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Sohinki DA, Mathew ST. Ventricular Arrhythmias in the Patient with a Structurally Normal Heart. J Innov Card Rhythm Manag 2018; 9:3338-3353. [PMID: 32477784 PMCID: PMC7252725 DOI: 10.19102/icrm.2018.091004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Accepted: 02/04/2018] [Indexed: 11/24/2022] Open
Abstract
Ventricular arrhythmias (VAs) are among the most common cardiac rhythm disturbances encountered in clinical practice. Patients presenting with frequent ventricular ectopy or sustained ventricular tachycardia represent a challenging and worrisome clinical scenario for many practitioners because of concerning symptoms, frequent associated acute hemodynamic compromise, and the adverse prognostic implications inherent to these cases. While an underlying structural or functional cardiac abnormality, metabolic derangement, or medication toxicity is often readily apparent, many patients have no obvious underlying condition, despite a comprehensive diagnostic evaluation. Such patients are diagnosed as having an idiopathic VA, which is a label with specific implications regarding arrhythmia origin, prognosis, and potential for pharmacologic and invasive management. Further, a subset of patients with otherwise benign idiopathic ventricular ectopy can present with polymorphic ventricular tachycardia and ventricular fibrillation, adding a layer of complexity to a clinical syndrome previously felt to have a benign clinical course. Thus, this review seeks to highlight the most common types of idiopathic VAs with a focus on their prognostic implications, underlying electrophysiologic mechanisms, unique electrocardiographic signatures, and considerations for invasive electrophysiologic study and catheter ablation. We further address some of the data regarding idiopathic ventricular fibrillation with respect to the heterogeneous nature of this diagnosis.
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Affiliation(s)
- Daniel A Sohinki
- Department of Cardiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Sunil T Mathew
- Department of Cardiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA.,Heart Rhythm Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
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2
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Lipovsky CE, Brumback BD, Khandekar A, Rentschler SL. Multi-Scale Assessments of Cardiac Electrophysiology Reveal Regional Heterogeneity in Health and Disease. J Cardiovasc Dev Dis 2018; 5:E16. [PMID: 29517992 PMCID: PMC5872364 DOI: 10.3390/jcdd5010016] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Revised: 02/27/2018] [Accepted: 03/05/2018] [Indexed: 12/19/2022] Open
Abstract
The left and right ventricles of the four-chambered heart have distinct developmental origins and functions. Chamber-specific developmental programming underlies the differential gene expression of ion channel subunits regulating cardiac electrophysiology that persists into adulthood. Here, we discuss regional specific electrical responses to genetic mutations and cardiac stressors, their clinical correlations, and describe many of the multi-scale techniques commonly used to analyze electrophysiological regional heterogeneity.
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Affiliation(s)
- Catherine E Lipovsky
- Department of Medicine, Cardiovascular Division, Washington University School of Medicine, Campus Box 8103, 660 S Euclid Ave, St. Louis, MO 63110, USA.
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO 63110, USA.
| | - Brittany D Brumback
- Department of Medicine, Cardiovascular Division, Washington University School of Medicine, Campus Box 8103, 660 S Euclid Ave, St. Louis, MO 63110, USA.
- Department of Biomedical Engineering, Washington University, St. Louis, MO 63130, USA.
| | - Aditi Khandekar
- Department of Medicine, Cardiovascular Division, Washington University School of Medicine, Campus Box 8103, 660 S Euclid Ave, St. Louis, MO 63110, USA.
| | - Stacey L Rentschler
- Department of Medicine, Cardiovascular Division, Washington University School of Medicine, Campus Box 8103, 660 S Euclid Ave, St. Louis, MO 63110, USA.
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO 63110, USA.
- Department of Biomedical Engineering, Washington University, St. Louis, MO 63130, USA.
