95% CI, 1.05–1.13], P=2.28×10-5), but the association was not significant after adjusting for clinical risk factors. Conclusions: QT interval dynamics during exercise and recovery are heritable markers but do not carry independent prognostic information for clinical outcomes in the UK Biobank, a population-based cohort. Their prognostic importance may relate to cardiovascular disease cohorts where structural heart disease or ischemia may influence repolarization dynamics. The strong overlap between QT dynamics and resting QT interval loci suggests common biological pathways; however, nonoverlapping loci suggests alternative mechanisms may exist that underlie QT interval dynamics.
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Affiliation(s)
- Stefan van Duijvenboden
- Institute of Cardiovascular Science, University College London, United Kingdom (S.v.D., J.R., M.O., P.D.L.).,Clinical Pharmacology, William Harvey Research Institute (S.v.D., J.R., W.J.Y., B.M., M.O., A.T., P.B.M.), Barts & The London School of Medicine and Dentistry, Queen Mary University of London, United Kingdom
| | - Julia Ramírez
- Institute of Cardiovascular Science, University College London, United Kingdom (S.v.D., J.R., M.O., P.D.L.).,Clinical Pharmacology, William Harvey Research Institute (S.v.D., J.R., W.J.Y., B.M., M.O., A.T., P.B.M.), Barts & The London School of Medicine and Dentistry, Queen Mary University of London, United Kingdom
| | - William J Young
- Clinical Pharmacology, William Harvey Research Institute (S.v.D., J.R., W.J.Y., B.M., M.O., A.T., P.B.M.), Barts & The London School of Medicine and Dentistry, Queen Mary University of London, United Kingdom.,Barts Heart Centre, St Bartholomew's Hospital, London, United Kingdom (W.J.Y., P.D.L.)
| | - Borbala Mifsud
- Clinical Pharmacology, William Harvey Research Institute (S.v.D., J.R., W.J.Y., B.M., M.O., A.T., P.B.M.), Barts & The London School of Medicine and Dentistry, Queen Mary University of London, United Kingdom.,College of Health and Life Sciences, Doha, Qatar (B.M.)
| | - Michele Orini
- Institute of Cardiovascular Science, University College London, United Kingdom (S.v.D., J.R., M.O., P.D.L.).,Clinical Pharmacology, William Harvey Research Institute (S.v.D., J.R., W.J.Y., B.M., M.O., A.T., P.B.M.), Barts & The London School of Medicine and Dentistry, Queen Mary University of London, United Kingdom
| | - Andrew Tinker
- Clinical Pharmacology, William Harvey Research Institute (S.v.D., J.R., W.J.Y., B.M., M.O., A.T., P.B.M.), Barts & The London School of Medicine and Dentistry, Queen Mary University of London, United Kingdom.,NIHR Barts Cardiovascular Biomedical Research Unit (A.T., P.B.M.), Barts & The London School of Medicine and Dentistry, Queen Mary University of London, United Kingdom
| | - Patricia B Munroe
- Clinical Pharmacology, William Harvey Research Institute (S.v.D., J.R., W.J.Y., B.M., M.O., A.T., P.B.M.), Barts & The London School of Medicine and Dentistry, Queen Mary University of London, United Kingdom.,NIHR Barts Cardiovascular Biomedical Research Unit (A.T., P.B.M.), Barts & The London School of Medicine and Dentistry, Queen Mary University of London, United Kingdom
| | - Pier D Lambiase
- Institute of Cardiovascular Science, University College London, United Kingdom (S.v.D., J.R., M.O., P.D.L.).,Barts Heart Centre, St Bartholomew's Hospital, London, United Kingdom (W.J.Y., P.D.L.)
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24
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Veasy J, Lai YM, Coombes S, Thul R. Complex patterns of subcellular cardiac alternans. J Theor Biol 2019; 478:102-114. [PMID: 31220466 DOI: 10.1016/j.jtbi.2019.06.016] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Revised: 06/12/2019] [Accepted: 06/16/2019] [Indexed: 10/26/2022]
Abstract
Cardiac alternans, in which the membrane potential and the intracellular calcium concentration exhibit alternating durations and peak amplitudes at consecutive beats, constitute a precursor to fatal cardiac arrhythmia such as sudden cardiac death. A crucial question therefore concerns the onset of cardiac alternans. Typically, alternans are only reported when they are fully developed. Here, we present a modelling approach to explore recently discovered microscopic alternans, which represent one of the earliest manifestations of cardiac alternans. In this case, the regular periodic dynamics of the local intracellular calcium concentration is already unstable, while the whole-cell behaviour suggests a healthy cell state. In particular, we use our model to investigate the impact of calcium diffusion in both the cytosol and the sarcoplasmic reticulum on the formation of microscopic calcium alternans. We find that for dominant cytosolic coupling, calcium alternans emerge via the traditional period doubling bifurcation. In contrast, dominant luminal coupling leads to a novel route to calcium alternans through a saddle-node bifurcation at the network level. Combining semi-analytical and computational approaches, we compute areas of stability in parameter space and find that as we cross from stable to unstable regions, the emergent patterns of the intracellular calcium concentration change abruptly in a fashion that is highly dependent upon position along the stability boundary. Our results demonstrate that microscopic calcium alternans may possess a much richer dynamical repertoire than previously thought and further strengthen the role of luminal calcium in shaping cardiac calcium dynamics.
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Affiliation(s)
- Joshua Veasy
- Centre for Mathematical Medicine and Biology, School of Mathematical Sciences, University of Nottingham, Nottingham NG7 2RD, UK
| | - Yi Ming Lai
- Centre for Mathematical Medicine and Biology, School of Mathematical Sciences, University of Nottingham, Nottingham NG7 2RD, UK
| | - Stephen Coombes
- Centre for Mathematical Medicine and Biology, School of Mathematical Sciences, University of Nottingham, Nottingham NG7 2RD, UK
| | - Rüdiger Thul
- Centre for Mathematical Medicine and Biology, School of Mathematical Sciences, University of Nottingham, Nottingham NG7 2RD, UK.
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25
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Monga B, Wilson D, Matchen T, Moehlis J. Phase reduction and phase-based optimal control for biological systems: a tutorial. BIOLOGICAL CYBERNETICS 2019; 113:11-46. [PMID: 30203130 DOI: 10.1007/s00422-018-0780-z] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Accepted: 08/25/2018] [Indexed: 05/20/2023]
Abstract
A powerful technique for the analysis of nonlinear oscillators is the rigorous reduction to phase models, with a single variable describing the phase of the oscillation with respect to some reference state. An analog to phase reduction has recently been proposed for systems with a stable fixed point, and phase reduction for periodic orbits has recently been extended to take into account transverse directions and higher-order terms. This tutorial gives a unified treatment of such phase reduction techniques and illustrates their use through mathematical and biological examples. It also covers the use of phase reduction for designing control algorithms which optimally change properties of the system, such as the phase of the oscillation. The control techniques are illustrated for example neural and cardiac systems.
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Affiliation(s)
- Bharat Monga
- Department of Mechanical Engineering, University of California, Santa Barbara, CA, 93106, USA
| | - Dan Wilson
- Department of Electrical Engineering and Computer Science, University of Tennessee, Knoxville, TN, 37996, USA
| | - Tim Matchen
- Department of Mechanical Engineering, University of California, Santa Barbara, CA, 93106, USA
| | - Jeff Moehlis
- Department of Mechanical Engineering, University of California, Santa Barbara, CA, 93106, USA.
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26
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Denham NC, Pearman CM, Caldwell JL, Madders GWP, Eisner DA, Trafford AW, Dibb KM. Calcium in the Pathophysiology of Atrial Fibrillation and Heart Failure. Front Physiol 2018; 9:1380. [PMID: 30337881 PMCID: PMC6180171 DOI: 10.3389/fphys.2018.01380] [Citation(s) in RCA: 99] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Accepted: 09/11/2018] [Indexed: 12/20/2022] Open
Abstract
Atrial fibrillation (AF) is commonly associated with heart failure. A bidirectional relationship exists between the two-AF exacerbates heart failure causing a significant increase in heart failure symptoms, admissions to hospital and cardiovascular death, while pathological remodeling of the atria as a result of heart failure increases the risk of AF. A comprehensive understanding of the pathophysiology of AF is essential if we are to break this vicious circle. In this review, the latest evidence will be presented showing a fundamental role for calcium in both the induction and maintenance of AF. After outlining atrial electrophysiology and calcium handling, the role of calcium-dependent afterdepolarizations and atrial repolarization alternans in triggering AF will be considered. The atrial response to rapid stimulation will be discussed, including the short-term protection from calcium overload in the form of calcium signaling silencing and the eventual progression to diastolic calcium leak causing afterdepolarizations and the development of an electrical substrate that perpetuates AF. The role of calcium in the bidirectional relationship between heart failure and AF will then be covered. The effects of heart failure on atrial calcium handling that promote AF will be reviewed, including effects on both atrial myocytes and the pulmonary veins, before the aspects of AF which exacerbate heart failure are discussed. Finally, the limitations of human and animal studies will be explored allowing contextualization of what are sometimes discordant results.
