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Perspective: a dynamics-based classification of ventricular arrhythmias. J Mol Cell Cardiol 2015; 82:136-52. [PMID: 25769672 DOI: 10.1016/j.yjmcc.2015.02.017] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Revised: 02/05/2015] [Accepted: 02/20/2015] [Indexed: 02/04/2023]
Abstract
Despite key advances in the clinical management of life-threatening ventricular arrhythmias, culminating with the development of implantable cardioverter-defibrillators and catheter ablation techniques, pharmacologic/biologic therapeutics have lagged behind. The fundamental issue is that biological targets are molecular factors. Diseases, however, represent emergent properties at the scale of the organism that result from dynamic interactions between multiple constantly changing molecular factors. For a pharmacologic/biologic therapy to be effective, it must target the dynamic processes that underlie the disease. Here we propose a classification of ventricular arrhythmias that is based on our current understanding of the dynamics occurring at the subcellular, cellular, tissue and organism scales, which cause arrhythmias by simultaneously generating arrhythmia triggers and exacerbating tissue vulnerability. The goal is to create a framework that systematically links these key dynamic factors together with fixed factors (structural and electrophysiological heterogeneity) synergistically promoting electrical dispersion and increased arrhythmia risk to molecular factors that can serve as biological targets. We classify ventricular arrhythmias into three primary dynamic categories related generally to unstable Ca cycling, reduced repolarization, and excess repolarization, respectively. The clinical syndromes, arrhythmia mechanisms, dynamic factors and what is known about their molecular counterparts are discussed. Based on this framework, we propose a computational-experimental strategy for exploring the links between molecular factors, fixed factors and dynamic factors that underlie life-threatening ventricular arrhythmias. The ultimate objective is to facilitate drug development by creating an in silico platform to evaluate and predict comprehensively how molecular interventions affect not only a single targeted arrhythmia, but all primary arrhythmia dynamics categories as well as normal cardiac excitation-contraction coupling.
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52
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Cardiac late Na+ current: Proarrhythmic effects, roles in long QT syndromes, and pathological relationship to CaMKII and oxidative stress. Heart Rhythm 2015; 12:440-8. [DOI: 10.1016/j.hrthm.2014.11.009] [Citation(s) in RCA: 105] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Indexed: 12/16/2022]
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53
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Morita N, Mandel WJ, Kobayashi Y, Karagueuzian HS. Cardiac fibrosis as a determinant of ventricular tachyarrhythmias. J Arrhythm 2014; 30:389-394. [PMID: 25642299 DOI: 10.1016/j.joa.2013.12.008] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Animal and emerging clinical studies have demonstrated that increased ventricular fibrosis in a setting of reduced repolarization reserve promotes early afterdepolarizations (EADs) and triggered activity that can initiate ventricular tachycardia and ventricular fibrillation (VT/VF). Increased ventricular fibrosis plays a key facilitatory role in allowing oxidative and metabolic stress-induced EADs to manifest as triggered activity causing VT/VF. The lack of such an arrhythmogenic effect by the same stressors in normal non-fibrotic hearts highlights the importance of fibrosis in the initiation of VT/VF. These findings suggest that antifibrotic therapy combined with therapy designed to increase ventricular repolarization reserve may act synergistically to reduce the risk of sudden cardiac death.
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Affiliation(s)
- Norishige Morita
- Division of Cardiology, Department of Medicine, Tokai University Hachioji Hospital, Tokyo, Japan
| | - William J Mandel
- Translational Arrhythmia Research Section, Division of Cardiology, Department of Medicine, David Geffen School of Medicine at UCLA, Los Angeles, California
| | - Yoshinori Kobayashi
- Division of Cardiology, Department of Medicine, Tokai University Hachioji Hospital, Tokyo, Japan
| | - Hrayr S Karagueuzian
- Division of Cardiology, Department of Medicine, Tokai University Hachioji Hospital, Tokyo, Japan
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Khwaounjoo P, Rutherford SL, Svrcek M, LeGrice IJ, Trew ML, Smaill BH. Image-Based Motion Correction for Optical Mapping of Cardiac Electrical Activity. Ann Biomed Eng 2014; 43:1235-46. [DOI: 10.1007/s10439-014-1172-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Accepted: 10/17/2014] [Indexed: 10/24/2022]
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Horvath B, Bers DM. The late sodium current in heart failure: pathophysiology and clinical relevance. ESC Heart Fail 2014; 1:26-40. [PMID: 28834665 DOI: 10.1002/ehf2.12003] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Revised: 07/13/2014] [Accepted: 07/14/2014] [Indexed: 12/19/2022] Open
Abstract
Large and growing body of data suggest that an increased late sodium current (INa,late ) can have a significant pathophysiological role in heart failure and other heart diseases. The first goal of this article is to describe how INa,late functions under physiological circumstances. The second goal is to show the wide range of cellular mechanisms that can increase INa,late in cardiac disease, and also to describe how the up-regulated INa,late contributes to the pathophysiology of heart failure. The final section of the article discusses the possible use of INa,late -modifying drugs in heart failure, on the basis of experimental and preclinical data.
