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Wang XC, Zhou Y, Chen HX, Hou HT, He GW, Yang Q. ER stress modulates Kv1.5 channels via PERK branch in HL-1 atrial myocytes: Relevance to atrial arrhythmogenesis and the effect of tetramethylpyrazine. Heliyon 2024; 10:e37767. [PMID: 39318794 PMCID: PMC11420496 DOI: 10.1016/j.heliyon.2024.e37767] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2024] [Revised: 09/05/2024] [Accepted: 09/09/2024] [Indexed: 09/26/2024] Open
Abstract
Endoplasmic reticulum (ER) stress is implicated in cardiac arrhythmia whereas the associated mechanisms remain inadequately understood. Kv1.5 channels are essential for atrial repolarization. Whether ER stress affects Kv1.5 channels is unknown. This study aimed to elucidate the response of Kv1.5 channels to ER stress by clarifying the unfolded protein response (UPR) branch responsible for the channel modulation. In addition, the effect of tetramethylpyrazine (TMP) on Kv1.5 channels was studied. Patch clamp and western-blot results revealed that exposure of HL-1 atrial myocytes to ER stress inducer tunicamycin upregulates Kv1.5 expression, increases Kv1.5 channel current (I Kur ) (14.91 ± 1.11 vs. 6.11 ± 1.31 pA/pF, P < 0.001), and shortened action potential duration (APD) (APD90: 82.79 ± 5.25 vs.121.11 ± 6.72 ms, P < 0.01), which could be reverted by ER stress inhibitors. Blockade of the PERK branch while not IRE1 and ATF6 branches of UPR downregulated Kv1.5 expression, accompanied by a decreased I Kur (9.03 ± 0.99 pA/pF) and a prolonged APD90 (113.69 ± 4.41 ms) (P < 0.01). PERK-mediated increases of Kv1.5 expression and I Kur were also observed in HL-1 cells incubated with thapsigargin. TMP suppressed the enhancement of I Kur (10.52 ± 0.97 vs. 17.52 ± 2.25 pA/pF, P < 0.05), prevented the shortening of APD (APD90: 110.16 ± 5.36 vs. 84.84 ± 4.58 ms, P < 0.05), and inhibited the upregulation of Kv1.5 triggered by ER stress. Our study suggests that ER stress induces upregulation and activation of Kv1.5 channels in atrial myocytes through the PERK branch of UPR. TMP prevents Kv1.5 upregulation/activation and the resultant APD shortening by inhibiting ER stress. These results may shed light on the mechanisms of atrial arrhythmogenesis and the antiarrhythmic effect of the traditional Chinese herb TMP.
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Affiliation(s)
- Xiang-Chong Wang
- Institute of Cardiovascular Diseases & Department of Cardiac Surgery, TEDA International Cardiovascular Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College & Tianjin University, Tianjin, 300457, China
- Tianjin Key Laboratory of Molecular Regulation of Cardiovascular Diseases and Translational Medicine, Tianjin, China
- Department of Pharmacology, Hebei Higher Education Institute Applied Technology Research Center on TCM Formula Preparation, Hebei International Cooperation Center for Ion channel Function and Innovative Traditional Chinese Medicine, Hebei University of Chinese Medicine, Shijiazhuang, 050091, China
- School of Medicine, Nankai University, Tianjin, 300457, China
| | - Yang Zhou
- Institute of Cardiovascular Diseases & Department of Cardiac Surgery, TEDA International Cardiovascular Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College & Tianjin University, Tianjin, 300457, China
- Tianjin Key Laboratory of Molecular Regulation of Cardiovascular Diseases and Translational Medicine, Tianjin, China
| | - Huan-Xin Chen
- Institute of Cardiovascular Diseases & Department of Cardiac Surgery, TEDA International Cardiovascular Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College & Tianjin University, Tianjin, 300457, China
- Tianjin Key Laboratory of Molecular Regulation of Cardiovascular Diseases and Translational Medicine, Tianjin, China
| | - Hai-Tao Hou
- Institute of Cardiovascular Diseases & Department of Cardiac Surgery, TEDA International Cardiovascular Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College & Tianjin University, Tianjin, 300457, China
- Tianjin Key Laboratory of Molecular Regulation of Cardiovascular Diseases and Translational Medicine, Tianjin, China
| | - Guo-Wei He
- Institute of Cardiovascular Diseases & Department of Cardiac Surgery, TEDA International Cardiovascular Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College & Tianjin University, Tianjin, 300457, China
- Tianjin Key Laboratory of Molecular Regulation of Cardiovascular Diseases and Translational Medicine, Tianjin, China
| | - Qin Yang
- Institute of Cardiovascular Diseases & Department of Cardiac Surgery, TEDA International Cardiovascular Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College & Tianjin University, Tianjin, 300457, China
- Tianjin Key Laboratory of Molecular Regulation of Cardiovascular Diseases and Translational Medicine, Tianjin, China
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Iqbal M, Kamarullah W, Achmad C, Karwiky G, Akbar MR. The pivotal role of compelling high-risk electrocardiographic markers in prediction of ventricular arrhythmic risk in arrhythmogenic right ventricular cardiomyopathy: A systematic review and meta-analysis. Curr Probl Cardiol 2024; 49:102241. [PMID: 38040211 DOI: 10.1016/j.cpcardiol.2023.102241] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2023] [Accepted: 11/28/2023] [Indexed: 12/03/2023]
Abstract
INTRODUCTION Several investigations have shown that existing risk stratification processes remain insufficient for stratifying sudden cardiac death risk in arrhythmogenic right ventricular cardiomyopathy (ARVC). Multiple auxiliary parameters are investigated to offer a more precise prognostic model. Our aim was to assess the association between several ECG markers (epsilon waves, prolonged terminal activation duration (TAD) of QRS, fragmented QRS (fQRS), late potentials on signal-averaged electrocardiogram (SA-ECG), T-wave inversion (TWI) in right precordial leads, and extension of TWI in inferior leads) with the risk of developing poor outcomes in ARVC. METHODS A systematic literature search from several databases was conducted until September 9th, 2023. Studies were eligible if it investigated the relationship between the ECG markers with the risk of developing ventricular arrhythmic events. RESULTS This meta-analysis encompassed 25 studies with a total of 3767 participants. Our study disclosed that epsilon waves, prolonged TAD of QRS, fQRS, late potentials on SA-ECG, TWI in right precordial leads, and extension of TWI in inferior leads were associated with the incremental risk of ventricular arrhythmias, implantable cardioverter-defibrillator shock, and sudden cardiac death, with the risk ratios ranging from 1.46 to 2.11. In addition, diagnostic test accuracy meta-analysis stipulated that the extension of TWI in inferior leads had the uppermost overall area under curve (AUC) value amidst other ECG markers apropos of our outcomes of interest. CONCLUSION A multivariable risk assessment strategy based on the previously stated ECG markers potentially enhances the current risk stratification models in ARVC patients, especially extension of TWI in inferior leads.
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Affiliation(s)
- Mohammad Iqbal
- Department of Cardiology and Vascular Medicine, Faculty of Medicine, Padjadjaran University, Jl. Pasteur No.38, Pasteur, Kec. Sukajadi, Bandung, Jawa Barat, Indonesia.
| | - William Kamarullah
- Department of Cardiology and Vascular Medicine, Faculty of Medicine, Padjadjaran University, Jl. Pasteur No.38, Pasteur, Kec. Sukajadi, Bandung, Jawa Barat, Indonesia
| | - Chaerul Achmad
- Department of Cardiology and Vascular Medicine, Faculty of Medicine, Padjadjaran University, Jl. Pasteur No.38, Pasteur, Kec. Sukajadi, Bandung, Jawa Barat, Indonesia
| | - Giky Karwiky
- Department of Cardiology and Vascular Medicine, Faculty of Medicine, Padjadjaran University, Jl. Pasteur No.38, Pasteur, Kec. Sukajadi, Bandung, Jawa Barat, Indonesia
| | - Mohammad Rizki Akbar
- Department of Cardiology and Vascular Medicine, Faculty of Medicine, Padjadjaran University, Jl. Pasteur No.38, Pasteur, Kec. Sukajadi, Bandung, Jawa Barat, Indonesia
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Needs D, Wu T, Nguyen HX, Henriquez CS, Bursac N. Prokaryotic voltage-gated sodium channels are more effective than endogenous Na v1.5 channels in rescuing cardiac action potential conduction: an in silico study. Am J Physiol Heart Circ Physiol 2023; 325:H1178-H1192. [PMID: 37737736 PMCID: PMC10908372 DOI: 10.1152/ajpheart.00287.2023] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Revised: 09/14/2023] [Accepted: 09/18/2023] [Indexed: 09/23/2023]
Abstract
Methods to augment Na+ current in cardiomyocytes hold potential for the treatment of various cardiac arrhythmias involving conduction slowing. Because the gene coding cardiac Na+ channel (Nav1.5) is too large to fit in a single adeno-associated virus (AAV) vector, new gene therapies are being developed to enhance endogenous Nav1.5 current (by overexpression of chaperon molecules or use of multiple AAV vectors) or to exogenously introduce prokaryotic voltage-gated Na+ channels (BacNav) whose gene size is significantly smaller than that of the Nav1.5. In this study, based on experimental measurements in heterologous expression systems, we developed an improved computational model of the BacNav channel, NavSheP D60A. We then compared in silico how NavSheP D60A expression vs. Nav1.5 augmentation affects the electrophysiology of cardiac tissue. We found that the incorporation of BacNav channels in both adult guinea pig and human cardiomyocyte models increased their excitability and reduced action potential duration. When compared with equivalent augmentation of Nav1.5 current in simulated settings of reduced tissue excitability, the addition of the BacNav current was superior in improving the safety of conduction under conditions of current source-load mismatch, reducing the vulnerability to unidirectional conduction block during premature pacing, preventing the instability and breakup of spiral waves, and normalizing the conduction and ECG in Brugada syndrome tissues with mutated Nav1.5. Overall, our studies show that compared with a potential enhancement of the endogenous Nav1.5 current, expression of the BacNav channels with their slower inactivation kinetics can provide greater anti-arrhythmic benefits in hearts with compromised action potential conduction.NEW & NOTEWORTHY Slow action potential conduction is a common cause of various cardiac arrhythmias; yet, current pharmacotherapies cannot augment cardiac conduction. This in silico study compared the efficacy of recently proposed antiarrhythmic gene therapy approaches that increase peak sodium current in cardiomyocytes. When compared with the augmentation of endogenous sodium current, expression of slower-inactivating bacterial sodium channels was superior in preventing conduction block and arrhythmia induction. These results further the promise of antiarrhythmic gene therapies targeting sodium channels.