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Watanabe M, Rollins AM, Polo-Parada L, Ma P, Gu S, Jenkins MW. Probing the Electrophysiology of the Developing Heart. J Cardiovasc Dev Dis 2016; 3:jcdd3010010. [PMID: 29367561 PMCID: PMC5715694 DOI: 10.3390/jcdd3010010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Revised: 03/08/2016] [Accepted: 03/10/2016] [Indexed: 12/14/2022] Open
Abstract
Many diseases that result in dysfunction and dysmorphology of the heart originate in the embryo. However, the embryonic heart presents a challenging subject for study: especially challenging is its electrophysiology. Electrophysiological maturation of the embryonic heart without disturbing its physiological function requires the creation and deployment of novel technologies along with the use of classical techniques on a range of animal models. Each tool has its strengths and limitations and has contributed to making key discoveries to expand our understanding of cardiac development. Further progress in understanding the mechanisms that regulate the normal and abnormal development of the electrophysiology of the heart requires integration of this functional information with the more extensively elucidated structural and molecular changes.
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Affiliation(s)
- Michiko Watanabe
- Department of Pediatrics, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA.
- Rainbow Babies and Children's Hospital, Case Western Reserve University, Cleveland, OH 44106, USA.
| | - Andrew M Rollins
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA.
| | - Luis Polo-Parada
- Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO 65201, USA.
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO 65201, USA.
| | - Pei Ma
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA.
| | - Shi Gu
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA.
| | - Michael W Jenkins
- Department of Pediatrics, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA.
- Rainbow Babies and Children's Hospital, Case Western Reserve University, Cleveland, OH 44106, USA.
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Tsai SY, Maass K, Lu J, Fishman GI, Chen S, Evans T. Efficient Generation of Cardiac Purkinje Cells from ESCs by Activating cAMP Signaling. Stem Cell Reports 2015; 4:1089-102. [PMID: 26028533 PMCID: PMC4471825 DOI: 10.1016/j.stemcr.2015.04.015] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Revised: 04/27/2015] [Accepted: 04/30/2015] [Indexed: 12/13/2022] Open
Abstract
Dysfunction of the specialized cardiac conduction system (CCS) is associated with life-threatening arrhythmias. Strategies to derive CCS cells, including rare Purkinje cells (PCs), would facilitate models for mechanistic studies and drug discovery and also provide new cellular materials for regenerative therapies. A high-throughput chemical screen using CCS:lacz and Contactin2:egfp (Cntn2:egfp) reporter embryonic stem cell (ESC) lines was used to discover a small molecule, sodium nitroprusside (SN), that efficiently promotes the generation of cardiac cells that express gene profiles and generate action potentials of PC-like cells. Imaging and mechanistic studies suggest that SN promotes the generation of PCs from cardiac progenitors initially expressing cardiac myosin heavy chain and that it does so by activating cyclic AMP signaling. These findings provide a strategy to derive scalable PCs, along with insight into the ontogeny of CCS development. A chemical screen was carried out for compounds that induce cardiac conduction cells Two ESC reporter lines were used to identify lead hits Sodium nitroprusside efficiently generated scalable amounts of PC-like cells By activating cAMP signaling, PCs are derived from cardiac progenitors
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Affiliation(s)
- Su-Yi Tsai
- Department of Surgery, Weill Cornell Medical College, New York, NY 10065, USA
| | - Karen Maass
- Leon H. Charney Division of Cardiology, New York University School of Medicine, New York, NY 10016, USA
| | - Jia Lu
- Leon H. Charney Division of Cardiology, New York University School of Medicine, New York, NY 10016, USA
| | - Glenn I Fishman
- Leon H. Charney Division of Cardiology, New York University School of Medicine, New York, NY 10016, USA.
| | - Shuibing Chen
- Department of Surgery, Weill Cornell Medical College, New York, NY 10065, USA.
| | - Todd Evans
- Department of Surgery, Weill Cornell Medical College, New York, NY 10065, USA.