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Affiliation(s)
- Balazs Horvath
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
- Faculty of Pharmacy, University of Debrecen, Debrecen, Hungary
| | - Donald M Bers
- Department of Pharmacology, School of Medicine, University of California, Davis, CA, USA
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56
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Xie C, Kauffman J, Akar FG. Functional crosstalk between the mitochondrial PTP and KATP channels determine arrhythmic vulnerability to oxidative stress. Front Physiol 2014; 5:264. [PMID: 25076913 PMCID: PMC4099963 DOI: 10.3389/fphys.2014.00264] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2014] [Accepted: 06/24/2014] [Indexed: 01/18/2023] Open
Abstract
Background: Mitochondrial permeability transition pore (mPTP) opening is a terminal event leading to mitochondrial dysfunction and cell death under conditions of oxidative stress (OS). However, mPTP blockade with cyclosporine A (CsA) has shown variable efficacy in limiting post-ischemic dysfunction and arrhythmias. We hypothesized that strong feedback between energy dissipating (mPTP) and cardioprotective (mKATP) channels determine vulnerability to OS. Methods and Results: Guinea pig hearts (N = 61) were challenged with H2O2 (200 μM) to elicit mitochondrial membrane potential (ΔΨm) depolarization. High-resolution optical mapping was used to measure ΔΨm or action potentials (AP) across the intact heart. Hearts were treated with CsA (0.1 μM) under conditions that altered the activity of mKATP channels either directly or indirectly via its regulation by protein kinase C. mPTP blockade with CsA markedly blunted (P < 0.01) OS-induced ΔΨm depolarization and delayed loss of LV pressure (LVP), but did not affect arrhythmia propensity. Surprisingly, prevention of mKATP activation with the chemical phosphatase BDM reversed the protective effect of CsA, paradoxically exacerbating OS-induced ΔΨm depolarization and accelerating arrhythmia onset in CsA treated compared to untreated hearts (P < 0.05). To elucidate the putative molecular mechanisms, mPTP inhibition by CsA was tested during conditions of selective PKC inhibition or direct mKATP channel activation or blockade. Similar to BDM, the specific PKC inhibitor, CHE (10 μM) did not alter OS-induced ΔΨm depolarization directly. However, it completely abrogated CsA-mediated protection against OS. Direct pharmacological blockade of mKATP, a mitochondrial target of PKC signaling, equally abolished the protective effect of CsA on ΔΨm depolarization, whereas channel activation with 30 μM Diazoxide protected against ΔΨm depolarization (P < 0.0001). Conditions that prevented mKATP activation either directly or indirectly via PKC inhibition led to accelerated ΔΨm depolarization and early onset of VF in response to OS. Investigation of the electrophysiological substrate revealed accelerated APD shortening in response to OS in arrhythmia-prone hearts. Conclusions: Cardioprotection by CsA requires mKATP channel activation through a PKC-dependent pathway. Increasing mKATP activity during CsA administration is required for limiting OS-induced electrical dysfunction.
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Affiliation(s)
- Chaoqin Xie
- Department of Medicine, Cardiovascular Institute, Mount Sinai School of Medicine New York, NY, USA
| | - Justin Kauffman
- Department of Medicine, Cardiovascular Institute, Mount Sinai School of Medicine New York, NY, USA
| | - Fadi G Akar
- Department of Medicine, Cardiovascular Institute, Mount Sinai School of Medicine New York, NY, USA
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Nieminen T, Scirica BM, Pegler JRM, Tavares C, Pagotto VPF, Kanas AF, Sobrado MF, Nearing BD, Umez-Eronini AA, Morrow DA, Belardinelli L, Verrier RL. Relation of T-wave alternans to mortality and nonsustained ventricular tachycardia in patients with non-ST-segment elevation acute coronary syndrome from the MERLIN-TIMI 36 trial of ranolazine versus placebo. Am J Cardiol 2014; 114:17-23. [PMID: 24852915 DOI: 10.1016/j.amjcard.2014.03.056] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Revised: 03/25/2014] [Accepted: 03/25/2014] [Indexed: 12/19/2022]
Abstract
We explored the utility of T-wave alternans (TWA) in predicting mortality in patients with non-ST-segment elevation acute coronary syndrome (NSTEACS). Maximum TWA was calculated using Modified Moving Average method from continuous electrocardiographic recordings in patients with left ventricular ejection fraction <40% and ventricular tachycardia (VT) ≥4 beats during index hospitalization or sudden cardiac death during the follow-up year and age- and sex-matched controls in the Metabolic Efficiency with Ranolazine for Less Ischemia in Non-ST Elevation Acute Coronary Syndrome-Thrombolysis In Myocardial Infarction (MERLIN-TIMI) 36 trial. All patients received standard therapy for NSTEACS plus ranolazine (n = 109) or placebo (n = 101). Median follow-up was 1 year. Baseline clinical characteristics did not differ between patients with elevated TWA (≥47 μV) compared with lower levels. Patients with TWA ≥47 μV at admission had increased risk of total mortality (adjusted odds ratio [ORadj] 2.35, p = 0.04) during follow-up and VT ≥4 beats (ORadj 2.70, p = 0.01) during hospitalization with a trend toward increased cardiovascular death risk (ORadj 2.18, p = 0.07) during follow-up. In patients receiving placebo, TWA ≥47 μV on day 6 was associated with increased risk of total mortality (OR 4.12, 95% confidence interval 1.25 to 13.64, p = 0.02) and cardiovascular death (OR 4.73, p = 0.01) during follow-up. No deaths occurred among patients with TWA ≥47 μV assigned to ranolazine. In conclusion, in patients with NSTEACS and left ventricular ejection fraction <40%, TWA ≥47 μV early after admission is associated with increased risk of mortality at 1 year and with nonsustained VT during hospitalization. TWA may be useful in risk estimation in patients with NSTEACS. The possibility that TWA may serve as a therapeutic target deserves further exploration.
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Affiliation(s)
- Tuomo Nieminen
- University of Helsinki and Department of Cardiology, Helsinki University Central Hospital, Helsinki, Finland; Division of Cardiovascular Medicine, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts; Harvard Medical School, Boston, Massachusetts
| | - Benjamin M Scirica
- Harvard Medical School, Boston, Massachusetts; Thrombolysis in Myocardial Infarction (TIMI) Study Group and Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts
| | - Jose R M Pegler
- Division of Cardiovascular Medicine, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts; Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil
| | - Caio Tavares
- Division of Cardiovascular Medicine, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts; Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil
| | - Vitor P F Pagotto
- Division of Cardiovascular Medicine, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts; Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil
| | - Alexandre F Kanas
- Division of Cardiovascular Medicine, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts; Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil
| | - Marcel F Sobrado
- Division of Cardiovascular Medicine, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts; Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil
| | - Bruce D Nearing
- Division of Cardiovascular Medicine, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts; Harvard Medical School, Boston, Massachusetts
| | - Amarachi A Umez-Eronini
- Thrombolysis in Myocardial Infarction (TIMI) Study Group and Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts
| | - David A Morrow
- Harvard Medical School, Boston, Massachusetts; Thrombolysis in Myocardial Infarction (TIMI) Study Group and Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts
| | | | - Richard L Verrier
- Division of Cardiovascular Medicine, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts; Harvard Medical School, Boston, Massachusetts.