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Affiliation(s)
- Nathan C. Denham
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Manchester Academic Health Science Centre, University of Manchester, Manchester, United Kingdom
| | | | | | | | | | | | - Katharine M. Dibb
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Manchester Academic Health Science Centre, University of Manchester, Manchester, United Kingdom
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27
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Shiferaw Y, Aistrup GL, Wasserstrom JA. Synchronization of Triggered Waves in Atrial Tissue. Biophys J 2018; 115:1130-1141. [PMID: 30195941 DOI: 10.1016/j.bpj.2018.08.015] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Revised: 07/31/2018] [Accepted: 08/10/2018] [Indexed: 10/28/2022] Open
Abstract
When an atrial cell is paced rapidly, calcium (Ca) waves can form on the cell boundary and propagate to the cell interior. These waves are referred to as "triggered waves" because they are initiated by Ca influx from the L-type Ca channel and occur during the action potential. However, the consequences of triggered waves in atrial tissue are not known. Here, we develop a phenomenological model of Ca cycling in atrial myocytes that accounts for the formation of triggered waves. Using this model, we show that a fundamental requirement for triggered waves to induce abnormal electrical activity in tissue is that these waves must be synchronized over large populations of cells. This is partly because triggered waves induce a long action potential duration (APD) followed by a short APD. Thus, if these events are not synchronized between cells, then they will on average cancel and have minimal effects on the APD in tissue. Using our computational model, we identify two distinct mechanisms for triggered wave synchronization. The first relies on cycle length (CL) variability, which can prolong the CL at a given beat. In cardiac tissue, we show that CL prolongation leads to a substantial amplification of APD because of the synchronization of triggered waves. A second synchronization mechanism applies in a parameter regime in which the cell exhibits stochastic alternans in which a triggered wave fires, on average, only every other beat. In this scenario, we identify a slow synchronization mechanism that relies on the bidirectional feedback between the APD in tissue and triggered wave initiation. On large cables, this synchronization mechanism leads to spatially discordant APD alternans with spatial variations on a scale of hundreds of cells. We argue that these spatial patterns can potentially serve as an arrhythmogenic substrate for the initiation of atrial fibrillation.
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Affiliation(s)
- Yohannes Shiferaw
- Department of Physics, California State University, Northridge, California.
| | - Gary L Aistrup
- Department of Experimental Cardiology, Masonic Medical Research Laboratory, Utica, New York
| | - John A Wasserstrom
- Department of Medicine (Cardiology) and The Feinberg Cardiovascular Research Institute, Northwestern University Feinberg School of Medicine, Chicago, Illinois
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28
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Sun B, Wei J, Zhong X, Guo W, Yao J, Wang R, Vallmitjana A, Benitez R, Hove-Madsen L, Chen SRW. The cardiac ryanodine receptor, but not sarcoplasmic reticulum Ca 2+-ATPase, is a major determinant of Ca 2+ alternans in intact mouse hearts. J Biol Chem 2018; 293:13650-13661. [PMID: 29986885 DOI: 10.1074/jbc.ra118.003760] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2018] [Revised: 07/06/2018] [Indexed: 11/06/2022] Open
Abstract
Sarcoplasmic reticulum (SR) Ca2+ cycling is governed by the cardiac ryanodine receptor (RyR2) and SR Ca2+-ATPase (SERCA2a). Abnormal SR Ca2+ cycling is thought to be the primary cause of Ca2+ alternans that can elicit ventricular arrhythmias and sudden cardiac arrest. Although alterations in either RyR2 or SERCA2a function are expected to affect SR Ca2+ cycling, whether and to what extent altered RyR2 or SERCA2a function affects Ca2+ alternans is unclear. Here, we employed a gain-of-function RyR2 variant (R4496C) and the phospholamban-knockout (PLB-KO) mouse model to assess the effect of genetically enhanced RyR2 or SERCA2a function on Ca2+ alternans. Confocal Ca2+ imaging revealed that RyR2-R4496C shortened SR Ca2+ release refractoriness and markedly suppressed rapid pacing-induced Ca2+ alternans. Interestingly, despite enhancing RyR2 function, intact RyR2-R4496C hearts exhibited no detectable spontaneous SR Ca2+ release events during pacing. Unlike for RyR2, enhancing SERCA2a function by ablating PLB exerted a relatively minor effect on Ca2+ alternans in intact hearts expressing RyR2 WT or a loss-of-function RyR2 variant, E4872Q, that promotes Ca2+ alternans. Furthermore, partial SERCA2a inhibition with 3 μm 2,5-di-tert-butylhydroquinone (tBHQ) also had little impact on Ca2+ alternans, whereas strong SERCA2a inhibition with 10 μm tBHQ markedly reduced the amplitude of Ca2+ transients and suppressed Ca2+ alternans in intact hearts. Our results demonstrate that enhanced RyR2 function suppresses Ca2+ alternans in the absence of spontaneous Ca2+ release and that RyR2, but not SERCA2a, is a key determinant of Ca2+ alternans in intact working hearts, making RyR2 an important therapeutic target for cardiac alternans.
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Affiliation(s)
- Bo Sun
- From the Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Jinhong Wei
- From the Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Xiaowei Zhong
- From the Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Wenting Guo
- From the Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Jinjing Yao
- From the Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Ruiwu Wang
- From the Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Alexander Vallmitjana
- the Department of Automatic Control, Universitat Politècnica de Catalunya, Barcelona 08034, Spain, and
| | - Raul Benitez
- the Department of Automatic Control, Universitat Politècnica de Catalunya, Barcelona 08034, Spain, and
| | - Leif Hove-Madsen
- the Biomedical Research Institute of Barcelona (IIBB), CSIC, Sant Pau, Hospital de Sant Pau, Barcelona 08025, Spain
| | - S R Wayne Chen
- From the Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta T2N 4N1, Canada,
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29
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Wilson D, Ermentrout B. Stochastic Pacing Inhibits Spatially Discordant Cardiac Alternans. Biophys J 2017; 113:2552-2572. [PMID: 29212008 DOI: 10.1016/j.bpj.2017.10.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Revised: 09/28/2017] [Accepted: 10/02/2017] [Indexed: 12/19/2022] Open
Abstract
Depressed heart rate variability is a well-established risk factor for sudden cardiac death in survivors of acute myocardial infarction and for those with congestive heart failure. Although measurements of heart rate variability provide a valuable prognostic tool, it is unclear whether reduced heart rate variability itself is proarrhythmic or if it simply correlates with the severity of autonomic nervous system dysfunction. In this work, we investigate a possible mechanism by which heart rate variability could protect against cardiac arrhythmia. Specifically, in numerical simulations, we observe an inverse relationship between the variance of stochastic pacing and the occurrence of spatially discordant alternans, an arrhythmia that is widely believed to facilitate the development of cardiac fibrillation. By analyzing the effects of conduction velocity restitution, cellular dynamics, electrotonic coupling, and stochastic pacing on the nodal dynamics of spatially discordant alternans, we provide intuition for this observed behavior and propose control strategies to inhibit discordant alternans.
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Affiliation(s)
- Dan Wilson
- Department of Mathematics, University of Pittsburgh, Pittsburgh, Pennsylvania.
| | - Bard Ermentrout
- Department of Mathematics, University of Pittsburgh, Pittsburgh, Pennsylvania
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30
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Cantalapiedra IR, Alvarez-Lacalle E, Peñaranda A, Echebarria B. Minimal model for calcium alternans due to SR release refractoriness. CHAOS (WOODBURY, N.Y.) 2017; 27:093928. [PMID: 28964152 DOI: 10.1063/1.5000709] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
In the heart, rapid pacing rates may induce alternations in the strength of cardiac contraction, termed pulsus alternans. Often, this is due to an instability in the dynamics of the intracellular calcium concentration, whose transients become larger and smaller at consecutive beats. This alternation has been linked experimentally and theoretically to two different mechanisms: an instability due to (1) a strong dependence of calcium release on sarcoplasmic reticulum (SR) load, together with a slow calcium reuptake into the SR or (2) to SR release refractoriness, due to a slow recovery of the ryanodine receptors (RyR2) from inactivation. The relationship between calcium alternans and refractoriness of the RyR2 has been more elusive than the corresponding SR Ca load mechanism. To study the former, we reduce a general calcium model, which mimics the deterministic evolution of a calcium release unit, to its most basic elements. We show that calcium alternans can be understood using a simple nonlinear equation for calcium concentration at the dyadic space, coupled to a relaxation equation for the number of recovered RyR2s. Depending on the number of RyR2s that are recovered at the beginning of a stimulation, the increase in calcium concentration may pass, or not, over an excitability threshold that limits the occurrence of a large calcium transient. When the recovery of the RyR2 is slow, this produces naturally a period doubling bifurcation, resulting in calcium alternans. We then study the effects of inactivation, calcium diffusion, and release conductance for the onset of alternans. We find that the development of alternans requires a well-defined value of diffusion while it is less sensitive to the values of inactivation or release conductance.