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Affiliation(s)
- Daniel Needs
- Department of Biomedical Engineering, Duke University, Durham, North Carolina, United States
| | - Tianyu Wu
- Department of Biomedical Engineering, Duke University, Durham, North Carolina, United States
| | - Hung X Nguyen
- Department of Biomedical Engineering, Duke University, Durham, North Carolina, United States
| | - Craig S Henriquez
- Department of Biomedical Engineering, Duke University, Durham, North Carolina, United States
| | - Nenad Bursac
- Department of Biomedical Engineering, Duke University, Durham, North Carolina, United States
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4
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Maciunas K, Snipas M, Kraujalis T, Kraujalienė L, Panfilov AV. The role of the Cx43/Cx45 gap junction voltage gating on wave propagation and arrhythmogenic activity in cardiac tissue. Sci Rep 2023; 13:14863. [PMID: 37684404 PMCID: PMC10491658 DOI: 10.1038/s41598-023-41796-w] [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: 03/25/2023] [Accepted: 08/31/2023] [Indexed: 09/10/2023] Open
Abstract
Gap junctions (GJs) formed of connexin (Cx) protein are the main conduits of electrical signals in the heart. Studies indicate that the transitional zone of the atrioventricular (AV) node contains heterotypic Cx43/Cx45 GJ channels which are highly sensitive to transjunctional voltage (Vj). To investigate the putative role of Vj gating of Cx43/Cx45 channels, we performed electrophysiological recordings in cell cultures and developed a novel mathematical/computational model which, for the first time, combines GJ channel Vj gating with a model of membrane excitability to simulate a spread of electrical pulses in 2D. Our simulation and electrophysiological data show that Vj transients during the spread of cardiac excitation can significantly affect the junctional conductance (gj) of Cx43/Cx45 GJs in a direction- and frequency-dependent manner. Subsequent simulation data indicate that such pulse-rate-dependent regulation of gj may have a physiological role in delaying impulse propagation through the AV node. We have also considered the putative role of the Cx43/Cx45 channel gating during pathological impulse propagation. Our simulation data show that Vj gating-induced changes in gj can cause the drift and subsequent termination of spiral waves of excitation. As a result, the development of fibrillation-like processes was significantly reduced in 2D clusters, which contained Vj-sensitive Cx43/Cx45 channels.
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Affiliation(s)
- Kestutis Maciunas
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Mindaugas Snipas
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas, Lithuania.
- Department of Mathematical Modelling, Kaunas University of Technology, Kaunas, Lithuania.
| | - Tadas Kraujalis
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas, Lithuania
- Department of Applied Informatics, Kaunas University of Technology, Kaunas, Lithuania
| | - Lina Kraujalienė
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Alexander V Panfilov
- Department of Physics and Astronomy, Ghent University, Ghent, Belgium
- Department of Cardiology, Leiden University Medical Center, Leiden, The Netherlands
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5
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Zhou Y, Suo W, Zhang X, Lv J, Liu Z, Liu R. Roles and mechanisms of quercetin on cardiac arrhythmia: A review. Biomed Pharmacother 2022; 153:113447. [DOI: 10.1016/j.biopha.2022.113447] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2022] [Revised: 07/14/2022] [Accepted: 07/18/2022] [Indexed: 11/02/2022] Open
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6
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Nguyen HX, Wu T, Needs D, Zhang H, Perelli RM, DeLuca S, Yang R, Pan M, Landstrom AP, Henriquez C, Bursac N. Engineered bacterial voltage-gated sodium channel platform for cardiac gene therapy. Nat Commun 2022; 13:620. [PMID: 35110560 PMCID: PMC8810800 DOI: 10.1038/s41467-022-28251-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Accepted: 01/11/2022] [Indexed: 12/19/2022] Open
Abstract
Therapies for cardiac arrhythmias could greatly benefit from approaches to enhance electrical excitability and action potential conduction in the heart by stably overexpressing mammalian voltage-gated sodium channels. However, the large size of these channels precludes their incorporation into therapeutic viral vectors. Here, we report a platform utilizing small-size, codon-optimized engineered prokaryotic sodium channels (BacNav) driven by muscle-specific promoters that significantly enhance excitability and conduction in rat and human cardiomyocytes in vitro and adult cardiac tissues from multiple species in silico. We also show that the expression of BacNav significantly reduces occurrence of conduction block and reentrant arrhythmias in fibrotic cardiac cultures. Moreover, functional BacNav channels are stably expressed in healthy mouse hearts six weeks following intravenous injection of self-complementary adeno-associated virus (scAAV) without causing any adverse effects on cardiac electrophysiology. The large diversity of prokaryotic sodium channels and experimental-computational platform reported in this study should facilitate the development and evaluation of BacNav-based gene therapies for cardiac conduction disorders.
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Affiliation(s)
- Hung X Nguyen
- Department of Biomedical Engineering, Duke University, Durham, NC, USA
| | - Tianyu Wu
- Department of Biomedical Engineering, Duke University, Durham, NC, USA
| | - Daniel Needs
- Department of Biomedical Engineering, Duke University, Durham, NC, USA
| | - Hengtao Zhang
- Department of Biomedical Engineering, Duke University, Durham, NC, USA
| | - Robin M Perelli
- Department of Pediatrics, Division of Cardiology, Duke University School of Medicine, Durham, NC, USA
- Department of Cell Biology, Duke University School of Medicine, Durham, NC, USA
| | - Sophia DeLuca
- Department of Cell Biology, Duke University School of Medicine, Durham, NC, USA
| | - Rachel Yang
- Department of Biomedical Engineering, Duke University, Durham, NC, USA
| | - Michael Pan
- Department of Biomedical Engineering, Duke University, Durham, NC, USA
| | - Andrew P Landstrom
- Department of Pediatrics, Division of Cardiology, Duke University School of Medicine, Durham, NC, USA
- Department of Cell Biology, Duke University School of Medicine, Durham, NC, USA
| | - Craig Henriquez
- Department of Biomedical Engineering, Duke University, Durham, NC, USA
| | - Nenad Bursac
- Department of Biomedical Engineering, Duke University, Durham, NC, USA.
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7
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Wu T, Nguyen HX, Bursac N. In vitro discovery of novel prokaryotic ion channel candidates for antiarrhythmic gene therapy. Methods Enzymol 2021; 654:407-434. [PMID: 34120724 DOI: 10.1016/bs.mie.2021.03.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Sudden cardiac death continues to have a devastating impact on public health prompting the continued efforts to develop more effective therapies for cardiac arrhythmias. Among different approaches to normalize function of ion channels and prevent arrhythmogenic remodeling of tissue substrate, cardiac cell and gene therapies are emerging as promising strategies to restore and maintain normal heart rhythm. Specifically, the ability to genetically enhance electrical excitability of diseased hearts through voltage-gated sodium channel (VGSC) gene transfer could improve velocity of action potential conduction and act to stop reentrant circuits underlying sustained arrhythmias. For this purpose, prokaryotic VGSC genes are promising therapeutic candidates due to their small size (<1kb) and potential to be effectively packaged in adeno-associated viral (AAV) vectors and delivered to cardiomyocytes for stable, long-term expression. This article describes a versatile method to discover and characterize novel prokaryotic ion channels for use in gene and cell therapies for heart disease including cardiac arrhythmias. Detailed protocols are provided for: (1) identification of potential ion channel candidates from large genomic databases, (2) candidate screening and characterization using site-directed mutagenesis and engineered human excitable cell system and, (3) candidate validation using electrophysiological techniques and an in vitro model of impaired cardiac impulse conduction.
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Affiliation(s)
- Tianyu Wu
- Department of Biomedical Engineering, Duke University, Durham, NC, United States
| | - Hung X Nguyen
- Department of Biomedical Engineering, Duke University, Durham, NC, United States
| | - Nenad Bursac
- Department of Biomedical Engineering, Duke University, Durham, NC, United States.