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58
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Driessen HE, Bourgonje VJA, van Veen TAB, Vos MA. New antiarrhythmic targets to control intracellular calcium handling. Neth Heart J 2014; 22:198-213. [PMID: 24733689 PMCID: PMC4016334 DOI: 10.1007/s12471-014-0549-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Sudden cardiac death due to ventricular arrhythmias is a major problem. Drug therapies to prevent SCD do not provide satisfying results, leading to the demand for new antiarrhythmic strategies. New targets include Ca2+/Calmodulin-dependent protein kinase II (CaMKII), the Na/Ca exchanger (NCX), the Ryanodine receptor (RyR, and its associated protein FKBP12.6 (Calstabin)) and the late component of the sodium current (INa-Late), all related to intracellular calcium (Ca2+) handling. In this review, drugs interfering with these targets (SEA-0400, K201, KN-93, W7, ranolazine, sophocarpine, and GS-967) are evaluated and their future as clinical compounds is considered. These new targets prove to be interesting; however more insight into long-term drug effects is necessary before clinical applicability becomes reality.
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Affiliation(s)
- H E Driessen
- Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, Yalelaan 50, 3584 CM, Utrecht, the Netherlands,
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59
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Bunch TJ, Anderson JL. Adjuvant antiarrhythmic therapy in patients with implantable cardioverter defibrillators. Am J Cardiovasc Drugs 2014; 14:89-100. [PMID: 24288157 DOI: 10.1007/s40256-013-0056-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The risk of sudden cardiac death from ventricular fibrillation or ventricular tachycardia in patients with cardiomyopathy related to structural heart disease has been favorably impacted by the wide adaptation of implantable cardioverter defibrillators (ICDs) for both primary and secondary prevention. Unfortunately, after ICD implantation both appropriate and inappropriate ICD therapies are common. ICD shocks in particular can have significant effects on quality of life and disease-related morbidity and mortality. While not indicated for primary prevention of ICD therapies, beta-blockers and antiarrhythmic drugs are a cornerstone for secondary prevention of them. This review will summarize our current understanding of adjuvant antiarrhythmic drug therapy in ICD patients. The review will also discuss the roles of nonantiarrhythmic drug approaches that are used in isolation and in combination with antiarrhythmic drugs to reduce subsequent risk of ICD shocks.
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Affiliation(s)
- T Jared Bunch
- Intermountain Heart Institute, Intermountain Medical Center, Eccles Outpatient Care Center, 5169 Cottonwood St, Suite 510, Murray, UT, 84107, USA,
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60
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Sovari AA, Shroff A, Kocheril AG. Postinfarct cardiac remodeling and the substrate for sudden cardiac death: role of oxidative stress and myocardial fibrosis. Expert Rev Cardiovasc Ther 2014; 10:267-70. [DOI: 10.1586/erc.12.3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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61
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Corradi F, Paolini L, De Caterina R. Ranolazine in the prevention of anthracycline cardiotoxicity. Pharmacol Res 2014; 79:88-102. [DOI: 10.1016/j.phrs.2013.11.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/14/2013] [Revised: 11/06/2013] [Accepted: 11/06/2013] [Indexed: 12/19/2022]
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62
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Pezhouman A, Madahian S, Stepanyan H, Ghukasyan H, Qu Z, Belardinelli L, Karagueuzian HS. Selective inhibition of late sodium current suppresses ventricular tachycardia and fibrillation in intact rat hearts. Heart Rhythm 2013; 11:492-501. [PMID: 24291413 DOI: 10.1016/j.hrthm.2013.11.026] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/25/2013] [Indexed: 01/02/2023]
Abstract
BACKGROUND Enhanced late inward Na current (INa-L) modulates action potential duration (APD) and plays a key role in the genesis of early afterdepolarizations (EADs) and delayed afterdepolarizations (DADs) and triggered activity. OBJECTIVE The purpose of this study was to define the influence of selective block of INa-L on EAD- and DAD-mediated triggered ventricular tachycardia (VT) and ventricular fibrillation (VF) in intact hearts using (GS967), a selective and potent (IC50 = 0.13 ± 0.01 μM) blocker of INa-L. METHODS VT/VF were induced either by local aconitine injection (50 μg) in the left ventricular muscle of adult (3-4 months) male rats (N = 21) or by arterial perfusion of 0.1 mM hydrogen peroxide (H2O2) in aged male rats (24-26 months, N = 16). The left ventricular epicardial surface of the isolated-perfused hearts was optically mapped using fluorescent voltage-sensitive dye, and microelectrode recordings of action potentials were made adjacent to the aconitine injection site. The suppressive and preventive effects of GS967 (1 μM) against EAD/DAD-mediated VT/VF were then determined. RESULTS Aconitine induced VT in all 13 hearts studied. Activation map (N = 6) showed that the VT was initiated by a focal activity arising from the aconitine injection site (cycle length [CL] 84 ± 12) that degenerated to VF (CL 52 ± 8 ms) within a few seconds. VF was maintained by multifocal activity with occasional incomplete reentrant wavefronts. Administration of GS967 suppressed the VT/VF in 10 of 13 hearts (P < .001). Preexposure to GS967 for 15 minutes before aconitine injection prevented initiation of VT/VF in 5 of 8 additional hearts (P < .02). VF reoccurred within 10 minutes on washout of GS967. Microelectrode recordings (N = 7) showed that VT/VF was initiated by EAD- and DAD-mediated triggered activity at CL of 86 ± 14 ms (NS from VT CL) that preceded the VF. GS967 shortened APD, flattened the slope of the dynamic APD restitution curve, and reduced APD dispersion from 42 ± 12 ms to 8 ± 3 ms (P < .01). H2O2 perfusion in eight fibrotic aged hearts promoted EAD-mediated focal VT/VF, which was suppressed by GS967 in five hearts (P < .02). CONCLUSION The selective INa-L blocker GS967 effectively suppresses and prevents aconitine and oxidative stress-induced EADs, DADs, and focal VT/VF. Suppression of EADs, DADs, and reduction of APD dispersion make GS967 a potentially useful antiarrhythmic drug in conditions of enhanced INa-L.