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Liang X, Evans SM, Sun Y. Insights into cardiac conduction system formation provided by HCN4 expression. Trends Cardiovasc Med 2015; 25:1-9. [PMID: 25442735 PMCID: PMC5544420 DOI: 10.1016/j.tcm.2014.08.009] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/14/2014] [Revised: 08/28/2014] [Accepted: 08/28/2014] [Indexed: 11/22/2022]
Abstract
Specialized myocytes of the cardiac conduction system (CCS) are essential to coordinate sequential contraction of cardiac atria and ventricles. Anomalies of the CCS can result in lethal cardiac arrhythmias, including sick sinus syndrome and atrial or ventricular fibrillation. To develop future therapies and regenerative medicine aimed at cardiac arrhythmias, it is important to understand formation and function of distinct components of the CCS. Essential to this understanding is the development of CCS-specific markers. In this review, we briefly summarize available mouse models of CCS markers and focus on those involving the hyperpolarization cation-selective nucleotide-gated cation channel, HCN4, which selectively marks all components of the specialized CCS in adult heart. Recent studies have revealed, however, that HCN4 expression during development is highly dynamic in cardiac precursors. These studies have offered insights into the contributions of the first and second heart field to myocyte and conduction system lineages and suggested the timing of allocation of specific conduction system precursors during development. Altogether, they have highlighted the utility of HCN4 as a cell surface marker for distinct components of the CCS at distinct stages of development, which can be utilized to facilitate purification and characterization of CCS precursors in mouse and human model systems and pave the way for regenerative therapies.
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Affiliation(s)
- Xingqun Liang
- Key Laboratory of Arrhythmia, Ministry of Education, East Hospital, Tongji University School of Medicine, Shanghai, China; Department of Medicine, University of California, San Diego, San Diego, CA
| | - Sylvia M Evans
- Department of Medicine, University of California, San Diego, San Diego, CA; Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, San Diego, CA; Department of Pharmacology, University of California, San Diego, San Diego, CA.
| | - Yunfu Sun
- Key Laboratory of Arrhythmia, Ministry of Education, East Hospital, Tongji University School of Medicine, Shanghai, China.
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Mouse models of cardiac conduction system markers: revealing the past, present, and future of pacemaking and conduction. Trends Cardiovasc Med 2014; 25:10-1. [PMID: 25446050 DOI: 10.1016/j.tcm.2014.09.007] [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] [Received: 09/16/2014] [Accepted: 09/19/2014] [Indexed: 11/21/2022]
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Vedantham V, Evangelista M, Huang Y, Srivastava D. Spatiotemporal regulation of an Hcn4 enhancer defines a role for Mef2c and HDACs in cardiac electrical patterning. Dev Biol 2012; 373:149-62. [PMID: 23085412 DOI: 10.1016/j.ydbio.2012.10.017] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2012] [Revised: 10/11/2012] [Accepted: 10/12/2012] [Indexed: 11/17/2022]
Abstract
Regional differences in cardiomyocyte automaticity permit the sinoatrial node (SAN) to function as the leading cardiac pacemaker and the atrioventricular (AV) junction as a subsidiary pacemaker. The regulatory mechanisms controlling the distribution of automaticity within the heart are not understood. To understand regional variation in cardiac automaticity, we carried out an in vivo analysis of cis-regulatory elements that control expression of the hyperpolarization-activated cyclic-nucleotide gated ion channel 4 (Hcn4). Using transgenic mice, we found that spatial and temporal patterning of Hcn4 expression in the AV conduction system required cis-regulatory elements with multiple conserved fragments. One highly conserved region, which contained a myocyte enhancer factor 2C (Mef2C) binding site previously described in vitro, induced reporter expression specifically in the embryonic non-chamber myocardium and the postnatal AV bundle in a Mef2c-dependent manner in vivo. Inhibition of histone deacetylase (HDAC) activity in cultured transgenic embryos showed expansion of reporter activity to working myocardium. In adult animals, hypertrophy induced by transverse aortic constriction, which causes translocation of HDACs out of the nucleus, resulted in ectopic activation of the Hcn4 enhancer in working myocardium, recapitulating pathological electrical remodeling. These findings reveal mechanisms that control the distribution of automaticity among cardiomyocytes during development and in response to stress.