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8
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Arrhythmia Mechanisms in Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes. J Cardiovasc Pharmacol 2020; 77:300-316. [PMID: 33323698 DOI: 10.1097/fjc.0000000000000972] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Accepted: 12/08/2020] [Indexed: 12/30/2022]
Abstract
ABSTRACT Despite major efforts by clinicians and researchers, cardiac arrhythmia remains a leading cause of morbidity and mortality in the world. Experimental work has relied on combining high-throughput strategies with standard molecular and electrophysiological studies, which are, to a great extent, based on the use of animal models. Because this poses major challenges for translation, the progress in the development of novel antiarrhythmic agents and clinical care has been mostly disappointing. Recently, the advent of human induced pluripotent stem cell-derived cardiomyocytes has opened new avenues for both basic cardiac research and drug discovery; now, there is an unlimited source of cardiomyocytes of human origin, both from healthy individuals and patients with cardiac diseases. Understanding arrhythmic mechanisms is one of the main use cases of human induced pluripotent stem cell-derived cardiomyocytes, in addition to pharmacological cardiotoxicity and efficacy testing, in vitro disease modeling, developing patient-specific models and personalized drugs, and regenerative medicine. Here, we review the advances that the human induced pluripotent stem cell-derived-based modeling systems have brought so far regarding the understanding of both arrhythmogenic triggers and substrates, while also briefly speculating about the possibilities in the future.
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9
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Nguyen TD, Kadri OE, Voronov RS. An Introductory Overview of Image-Based Computational Modeling in Personalized Cardiovascular Medicine. Front Bioeng Biotechnol 2020; 8:529365. [PMID: 33102452 PMCID: PMC7546862 DOI: 10.3389/fbioe.2020.529365] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Accepted: 08/31/2020] [Indexed: 02/05/2023] Open
Abstract
Cardiovascular diseases account for the number one cause of deaths in the world. Part of the reason for such grim statistics is our limited understanding of the underlying mechanisms causing these devastating pathologies, which is made difficult by the invasiveness of the procedures associated with their diagnosis (e.g., inserting catheters into the coronal artery to measure blood flow to the heart). Likewise, it is also difficult to design and test assistive devices without implanting them in vivo. However, with the recent advancements made in biomedical scanning technologies and computer simulations, image-based modeling (IBM) has arisen as the next logical step in the evolution of non-invasive patient-specific cardiovascular medicine. Yet, due to its novelty, it is still relatively unknown outside of the niche field. Therefore, the goal of this manuscript is to review the current state-of-the-art and the limitations of the methods used in this area of research, as well as their applications to personalized cardiovascular investigations and treatments. Specifically, the modeling of three different physics – electrophysiology, biomechanics and hemodynamics – used in the cardiovascular IBM is discussed in the context of the physiology that each one of them describes and the mechanisms of the underlying cardiac diseases that they can provide insight into. Only the “bare-bones” of the modeling approaches are discussed in order to make this introductory material more accessible to an outside observer. Additionally, the imaging methods, the aspects of the unique cardiac anatomy derived from them, and their relation to the modeling algorithms are reviewed. Finally, conclusions are drawn about the future evolution of these methods and their potential toward revolutionizing the non-invasive diagnosis, virtual design of treatments/assistive devices, and increasing our understanding of these lethal cardiovascular diseases.
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Affiliation(s)
- Thanh Danh Nguyen
- Otto H. York Department of Chemical and Materials Engineering, Newark College of Engineering, New Jersey Institute of Technology, Newark, NJ, United States
| | - Olufemi E Kadri
- Otto H. York Department of Chemical and Materials Engineering, Newark College of Engineering, New Jersey Institute of Technology, Newark, NJ, United States.,UC-P&G Simulation Center, University of Cincinnati, Cincinnati, OH, United States
| | - Roman S Voronov
- Otto H. York Department of Chemical and Materials Engineering, Newark College of Engineering, New Jersey Institute of Technology, Newark, NJ, United States.,Department of Biomedical Engineering, Newark College of Engineering, New Jersey Institute of Technology, Newark, NJ, United States
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10
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Chadda KR, Fazmin IT, Ahmad S, Valli H, Edling CE, Huang CLH, Jeevaratnam K. Arrhythmogenic mechanisms of obstructive sleep apnea in heart failure patients. Sleep 2019; 41:5054592. [PMID: 30016501 DOI: 10.1093/sleep/zsy136] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2017] [Accepted: 07/13/2018] [Indexed: 01/01/2023] Open
Abstract
Heart failure (HF) affects 23 million people worldwide and results in 300000 annual deaths. It is associated with many comorbidities, such as obstructive sleep apnea (OSA), and risk factors for both conditions overlap. Eleven percent of HF patients have OSA and 7.7% of OSA patients have left ventricular ejection fraction <50% with arrhythmias being a significant comorbidity in HF and OSA patients. Forty percent of HF patients develop atrial fibrillation (AF) and 30%-50% of deaths from cardiac causes in HF patients are from sudden cardiac death. OSA is prevalent in 32%-49% of patients with AF and there is a dose-dependent relationship between OSA severity and resistance to anti-arrhythmic therapies. HF and OSA lead to various downstream arrhythmogenic mechanisms, including metabolic derangement, remodeling, inflammation, and autonomic imbalance. (1) Metabolic derangement and production of reactive oxidative species increase late Na+ currents, decrease outward K+ currents and downregulate connexin-43 and cell-cell coupling. (2) remodeling also features downregulated K+ currents in addition to decreased Na+/K+ ATPase currents, altered Ca2+ homeostasis, and increased density of If current. (3) Chronic inflammation leads to downregulation of both Nav1.5 channels and K+ channels, altered Ca2+ homeostasis and reduced cellular coupling from alterations of connexin expression. (4) Autonomic imbalance causes arrhythmias by evoking triggered activity through increased Ca2+ transients and reduction of excitation wavefront wavelength. Thus, consideration of these multiple pathophysiological pathways (1-4) will enable the development of novel therapeutic strategies that can be targeted against arrhythmias in the context of complex disease, such as the comorbidities of HF and OSA.
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Affiliation(s)
- Karan R Chadda
- Faculty of Health and Medical Science, University of Surrey, Guildford, United Kingdom.,Physiological Laboratory, University of Cambridge, Downing Street, Cambridge, United Kingdom
| | - Ibrahim T Fazmin
- Faculty of Health and Medical Science, University of Surrey, Guildford, United Kingdom.,Physiological Laboratory, University of Cambridge, Downing Street, Cambridge, United Kingdom
| | - Shiraz Ahmad
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge, United Kingdom
| | - Haseeb Valli
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge, United Kingdom
| | - Charlotte E Edling
- Faculty of Health and Medical Science, University of Surrey, Guildford, United Kingdom
| | - Christopher L-H Huang
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge, United Kingdom.,Department of Biochemistry, Hopkins Building, University of Cambridge, Cambridge, United Kingdom
| | - Kamalan Jeevaratnam
- Faculty of Health and Medical Science, University of Surrey, Guildford, United Kingdom.,Physiological Laboratory, University of Cambridge, Downing Street, Cambridge, United Kingdom
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11
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Li GL, Saguner AM, Fontaine GH, Frank R. Fragmented endocardial signals and early afterdepolarizations during torsades de pointes tachycardia. Cardiol J 2018; 27:54-61. [PMID: 30009377 DOI: 10.5603/cj.a2018.0070] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2018] [Revised: 07/08/2018] [Accepted: 07/08/2018] [Indexed: 11/25/2022] Open
Abstract
BACKGROUND Bradycardia-induced torsade de pointes (TdP) tachycardia in patients with spontaneous high-degree atrioventricular block (AVB) is common. The aim of this study was to analyze endocardial recordings during TdP in spontaneous high-degree AVB in humans to better understand the electrophysiological mechanisms underlying this phenomenon. METHODS The study group consisted of 5 patients with typical episodes of TdP during spontaneous high-degree AVB. A standard (USCI) temporary bipolar endocardial catheter positioned at the apex of the right ventricle (RV) and bipolar chest leads from two precordial leads V1 and V4 were used to record the tracings during TdP. RESULTS The presence of a wide spectrum of fragmentations was noted on endocardial electrograms (EGMs), which were invisible on the surface electrocardiogram (ECG) tracing. Endocardial signals indicated that TdP started in the proximity of the RV apex, since the local EGM began prior to the QRS complex on the surface ECG. Early afterdepolarizations (EADs) were observed in 2 out of 5 cases confirming a common opinion about the mechanism of TdP. However, this phenomenon was not observed in 3 other patients suggesting that the arrhythmia was the result of a different mechanism originating in proximity to the RV apex. CONCLUSIONS This work demonstrated early endocardial signals in the RV apex during TdP associated with high-degree AVB in humans, and exhibits a spectrum of fragmented signals in this area occurring on a single or multiple beats. These fragmentations indicate areas of poor conduction and various degrees of intramyocardial block, and therefore a new mechanism of TdP tachycardia in some patients with spontaneous high-degree AVB.
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Affiliation(s)
- Guo-Liang Li
- Arrhythmia Unit, Department of Cardiovascular Medicine, First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi, P.R. China. .,Institut de Cardiologie, Unité de Rythmologie, Groupe Hospitalier Pitié-Salpêtrière, Paris, France.
| | - Ardan M Saguner
- Department of Cardiology, University Heart Center Zurich, Switzerland
| | - Guy H Fontaine
- Institut de Cardiologie, Unité de Rythmologie, Groupe Hospitalier Pitié-Salpêtrière, Paris, France
| | - Robert Frank
- Institut de Cardiologie, Unité de Rythmologie, Groupe Hospitalier Pitié-Salpêtrière, Paris, France
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12
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Zhang D, Tu H, Wadman MC, Li YL. Substrates and potential therapeutics of ventricular arrhythmias in heart failure. Eur J Pharmacol 2018; 833:349-356. [PMID: 29940156 DOI: 10.1016/j.ejphar.2018.06.024] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2018] [Revised: 04/30/2018] [Accepted: 06/19/2018] [Indexed: 12/30/2022]
Abstract
Heart failure (HF) is a clinical syndrome characterized by ventricular contractile dysfunction. About 50% of death in patients with HF are due to fetal ventricular arrhythmias including ventricular tachycardia and ventricular fibrillation. Understanding ventricular arrhythmic substrates and discovering effective antiarrhythmic interventions are extremely important for improving the prognosis of patients with HF and reducing its mortality. In this review, we discussed ventricular arrhythmic substrates and current clinical therapeutics for ventricular arrhythmias in HF. Base on the fact that classic antiarrhythmic drugs have the limited efficacy, side effects, and proarrhythmic potentials, we also updated some therapeutic strategies for the development of potential new antiarrhythmic interventions for patients with HF.