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Affiliation(s)
- Arash Pezhouman
- Translational Arrhythmia Research Section, UCLA Cardiovascular Research Laboratory, Department of Medicine Division of Cardiology, David Geffen School of Medicine at UCLA, Los Angeles, California
| | - Sepideh Madahian
- Translational Arrhythmia Research Section, UCLA Cardiovascular Research Laboratory, Department of Medicine Division of Cardiology, David Geffen School of Medicine at UCLA, Los Angeles, California
| | - Hayk Stepanyan
- Translational Arrhythmia Research Section, UCLA Cardiovascular Research Laboratory, Department of Medicine Division of Cardiology, David Geffen School of Medicine at UCLA, Los Angeles, California
| | - Hayk Ghukasyan
- Translational Arrhythmia Research Section, UCLA Cardiovascular Research Laboratory, Department of Medicine Division of Cardiology, David Geffen School of Medicine at UCLA, Los Angeles, California
| | - Zhilin Qu
- Translational Arrhythmia Research Section, UCLA Cardiovascular Research Laboratory, Department of Medicine Division of Cardiology, David Geffen School of Medicine at UCLA, Los Angeles, California
| | | | - Hrayr S Karagueuzian
- Translational Arrhythmia Research Section, UCLA Cardiovascular Research Laboratory, Department of Medicine Division of Cardiology, David Geffen School of Medicine at UCLA, Los Angeles, California.
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63
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A Review of JACC Articles on the Topic of Heart Rhythm Disorders: 2011–2012. J Am Coll Cardiol 2013; 62:e451-e519. [DOI: 10.1016/j.jacc.2013.09.026] [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: 10/26/2022]
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64
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Li W, Wang YP, Gao L, Zhang PP, Zhou Q, Xu QF, Zhou ZW, Guo K, Chen RH, Yang HT, Li YG. Resveratrol protects rabbit ventricular myocytes against oxidative stress-induced arrhythmogenic activity and Ca2+ overload. Acta Pharmacol Sin 2013; 34:1164-73. [PMID: 23912472 DOI: 10.1038/aps.2013.82] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Accepted: 05/15/2013] [Indexed: 12/31/2022] Open
Abstract
AIM To investigate whether resveratrol suppressed oxidative stress-induced arrhythmogenic activity and Ca(2+) overload in ventricular myocytes and to explore the underlying mechanisms. METHODS Hydrogen peroxide (H2O2, 200 μmol/L)) was used to induce oxidative stress in rabbit ventricular myocytes. Cell shortening and calcium transients were simultaneously recorded to detect arrhythmogenic activity and to measure intracellular Ca(2+) ([Ca(2+)]i). Ca(2+)/calmodulin-dependent protein kinases II (CaMKII) activity was measured using a CaMKII kit or Western blotting analysis. Voltage-activated Na(+) and Ca(2+) currents were examined using whole-cell recording in myocytes. RESULTS H2O2 markedly prolonged Ca(2+) transient duration (CaTD), and induced early afterdepolarization (EAD)-like and delayed afterdepolarization (DAD)-like arrhythmogenic activity in myocytes paced at 0.16 Hz or 0.5 Hz. Application of resveratrol (30 or 50 μmol/L) dose-dependently suppressed H2O2-induced EAD-like arrhythmogenic activity and attenuated CaTD prolongation. Co-treatment with resveratrol (50 μmol/L) effectively prevented both EAD-like and DAD-like arrhythmogenic activity induced by H2O2. In addition, resveratrol markedly blunted H2O2-induced diastolic [Ca(2+)]i accumulation and prevented the myocytes from developing hypercontracture. In whole-cell recording studies, H2O2 significantly enhanced the late Na(+) current (I(Na,L)) and L-type Ca(2+) current (I(Ca,L)) in myocytes, which were dramatically suppressed or prevented by resveratrol. Furthermore, H2O2-induced ROS production and CaMKII activation were significantly prevented by resveratrol. CONCLUSION Resveratrol protects ventricular myocytes against oxidative stress-induced arrhythmogenic activity and Ca(2+) overload through inhibition of I(Na,L)/I(Ca,L), reduction of ROS generation, and prevention of CaMKII activation.