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Affiliation(s)
- Vasanth Vedantham
- Gladstone Institute of Cardiovascular Disease, University of California, San Francisco, CA 94158, USA.
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Tbx2 and Tbx3 induce atrioventricular myocardial development and endocardial cushion formation. Cell Mol Life Sci 2011; 69:1377-89. [PMID: 22130515 PMCID: PMC3314179 DOI: 10.1007/s00018-011-0884-2] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2011] [Revised: 10/25/2011] [Accepted: 11/07/2011] [Indexed: 11/03/2022]
Abstract
A key step in heart development is the coordinated development of the atrioventricular canal (AVC), the constriction between the atria and ventricles that electrically and physically separates the chambers, and the development of the atrioventricular valves that ensure unidirectional blood flow. Using knock-out and inducible overexpression mouse models, we provide evidence that the developmentally important T-box factors Tbx2 and Tbx3, in a functionally redundant manner, maintain the AVC myocardium phenotype during the process of chamber differentiation. Expression profiling and ChIP-sequencing analysis of Tbx3 revealed that it directly interacts with and represses chamber myocardial genes, and induces the atrioventricular pacemaker-like phenotype by activating relevant genes. Moreover, mutant mice lacking 3 or 4 functional alleles of Tbx2 and Tbx3 failed to form atrioventricular cushions, precursors of the valves and septa. Tbx2 and Tbx3 trigger development of the cushions through a regulatory feed-forward loop with Bmp2, thus providing a mechanism for the co-localization and coordination of these important processes in heart development.
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Pallante BA, Giovannone S, Fang-Yu L, Zhang J, Liu N, Kang G, Dun W, Boyden PA, Fishman GI. Contactin-2 expression in the cardiac Purkinje fiber network. Circ Arrhythm Electrophysiol 2010; 3:186-94. [PMID: 20110552 DOI: 10.1161/circep.109.928820] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
BACKGROUND Purkinje cells (PCs) comprise the most distal component of the cardiac conduction system, and their unique electrophysiological properties and the anatomic complexity of the Purkinje fiber network may account for the prominent role these cells play in the genesis of various arrhythmic syndromes. METHODS AND RESULTS Differential transcriptional profiling of murine Purkinje fibers and working ventricular myocytes was performed to identify novel genes expressed in PCs. The most highly enriched transcript in Purkinje fibers encoded Contactin-2 (Cntn2), a cell adhesion molecule critical for neuronal patterning and ion channel clustering. Endogenous expression of Cntn2 in the murine ventricle was restricted to a subendocardial network of myocytes that also express beta-galactosidase in CCS-lacZ transgenic mice and the connexin40 gap junction protein. Both Cntn2-lacZ knockin mice and Cntn2-EGFP BAC transgenic reporter mice confirmed expression of Cntn2 in the Purkinje fiber network, as did immunohistochemical staining of single canine Purkinje fibers. Whole-cell patch-clamp recordings and measurements of Ca(2+) transients in Cntn2-EGFP(+) cells revealed electrophysiological properties indicative of PCs and distinctive from those of cardiac myocytes, including prolonged action potentials and frequent afterdepolarizations. CONCLUSIONS Cntn2 is a novel marker of the specialized cardiac conduction system. Endogenous expression of Cntn2 as well as Cntn2-dependent transcriptional reporters provides a new tool through which Purkinje cell biology and pathophysiology can now more readily be deciphered. Expression of a contactin family member within the CCS may provide a mechanistic basis for patterning of the conduction system network and the organization of ion channels within Purkinje cells.
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Affiliation(s)
- Benedetta A Pallante
- Leon H. Charney Division of Cardiology, NYU School of Medicine, New York, NY 10016, USA
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