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Affiliation(s)
- Dongze Zhang
- Department of Emergency Medicine, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Huiyin Tu
- Department of Emergency Medicine, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Michael C Wadman
- Department of Emergency Medicine, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Yu-Long Li
- Department of Emergency Medicine, University of Nebraska Medical Center, Omaha, NE 68198, USA.
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13
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Beiert T, Knappe V, Tiyerili V, Stöckigt F, Effelsberg V, Linhart M, Steinmetz M, Klein S, Schierwagen R, Trebicka J, Roell W, Nickenig G, Schrickel JW, Andrié RP. Chronic lower-dose relaxin administration protects from arrhythmia in experimental myocardial infarction due to anti-inflammatory and anti-fibrotic properties. Int J Cardiol 2018; 250:21-28. [DOI: 10.1016/j.ijcard.2017.09.017] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Revised: 08/30/2017] [Accepted: 09/06/2017] [Indexed: 12/11/2022]
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Abstract
Myocardial injury, mechanical stress, neurohormonal activation, inflammation, and/or aging all lead to cardiac remodeling, which is responsible for cardiac dysfunction and arrhythmogenesis. Of the key histological components of cardiac remodeling, fibrosis either in the form of interstitial, patchy, or dense scars, constitutes a key histological substrate of arrhythmias. Here we discuss current research findings focusing on the role of fibrosis, in arrhythmogenesis. Numerous studies have convincingly shown that patchy or interstitial fibrosis interferes with myocardial electrophysiology by slowing down action potential propagation, initiating reentry, promoting after-depolarizations, and increasing ectopic automaticity. Meanwhile, there has been increasing appreciation of direct involvement of myofibroblasts, the activated form of fibroblasts, in arrhythmogenesis. Myofibroblasts undergo phenotypic changes with expression of gap-junctions and ion channels thereby forming direct electrical coupling with cardiomyocytes, which potentially results in profound disturbances of electrophysiology. There is strong evidence that systemic and regional inflammatory processes contribute to fibrogenesis (i.e., structural remodeling) and dysfunction of ion channels and Ca2+ homeostasis (i.e., electrical remodeling). Recognizing the pivotal role of fibrosis in the arrhythmogenesis has promoted clinical research on characterizing fibrosis by means of cardiac imaging or fibrosis biomarkers for clinical stratification of patients at higher risk of lethal arrhythmia, as well as preclinical research on the development of antifibrotic therapies. At the end of this review, we discuss remaining key questions in this area and propose new research approaches. © 2017 American Physiological Society. Compr Physiol 7:1009-1049, 2017.
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Affiliation(s)
- My-Nhan Nguyen
- Baker Heart and Diabetes Institute, Melbourne, Australia.,Central Clinical School, Monash University, Melbourne, Australia
| | - Helen Kiriazis
- Baker Heart and Diabetes Institute, Melbourne, Australia
| | - Xiao-Ming Gao
- Baker Heart and Diabetes Institute, Melbourne, Australia.,Central Clinical School, Monash University, Melbourne, Australia
| | - Xiao-Jun Du
- Baker Heart and Diabetes Institute, Melbourne, Australia.,Central Clinical School, Monash University, Melbourne, Australia
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15
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Huang H, Pugsley MK, Fermini B, Curtis MJ, Koerner J, Accardi M, Authier S. Cardiac voltage-gated ion channels in safety pharmacology: Review of the landscape leading to the CiPA initiative. J Pharmacol Toxicol Methods 2017; 87:11-23. [PMID: 28408211 DOI: 10.1016/j.vascn.2017.04.002] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2016] [Revised: 03/27/2017] [Accepted: 04/06/2017] [Indexed: 12/15/2022]
Abstract
Voltage gated ion channels are central in defining the fundamental properties of the ventricular cardiac action potential (AP), and are also involved in the development of drug-induced arrhythmias. Many drugs can inhibit cardiac ion currents, including the Na+ current (INa), L-type Ca2+ current (Ica-L), and K+ currents (Ito, IK1, IKs, and IKr), and thereby affect AP properties in a manner that can trigger or sustain cardiac arrhythmias. Since publication of ICH E14 and S7B over a decade ago, there has been a focus on drug effects on QT prolongation clinically, and on the rapidly activating delayed rectifier current (IKr), nonclinically, for evaluation of proarrhythmic risk. This focus on QT interval prolongation and a single ionic current likely impacted negatively some drugs that lack proarrhythmic liability in humans. To rectify this issue, the Comprehensive in vitro proarrhythmia assay (CiPA) initiative has been proposed to integrate drug effects on multiple cardiac ionic currents with in silico modelling of human ventricular action potentials, and in vitro data obtained from human stem cell-derived ventricular cardiomyocytes to estimate proarrhythmic risk of new drugs with improved accuracy. In this review, we present the physiological functions and the molecular basis of major cardiac ion channels that contribute to the ventricle AP, and discuss the CiPA paradigm in drug development.
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Affiliation(s)
- Hai Huang
- CiToxLAB North America, 445, Armand-Frappier Boul, Laval H7V 4B3, QC, Canada
| | - Michael K Pugsley
- Department of Toxicology, Purdue Pharma L.P., Cranbury, NJ 08512, USA
| | | | - Michael J Curtis
- Cardiovascular Division, Faculty of Life Sciences & Medicine, King's College London, Rayne Institute, St Thomas' Hospital, London SE17EH, UK
| | - John Koerner
- Center for Drug Evaluation and Research, US Food and Drug Administration, Silver Spring, MD 20993, USA
| | - Michael Accardi
- CiToxLAB North America, 445, Armand-Frappier Boul, Laval H7V 4B3, QC, Canada
| | - Simon Authier
- CiToxLAB North America, 445, Armand-Frappier Boul, Laval H7V 4B3, QC, Canada.
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16
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Chadda KR, Jeevaratnam K, Lei M, Huang CLH. Sodium channel biophysics, late sodium current and genetic arrhythmic syndromes. Pflugers Arch 2017; 469:629-641. [PMID: 28265756 PMCID: PMC5438422 DOI: 10.1007/s00424-017-1959-1] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2017] [Accepted: 02/14/2017] [Indexed: 12/11/2022]
Abstract
Arrhythmias arise from breakdown of orderly action potential (AP) activation, propagation and recovery driven by interactive opening and closing of successive voltage-gated ion channels, in which one or more Na+ current components play critical parts. Early peak, Na+ currents (INa) reflecting channel activation drive the AP upstroke central to cellular activation and its propagation. Sustained late Na+ currents (INa-L) include contributions from a component with a delayed inactivation timecourse influencing AP duration (APD) and refractoriness, potentially causing pro-arrhythmic phenotypes. The magnitude of INa-L can be analysed through overlaps or otherwise in the overall voltage dependences of the steady-state properties and kinetics of activation and inactivation of the Na+ conductance. This was useful in analysing repetitive firing associated with paramyotonia congenita in skeletal muscle. Similarly, genetic cardiac Na+ channel abnormalities increasing INa-L are implicated in triggering phenomena of automaticity, early and delayed afterdepolarisations and arrhythmic substrate. This review illustrates a wide range of situations that may accentuate INa-L. These include (1) overlaps between steady-state activation and inactivation increasing window current, (2) kinetic deficiencies in Na+ channel inactivation leading to bursting phenomena associated with repetitive channel openings and (3) non-equilibrium gating processes causing channel re-opening due to more rapid recoveries from inactivation. All these biophysical possibilities were identified in a selection of abnormal human SCN5A genotypes. The latter presented as a broad range of clinical arrhythmic phenotypes, for which effective therapeutic intervention would require specific identification and targeting of the diverse electrophysiological abnormalities underlying their increased INa-L.
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Affiliation(s)
- Karan R Chadda
- Faculty of Health and Medical Sciences, University of Surrey, VSM Building, Guildford, GU2 7AL, UK
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge, CB2 3EG, UK
| | - Kamalan Jeevaratnam
- Faculty of Health and Medical Sciences, University of Surrey, VSM Building, Guildford, GU2 7AL, UK
- School of Medicine, Perdana University-Royal College of Surgeons Ireland, 43400, Serdang, Selangor Darul Ehsan, Malaysia
| | - Ming Lei
- Department of Pharmacology, University of Oxford, Oxford, OX1 3QT, UK
| | - Christopher L-H Huang
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge, CB2 3EG, UK.
- Department of Biochemistry, University of Cambridge, Hopkins Building, Cambridge, CB2 1QW, UK.