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Ling LH, Kalman JM, Ellims AH, Iles LM, Medi C, Sherratt C, Kaye DM, Hare JL, Kistler PM, Taylor AJ. Diffuse ventricular fibrosis is a late outcome of tachycardia-mediated cardiomyopathy after successful ablation. Circ Arrhythm Electrophysiol 2013; 6:697-704. [PMID: 23884195 DOI: 10.1161/circep.113.000681] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
BACKGROUND Successful arrhythmia ablation normalizes ejection fraction (EF) in tachycardia-mediated cardiomyopathy, but recurrent heart failure and late sudden death have been reported. The aim of this study was to characterize the left ventricle (LV) of tachycardia-mediated cardiomyopathy patients long after definitive arrhythmia cure. METHODS AND RESULTS Thirty-three patients with a history of successfully ablated incessant focal atrial tachycardia 64±36 months prior, and 20 healthy controls were recruited. At ablation, 18 patients had EF<50% (AT-low EF) that recovered within 3 months from 37±12 to 56±4% (P<0.001), whereas 15 patients had EF>55% (AT-normal EF). No subjects had EF of 50% to 55%. Subjects underwent echocardiography with speckle tracking and contrast-enhanced cardiac MRI with ventricular T1 mapping as an index of diffuse fibrosis. Contrast-enhanced cardiac MRI was performed using a clinical 1.5-T scanner and 0.2 mmol/kg gadolinium-diethylene triamine penta-acetic acid for contrast. Subject characteristics were similar across the 3 groups. Compared with AT-normal EF patients and controls, AT-low EF patients had lower EF (60±6 versus 64±4 and 65±4%; P<0.05), greater indexed LV end-diastolic volume (102±34 versus 84±14 and 85±16 mL/m(2); P<0.05), and greater indexed LV end-systolic volume (41±11 versus 31±7 and 30±8 mL/m(2); P<0.01) on contrast-enhanced cardiac MRI. Compared with controls, AT-low EF patients had reduced global LV corrected T1 time (442±53 versus 529±61; P<0.05) consistent with diffuse fibrosis. CONCLUSIONS Tachycardia-mediated cardiomyopathy patients exhibit differences in LV structure and function including diffuse fibrosis long after arrhythmia cure, indicating that recovery is incomplete.
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Affiliation(s)
- Liang-han Ling
- Alfred Hospital and Baker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia
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66
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Affiliation(s)
- Antonio Zaza
- Dipartimento di Biotecnologie e Bioscienze, Università degli Studi Milano-Bicocca, Milano, Italy,
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67
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Late sodium current inhibition in acquired and inherited ventricular (dys)function and arrhythmias. Cardiovasc Drugs Ther 2013; 27:91-101. [PMID: 23292167 DOI: 10.1007/s10557-012-6433-x] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The late sodium current has been increasingly recognized for its mechanistic role in various cardiovascular pathologies, including angina pectoris, myocardial ischemia, atrial fibrillation, heart failure and congenital long QT syndrome. Although relatively small in magnitude, the late sodium current (I(NaL)) represents a functionally relevant contributor to cardiomyocyte (electro)physiology. Many aspects of I(NaL) itself are as yet still unresolved, including its distribution and function in different cell types throughout the heart, and its regulation by sodium channel accessory proteins and intracellular signalling pathways. Its complexity is further increased by a close interrelationship with the peak sodium current and other ion currents, hindering the development of inhibitors with selective and specific properties. Thus, increased knowledge of the intricacies of the complex nature of I(NaL) during distinct cardiovascular conditions and its potential as a pharmacological target is essential. Here, we provide an overview of the functional and electrophysiological effects of late sodium current inhibition on the level of the ventricular myocyte, and its potential cardioprotective and anti-arrhythmic efficacy in the setting of acquired and inherited ventricular dysfunction and arrhythmias.
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Shryock JC, Song Y, Rajamani S, Antzelevitch C, Belardinelli L. The arrhythmogenic consequences of increasing late INa in the cardiomyocyte. Cardiovasc Res 2013; 99:600-11. [PMID: 23752976 DOI: 10.1093/cvr/cvt145] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
This review presents the roles of cardiac sodium channel NaV1.5 late current (late INa) in generation of arrhythmic activity. The assumption of the authors is that proper Na(+) channel function is necessary to the maintenance of the transmembrane electrochemical gradient of Na(+) and regulation of cardiac electrical activity. Myocyte Na(+) channels' openings during the brief action potential upstroke contribute to peak INa and initiate excitation-contraction coupling. Openings of Na(+) channels outside the upstroke contribute to late INa, a depolarizing current that persists throughout the action potential plateau. The small, physiological late INa does not appear to be critical for normal electrical or contractile function in the heart. Late INa does, however, reduce the net repolarizing current, prolongs action potential duration, and increases cellular Na(+) loading. An increase of late INa, due to acquired conditions (e.g. heart failure) or inherited Na(+) channelopathies, facilitates the formation of early and delayed afterpolarizations and triggered arrhythmias, spontaneous diastolic depolarization, and cellular Ca(2+) loading. These in turn increase the spatial and temporal dispersion of repolarization time and may lead to reentrant arrhythmias.
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Affiliation(s)
- John C Shryock
- Department of Biology, Cardiovascular Therapeutic Area, Gilead Sciences, Foster City, CA, USA
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69
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Trayanova NA, O'Hara T, Bayer JD, Boyle PM, McDowell KS, Constantino J, Arevalo HJ, Hu Y, Vadakkumpadan F. Computational cardiology: how computer simulations could be used to develop new therapies and advance existing ones. Europace 2013; 14 Suppl 5:v82-v89. [PMID: 23104919 DOI: 10.1093/europace/eus277] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
This article reviews the latest developments in computational cardiology. It focuses on the contribution of cardiac modelling to the development of new therapies as well as the advancement of existing ones for cardiac arrhythmias and pump dysfunction. Reviewed are cardiac modelling efforts aimed at advancing and optimizing existent therapies for cardiac disease (defibrillation, ablation of ventricular tachycardia, and cardiac resynchronization therapy) and at suggesting novel treatments, including novel molecular targets, as well as efforts to use cardiac models in stratification of patients likely to benefit from a given therapy, and the use of models in diagnostic procedures.
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Affiliation(s)
- Natalia A Trayanova
- Department of Biomedical Engineering, Institute for Computational Medicine, Johns Hopkins University, Baltimore, MD 21218, USA.