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Affiliation(s)
- Inma R Cantalapiedra
- Departament de Física. Universitat Politècnica de Catalunya, Av Dr. Marañon 50 (EPSEB), Barcelona, Spain
| | - Enrique Alvarez-Lacalle
- Departament de Física. Universitat Politècnica de Catalunya, Av Dr. Marañon 50 (EPSEB), Barcelona, Spain
| | - Angelina Peñaranda
- Departament de Física. Universitat Politècnica de Catalunya, Av Dr. Marañon 50 (EPSEB), Barcelona, Spain
| | - Blas Echebarria
- Departament de Física. Universitat Politècnica de Catalunya, Av Dr. Marañon 50 (EPSEB), Barcelona, Spain
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31
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Comlekoglu T, Weinberg SH. Memory in a fractional-order cardiomyocyte model alters properties of alternans and spontaneous activity. CHAOS (WOODBURY, N.Y.) 2017; 27:093904. [PMID: 28964143 DOI: 10.1063/1.4999351] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Cardiac memory is the dependence of electrical activity on the prior history of one or more system state variables, including transmembrane potential (Vm), ionic current gating, and ion concentrations. While prior work has represented memory either phenomenologically or with biophysical detail, in this study, we consider an intermediate approach of a minimal three-variable cardiomyocyte model, modified with fractional-order dynamics, i.e., a differential equation of order between 0 and 1, to account for history-dependence. Memory is represented via both capacitive memory, due to fractional-order Vm dynamics, that arises due to non-ideal behavior of membrane capacitance; and ionic current gating memory, due to fractional-order gating variable dynamics, that arises due to gating history-dependence. We perform simulations for varying Vm and gating variable fractional-orders and pacing cycle length and measure action potential duration (APD) and incidence of alternans, loss of capture, and spontaneous activity. In the absence of ionic current gating memory, we find that capacitive memory, i.e., decreased Vm fractional-order, typically shortens APD, suppresses alternans, and decreases the minimum cycle length (MCL) for loss of capture. However, in the presence of ionic current gating memory, capacitive memory can prolong APD, promote alternans, and increase MCL. Further, we find that reduced Vm fractional order (typically less than 0.75) can drive phase 4 depolarizations that promote spontaneous activity. Collectively, our results demonstrate that memory reproduced by a fractional-order model can play a role in alternans formation and pacemaking, and in general, can greatly increase the range of electrophysiological characteristics exhibited by a minimal model.
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Affiliation(s)
- T Comlekoglu
- Virginia Commonwealth University, 401 West Main Street, Richmond, Virginia 23284, USA
| | - S H Weinberg
- Virginia Commonwealth University, 401 West Main Street, Richmond, Virginia 23284, USA
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32
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Kofron CM, Kim TY, King ME, Xie A, Feng F, Park E, Qu Z, Choi BR, Mende U. G q-activated fibroblasts induce cardiomyocyte action potential prolongation and automaticity in a three-dimensional microtissue environment. Am J Physiol Heart Circ Physiol 2017; 313:H810-H827. [PMID: 28710068 DOI: 10.1152/ajpheart.00181.2017] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Revised: 06/13/2017] [Accepted: 07/03/2017] [Indexed: 11/22/2022]
Abstract
Cardiac fibroblasts (CFs) are known to regulate cardiomyocyte (CM) function in vivo and in two-dimensional in vitro cultures. This study examined the effect of CF activation on the regulation of CM electrical activity in a three-dimensional (3-D) microtissue environment. Using a scaffold-free 3-D platform with interspersed neonatal rat ventricular CMs and CFs, Gq-mediated signaling was selectively enhanced in CFs by Gαq adenoviral infection before coseeding with CMs in nonadhesive hydrogels. After 3 days, the microtissues were analyzed by signaling assay, histological staining, quantitative PCR, Western blots, optical mapping with voltage- or Ca2+-sensitive dyes, and microelectrode recordings of CF resting membrane potential (RMPCF). Enhanced Gq signaling in CFs increased microtissue size and profibrotic and prohypertrophic markers. Expression of constitutively active Gαq in CFs prolonged CM action potential duration (by 33%) and rise time (by 31%), prolonged Ca2+ transient duration (by 98%) and rise time (by 65%), and caused abnormal electrical activity based on depolarization-induced automaticity. Constitutive Gq activation in CFs also depolarized RMPCF from -33 to -20 mV and increased connexin 43 and connexin 45 expression. Computational modeling confers that elevated RMPCF and increased cell-cell coupling between CMs and CFs in a 3-D environment could lead to automaticity. In conclusion, our data demonstrate that CF activation alone is capable of altering action potential and Ca2+ transient characteristics of CMs, leading to proarrhythmic electrical activity. Our results also emphasize the importance of a 3-D environment where cell-cell interactions are prevalent, underscoring that CF activation in 3-D tissue plays a significant role in modulating CM electrophysiology and arrhythmias.NEW & NOTEWORTHY In a three-dimensional microtissue model, which lowers baseline activation of cardiac fibroblasts but enables cell-cell, paracrine, and cell-extracellular matrix interactions, we demonstrate that selective cardiac fibroblast activation by enhanced Gq signaling, a pathophysiological trigger in the diseased heart, modulates cardiomyocyte electrical activity, leading to proarrhythmogenic automaticity.
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Affiliation(s)
- C M Kofron
- Cardiovascular Research Center, Cardiovascular Institute, Rhode Island Hospital and Alpert Medical School of Brown University, Providence, Rhode Island; and
| | - T Y Kim
- Cardiovascular Research Center, Cardiovascular Institute, Rhode Island Hospital and Alpert Medical School of Brown University, Providence, Rhode Island; and
| | - M E King
- Cardiovascular Research Center, Cardiovascular Institute, Rhode Island Hospital and Alpert Medical School of Brown University, Providence, Rhode Island; and
| | - A Xie
- Cardiovascular Research Center, Cardiovascular Institute, Rhode Island Hospital and Alpert Medical School of Brown University, Providence, Rhode Island; and
| | - F Feng
- Cardiovascular Research Center, Cardiovascular Institute, Rhode Island Hospital and Alpert Medical School of Brown University, Providence, Rhode Island; and
| | - E Park
- Cardiovascular Research Center, Cardiovascular Institute, Rhode Island Hospital and Alpert Medical School of Brown University, Providence, Rhode Island; and
| | - Z Qu
- Department of Medicine, University of California, Los Angeles, California
| | - B-R Choi
- Cardiovascular Research Center, Cardiovascular Institute, Rhode Island Hospital and Alpert Medical School of Brown University, Providence, Rhode Island; and
| | - U Mende
- Cardiovascular Research Center, Cardiovascular Institute, Rhode Island Hospital and Alpert Medical School of Brown University, Providence, Rhode Island; and
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Verrier RL. Statins protect against arrhythmogenic calcium alternans in the post-myocardial infarction diabetic heart: Pleiotropy on steroids. Heart Rhythm 2017; 14:1417-1418. [PMID: 28606636 DOI: 10.1016/j.hrthm.2017.06.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Indexed: 02/05/2023]
Affiliation(s)
- Richard L Verrier
- Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts.
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34
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Jin H, Welzig CM, Aronovitz M, Noubary F, Blanton R, Wang B, Rajab M, Albano A, Link MS, Noujaim SF, Park HJ, Galper JB. QRS/T-wave and calcium alternans in a type I diabetic mouse model for spontaneous postmyocardial infarction ventricular tachycardia: A mechanism for the antiarrhythmic effect of statins. Heart Rhythm 2017; 14:1406-1416. [PMID: 28522367 DOI: 10.1016/j.hrthm.2017.05.026] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/16/2017] [Indexed: 11/29/2022]
Abstract
BACKGROUND The incidence of sudden arrhythmic death is markedly increased in diabetics. OBJECTIVE The purpose of this study was to develop a mouse model for postmyocardial infarction (post-MI) ventricular tachycardia (VT) in the diabetic heart and determine the mechanism of an antiarrhythmic effect of statins. METHODS ECG transmitters were implanted in wild-type (WT), placebo, and pravastatin-treated type I diabetic Akita mice. MIs were induced by coronary ligation, and Ca2+ transients were studied by optical mapping, and Ca2+ transients and sparks in left ventricular myocytes (VM) by the Ionoptix system and confocal microscopy. RESULTS Burst pacing of Akita mouse hearts resulted in rate-related QRS/T-wave alternans, which was attenuated in pravastatin-treated mice. Post-MI Akita mice developed QRS/T-wave alternans and VT at 2820 ± 879 beats per mouse, which decreased to 343 ± 115 in pravastatin-treated mice (n = 13, P <.05). Optical mapping demonstrated pacing-induced VT originating in the peri-infarction zone and Ca2+ alternans, both attenuated in hearts of statin-treated mice. Akita VM displayed Ca2+ alternans, and triggered activity as well as increased Ca2+ transient decay time (Tau), Ca2+ sparks, and cytosolic Ca2+ and decreased SR Ca2+ stores all of which were in part reversed in cells from statin treated mice. Homogenates of Akita ventricles demonstrated decreased SERCA2a/PLB ratio and increased ratio of protein phosphatase (PP-1) to the PP-1 inhibitor PPI-1 which were reversed in homogenates of pravastatin-treated Akita mice. CONCLUSION Pravastatin decreased the incidence of post-MI VT and Ca2+ alternans in Akita mouse hearts in part by revering abnormalities of Ca2+ handling via the PP-1/PPI-1 pathway.