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17
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Connolly A, Trew ML, Smaill BH, Plank G, Bishop MJ. Local Gradients in Electrotonic Loading Modulate the Local Effective Refractory Period: Implications for Arrhythmogenesis in the Infarct Border Zone. IEEE Trans Biomed Eng 2015; 62:2251-2259. [PMID: 25872206 PMCID: PMC5395087 DOI: 10.1109/tbme.2015.2421296] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Ectopic electrical activity that originates in the peri-infarct region can give rise to potentially lethal re-entrant arrhythmias. The spatial variation in electrotonic loading that results from structural remodelling in the infarct border zone may increase the probability that focal activity will trigger electrical capture, but this has not previously been investigated systematically. This study uses in-silico experiments to examine the structural modulation of effective refractory period on ectopic beat capture. Informed by 3-D reconstructions of myocyte organization in the infarct border zone, a region of rapid tissue expansion is abstracted to an idealized representation. A novel metric is introduced that defines the local electrotonic loading as a function of passive tissue properties and boundary conditions. The effective refractory period correlates closely with local electrotonic loading, while the action potential duration, conduction, and upstroke velocity reduce in regions of increasing electrotonic load. In the presence of focal ectopic stimuli, spatial variation in effective refractory period can cause unidirectional conduction block providing a substrate for reentrant arrhythmias. Consequently, based on the observed results, a possible novel mechanism for arrhythmogenesis in the infarct border zone is proposed.
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Affiliation(s)
- Adam Connolly
- Department of Biomedical Engineering, Kings College London, London WC2R 2LS, U.K
| | - Mark L. Trew
- Auckland Bioengineering Institute, University of Auckland
| | | | - Gernot Plank
- Institute of Biophysics, Medical University of Graz
| | - Martin J. Bishop
- Department of Biomedical Engineering, Kings College London, London WC2R 2LS, U.K
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18
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Sonoda K, Watanabe H, Hisamatsu T, Ashihara T, Ohno S, Hayashi H, Horie M, Minamino T. High Frequency of Early Repolarization and Brugada-Type Electrocardiograms in Hypercalcemia. Ann Noninvasive Electrocardiol 2015; 21:30-40. [PMID: 26263049 DOI: 10.1111/anec.12303] [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: 06/11/2015] [Accepted: 06/26/2015] [Indexed: 01/03/2023] Open
Abstract
BACKGROUND J wave, or early repolarization has recently been associated with an increased risk of lethal arrhythmia and sudden death, both in idiopathic ventricular fibrillation and in the general population. Hypercalcemia is one of the causes of J point and ST segment elevation, but the relationship has not been well studied. The aim of this study was to examine the effects of hypercalcemia on J point elevation. METHODS Electrocardiographic findings were compared in 89 patients with hypercalcemia and 267 age- and sex-matched healthy controls with normocalcemia. The association of J point elevation with arrhythmia events in patients with hypercalcemia was also studied. RESULTS The PR interval and the QRS duration were longer in patients with hypercalcemia than in normocalcemic controls. Both the QT and the corrected QT intervals were shorter in patients with hypercalcemia compared with normocalcemic controls. Conduction disorders, ST-T abnormalities, and J point elevation were more common in patients with hypercalcemia than normocalcemic controls. Following the resolution of hypercalcemia, the frequency of J point elevation decreased to a level similar to that noted in controls. During hospitalization, no arrhythmia event occurred in patients with hypercalcemia. CONCLUSION Hypercalcemia was associated with J point elevation.
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Affiliation(s)
- Keiko Sonoda
- Department of Cardiovascular Biology and Medicine, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Hiroshi Watanabe
- Department of Cardiovascular Biology and Medicine, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Takashi Hisamatsu
- Center for Epidemiologic Research in Asia, Shiga University of Medical Science, Otsu, Japan.,Department of Public Health, Shiga University of Medical Science, Otsu, Japan.,Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Japan
| | - Takashi Ashihara
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Japan
| | - Seiko Ohno
- Center for Epidemiologic Research in Asia, Shiga University of Medical Science, Otsu, Japan.,Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Japan
| | - Hideki Hayashi
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Japan
| | - Minoru Horie
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Japan
| | - Tohru Minamino
- Department of Cardiovascular Biology and Medicine, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
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19
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Mulpuru SK, Konecny T, Madhavan M, Kapa S, Noseworthy PA, McLeod CJ, Friedman PA, Packer DL, Asirvatham SJ. Atypical variants of right ventricular outflow arrhythmias. J Cardiovasc Electrophysiol 2014; 25:1321-7. [PMID: 25065643 DOI: 10.1111/jce.12488] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/02/2014] [Revised: 07/08/2014] [Accepted: 07/09/2014] [Indexed: 01/17/2023]
Abstract
BACKGROUND Right ventricular outflow tract (RVOT) arrhythmias are a common form of ventricular tachycardia (VT) in patients with structurally normal heart. The underlying mechanism is due to triggered activity. Mapping and ablation is relatively straightforward targeting the earliest point of activation. Previously reported causes of difficult ablation in the RVOT region include under recognized right ventricular cardiomyopathy/sarcoidosis, presence of endocavitary structures, close proximity to the coronary vasculature, and origin from non-RVOT structures. METHODS AND RESULTS We identified all patients undergoing PVCs/sustained RVOT VT ablation from January 2013 to December 2013. This included 33 patients. Of these, we identified procedures that were considered difficult despite a single morphology arrhythmia being targeted and no underlying cardiomyopathy present. Difficulty was specifically considered when ablation at the earliest site of activation was not successful and eventual successful ablation was at a distance of greater than 15 mm from the early activation site. We identified 3 patients (n = 3, 100% male) with evidence of reentrant arrhythmia based on slow conduction zones necessary for the tachycardia/arrhythmia, mid diastolic signals during VT or preceding bigeminal PVCs, pace mapping from the site abnormal signals reproducing the arrhythmia morphology but with prominent conduction delay, the entire cycle length of the tachycardia or coupling interval for the PVCs being mapping, or based on reset characteristics. CONCLUSION In patients with atypical forms of RVOT VT, careful mapping and ablation of the myocardial sleeves near the pulmonic valve can eliminate the arrhythmia.
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Affiliation(s)
- Siva K Mulpuru
- Division of Cardiovascular Diseases, Mayo Clinic, Rochester, Minnesota, USA
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20
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Lipid metabolites and their differential pro-arrhythmic profiles: of importance in the development of a new anti-arrhythmic pharmacology. Mol Cell Biochem 2014; 393:191-7. [DOI: 10.1007/s11010-014-2060-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2013] [Accepted: 04/11/2014] [Indexed: 01/12/2023]
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21
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Kaese S, Verheule S. Cardiac electrophysiology in mice: a matter of size. Front Physiol 2012; 3:345. [PMID: 22973235 PMCID: PMC3433738 DOI: 10.3389/fphys.2012.00345] [Citation(s) in RCA: 117] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2012] [Accepted: 08/09/2012] [Indexed: 12/27/2022] Open
Abstract
Over the last decade, mouse models have become a popular instrument for studying cardiac arrhythmias. This review assesses in which respects a mouse heart is a miniature human heart, a suitable model for studying mechanisms of cardiac arrhythmias in humans and in which respects human and murine hearts differ. Section I considers the issue of scaling of mammalian cardiac (electro) physiology to body mass. Then, we summarize differences between mice and humans in cardiac activation (section II) and the currents underlying the action potential in the murine working myocardium (section III). Changes in cardiac electrophysiology in mouse models of heart disease are briefly outlined in section IV, while section V discusses technical considerations pertaining to recording cardiac electrical activity in mice. Finally, section VI offers general considerations on the influence of cardiac size on the mechanisms of tachy-arrhythmias.
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Affiliation(s)
- Sven Kaese
- Division of Experimental and Clinical Electrophysiology, Department of Cardiology and Angiology, University Hospital Münster Münster, Germany
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22
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Gaztañaga L, Marchlinski FE, Betensky BP. Mecanismos de las arritmias cardiacas. Rev Esp Cardiol 2012; 65:174-85. [DOI: 10.1016/j.recesp.2011.09.018] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2011] [Accepted: 09/18/2011] [Indexed: 10/14/2022]
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23
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Kalin A, Usher-Smith J, Jones VJ, Huang CLH, Sabir IN. Cardiac arrhythmia: a simple conceptual framework. Trends Cardiovasc Med 2011; 20:103-7. [PMID: 21130954 DOI: 10.1016/j.tcm.2010.09.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 08/31/2010] [Indexed: 10/18/2022]
Abstract
This review presents a simple trigger-substrate model of arrhythmogenesis and its application to the generation of reentrant ventricular arrhythmias. We demonstrate its broad applicability to the understanding of arrhythmic phenomena in a wide range of both hereditary and acquired arrhythmic disorders.
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Affiliation(s)
- Asli Kalin
- John Radcliffe Hospital, Headington, Oxford OX3 9DU, UK
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24
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Thireau J, Pasquié JL, Martel E, Le Guennec JY, Richard S. New drugs vs. old concepts: a fresh look at antiarrhythmics. Pharmacol Ther 2011; 132:125-45. [PMID: 21420430 DOI: 10.1016/j.pharmthera.2011.03.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2011] [Accepted: 03/01/2011] [Indexed: 01/10/2023]
Abstract
Common arrhythmias, particularly atrial fibrillation (AF) and ventricular tachycardia/fibrillation (VT/VF) are a major public health concern. Classic antiarrhythmic (AA) drugs for AF are of limited effectiveness, and pose the risk of life-threatening VT/VF. For VT/VF, implantable cardiac defibrillators appear to be the unique, yet unsatisfactory, solution. Very few AA drugs have been successful in the last few decades, due to safety concerns or limited benefits in comparison to existing therapy. The Vaughan-Williams classification (one drug for one molecular target) appears too restrictive in light of current knowledge of molecular and cellular mechanisms. New AA drugs such as atrial-specific and/or multichannel blockers, upstream therapy and anti-remodeling drugs, are emerging. We focus on the cellular mechanisms related to abnormal Na⁺ and Ca²⁺ handling in AF, heart failure, and inherited arrhythmias, and on novel strategies aimed at normalizing ionic homeostasis. Drugs that prevent excessive Na⁺ entry (ranolazine) and aberrant diastolic Ca²⁺ release via the ryanodine receptor RyR2 (rycals, dantrolene, and flecainide) exhibit very interesting antiarrhythmic properties. These drugs act by normalizing, rather than blocking, channel activity. Ranolazine preferentially blocks abnormal persistent (vs. normal peak) Na⁺ currents, with minimal effects on normal channel function (cell excitability, and conduction). A similar "normalization" concept also applies to RyR2 stabilizers, which only prevent aberrant opening and diastolic Ca²⁺ leakage in diseased tissues, with no effect on normal function during systole. The different mechanisms of action of AA drugs may increase the therapeutic options available for the safe treatment of arrhythmias in a wide variety of pathophysiological situations.