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70
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Qu Z, Xie LH, Olcese R, Karagueuzian HS, Chen PS, Garfinkel A, Weiss JN. Early afterdepolarizations in cardiac myocytes: beyond reduced repolarization reserve. Cardiovasc Res 2013; 99:6-15. [PMID: 23619423 DOI: 10.1093/cvr/cvt104] [Citation(s) in RCA: 119] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Early afterdepolarizations (EADs) are secondary voltage depolarizations during the repolarizing phase of the action potential, which can cause lethal cardiac arrhythmias. The occurrence of EADs requires a reduction in outward current and/or an increase in inward current, a condition called reduced repolarization reserve. However, this generalized condition is not sufficient for EAD genesis and does not explain the voltage oscillations manifesting as EADs. Here, we summarize recent progress that uses dynamical theory to build on and advance our understanding of EADs beyond the concept of repolarization reserve, towards the goal of developing a holistic and integrative view of EADs and their role in arrhythmogenesis. We first introduce concepts from nonlinear dynamics that are relevant to EADs, namely, Hopf bifurcation leading to oscillations and basin of attraction of an equilibrium or oscillatory state. We then present a theory of phase-2 EADs in nonlinear dynamics, which includes the formation of quasi-equilibrium states at the plateau voltage, their stabilities, and the bifurcations leading to and terminating the oscillations. This theory shows that the L-type calcium channel plays a unique role in causing the nonlinear dynamical behaviours necessary for EADs. We also summarize different mechanisms of phase-3 EADs. Based on the dynamical theory, we discuss the roles of each of the major ionic currents in the genesis of EADs, and potential therapeutic targets.
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Affiliation(s)
- Zhilin Qu
- Department of Medicine , David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA.
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71
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Winslow RL, Trayanova N, Geman D, Miller MI. Computational medicine: translating models to clinical care. Sci Transl Med 2013; 4:158rv11. [PMID: 23115356 DOI: 10.1126/scitranslmed.3003528] [Citation(s) in RCA: 119] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Because of the inherent complexity of coupled nonlinear biological systems, the development of computational models is necessary for achieving a quantitative understanding of their structure and function in health and disease. Statistical learning is applied to high-dimensional biomolecular data to create models that describe relationships between molecules and networks. Multiscale modeling links networks to cells, organs, and organ systems. Computational approaches are used to characterize anatomic shape and its variations in health and disease. In each case, the purposes of modeling are to capture all that we know about disease and to develop improved therapies tailored to the needs of individuals. We discuss advances in computational medicine, with specific examples in the fields of cancer, diabetes, cardiology, and neurology. Advances in translating these computational methods to the clinic are described, as well as challenges in applying models for improving patient health.
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Affiliation(s)
- Raimond L Winslow
- The Institute for Computational Medicine, Center for Cardiovascular Bioinformatics and Modeling, and Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD 21218, USA.
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72
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Maier LS, Sossalla S. The late Na current as a therapeutic target: where are we? J Mol Cell Cardiol 2013; 61:44-50. [PMID: 23500390 DOI: 10.1016/j.yjmcc.2013.03.001] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/11/2013] [Revised: 02/26/2013] [Accepted: 03/04/2013] [Indexed: 12/19/2022]
Abstract
In this article we review the late Na current which functionally can be measured using patch-clamp electrophysiology (INa,late). This current is largely enhanced under pathological myocardial conditions such as ischemia and heart failure. In addition, INa,late can cause systolic and diastolic contractile dysfunction via a Na-dependent Ca-overload of the myocyte. Moreover, INa,late plays a crucial role as ventricular and atrial proarrhythmic substrate in myocardial pathology by changing cellular electrophysiology. We summarize recent experimental and clinical studies that investigate therapeutic inhibition of this current and discuss the significance of the available data and try to answer not only the question, where we currently are but also where we may go in the near future. This article is part of a Special Issue entitled "Na(+) Regulation in Cardiac Myocytes".
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Affiliation(s)
- Lars S Maier
- Abt. Kardiologie und Pneumologie/Herzzentrum, Deutsches Zentrum für Herzkreislaufforschung, Georg-August-Universität, Göttingen, Germany.
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73
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Verrier RL, Kumar K, Nieminen T, Belardinelli L. Mechanisms of ranolazine's dual protection against atrial and ventricular fibrillation. Europace 2013; 15:317-24. [PMID: 23220484 PMCID: PMC3578672 DOI: 10.1093/europace/eus380] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2012] [Accepted: 10/22/2012] [Indexed: 12/19/2022] Open
Abstract
Coronary artery disease and heart failure carry concurrent risk for atrial fibrillation and life-threatening ventricular arrhythmias. We review evidence indicating that at therapeutic concentrations, ranolazine has potential for dual suppression of these arrhythmias. Mechanisms and clinical implications are discussed.
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Affiliation(s)
- Richard L Verrier
- Division of Cardiovascular Medicine, Harvard-Thorndike Electrophysiology Institute, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215-3908, USA.
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74
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Electrical storm: recent pathophysiological insights and therapeutic consequences. Basic Res Cardiol 2013; 108:336. [DOI: 10.1007/s00395-013-0336-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Revised: 01/29/2013] [Accepted: 02/04/2013] [Indexed: 01/01/2023]
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Karagueuzian HS, Stepanyan H, Mandel WJ. Bifurcation theory and cardiac arrhythmias. AMERICAN JOURNAL OF CARDIOVASCULAR DISEASE 2013; 3:1-16. [PMID: 23459417 PMCID: PMC3584649] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Received: 11/26/2012] [Accepted: 01/16/2013] [Indexed: 06/01/2023]
Abstract
In this paper we review two types of dynamic behaviors defined by the bifurcation theory that are found to be particularly useful in describing two forms of cardiac electrical instabilities that are of considerable importance in cardiac arrhythmogenesis. The first is action potential duration (APD) alternans with an underlying dynamics consistent with the period doubling bifurcation theory. This form of electrical instability could lead to spatially discordant APD alternans leading to wavebreak and reentrant form of tachyarrhythmias. Factors that modulate the APD alternans are discussed. The second form of bifurcation of importance to cardiac arrhythmogenesis is the Hopf-homoclinic bifurcation that adequately describes the dynamics of the onset of early afterdepolarization (EAD)-mediated triggered activity (Hopf) that may cause ventricular tachycardia and ventricular fibrillation (VT/VF respectively). The self-termination of the triggered activity is compatible with the homoclinic bifurcation. Ionic and intracellular calcium dynamics underlying these dynamics are discussed using available experimental and simulation data. The dynamic analysis provides novel insights into the mechanisms of VT/VF, a major cause of sudden cardiac death in the US.