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Affiliation(s)
- Hongwei Jin
- Tufts Medical Center, Tufts University School of Medicine, Boston, Massachusetts; Molecular Cardiology Research Institute, Tufts Medical Center, Boston, Massachusetts.
| | - Charles M Welzig
- Tufts Medical Center, Tufts University School of Medicine, Boston, Massachusetts; Departments of Neurology, Physiology and Biomedical Engineering, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Mark Aronovitz
- Tufts Medical Center, Tufts University School of Medicine, Boston, Massachusetts; Molecular Cardiology Research Institute, Tufts Medical Center, Boston, Massachusetts
| | - Farzad Noubary
- Tufts Medical Center, Tufts University School of Medicine, Boston, Massachusetts; Tufts Clinical and Translational Science Institute, Boston, Massachusetts
| | - Robert Blanton
- Tufts Medical Center, Tufts University School of Medicine, Boston, Massachusetts; Molecular Cardiology Research Institute, Tufts Medical Center, Boston, Massachusetts; Cardiovascular Division, Cardiovascular Center, Department of Medicine, Tufts Medical Center, Boston, Massachusetts
| | - Bo Wang
- Tufts Medical Center, Tufts University School of Medicine, Boston, Massachusetts; Molecular Cardiology Research Institute, Tufts Medical Center, Boston, Massachusetts
| | - Mohammad Rajab
- Molecular Cardiology Research Institute, Tufts Medical Center, Boston, Massachusetts; Department of Internal Medicine, Virginia Commonwealth University Medical Center, Richmond, Virginia
| | - Alfred Albano
- Tufts Medical Center, Tufts University School of Medicine, Boston, Massachusetts; Molecular Cardiology Research Institute, Tufts Medical Center, Boston, Massachusetts; Spectrum Health, Grand Rapids, Michigan
| | - Mark S Link
- Tufts Medical Center, Tufts University School of Medicine, Boston, Massachusetts; Tufts Clinical and Translational Science Institute, Boston, Massachusetts; UT Southwestern Medical Center, Dallas, Texas
| | - Sami F Noujaim
- Tufts Medical Center, Tufts University School of Medicine, Boston, Massachusetts; Molecular Cardiology Research Institute, Tufts Medical Center, Boston, Massachusetts; Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, Tampa, Florida
| | - Ho-Jin Park
- Tufts Medical Center, Tufts University School of Medicine, Boston, Massachusetts; Molecular Cardiology Research Institute, Tufts Medical Center, Boston, Massachusetts.
| | - Jonas B Galper
- Tufts Medical Center, Tufts University School of Medicine, Boston, Massachusetts; Molecular Cardiology Research Institute, Tufts Medical Center, Boston, Massachusetts; Cardiovascular Division, Cardiovascular Center, Department of Medicine, Tufts Medical Center, Boston, Massachusetts.
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35
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Chiamvimonvat N, Chen-Izu Y, Clancy CE, Deschenes I, Dobrev D, Heijman J, Izu L, Qu Z, Ripplinger CM, Vandenberg JI, Weiss JN, Koren G, Banyasz T, Grandi E, Sanguinetti MC, Bers DM, Nerbonne JM. Potassium currents in the heart: functional roles in repolarization, arrhythmia and therapeutics. J Physiol 2017; 595:2229-2252. [PMID: 27808412 DOI: 10.1113/jp272883] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Accepted: 10/11/2016] [Indexed: 12/19/2022] Open
Abstract
This is the second of the two White Papers from the fourth UC Davis Cardiovascular Symposium Systems Approach to Understanding Cardiac Excitation-Contraction Coupling and Arrhythmias (3-4 March 2016), a biennial event that brings together leading experts in different fields of cardiovascular research. The theme of the 2016 symposium was 'K+ channels and regulation', and the objectives of the conference were severalfold: (1) to identify current knowledge gaps; (2) to understand what may go wrong in the diseased heart and why; (3) to identify possible novel therapeutic targets; and (4) to further the development of systems biology approaches to decipher the molecular mechanisms and treatment of cardiac arrhythmias. The sessions of the Symposium focusing on the functional roles of the cardiac K+ channel in health and disease, as well as K+ channels as therapeutic targets, were contributed by Ye Chen-Izu, Gideon Koren, James Weiss, David Paterson, David Christini, Dobromir Dobrev, Jordi Heijman, Thomas O'Hara, Crystal Ripplinger, Zhilin Qu, Jamie Vandenberg, Colleen Clancy, Isabelle Deschenes, Leighton Izu, Tamas Banyasz, Andras Varro, Heike Wulff, Eleonora Grandi, Michael Sanguinetti, Donald Bers, Jeanne Nerbonne and Nipavan Chiamvimonvat as speakers and panel discussants. This article summarizes state-of-the-art knowledge and controversies on the functional roles of cardiac K+ channels in normal and diseased heart. We endeavour to integrate current knowledge at multiple scales, from the single cell to the whole organ levels, and from both experimental and computational studies.
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Affiliation(s)
- Nipavan Chiamvimonvat
- Department of Internal Medicine, University of California, Davis, Genome and Biomedical Science Facility, Rm 6315, Davis, CA, 95616, USA.,Department of Veterans Affairs, Northern California Health Care System, Mather, CA, 95655, USA
| | - Ye Chen-Izu
- Department of Internal Medicine, University of California, Davis, Genome and Biomedical Science Facility, Rm 6315, Davis, CA, 95616, USA.,Department of Pharmacology, University of California, Davis, Genome and Biomedical Science Facility, Rm 3503, Davis, CA, 95616, USA.,Department of Biomedical Engineering, University of California, Davis, Genome and Biomedical Science Facility, Rm 2303, Davis, CA, 95616, USA
| | - Colleen E Clancy
- Department of Pharmacology, University of California, Davis, Genome and Biomedical Science Facility, Rm 3503, Davis, CA, 95616, USA
| | - Isabelle Deschenes
- Department of Physiology and Biophysics, and Biomedical Engineering, Case Western Reserve University, Cleveland, OH, 44109, USA.,Heart and Vascular Research Center, MetroHealth Medical Center, Cleveland, OH, 44109, USA
| | - Dobromir Dobrev
- Institute of Pharmacology, West German Heart and Vascular Center, University Duisburg-Essen, Hufelandstrasse 55, 45122, Essen, Germany
| | - Jordi Heijman
- Department of Cardiology, Cardiovascular Research Institute Maastricht, Faculty of Health, Medicine, and Life Sciences, Maastricht University, Maastricht, The Netherlands
| | - Leighton Izu
- Department of Pharmacology, University of California, Davis, Genome and Biomedical Science Facility, Rm 3503, Davis, CA, 95616, USA
| | - Zhilin Qu
- Division of Cardiology, Cardiovascular Research Laboratory, David Geffen School of Medicine at UCLA, 3645 MRL, Los Angeles, CA, 90095, USA
| | - Crystal M Ripplinger
- Department of Pharmacology, University of California, Davis, Genome and Biomedical Science Facility, Rm 3503, Davis, CA, 95616, USA
| | - Jamie I Vandenberg
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, NSW, 2010, Australia
| | - James N Weiss
- Division of Cardiology, Cardiovascular Research Laboratory, David Geffen School of Medicine at UCLA, 3645 MRL, Los Angeles, CA, 90095, USA
| | - Gideon Koren
- Cardiovascular Research Center, Rhode Island Hospital and the Cardiovascular Institute, The Warren Alpert Medical School of Brown University, Providence, RI, 02903, USA
| | - Tamas Banyasz
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Eleonora Grandi
- Department of Pharmacology, University of California, Davis, Genome and Biomedical Science Facility, Rm 3503, Davis, CA, 95616, USA
| | - Michael C Sanguinetti
- Department of Internal Medicine, University of Utah, Nora Eccles Harrison Cardiovascular Research & Training Institute, Salt Lake City, UT, 84112, USA
| | - Donald M Bers
- Department of Pharmacology, University of California, Davis, Genome and Biomedical Science Facility, Rm 3503, Davis, CA, 95616, USA
| | - Jeanne M Nerbonne
- Departments of Developmental Biology and Internal Medicine, Cardiovascular Division, Washington University Medical School, St Louis, MO, 63110, USA
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36
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Lu JL, Molnar MZ, Ma JZ, George LK, Sumida K, Kalantar-Zadeh K, Kovesdy CP. Racial Differences in Association of Serum Calcium with Mortality and Incident Cardio- and Cerebrovascular Events. J Clin Endocrinol Metab 2016; 101:4851-4859. [PMID: 27631543 PMCID: PMC5155693 DOI: 10.1210/jc.2016-1802] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
CONTEXT Abnormalities in calcium metabolism may potentially contribute to the development of vascular disease. Calcium metabolism may be different in African American (AA) vs white individuals, but the effect of race on the association of serum calcium with clinical outcomes remains unclear. OBJECTIVE This study sought to examine race-specific associations of serum calcium levels with mortality and with major incident cardiovascular events. DESIGN AND SETTING This was a historical cohort study in the U.S. Department of Veterans Affairs health care facilities. PARTICIPANTS Participants included veterans (n = 1 967 622) with estimated glomerular filtration rate ≥ 60 mL/min/1.73 m2. MAIN OUTCOME MEASURES The association between serum calcium levels with all-cause mortality, incident coronary heart disease (CHD), and ischemic stroke incidence was examined in multivariable adjusted Cox proportional hazards models, including an interaction term for calcium and race. RESULTS The association of calcium with all-cause mortality was U-shaped in both AA and white patients, but race modified the association of calcium with all-cause mortality. Compared with white patients, AA patients experienced lower risk of mortality when calcium was ≥ 8.8 mg/dL, with a statistically significant interaction (P < .001). Conversely, AA vs white race was associated with higher mortality when calcium was < 8.8 mg/dL. Calcium showed no significant association with ischemic stroke or CHD in both races; and race did not modify these associations (P = .37 and 0.11, respectively for interaction term). CONCLUSIONS Race modified the U-shaped association between calcium and all-cause mortality. Serum calcium is not associated with incident stroke or CHD in either AA or white patients. The race-specific difference in the association of calcium levels with mortality warrants further examination.