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Affiliation(s)
- Jérôme Thireau
- Inserm U1046 Physiologie & Médecine Expérimentale du Cœur et des Muscles, Université Montpellier-1, Université Montpellier-2, 34295 Montpellier Cedex 5, France
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25
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Li LD, Zhang CT, Ruan L, Ni MK, Quan XQ. Gap junctions enhancer combined with Vaughan Williams class III antiarrhythmic drugs, a promising antiarrhythmic method? Med Hypotheses 2010; 76:119-21. [PMID: 20889260 DOI: 10.1016/j.mehy.2010.08.047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2010] [Revised: 08/24/2010] [Accepted: 08/27/2010] [Indexed: 11/18/2022]
Abstract
Arrhythmias is one of the leading causes of death in the world. Current antiarrhythmic drugs are limited by unsatisfactory efficacy and adverse effects such as proarrhythmias. Reentry mechanism plays an important role in persistence of arrhythmias. Reentry can only continue when reentry path-length is longer than cardiac wavelength which is equal to the product of conduction velocity (CV) and effective refractory period (ERP). Gap junctions uncoupling is associated with proarrhythmic CV slowing and transmural dispersion of repolarization (TDR) increasing in many cardiac diseases. Vaughan Williams class III antiarrhythmic drugs prolong ERP with an augmented TDR which is the main mechanism of the proarrhythmic effects. Gap junctions enhancer can augment CV and diminish TDR. As a result, gap junctions enhancer combined with class III drugs may be a promising antiarrhythmic method.
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Affiliation(s)
- Lian-dong Li
- Department of Geriatrics, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, PR China
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CHEN FRANKC, ASIRVATHAM SAMUELJ. Determining Arrhythmia Mechanism: Still Critical or Now Obsolete? Pacing Clin Electrophysiol 2010; 33:125-8. [DOI: 10.1111/j.1540-8159.2009.02618.x] [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: 11/29/2022]
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27
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Paroxysmal β-adrenergic Receptor-mediated Alterations in Ventricular Repolarization at Rapid Heart Rates During Inhibition of Delayed Rectifier Currents. J Cardiovasc Pharmacol 2009; 54:253-62. [DOI: 10.1097/fjc.0b013e3181b2b706] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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28
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Fernandes S, van Rijen HVM, Forest V, Evain S, Leblond AL, Mérot J, Charpentier F, de Bakker JMT, Lemarchand P. Cardiac cell therapy: overexpression of connexin43 in skeletal myoblasts and prevention of ventricular arrhythmias. J Cell Mol Med 2009; 13:3703-12. [PMID: 19438811 PMCID: PMC3189515 DOI: 10.1111/j.1582-4934.2009.00740.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Cell-based therapies have great potential for the treatment of cardiovascular diseases. Recently, using a transgenic mouse model Roell et al. reported that cardiac engraftment of connexin43 (Cx43)-overexpressing myoblasts in vivo prevents post-infarct arrhythmia, a common cause of death in patients following heart attack. We carried out a similar study but in a clinically relevant context via transplantation of autologous connexin43-overexpressing myoblasts in infarcted rats. Seven days after coronary ligation, rats were randomized into three groups: a control group injected with myoblasts, a null group injected with myoblasts transduced with an empty lentivirus vector (null) and a Cx43 group injected with myoblasts transduced with a lentivirus vector encoding connexin43. In contrast to Roell’s report, arrhythmia occurrence was not statistically different between groups (58%, 64% and 48% for the control (n= 12), null (n= 14) and Cx43 (n= 23) groups, respectively, P= 0.92). Using ex vivo intramural monophasic action potential recordings synchronous electrical activity was observed between connexin43-overexpressing myoblasts and host cardiomyocytes, whereas such synchrony did not occur in the null-transduced group. This suggests that ex vivo connexin43 gene transfer and expression in myoblasts improved intercellular electrical coupling between myoblasts and cardiomyocytes. However, in our model such electrical coupling was not sufficient to decrease arrhythmia induction. Therefore, we would suggest a note of caution on the use of combined Cx43 gene and cell therapy to prevent post-infarct arrhythmias in heart failure patients.
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29
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Dautova Y, Zhang Y, Sabir I, Grace AA, Huang CLH. Atrial arrhythmogenesis in wild-type and Scn5a+/delta murine hearts modelling LQT3 syndrome. Pflugers Arch 2009; 458:443-57. [PMID: 19184093 PMCID: PMC2691533 DOI: 10.1007/s00424-008-0633-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2008] [Accepted: 12/25/2008] [Indexed: 01/02/2023]
Abstract
Long QT(3) (LQT3) syndrome is associated with abnormal repolarisation kinetics, prolonged action potential durations (APD) and QT intervals and may lead to life-threatening ventricular arrhythmias. However, there have been few physiological studies of its effects on atrial electrophysiology. Programmed electrical stimulation and burst pacing induced atrial arrhythmic episodes in 16 out of 16 (16/16) wild-type (WT) and 7/16 genetically modified Scn5a+/Δ (KPQ) Langendorff-perfused murine hearts modelling LQT3 (P < 0.001 for both), and in 14/16 WT and 1/16 KPQ hearts (P < 0.001 for both; Fisher’s exact test), respectively. The arrhythmogenic WT hearts had significantly larger positive critical intervals (CI), given by the difference between atrial effective refractory periods (AERPs) and action potential durations at 90% recovery (APD90), compared to KPQ hearts (8.1 and 3.2 ms, respectively, P < 0.001). Flecainide prevented atrial arrhythmias in all arrhythmogenic WT (P < 0.001) and KPQ hearts (P < 0.05). It prolonged the AERP to a larger extent than it did the APD90 in both WT and KPQ groups, giving negative CIs. Quinidine similarly exerted anti-arrhythmic effects, prolonged AERP over corresponding APD90 in both WT and KPQ groups. These findings, thus, demonstrate, for the first time, inhibitory effects of the KPQ mutation on atrial arrhythmogenesis and its modification by flecainide and quinidine. They attribute these findings to differences in the CI between WT and mutant hearts, in the presence or absence of these drugs. Thus, prolongation of APD90 over AERP gave positive CI values and increased atrial arrhythmogenicity whereas lengthening of AERP over APD90 reduced such CI values and produced the opposite effect.
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Affiliation(s)
- Yana Dautova
- Cardiovascular Biology Group, Physiological Laboratory, University of Cambridge, Cambridge, UK
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Sabir IN, Killeen MJ, Grace AA, Huang CLH. Ventricular arrhythmogenesis: Insights from murine models. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2008; 98:208-18. [DOI: 10.1016/j.pbiomolbio.2008.10.011] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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31
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Restier-Miron L, Fayn J, Millat G, Denjoy I, Rodriguez-Lafrasse C, Rubel P, Chevalier P. Spatiotemporal electrocardiographic characterization of ventricular depolarization and repolarization abnormalities in long QT syndrome. J Electrocardiol 2007; 40:368-74. [PMID: 17316676 DOI: 10.1016/j.jelectrocard.2006.12.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2006] [Accepted: 12/15/2006] [Indexed: 11/26/2022]
Abstract
BACKGROUND AND PURPOSE If only a standard electrocardiogram (ECG) is available, at least 25% of patients with long QT syndrome (LQTS) may be missed. Our goal is to quantify abnormal electrical activity and to develop an ECG decision rule for the patients with LQTS. METHODS One hundred forty-one subjects were included in this study (71 patients with LQTS and 70 healthy subjects). A 12-lead digital ECG was recorded for each subject and analyzed using the CAVIAR (comparative analysis of ECG-VCG and their interpretation with auto-reference to the patient) method. RESULTS A decision tree involving criteria based on 3 spatiotemporal ECG measurements-the QT interval and the maximum amplitude of the T wave, both corrected from heart rate, and the loss of planarity of the end of QRS-identified patients with LQTS from healthy subjects with a sensitivity of 89%, a specificity of 96%, and a total accuracy of 92%. CONCLUSIONS This study suggests that 3-dimensional ECG analysis may improve the detection of patients with LQTS.