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Affiliation(s)
- Hrayr S Karagueuzian
- Translational Arrhythmia Research Section, UCLA Cardiovascular Research Laboratory and the Division of Cardiology, Departments of Medicine David Geffen School of Medicine at UCLA Los Angeles, California
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Karagueuzian HS, Nguyen TP, Qu Z, Weiss JN. Oxidative stress, fibrosis, and early afterdepolarization-mediated cardiac arrhythmias. Front Physiol 2013; 4:19. [PMID: 23423152 PMCID: PMC3573324 DOI: 10.3389/fphys.2013.00019] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2012] [Accepted: 01/25/2013] [Indexed: 01/06/2023] Open
Abstract
Animal and clinical studies have demonstrated that oxidative stress, a common pathophysiological factor in cardiac disease, reduces repolarization reserve by enhancing the L-type calcium current, the late Na, and the Na-Ca exchanger, promoting early afterdepolarizations (EADs) that can initiate ventricular tachycardia and ventricular fibrillation (VT/VF) in structurally remodeled hearts. Increased ventricular fibrosis plays a key facilitatory role in allowing oxidative-stress induced EADs to manifest as triggered activity and VT/VF, since normal non-fibrotic hearts are resistant to arrhythmias when challenged with similar or higher levels of oxidative stress. The findings imply that antifibrotic therapy, in addition to therapies designed to suppress EAD formation at the cellular level, may be synergistic in reducing the risk of sudden cardiac death.
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Affiliation(s)
- Hrayr S Karagueuzian
- Cardiovascular Research Laboratory, Translational Arrhythmia Research Section, David Geffen School of Medicine at UCLA Los Angeles, CA, USA
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Abstract
Ranolazine is currently approved for use in chronic angina. The basis for this use is likely related to inhibition of late sodium channels with resultant beneficial downstream effects. Randomized clinical trials have demonstrated an improvement in exercise capacity and reduction in angina episodes with ranolazine. This therapeutic benefit occurs without the hemodynamic effects seen with the conventional antianginal agents. The inhibition of late sodium channels as well as other ion currents has a central role in the potential use of ranolazine in ischemic heart disease, arrhythmias, and heart failure. Despite its QTc-prolonging action, albeit minimal, clinical data have not shown a predisposition to torsades de pointes, and the medication has shown a reasonable safety profile even in those with structural heart disease. In this article we present the experimental and clinical data that support its current therapeutic role, and provide insight into potential future clinical applications.
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Affiliation(s)
- Nael Hawwa
- Internal Medicine Institute, Cleveland Clinic, Cleveland, OH 44195, USA
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78
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Abstract
The anti-arrhythmic efficacy of the late sodium channel current (late I(Na)) inhibition has been convincingly demonstrated in the ventricles, particularly under conditions of prolonged ventricular repolarization. The value of late I(Na) block in the setting of atrial fibrillation (AF) remains poorly investigated. All sodium channel blockers inhibit both peak and late I(Na) and are generally more potent in inhibiting late vs. early I(Na). Selective late I(Na) block does not prolong the effective refractory period (ERP), a feature common to practically all anti-AF agents. Although the late I(Na) blocker ranolazine has been shown to be effective in suppression of AF, it is noteworthy that at concentrations at which it blocks late I(Na) in the ventricles, it also potently blocks peak I(Na) in the atria, thus causing rate-dependent prolongation of ERP due to development of post-repolarization refractoriness. Late I(Na) inhibition in atria is thought to suppress intracellular calcium (Ca(i))-mediated triggered activity, secondary to a reduction in intracellular sodium (Na(i)). However, agents that block late I(Na) (ranolazine, amiodarone, vernakalant, etc) are also potent atrial-selective peak I(Na) blockers, so that the reduction of Na(i) loading in atrial cells by these agents can be in large part due to the block of peak I(Na). The impact of late I(Na) inhibition is reduced by the abbreviation of the action potential that occurs in AF patients secondary to electrical remodeling. It stands to reason that selective late I(Na) block may contribute more to inhibition of Ca(i)-mediated triggered activity responsible for initiation of AF in clinical pathologies associated with a prolonged atrial APD (such as long QT syndrome). Additional studies are clearly needed to test this hypothesis.
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79
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Coronary artery disease and ventricular tachyarrhythmia: pathophysiology and treatment. Curr Opin Pharmacol 2013; 13:210-7. [PMID: 23357129 DOI: 10.1016/j.coph.2013.01.001] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2012] [Revised: 01/04/2013] [Accepted: 01/07/2013] [Indexed: 01/01/2023]
Abstract
Ventricular tachyarrhythmias are common consequences of coronary artery disease. During the prehospital phase of acute myocardial infarction (MI), ischemia-induced electrophysiological changes and genetic factors are responsible for their occurrence, but the precise pathophysiologic mechanisms are ill-understood. Primary percutaneous coronary interventions (PCIs) have decreased the incidence of ventricular tachyarrhythmias during subsequent stages, and future treatments ameliorating reperfusion injury may provide further progress. In the chronic phase, antiarrhythmic drug therapy targeted toward arrhythmogenic substrate has relatively limited value, but alternative approaches are still uncertain. By contrast, prompt arrhythmia termination by implantable cardioverter-defibrillators (ICDs) is highly effective, although risk-stratification algorithms in candidate patients are inadequate. This review explores current views in the pathophysiology and treatment of ventricular tachyarrhythmias at different clinical stages.