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Affiliation(s)
- Jun Ling Lu
- Division of Nephrology (J.L.L., M.Z.M., L.K.G., K.S., C.P.K.), University of Tennessee Health Science Center, Memphis Tennessee 38163; Department of Public Health Sciences and Division of Nephrology, Department of Medicine (J.Z.M.), University of Virginia, Charlottesville, Virginia 22908; Nephrology Center (K.S.), Toranomon Hospital Kajigaya, Kanagawa 213-8587, Japan; Harold Simmons Center for Chronic Disease Research and Epidemiology, Division of Nephrology and Hypertension (K.K.-Z.), University of California-Irvine Medical Center, Orange, California 92868; and Nephrology Section (C.P.K.), Memphis VA Medical Center, Memphis, Tennessee 38104
| | - Miklos Z Molnar
- Division of Nephrology (J.L.L., M.Z.M., L.K.G., K.S., C.P.K.), University of Tennessee Health Science Center, Memphis Tennessee 38163; Department of Public Health Sciences and Division of Nephrology, Department of Medicine (J.Z.M.), University of Virginia, Charlottesville, Virginia 22908; Nephrology Center (K.S.), Toranomon Hospital Kajigaya, Kanagawa 213-8587, Japan; Harold Simmons Center for Chronic Disease Research and Epidemiology, Division of Nephrology and Hypertension (K.K.-Z.), University of California-Irvine Medical Center, Orange, California 92868; and Nephrology Section (C.P.K.), Memphis VA Medical Center, Memphis, Tennessee 38104
| | - Jennie Z Ma
- Division of Nephrology (J.L.L., M.Z.M., L.K.G., K.S., C.P.K.), University of Tennessee Health Science Center, Memphis Tennessee 38163; Department of Public Health Sciences and Division of Nephrology, Department of Medicine (J.Z.M.), University of Virginia, Charlottesville, Virginia 22908; Nephrology Center (K.S.), Toranomon Hospital Kajigaya, Kanagawa 213-8587, Japan; Harold Simmons Center for Chronic Disease Research and Epidemiology, Division of Nephrology and Hypertension (K.K.-Z.), University of California-Irvine Medical Center, Orange, California 92868; and Nephrology Section (C.P.K.), Memphis VA Medical Center, Memphis, Tennessee 38104
| | - Lekha K George
- Division of Nephrology (J.L.L., M.Z.M., L.K.G., K.S., C.P.K.), University of Tennessee Health Science Center, Memphis Tennessee 38163; Department of Public Health Sciences and Division of Nephrology, Department of Medicine (J.Z.M.), University of Virginia, Charlottesville, Virginia 22908; Nephrology Center (K.S.), Toranomon Hospital Kajigaya, Kanagawa 213-8587, Japan; Harold Simmons Center for Chronic Disease Research and Epidemiology, Division of Nephrology and Hypertension (K.K.-Z.), University of California-Irvine Medical Center, Orange, California 92868; and Nephrology Section (C.P.K.), Memphis VA Medical Center, Memphis, Tennessee 38104
| | - Keiichi Sumida
- Division of Nephrology (J.L.L., M.Z.M., L.K.G., K.S., C.P.K.), University of Tennessee Health Science Center, Memphis Tennessee 38163; Department of Public Health Sciences and Division of Nephrology, Department of Medicine (J.Z.M.), University of Virginia, Charlottesville, Virginia 22908; Nephrology Center (K.S.), Toranomon Hospital Kajigaya, Kanagawa 213-8587, Japan; Harold Simmons Center for Chronic Disease Research and Epidemiology, Division of Nephrology and Hypertension (K.K.-Z.), University of California-Irvine Medical Center, Orange, California 92868; and Nephrology Section (C.P.K.), Memphis VA Medical Center, Memphis, Tennessee 38104
| | - Kamyar Kalantar-Zadeh
- Division of Nephrology (J.L.L., M.Z.M., L.K.G., K.S., C.P.K.), University of Tennessee Health Science Center, Memphis Tennessee 38163; Department of Public Health Sciences and Division of Nephrology, Department of Medicine (J.Z.M.), University of Virginia, Charlottesville, Virginia 22908; Nephrology Center (K.S.), Toranomon Hospital Kajigaya, Kanagawa 213-8587, Japan; Harold Simmons Center for Chronic Disease Research and Epidemiology, Division of Nephrology and Hypertension (K.K.-Z.), University of California-Irvine Medical Center, Orange, California 92868; and Nephrology Section (C.P.K.), Memphis VA Medical Center, Memphis, Tennessee 38104
| | - Csaba P Kovesdy
- Division of Nephrology (J.L.L., M.Z.M., L.K.G., K.S., C.P.K.), University of Tennessee Health Science Center, Memphis Tennessee 38163; Department of Public Health Sciences and Division of Nephrology, Department of Medicine (J.Z.M.), University of Virginia, Charlottesville, Virginia 22908; Nephrology Center (K.S.), Toranomon Hospital Kajigaya, Kanagawa 213-8587, Japan; Harold Simmons Center for Chronic Disease Research and Epidemiology, Division of Nephrology and Hypertension (K.K.-Z.), University of California-Irvine Medical Center, Orange, California 92868; and Nephrology Section (C.P.K.), Memphis VA Medical Center, Memphis, Tennessee 38104
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37
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A unified theory of calcium alternans in ventricular myocytes. Sci Rep 2016; 6:35625. [PMID: 27762397 PMCID: PMC5071909 DOI: 10.1038/srep35625] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2016] [Accepted: 10/04/2016] [Indexed: 11/27/2022] Open
Abstract
Intracellular calcium (Ca2+) alternans is a dynamical phenomenon in ventricular myocytes, which is linked to the genesis of lethal arrhythmias. Iterated map models of intracellular Ca2+ cycling dynamics in ventricular myocytes under periodic pacing have been developed to study the mechanisms of Ca2+ alternans. Two mechanisms of Ca2+ alternans have been demonstrated in these models: one relies mainly on fractional sarcoplasmic reticulum Ca2+ release and uptake, and the other on refractoriness and other properties of Ca2+ sparks. Each of the two mechanisms can partially explain the experimental observations, but both have their inconsistencies with the experimental results. Here we developed an iterated map model that is composed of two coupled iterated maps, which unifies the two mechanisms into a single cohesive mathematical framework. The unified theory can consistently explain the seemingly contradictory experimental observations and shows that the two mechanisms work synergistically to promote Ca2+ alternans. Predictions of the theory were examined in a physiologically-detailed spatial Ca2+ cycling model of ventricular myocytes.
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38
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Shiferaw Y. Nonlinear onset of calcium wave propagation in cardiac cells. Phys Rev E 2016; 94:032405. [PMID: 27739779 DOI: 10.1103/physreve.94.032405] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Indexed: 12/20/2022]
Abstract
Spontaneous calcium (Ca) waves in cardiac myocytes are known to underlie a wide range of cardiac arrhythmias. However, it is not understood which physiological parameters determine the onset of waves. In this study, we explore the relationship between Ca signaling between ion channels and the nucleation of Ca waves. In particular, we apply a master equation approach to analyze the stochastic interaction between neighboring clusters of ryanodine receptor (RyR) channels. Using this analysis, we show that signaling between clusters can be described as a barrier hopping process with exponential sensitivity to system parameters. A consequence of this feature is that the probability that Ca release at a cluster induces release at a neighboring cluster exhibits a sigmoid dependence on the Ca content in the cell. This nonlinearity originates from the regulation of RyR opening due to more than one Ca ion binding site, in conjunction with Ca mediated cooperativity between RyR channels in clusters. We apply a spatially distributed stochastic model of Ca cycling to analyze the physiological consequences of this nonlinearity, and show that it explains the sharp onset of Ca wave nucleation in cardiac cells. Furthermore, we show that this sharp onset can serve as a mechanism for Ca alternans under physiologically relevant conditions. Thus our findings identify the nonlinear features of Ca signaling which potentially underlie the onset of Ca waves and Ca alternans in cardiac cells.
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Affiliation(s)
- Yohannes Shiferaw
- Department of Physics & Astronomy, California State University, Northridge, 18111 Nordhoff Street, Northridge, California 91330, USA
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39
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Abstract
Calcium/calmodulin-dependent protein kinase II (CaMKII) has emerged as key enzyme in many cardiac pathologies, especially heart failure (HF), myocardial infarction and cardiomyopathies, thus leading to contractile dysfunction and malignant arrhythmias. While many pathways leading to CaMKII activation have been elucidated in recent years, hardly any clinically viable compounds affecting CaMKII activity have progressed from basic in vitro science to in vivo studies. This review focuses on recent advances in anti-arrhythmic strategies involving CaMKII. Specifically, both inhibition of CaMKII itself to prevent arrhythmias, as well as anti-arrhythmic approaches affecting CaMKII activity via alterations in signaling cascades upstream and downstream of CaMKII will be discussed.
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Affiliation(s)
- Julian Mustroph
- Universitäres Herzzentrum Regensburg, Klinik und Poliklinik für Innere Medizin II, Universitätsklinikum Regensburg, Germany
| | - Stefan Neef
- Universitäres Herzzentrum Regensburg, Klinik und Poliklinik für Innere Medizin II, Universitätsklinikum Regensburg, Germany
| | - Lars S Maier
- Universitäres Herzzentrum Regensburg, Klinik und Poliklinik für Innere Medizin II, Universitätsklinikum Regensburg, Germany.