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Abstract
This study examines how a zigzag pattern of conduction, a form of structural heterogeneity frequently found in old or diseased hearts, affects the vulnerability to reentry during rapid pacing. A central rectangular island (8×4 mm) containing a predefined zigzag pattern was created in cultured isotropic monolayers of neonatal rat ventricular myocytes. Impulse propagation was optically mapped from 253 sites using voltage-sensitive dye and was anisotropic within the zigzag island. With increasing interval between neighboring transverse connections (
a
), relative to the distance between longitudinal strands (
b
), transverse conduction velocity (CV) decreased to 66±6%, 20±2%, and 15±2% of CV in the surrounding isotropic region, whereas longitudinal CV increased to 102±8%, 113±12%, and 131±23% for
a
:
b
ratios of 1:1, 1:5, and 1:9, respectively. During rapid pacing, propagation distal to the island was steered from the side of the island with more transverse connections (“dominant” side) toward the side with fewer connections (“weak” side). Increased asymmetry in the pattern accentuated this effect, and resulted in increased rate-dependent differences in CV on the 2 sides. Consequently, a functional obstacle formed on the weak side, followed by development of single loop reentry. The reentrant wave revolved around a line of block defined by the border of the island. Reentry chirality was determined by the weak side location, and the pacing rate needed to initiate reentry decreased with increased asymmetry in the pattern. In conclusion, reentry is readily induced by rapid pacing in confluent cardiac cell monolayers containing a central and asymmetric island of zigzag conduction.
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Affiliation(s)
- Weining Bian
- Department of Biomedical Engineering, The Johns Hopkins University, Baltimore, MD 21205, USA
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Kizana E, Ginn SL, Allen DG, Ross DL, Alexander IE. Fibroblasts can be genetically modified to produce excitable cells capable of electrical coupling. Circulation 2005; 111:394-8. [PMID: 15687125 DOI: 10.1161/01.cir.0000153812.64956.ef] [Citation(s) in RCA: 180] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Cardiac conduction occurs in an electrical syncytium of excitable cells connected by gap junctions. Disruption of these electrophysiological properties causes conduction slowing or block. Depending on the location of affected cells within the heart, this has the potential to result in clinical syndromes such as atrioventricular block. With a view to developing gene therapy strategies for repairing cardiac conduction defects, we sought to establish whether the phenotype of fibroblasts can be modified by gene transfer to produce cells capable of electrical excitation and coupling. METHODS AND RESULTS High-titer lentiviral vectors encoding MyoD, a myogenic transcription factor, and connexin43, a gap junction protein, were produced by established methods. Human dermal fibroblasts (HDFs) were efficiently (>80%) transduced at a multiplicity of infection of 50. HDFs transduced with the MyoD-encoding vector underwent myogenic conversion, as evidenced by myotube formation and detection of muscle-specific proteins. Importantly, calcium transients indicative of membrane excitability were observed in MyoD-induced myotubes after loading with a calcium-sensitive dye and electrical stimulation. Transients from adjacent myotubes displayed different excitation thresholds, indicating an absence of coupling between cells, consistent with skeletal muscle biology. In contrast, simultaneous transduction of HDFs with MyoD and connexin43-encoding vectors resulted in the appearance of transients in adjacent myotubes with identical thresholds, indicative of electrical coupling. Notably, dye transfer studies confirmed gap junctional intercellular communication. CONCLUSIONS Fibroblasts can be genetically modified to produce excitable cells capable of electrical coupling. These observations strengthen the prospect of developing gene-based strategies for repairing cardiac conduction defects.
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Affiliation(s)
- Eddy Kizana
- Department of Cardiology, Westmead Hospital, Westmead, Australia
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Abraham MR, Henrikson CA, Tung L, Chang MG, Aon M, Xue T, Li RA, O' Rourke B, Marbán E. Antiarrhythmic engineering of skeletal myoblasts for cardiac transplantation. Circ Res 2005; 97:159-67. [PMID: 15976318 DOI: 10.1161/01.res.0000174794.22491.a0] [Citation(s) in RCA: 229] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Skeletal myoblasts are an attractive cell type for transplantation because they are autologous and resistant to ischemia. However, clinical trials of myoblast transplantation in heart failure have been plagued by ventricular tachyarrhythmias and sudden cardiac death. The pathogenesis of these arrhythmias is poorly understood, but may be related to the fact that skeletal muscle cells, unlike heart cells, are electrically isolated by the absence of gap junctions. Using a novel in vitro model of myoblast transplantation in cardiomyocyte monolayers, we investigated the mechanisms of transplant-associated arrhythmias. Cocultures of human skeletal myoblasts and rat cardiomyocytes resulted in reentrant arrhythmias (spiral waves) that reproduce the features of ventricular tachycardia seen in patients receiving myoblast transplants. These arrhythmias could be terminated by nitrendipine, an l-type calcium channel blocker, but not by the Na channel blocker lidocaine. Genetic modification of myoblasts to express the gap junction protein connexin43 decreased arrhythmogenicity in cocultures, suggesting a specific means for increasing the safety (and perhaps the efficacy) of myoblast transplantation in patients.
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Affiliation(s)
- M Roselle Abraham
- Institute of Molecular Cardiobiology, Johns Hopkins University, Carnegie 568, 600 N Wolfe St, Baltimore, MD 21205, USA
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35
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Liu C, Li G, He B. Localization of the site of origin of reentrant arrhythmia from body surface potential maps: a model study. Phys Med Biol 2005; 50:1421-32. [PMID: 15798333 DOI: 10.1088/0031-9155/50/7/006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We have developed a model-based imaging approach to estimate the site of origin of reentrant arrhythmia from body surface potential maps (BSPMs), with the aid of a cardiac arrhythmia model. The reentry was successfully simulated and maintained in the cardiac model, and the simulated ECG waveforms over the body surface corresponding to a maintained reentry have evident characteristics of ventricular tachycardia. The performance of the inverse imaging approach was evaluated by computer simulations. The present simulation results show that an averaged localization error of about 1.5 mm, when 5% Gaussian white noise was added to the BSPMs, was detected. The effects of the heart-torso geometry uncertainty on the localization were also initially assessed and the simulation results suggest that no significant influence was observed when 10% torso geometry uncertainty or 10 mm heart position shifting was considered. The present simulation study suggests the feasibility of localizing the site of origin of reentrant arrhythmia from non-invasive BSPMs, with the aid of a cardiac arrhythmia model.
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Affiliation(s)
- Chenguang Liu
- Department of Biomedical Engineering, University of Minnesota, 7-105 BSBE, 312 Church St., Minneapolis, MN 55455, USA
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36
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Terrenoire C, Clancy CE, Cormier JW, Sampson KJ, Kass RS. Autonomic control of cardiac action potentials: role of potassium channel kinetics in response to sympathetic stimulation. Circ Res 2005; 96:e25-34. [PMID: 15731462 DOI: 10.1161/01.res.0000160555.58046.9a] [Citation(s) in RCA: 118] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
I(Ks), the slowly activating component of the delayed rectifier current, plays a major role in repolarization of the cardiac action potential (AP). Genetic mutations in the alpha- (KCNQ1) and beta- (KCNE1) subunits of I(Ks) underlie Long QT Syndrome type 1 and 5 (LQT-1 and LQT-5), respectively, and predispose carriers to the development of polymorphic ventricular arrhythmias and sudden cardiac death. beta-adrenergic stimulation increases I(Ks) and results in rate dependent AP shortening, a control system that can be disrupted by some mutations linked to LQT-1 and LQT-5. The mechanisms by which I(Ks) regulates action potential duration (APD) during beta-adrenergic stimulation at different heart rates are not known, nor are the consequences of mutation induced disruption of this regulation. Here we develop a complementary experimental and theoretical approach to address these questions. We reconstituted I(Ks) in CHO cells (ie, KCNQ1 coexpressed with KCNE1 and the adaptator protein Yotiao) and quantitatively examined the effects of beta-adrenergic stimulation on channel kinetics. We then developed theoretical models of I(Ks) in the absence and presence of beta-adrenergic stimulation. We simulated the effects of sympathetic stimulation on channel activation (speeding) and deactivation (slowing) kinetics on the whole cell action potential under different pacing conditions. The model suggests these kinetic effects are critically important in rate-dependent control of action potential duration. We also investigate the effects of two LQT-5 mutations that alter kinetics and impair sympathetic stimulation of I(Ks) and show the likely mechanism by which they lead to tachyarrhythmias and indicate a distinct role of I(KS) kinetics in this electrical dysfunction. The full text of this article is available online at http://circres.ahajournals.org.