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40
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Kanaporis G, Blatter LA. Ca(2+)-activated chloride channel activity during Ca(2+) alternans in ventricular myocytes. Channels (Austin) 2016; 10:507-17. [PMID: 27356267 DOI: 10.1080/19336950.2016.1207020] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Cardiac alternans, defined beat-to-beat alternations in contraction, action potential (AP) morphology or cytosolic Ca transient (CaT) amplitude, is a high risk indicator for cardiac arrhythmias. We investigated mechanisms of cardiac alternans in single rabbit ventricular myocytes. CaTs were monitored simultaneously with membrane currents or APs recorded with the patch clamp technique. A strong correlation between beat-to-beat alternations of AP morphology and CaT alternans was observed. During CaT alternans application of voltage clamp protocols in form of pre-recorded APs revealed a prominent Ca(2+)-dependent membrane current consisting of a large outward component coinciding with AP phases 1 and 2, followed by an inward current during AP repolarization. Approximately 85% of the initial outward current was blocked by Cl(-) channel blocker DIDS or lowering external Cl(-) concentration identifying it as a Ca(2+)-activated Cl(-) current (ICaCC). The data suggest that ICaCC plays a critical role in shaping beat-to-beat alternations in AP morphology during alternans.
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Affiliation(s)
- Giedrius Kanaporis
- a Department of Molecular Biophysics and Physiology , Rush University Medical Center , Chicago , IL , USA
| | - Lothar A Blatter
- a Department of Molecular Biophysics and Physiology , Rush University Medical Center , Chicago , IL , USA
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Zhou X, Bueno-Orovio A, Orini M, Hanson B, Hayward M, Taggart P, Lambiase PD, Burrage K, Rodriguez B. In Vivo and In Silico Investigation Into Mechanisms of Frequency Dependence of Repolarization Alternans in Human Ventricular Cardiomyocytes. Circ Res 2015; 118:266-78. [PMID: 26602864 PMCID: PMC4719495 DOI: 10.1161/circresaha.115.307836] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/15/2015] [Accepted: 11/24/2015] [Indexed: 12/11/2022]
Abstract
RATIONALE Repolarization alternans (RA) are associated with arrhythmogenesis. Animal studies have revealed potential mechanisms, but human-focused studies are needed. RA generation and frequency dependence may be determined by cell-to-cell variability in protein expression, which is regulated by genetic and external factors. OBJECTIVE To characterize in vivo RA in human and to investigate in silico using human models, the ionic mechanisms underlying the frequency-dependent differences in RA behavior identified in vivo. METHODS AND RESULTS In vivo electrograms were acquired at 240 sites covering the epicardium of 41 patients at 6 cycle lengths (600-350 ms). In silico investigations were conducted using a population of biophysically detailed human models incorporating variability in protein expression and calibrated using in vivo recordings. Both in silico and in vivo, 2 types of RA were identified, with Fork- and Eye-type restitution curves, based on RA persistence or disappearance, respectively, at fast pacing rates. In silico simulations show that RA are strongly correlated with fluctuations in sarcoplasmic reticulum calcium, because of strong release and weak reuptake. Large L-type calcium current conductance is responsible for RA disappearance at fast frequencies in Eye-type (30% larger in Eye-type versus Fork-type; P<0.01), because of sarcoplasmic reticulum Ca(2+) ATPase pump potentiation caused by frequency-induced increase in intracellular calcium. Large Na(+)/Ca(2+) exchanger current is the main driver in translating Ca(2+) fluctuations into RA. CONCLUSIONS In human in vivo and in silico, 2 types of RA are identified, with RA persistence/disappearance as frequency increases. In silico, L-type calcium current and Na(+)/Ca(2+) exchanger current determine RA human cell-to-cell differences through intracellular and sarcoplasmic reticulum calcium regulation.
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Affiliation(s)
- Xin Zhou
- From the Department of Computer Science, BHF Centre of Research Excellence, University of Oxford, Oxford, United Kingdom (X.Z., A.B.-O., K.B., B.R.); Institute of Cardiovascular Science, University College London, London, United Kingdom (M.O., P.T., P.D.L.); Mechanical Engineering Department, University College London, London, United Kingdom (B.H.); The Heart Hospital, University College London Hospital, London, United Kingdom (M.O., M.H., P.T., P.D.L.); and ACEMS ARC Centre of Excellence and School of Mathematical Sciences, Queensland University of Technology, Brisbane, Queensland, Australia (K.B.)
| | - Alfonso Bueno-Orovio
- From the Department of Computer Science, BHF Centre of Research Excellence, University of Oxford, Oxford, United Kingdom (X.Z., A.B.-O., K.B., B.R.); Institute of Cardiovascular Science, University College London, London, United Kingdom (M.O., P.T., P.D.L.); Mechanical Engineering Department, University College London, London, United Kingdom (B.H.); The Heart Hospital, University College London Hospital, London, United Kingdom (M.O., M.H., P.T., P.D.L.); and ACEMS ARC Centre of Excellence and School of Mathematical Sciences, Queensland University of Technology, Brisbane, Queensland, Australia (K.B.)
| | - Michele Orini
- From the Department of Computer Science, BHF Centre of Research Excellence, University of Oxford, Oxford, United Kingdom (X.Z., A.B.-O., K.B., B.R.); Institute of Cardiovascular Science, University College London, London, United Kingdom (M.O., P.T., P.D.L.); Mechanical Engineering Department, University College London, London, United Kingdom (B.H.); The Heart Hospital, University College London Hospital, London, United Kingdom (M.O., M.H., P.T., P.D.L.); and ACEMS ARC Centre of Excellence and School of Mathematical Sciences, Queensland University of Technology, Brisbane, Queensland, Australia (K.B.)
| | - Ben Hanson
- From the Department of Computer Science, BHF Centre of Research Excellence, University of Oxford, Oxford, United Kingdom (X.Z., A.B.-O., K.B., B.R.); Institute of Cardiovascular Science, University College London, London, United Kingdom (M.O., P.T., P.D.L.); Mechanical Engineering Department, University College London, London, United Kingdom (B.H.); The Heart Hospital, University College London Hospital, London, United Kingdom (M.O., M.H., P.T., P.D.L.); and ACEMS ARC Centre of Excellence and School of Mathematical Sciences, Queensland University of Technology, Brisbane, Queensland, Australia (K.B.)
| | - Martin Hayward
- From the Department of Computer Science, BHF Centre of Research Excellence, University of Oxford, Oxford, United Kingdom (X.Z., A.B.-O., K.B., B.R.); Institute of Cardiovascular Science, University College London, London, United Kingdom (M.O., P.T., P.D.L.); Mechanical Engineering Department, University College London, London, United Kingdom (B.H.); The Heart Hospital, University College London Hospital, London, United Kingdom (M.O., M.H., P.T., P.D.L.); and ACEMS ARC Centre of Excellence and School of Mathematical Sciences, Queensland University of Technology, Brisbane, Queensland, Australia (K.B.)
| | - Peter Taggart
- From the Department of Computer Science, BHF Centre of Research Excellence, University of Oxford, Oxford, United Kingdom (X.Z., A.B.-O., K.B., B.R.); Institute of Cardiovascular Science, University College London, London, United Kingdom (M.O., P.T., P.D.L.); Mechanical Engineering Department, University College London, London, United Kingdom (B.H.); The Heart Hospital, University College London Hospital, London, United Kingdom (M.O., M.H., P.T., P.D.L.); and ACEMS ARC Centre of Excellence and School of Mathematical Sciences, Queensland University of Technology, Brisbane, Queensland, Australia (K.B.)
| | - Pier D Lambiase
- From the Department of Computer Science, BHF Centre of Research Excellence, University of Oxford, Oxford, United Kingdom (X.Z., A.B.-O., K.B., B.R.); Institute of Cardiovascular Science, University College London, London, United Kingdom (M.O., P.T., P.D.L.); Mechanical Engineering Department, University College London, London, United Kingdom (B.H.); The Heart Hospital, University College London Hospital, London, United Kingdom (M.O., M.H., P.T., P.D.L.); and ACEMS ARC Centre of Excellence and School of Mathematical Sciences, Queensland University of Technology, Brisbane, Queensland, Australia (K.B.)
| | - Kevin Burrage
- From the Department of Computer Science, BHF Centre of Research Excellence, University of Oxford, Oxford, United Kingdom (X.Z., A.B.-O., K.B., B.R.); Institute of Cardiovascular Science, University College London, London, United Kingdom (M.O., P.T., P.D.L.); Mechanical Engineering Department, University College London, London, United Kingdom (B.H.); The Heart Hospital, University College London Hospital, London, United Kingdom (M.O., M.H., P.T., P.D.L.); and ACEMS ARC Centre of Excellence and School of Mathematical Sciences, Queensland University of Technology, Brisbane, Queensland, Australia (K.B.)
| | - Blanca Rodriguez
- From the Department of Computer Science, BHF Centre of Research Excellence, University of Oxford, Oxford, United Kingdom (X.Z., A.B.-O., K.B., B.R.); Institute of Cardiovascular Science, University College London, London, United Kingdom (M.O., P.T., P.D.L.); Mechanical Engineering Department, University College London, London, United Kingdom (B.H.); The Heart Hospital, University College London Hospital, London, United Kingdom (M.O., M.H., P.T., P.D.L.); and ACEMS ARC Centre of Excellence and School of Mathematical Sciences, Queensland University of Technology, Brisbane, Queensland, Australia (K.B.).
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Abstract
Despite improvements in the therapy of underlying heart disease, sudden cardiac death is a major cause of death worldwide. Disturbed Na and Ca handling is known to be a major predisposing factor for life-threatening tachyarrhythmias. In cardiomyocytes, many ion channels and transporters, including voltage-gated Na and Ca channels, cardiac ryanodine receptors, Na/Ca-exchanger, and SR Ca-ATPase are involved in this regulation. We have learned a lot about the pathophysiological relevance of disturbed ion channel function from monogenetic disorders. Changes in the gating of a single ion channel and the activity of an ion pump suffice to dramatically increase the propensity for arrhythmias even in structurally normal hearts. Nevertheless, patients with heart failure with acquired dysfunction in many ion channels and transporters exhibit profound dysregulation of Na and Ca handling and Ca/calmodulin-dependent protein kinase and are especially prone to arrhythmias. A deeper understanding of the underlying arrhythmic principles is mandatory if we are to improve their outcome. This review addresses basic tachyarrhythmic mechanisms, the underlying ionic mechanisms and the consequences for ion homeostasis, and the situation in complex diseases like heart failure.
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Affiliation(s)
- Stefan Wagner
- From the Department of Internal Medicine II, University Hospital Regensburg, Regensburg, Germany (S.W., L.S.M.); and Department of Pharmacology, University of California, Davis, CA (D.M.B.)
| | - Lars S Maier
- From the Department of Internal Medicine II, University Hospital Regensburg, Regensburg, Germany (S.W., L.S.M.); and Department of Pharmacology, University of California, Davis, CA (D.M.B.).
| | - Donald M Bers
- From the Department of Internal Medicine II, University Hospital Regensburg, Regensburg, Germany (S.W., L.S.M.); and Department of Pharmacology, University of California, Davis, CA (D.M.B.)
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43
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Lau E, Kossidas K, Kim TY, Kunitomo Y, Ziv O, Zhen S, Taylor C, Schofield L, Yammine J, Liu G, Peng X, Qu Z, Koren G, Choi BR. Spatially Discordant Alternans and Arrhythmias in Tachypacing-Induced Cardiac Myopathy in Transgenic LQT1 Rabbits: The Importance of IKs and Ca2+ Cycling. PLoS One 2015; 10:e0122754. [PMID: 25970695 PMCID: PMC4430457 DOI: 10.1371/journal.pone.0122754] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2014] [Accepted: 02/12/2015] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND Remodeling of cardiac repolarizing currents, such as the downregulation of slowly activating K+ channels (IKs), could underlie ventricular fibrillation (VF) in heart failure (HF). We evaluated the role of Iks remodeling in VF susceptibility using a tachypacing HF model of transgenic rabbits with Long QT Type 1 (LQT1) syndrome. METHODS AND RESULTS LQT1 and littermate control (LMC) rabbits underwent three weeks of tachypacing to induce cardiac myopathy (TICM). In vivo telemetry demonstrated steepening of the QT/RR slope in LQT1 with TICM (LQT1-TICM; pre: 0.26±0.04, post: 0.52±0.01, P<0.05). In vivo electrophysiology showed that LQT1-TICM had higher incidence of VF than LMC-TICM (6 of 11 vs. 3 of 11, respectively). Optical mapping revealed larger APD dispersion (16±4 vs. 38±6 ms, p<0.05) and steep APD restitution in LQT1-TICM compared to LQT1-sham (0.53±0.12 vs. 1.17±0.13, p<0.05). LQT1-TICM developed spatially discordant alternans (DA), which caused conduction block and higher-frequency VF (15±1 Hz in LQT1-TICM vs. 13±1 Hz in LMC-TICM, p<0.05). Ca2+ DA was highly dynamic and preceded voltage DA in LQT1-TICM. Ryanodine abolished DA in 5 out of 8 LQT1-TICM rabbits, demonstrating the importance of Ca2+ in complex DA formation. Computer simulations suggested that HF remodeling caused Ca2+-driven alternans, which was further potentiated in LQT1-TICM due to the lack of IKs. CONCLUSIONS Compared with LMC-TICM, LQT1-TICM rabbits exhibit steepened APD restitution and complex DA modulated by Ca2+. Our results strongly support the contention that the downregulation of IKs in HF increases Ca2+ dependent alternans and thereby the risk of VF.
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Affiliation(s)
- Emily Lau
- Cardiovascular Research Center, Division of Cardiology, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, Rhode Island, United States of America
| | - Konstantinos Kossidas
- Cardiovascular Research Center, Division of Cardiology, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, Rhode Island, United States of America
| | - Tae Yun Kim
- Cardiovascular Research Center, Division of Cardiology, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, Rhode Island, United States of America
| | - Yukiko Kunitomo
- Cardiovascular Research Center, Division of Cardiology, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, Rhode Island, United States of America
| | - Ohad Ziv
- Cardiovascular Research Center, Division of Cardiology, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, Rhode Island, United States of America
| | - Song Zhen
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Chantel Taylor
- Cardiovascular Research Center, Division of Cardiology, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, Rhode Island, United States of America
| | - Lorraine Schofield
- Cardiovascular Research Center, Division of Cardiology, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, Rhode Island, United States of America
| | - Joe Yammine
- Cardiovascular Research Center, Division of Cardiology, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, Rhode Island, United States of America
| | - Gongxin Liu
- Cardiovascular Research Center, Division of Cardiology, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, Rhode Island, United States of America
| | - Xuwen Peng
- Department of Comparative Medicine, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, United States of America
| | - Zhilin Qu
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Gideon Koren
- Cardiovascular Research Center, Division of Cardiology, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, Rhode Island, United States of America
| | - Bum-Rak Choi
- Cardiovascular Research Center, Division of Cardiology, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, Rhode Island, United States of America
- * E-mail:
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44
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Edwards JN, Blatter LA. Cardiac alternans and intracellular calcium cycling. Clin Exp Pharmacol Physiol 2015; 41:524-32. [PMID: 25040398 DOI: 10.1111/1440-1681.12231] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Revised: 03/12/2014] [Accepted: 03/17/2014] [Indexed: 12/20/2022]
Abstract
Cardiac alternans refers to a condition in which there is a periodic beat-to-beat oscillation in electrical activity and the strength of cardiac muscle contraction at a constant heart rate. Clinically, cardiac alternans occurs in settings that are typical for cardiac arrhythmias and has been causally linked to these conditions. At the cellular level, alternans is defined as beat-to-beat alternations in contraction amplitude (mechanical alternans), action potential duration (APD; electrical or APD alternans) and Ca(2+) transient amplitude (Ca(2+) alternans). The cause of alternans is multifactorial; however, alternans always originate from disturbances of the bidirectional coupling between membrane voltage (Vm ) and intracellular calcium ([Ca(2+) ]i ). Bidirectional coupling refers to the fact that, in cardiac cells, Vm depolarization and the generation of action potentials cause the elevation of [Ca(2+) ]i that is required for contraction (a process referred to as excitation-contraction coupling); conversely, changes of [Ca(2+) ]i control Vm because important membrane currents are Ca(2+) dependent. Evidence is mounting that alternans is ultimately caused by disturbances of cellular Ca(2+) signalling. Herein we review how two key factors of cardiac cellular Ca(2+) cycling, namely the release of Ca(2+) from internal stores and the capability of clearing the cytosol from Ca(2+) after each beat, determine the conditions under which alternans occurs. The contributions from key Ca(2+) -handling proteins (i.e. surface membrane channels, ion pumps and transporters and internal Ca(2+) release channels) are discussed.
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Affiliation(s)
- Joshua N Edwards
- Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, IL, USA
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45
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Hammer KP, Ljubojevic S, Ripplinger CM, Pieske BM, Bers DM. Cardiac myocyte alternans in intact heart: Influence of cell-cell coupling and β-adrenergic stimulation. J Mol Cell Cardiol 2015; 84:1-9. [PMID: 25828762 DOI: 10.1016/j.yjmcc.2015.03.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/17/2015] [Accepted: 03/12/2015] [Indexed: 11/25/2022]
Abstract
BACKGROUND Cardiac alternans are proarrhythmic and mechanistically link cardiac mechanical dysfunction and sudden cardiac death. Beat-to-beat alternans occur when beats with large Ca(2+) transients and long action potential duration (APD) alternate with the converse. APD alternans are typically driven by Ca(2+) alternans and sarcoplasmic reticulum (SR) Ca(2+) release alternans. But the effect of intercellular communication via gap junctions (GJ) on alternans in the intact heart remains unknown. OBJECTIVE We assessed the effects of cell-to-cell coupling on local alternans in intact Langendorff-perfused mouse hearts, measuring single myocyte [Ca(2+)] alternans synchronization among neighboring cells, and effects of β-adrenergic receptor (β-AR) activation and reduced GJ coupling. METHODS AND RESULTS Mouse hearts (C57BL/6) were retrogradely perfused and loaded with Fluo8-AM to record cardiac myocyte [Ca(2+)] in situ with confocal microscopy. Single cell resolution allowed analysis of alternans within the intact organ during alternans induction. Carbenoxolone (25 μM), a GJ inhibitor, significantly increased the occurrence and amplitude of alternans in single cells within the intact heart. Alternans were concordant between neighboring cells throughout the field of view, except transiently during onset. β-AR stimulation only reduced Ca(2+) alternans in tissue that had reduced GJ coupling, matching effects seen in isolated myocytes. CONCLUSIONS Ca(2+) alternans among neighboring myocytes is predominantly concordant, likely because of electrical coupling between cells. Consistent with this, partial GJ uncoupling increased propensity and amplitude of Ca(2+) alternans, and made them more sensitive to reversal by β-AR activation, as in isolated myocytes. Electrical coupling between myocytes may thus limit the alternans initiation, but also allow alternans to be more stable once established.