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MESH Headings
- A Kinase Anchor Proteins
- Action Potentials/physiology
- Adaptor Proteins, Signal Transducing/genetics
- Adaptor Proteins, Signal Transducing/physiology
- Amino Acid Substitution
- Animals
- CHO Cells
- Computer Simulation
- Cricetinae
- Cricetulus
- Cyclic AMP/physiology
- Cyclic AMP-Dependent Protein Kinases/metabolism
- Cytoskeletal Proteins/genetics
- Cytoskeletal Proteins/physiology
- Delayed Rectifier Potassium Channels
- Humans
- Ion Channel Gating/physiology
- KCNQ Potassium Channels
- KCNQ1 Potassium Channel
- Kinetics
- Long QT Syndrome/genetics
- Long QT Syndrome/physiopathology
- Models, Cardiovascular
- Mutation, Missense
- Myocytes, Cardiac/physiology
- Patch-Clamp Techniques
- Phosphorylation
- Point Mutation
- Potassium/metabolism
- Potassium Channels, Voltage-Gated/genetics
- Potassium Channels, Voltage-Gated/physiology
- Protein Processing, Post-Translational
- Receptors, Adrenergic, beta/physiology
- Recombinant Fusion Proteins/physiology
- Second Messenger Systems/physiology
- Sympathetic Nervous System/physiology
- Tachycardia/physiopathology
- Transfection
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Affiliation(s)
- Cecile Terrenoire
- Department of Pharmacology, College of Physicians & Surgeons of Columbia University, New York, NY 10032, USA
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Kimura M, Kobayashi T, Owada S, Ashikaga K, Higuma T, Sasaki S, Iwasa A, Motomura S, Okumura K. Mechanism of ST Elevation and Ventricular Arrhythmias in an Experimental Brugada Syndrome Model. Circulation 2004; 109:125-31. [PMID: 14662710 DOI: 10.1161/01.cir.0000105762.94855.46] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Although phase 2 reentry is said to be responsible for initiation of ventricular tachycardia (VT) in Brugada syndrome, information about the activation sequence during VT is limited. METHODS AND RESULTS We developed an experimental Brugada syndrome model using a canine isolated right ventricular preparation cross-circulated with arterial blood of a supporter dog and examined the VT mechanism. Two plaque electrodes (35x30 mm) containing 96 bipolar electrodes were attached to the endocardium and epicardium. Saddleback and coved types of ST elevation in transmural ECG were induced by pilsicainide, a pure sodium channel blocker, and pinacidil, a KATP channel opener. Eighteen polymorphic VT episodes were recorded in 9 of the 12 preparations associated with ST elevation. Fourteen episodes spontaneously developed in 5 preparations after an extrasystole during basic drive pacing. Analysis of local recovery times revealed increased dispersion especially in epicardium, and the extrasystole originated from a site with a short recovery time, suggesting that phase 2 reentry was its mechanism. The other 4 VTs in 4 preparations were induced by premature stimulation. Analysis of the activation sequences during VT revealed reentry between epicardium and endocardium or reentry around an arc of a functional block confined to epicardium or endocardium with bystander activation of the other. CONCLUSIONS Electrical heterogeneity in the recovery phase was induced in this experimental Brugada syndrome model, which can be a substrate for the development of phase 2 reentry and the subsequent reentry around an arc of the functional block, resulting in sustained VT.
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Affiliation(s)
- Masaomi Kimura
- Second Department of Internal Medicine, Hirosaki University School of Medicine, Zaifu-cho 5, Hirosaki 036-8562, Japan
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38
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Kaprielian R, Sah R, Nguyen T, Wickenden AD, Backx PH. Myocardial infarction in rat eliminates regional heterogeneity of AP profiles, I(to) K(+) currents, and [Ca(2+)](i) transients. Am J Physiol Heart Circ Physiol 2002; 283:H1157-68. [PMID: 12181147 DOI: 10.1152/ajpheart.00518.2001] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Transient outward K(+) current density (I(to)) has been shown to vary between different regions of the normal myocardium and to be reduced in heart disease. In this study, we measured regional changes in action potential duration (APD), I(to), and intracellular Ca(2+) concentration ([Ca(2+)](i)) transients of ventricular myocytes derived from the right ventricular free wall (RVW) and interventricular septum (SEP) 8 wk after myocardial infarction (MI). At +40 mV, I(to) density in sham-operated hearts was significantly higher (P < 0.01) in the RVW (15.0 +/- 0.8 pA/pF, n = 47) compared with the SEP (7.0 +/- 1.1 pA/pF, n = 18). After MI, I(to) density was not reduced in SEP myocytes but was reduced (P < 0.01) in RVW myocytes (8.7 +/- 1.0 pA/pF, n = 26) to levels indistinguishable from post-MI SEP myocytes. These changes in I(to) density correlated with Kv4.2 (but not Kv4.3) protein expression. By contrast, Kv1.4 expression was significantly higher in the RVW compared with the SEP and increased significantly after MI in RVW. APD measured at 50% or 90% repolarization was prolonged, whereas peak [Ca(2+)](i) transients amplitude was higher in the SEP compared with the RVW in sham myocytes. These regional differences in APD and [Ca(2+)](i) transients were eliminated by MI. Our results demonstrate that the significant regional differences in I(to) density, APD, and [Ca(2+)](i) between RVW and SEP are linked to a variation in Kv4.2 expression, which largely disappears after MI.
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Affiliation(s)
- Roger Kaprielian
- Cardiovascular Research Center, Massachusetts General Hospital, Charlestown, Massachusetts 02129-0060, USA
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39
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Papadatos GA, Wallerstein PMR, Head CEG, Ratcliff R, Brady PA, Benndorf K, Saumarez RC, Trezise AEO, Huang CLH, Vandenberg JI, Colledge WH, Grace AA. Slowed conduction and ventricular tachycardia after targeted disruption of the cardiac sodium channel gene Scn5a. Proc Natl Acad Sci U S A 2002; 99:6210-5. [PMID: 11972032 PMCID: PMC122928 DOI: 10.1073/pnas.082121299] [Citation(s) in RCA: 294] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2001] [Accepted: 03/01/2002] [Indexed: 11/18/2022] Open
Abstract
Voltage-gated sodium channels drive the initial depolarization phase of the cardiac action potential and therefore critically determine conduction of excitation through the heart. In patients, deletions or loss-of-function mutations of the cardiac sodium channel gene, SCN5A, have been associated with a wide range of arrhythmias including bradycardia (heart rate slowing), atrioventricular conduction delay, and ventricular fibrillation. The pathophysiological basis of these clinical conditions is unresolved. Here we show that disruption of the mouse cardiac sodium channel gene, Scn5a, causes intrauterine lethality in homozygotes with severe defects in ventricular morphogenesis whereas heterozygotes show normal survival. Whole-cell patch clamp analyses of isolated ventricular myocytes from adult Scn5a(+/-) mice demonstrate a approximately 50% reduction in sodium conductance. Scn5a(+/-) hearts have several defects including impaired atrioventricular conduction, delayed intramyocardial conduction, increased ventricular refractoriness, and ventricular tachycardia with characteristics of reentrant excitation. These findings reconcile reduced activity of the cardiac sodium channel leading to slowed conduction with several apparently diverse clinical phenotypes, providing a model for the detailed analysis of the pathophysiology of arrhythmias.
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Affiliation(s)
- G Alex Papadatos
- Section of Cardiovascular Biology, Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW, United Kingdom
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40
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Kuo HC, Cheng CF, Clark RB, Lin JJ, Lin JL, Hoshijima M, Nguyêñ-Trân VT, Gu Y, Ikeda Y, Chu PH, Ross J, Giles WR, Chien KR. A defect in the Kv channel-interacting protein 2 (KChIP2) gene leads to a complete loss of I(to) and confers susceptibility to ventricular tachycardia. Cell 2001; 107:801-13. [PMID: 11747815 DOI: 10.1016/s0092-8674(01)00588-8] [Citation(s) in RCA: 319] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
KChIP2, a gene encoding three auxiliary subunits of Kv4.2 and Kv4.3, is preferentially expressed in the adult heart, and its expression is downregulated in cardiac hypertrophy. Mice deficient for KChIP2 exhibit normal cardiac structure and function but display a prolonged elevation in the ST segment on the electrocardiogram. The KChIP2(-/-) mice are highly susceptible to the induction of cardiac arrhythmias. Single-cell analysis revealed a substrate for arrhythmogenesis, including a complete absence of transient outward potassium current, I(to), and a marked increase in action potential duration. These studies demonstrate that a defect in KChIP2 is sufficient to confer a marked genetic susceptibility to arrhythmias, establishing a novel genetic pathway for ventricular tachycardia via a loss of the transmural gradient of I(to).
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Affiliation(s)
- H C Kuo
- Institute of Molecular Medicine, UCSD-Salk Program in Molecular Medicine, School of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
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41
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Oudit GY, Kassiri Z, Sah R, Ramirez RJ, Zobel C, Backx PH. The molecular physiology of the cardiac transient outward potassium current (I(to)) in normal and diseased myocardium. J Mol Cell Cardiol 2001; 33:851-72. [PMID: 11343410 DOI: 10.1006/jmcc.2001.1376] [Citation(s) in RCA: 131] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
G. Y. Oudit, Z. Kassiri, R. Sah, R. J. Ramirez, C. Zobel and P. H. Backx. The Molecular Physiology of the Cardiac Transient Outward Potassium Current (I(to)) in Normal and Diseased Myocardium. Journal of Molecular and Cellular Cardiology (2001) 33, 851-872. The Ca(2+)-independent transient outward potassium current (I(to)) plays an important role in early repolarization of the cardiac action potential. I(to)has been clearly demonstrated in myocytes from different cardiac regions and species. Two kinetic variants of cardiac I(to)have been identified: fast I(to), called I(to,f), and slow I(to), called I(to,s). Recent findings suggest that I(to,f)is formed by assembly of K(v4.2)and/or K(v4.3)alpha pore-forming voltage-gated subunits while I(to,s)is comprised of K(v1.4)and possibly K(v1.7)subunits. In addition, several regulatory subunits and pathways modulating the level and biophysical properties of cardiac I(to)have been identified. Experimental findings and data from computer modeling of cardiac action potentials have conclusively established an important physiological role of I(to)in rodents, with its role in large mammals being less well defined due to complex interplay between a multitude of cardiac ionic currents. A central and consistent electrophysiological change in cardiac disease is the reduction in I(to)density with a loss of heterogeneity of I(to)expression and associated action potential prolongation. Alterations of I(to)in rodent cardiac disease have been linked to repolarization abnormalities and alterations in intracellular Ca(2+)homeostasis, while in larger mammals the link with functional changes is far less certain. We review the current literature on the molecular basis for cardiac I(to)and the functional consequences of changes in I(to)that occur in cardiovascular disease.
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Affiliation(s)
- G Y Oudit
- Department of Medicine and Physiology, Toronto General Hospital, 101 College Street, Toronto, M5G 2C4, Canada
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