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Affiliation(s)
- Karin P Hammer
- Department of Pharmacology, University of California, Davis, GBSF, Davis, CA 95616-8636, USA.
| | - Senka Ljubojevic
- Department of Cardiology, Medical University of Graz, Auenbruggerplatz 15, 8010 Graz, Austria.
| | - Crystal M Ripplinger
- Department of Pharmacology, University of California, Davis, GBSF, Davis, CA 95616-8636, USA.
| | - Burkert M Pieske
- Department of Cardiology, Medical University of Graz, Auenbruggerplatz 15, 8010 Graz, Austria; Department of Cardiology, Charité - Medical University Berlin, Augustenburgerplatz 1, 13353 Berlin, Germany.
| | - Donald M Bers
- Department of Pharmacology, University of California, Davis, GBSF, Davis, CA 95616-8636, USA.
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46
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Alvarez-Lacalle E, Echebarria B, Spalding J, Shiferaw Y. Calcium alternans is due to an order-disorder phase transition in cardiac cells. PHYSICAL REVIEW LETTERS 2015; 114:108101. [PMID: 25815968 DOI: 10.1103/physrevlett.114.108101] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Indexed: 05/23/2023]
Abstract
Electromechanical alternans is a beat-to-beat alternation in the strength of contraction of a cardiac cell, which can be caused by an instability of calcium cycling. Using a distributed model of subcellular calcium we show that alternans occurs via an order-disorder phase transition which exhibits critical slowing down and a diverging correlation length. We apply finite size scaling along with a mapping to a stochastic coupled map model, to show that this transition in two dimensions is characterized by critical exponents consistent with the Ising universality class. These findings highlight the important role of cooperativity in biological cells, and suggest novel approaches to investigate the onset of the alternans instability in the heart.
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Affiliation(s)
- Enrique Alvarez-Lacalle
- Departament de Física Aplicada, Universitat Politècnica de Catalunya·BarcelonaTech, 08028 Barcelona, Spain
| | - Blas Echebarria
- Departament de Física Aplicada, Universitat Politècnica de Catalunya·BarcelonaTech, 08028 Barcelona, Spain
| | - Jon Spalding
- Department of Physics and Astronomy, California State University, Northridge, California 91330, USA
| | - Yohannes Shiferaw
- Department of Physics and Astronomy, California State University, Northridge, California 91330, USA
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47
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Perspective: a dynamics-based classification of ventricular arrhythmias. J Mol Cell Cardiol 2015; 82:136-52. [PMID: 25769672 DOI: 10.1016/j.yjmcc.2015.02.017] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Revised: 02/05/2015] [Accepted: 02/20/2015] [Indexed: 02/04/2023]
Abstract
Despite key advances in the clinical management of life-threatening ventricular arrhythmias, culminating with the development of implantable cardioverter-defibrillators and catheter ablation techniques, pharmacologic/biologic therapeutics have lagged behind. The fundamental issue is that biological targets are molecular factors. Diseases, however, represent emergent properties at the scale of the organism that result from dynamic interactions between multiple constantly changing molecular factors. For a pharmacologic/biologic therapy to be effective, it must target the dynamic processes that underlie the disease. Here we propose a classification of ventricular arrhythmias that is based on our current understanding of the dynamics occurring at the subcellular, cellular, tissue and organism scales, which cause arrhythmias by simultaneously generating arrhythmia triggers and exacerbating tissue vulnerability. The goal is to create a framework that systematically links these key dynamic factors together with fixed factors (structural and electrophysiological heterogeneity) synergistically promoting electrical dispersion and increased arrhythmia risk to molecular factors that can serve as biological targets. We classify ventricular arrhythmias into three primary dynamic categories related generally to unstable Ca cycling, reduced repolarization, and excess repolarization, respectively. The clinical syndromes, arrhythmia mechanisms, dynamic factors and what is known about their molecular counterparts are discussed. Based on this framework, we propose a computational-experimental strategy for exploring the links between molecular factors, fixed factors and dynamic factors that underlie life-threatening ventricular arrhythmias. The ultimate objective is to facilitate drug development by creating an in silico platform to evaluate and predict comprehensively how molecular interventions affect not only a single targeted arrhythmia, but all primary arrhythmia dynamics categories as well as normal cardiac excitation-contraction coupling.
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48
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Watanabe T, Kashimura T, Obata H, Minamino T. Cibenzoline Abolished Pulsus Alternans in a HOCM Patient. Intern Med 2015; 54:2273. [PMID: 26328660 DOI: 10.2169/internalmedicine.54.4500] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Affiliation(s)
- Tohru Watanabe
- Department of Cardiovascular Biology and Medicine, Niigata University Graduate School of Medical and Dental Sciences, Japan
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49
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Abstract
RATIONALE Alternans is a risk factor for cardiac arrhythmia, including atrial fibrillation. At the cellular level alternans manifests as beat-to-beat alternations in contraction, action potential duration (APD), and magnitude of the Ca(2+) transient (CaT). Electromechanical and CaT alternans are highly correlated, however, it has remained controversial whether the primary cause of alternans is a disturbance of cellular Ca(2+) signaling or electrical membrane properties. OBJECTIVE To determine whether a primary failure of intracellular Ca(2+) regulation or disturbances in membrane potential and AP regulation are responsible for the occurrence of alternans in atrial myocytes. METHODS AND RESULTS Pacing-induced APD and CaT alternans were studied in single rabbit atrial and ventricular myocytes using combined [Ca(2+)]i and electrophysiological measurements. In current-clamp experiments, APD and CaT alternans strongly correlated in time and magnitude. CaT alternans was observed without alternation in L-type Ca(2+) current, however, elimination of intracellular Ca(2+) release abolished APD alternans, indicating that [Ca(2+)]i dynamics have a profound effect on the occurrence of CaT alternans. Trains of 2 distinctive voltage commands in form of APs recorded during large and small alternans CaTs were applied to voltage-clamped cells. CaT alternans was observed with and without alternation in the voltage command shape. During alternans AP-clamp large CaTs coincided with both long and short AP waveforms, indicating that CaT alternans develop irrespective of AP dynamics. CONCLUSIONS The primary mechanism underlying alternans in atrial cells, similarly to ventricular cells, resides in a disturbance of Ca(2+) signaling, whereas APD alternans are a secondary consequence, mediated by Ca(2+)-dependent AP modulation.
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Affiliation(s)
- Giedrius Kanaporis
- From the Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, IL
| | - Lothar A Blatter
- From the Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, IL.
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50
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Nivala M, Song Z, Weiss JN, Qu Z. T-tubule disruption promotes calcium alternans in failing ventricular myocytes: mechanistic insights from computational modeling. J Mol Cell Cardiol 2014; 79:32-41. [PMID: 25450613 DOI: 10.1016/j.yjmcc.2014.10.018] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Revised: 10/25/2014] [Accepted: 10/28/2014] [Indexed: 10/24/2022]
Abstract
In heart failure (HF), T-tubule (TT) disruption contributes to dyssynchronous calcium (Ca) release and impaired contraction, but its role in arrhythmogenesis remains unclear. In this study, we investigate the effects of TT disruption and other HF remodeling factors on Ca alternans in ventricular myocytes using computer modeling. A ventricular myocyte model with detailed spatiotemporal Ca cycling modeled by a coupled Ca release unit (CRU) network was used, in which the L-type Ca channels and the ryanodine receptor (RyR) channels were simulated by random Markov transitions. TT disruption, which removes the L-type Ca channels from the associated CRUs, results in "orphaned" RyR clusters and thus provides increased opportunity for spark-induced Ca sparks to occur. This effect combined with other HF remodeling factors promoted alternans by two distinct mechanisms: 1) for normal sarco-endoplasmic reticulum Ca ATPase (SERCA) activity, alternans was caused by both CRU refractoriness and coupling. The increased opportunity for spark-induced sparks by TT disruption combined with the enhanced CRU coupling by Ca elevation in the presence or absence of increased RyR leakiness facilitated spark synchronization on alternate beats to promote Ca alternans; 2) for down-regulated SERCA, alternans was caused by the sarcoplasmic reticulum (SR) Ca load-dependent mechanism, independent of CRU refractoriness. TT disruption and increased RyR leakiness shifted and steepened the SR Ca release-load relationship, which combines with down-regulated SERCA to promote Ca alternans. In conclusion, the mechanisms of Ca alternans for normal and down-regulated SERCA are different, and TT disruption promotes Ca alternans by both mechanisms, which may contribute to alternans at different stages of HF.
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Affiliation(s)
- Michael Nivala
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA
| | - Zhen Song
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA
| | - James N Weiss
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA; Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA
| | - Zhilin Qu
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA.
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