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81
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Low doses of ranolazine and dronedarone in combination exert potent protection against atrial fibrillation and vulnerability to ventricular arrhythmias during acute myocardial ischemia. Heart Rhythm 2013; 10:121-7. [DOI: 10.1016/j.hrthm.2012.09.015] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/15/2012] [Indexed: 12/19/2022]
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82
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Frommeyer G, Rajamani S, Grundmann F, Stypmann J, Osada N, Breithardt G, Belardinelli L, Eckardt L, Milberg P. New Insights into the Beneficial Electrophysiologic Profile of Ranolazine in Heart Failure: Prevention of Ventricular Fibrillation With Increased Postrepolarization Refractoriness and Without Drug-Induced Proarrhythmia. J Card Fail 2012. [DOI: 10.1016/j.cardfail.2012.10.017] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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83
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Trayanova NA. Computational cardiology: the heart of the matter. ISRN CARDIOLOGY 2012; 2012:269680. [PMID: 23213566 PMCID: PMC3505657 DOI: 10.5402/2012/269680] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Accepted: 09/06/2012] [Indexed: 12/19/2022]
Abstract
This paper reviews the newest developments in computational cardiology. It focuses on the contribution of cardiac modeling to the development of new therapies as well as the advancement of existing ones for cardiac arrhythmias and pump dysfunction. Reviewed are cardiac modeling efforts aimed at advancing and optimizing existent therapies for cardiac disease (defibrillation, ablation of ventricular tachycardia, and cardiac resynchronization therapy) and at suggesting novel treatments, including novel molecular targets, as well as efforts to use cardiac models in stratification of patients likely to benefit from a given therapy, and the use of models in diagnostic procedures.
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Affiliation(s)
- Natalia A Trayanova
- Department of Biomedical Engineering and Institute for Computational Medicine, Johns Hopkins University, 3400 North Charles Street, Hackerman Hall Room 216, Baltimore, MD 21218, USA
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84
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Kujala K, Paavola J, Lahti A, Larsson K, Pekkanen-Mattila M, Viitasalo M, Lahtinen AM, Toivonen L, Kontula K, Swan H, Laine M, Silvennoinen O, Aalto-Setälä K. Cell model of catecholaminergic polymorphic ventricular tachycardia reveals early and delayed afterdepolarizations. PLoS One 2012; 7:e44660. [PMID: 22962621 PMCID: PMC3433449 DOI: 10.1371/journal.pone.0044660] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2012] [Accepted: 08/06/2012] [Indexed: 12/23/2022] Open
Abstract
Background Induced pluripotent stem cells (iPSC) provide means to study the pathophysiology of genetic disorders. Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a malignant inherited ion channel disorder predominantly caused by mutations in the cardiac ryanodine receptor (RyR2). In this study the cellular characteristics of CPVT are investigated and whether the electrophysiological features of this mutation can be mimicked using iPSC -derived cardiomyocytes (CM). Methodology/Principal Findings Spontaneously beating CMs were differentiated from iPSCs derived from a CPVT patient carrying a P2328S mutation in RyR2 and from two healthy controls. Calcium (Ca2+) cycling and electrophysiological properties were studied by Ca2+ imaging and patch-clamp techniques. Monophasic action potential (MAP) recordings and 24h-ECGs of CPVT-P2328S patients were analyzed for the presence of afterdepolarizations. We found defects in Ca2+ cycling and electrophysiology in CPVT CMs, reflecting the cardiac phenotype observed in the patients. Catecholaminergic stress led to abnormal Ca2+ signaling and induced arrhythmias in CPVT CMs. CPVT CMs also displayed reduced sarcoplasmic reticulum (SR) Ca2+ content, indicating leakage of Ca2+ from the SR. Patch-clamp recordings of CPVT CMs revealed both delayed afterdepolarizations (DADs) during spontaneous beating and in response to adrenaline and also early afterdepolarizations (EADs) during spontaneous beating, recapitulating the changes seen in MAP and 24h-ECG recordings of patients carrying the same mutation. Conclusions/Significance This cell model shows aberrant Ca2+ cycling characteristic of CPVT and in addition to DADs it displays EADs. This cell model for CPVT provides a platform to study basic pathology, to screen drugs, and to optimize drug therapy.
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Affiliation(s)
- Kirsi Kujala
- Institute of Biomedical Technology, University of Tampere, Tampere, Finland
- BioMediTech, Tampere, Finland
| | - Jere Paavola
- Institute of Biomedical Technology, University of Tampere, Tampere, Finland
- BioMediTech, Tampere, Finland
- Minerva Foundation Institute for Medical Research, Helsinki, Finland
| | - Anna Lahti
- Institute of Biomedical Technology, University of Tampere, Tampere, Finland
- BioMediTech, Tampere, Finland
| | - Kim Larsson
- Institute of Biomedical Technology, University of Tampere, Tampere, Finland
- BioMediTech, Tampere, Finland
| | - Mari Pekkanen-Mattila
- Institute of Biomedical Technology, University of Tampere, Tampere, Finland
- BioMediTech, Tampere, Finland
| | - Matti Viitasalo
- Department of Cardiology, Helsinki University Hospital, Helsinki, Finland
| | - Annukka M. Lahtinen
- Research Program’s Unit Molecular Medicine, University of Helsinki, Helsinki, Finland
| | - Lauri Toivonen
- Department of Cardiology, Helsinki University Hospital, Helsinki, Finland
| | - Kimmo Kontula
- Department of Medicine, University of Helsinki, Helsinki, Finland
| | - Heikki Swan
- Department of Medicine, University of Helsinki, Helsinki, Finland
| | - Mika Laine
- Minerva Foundation Institute for Medical Research, Helsinki, Finland
- Department of Cardiology, Helsinki University Hospital, Helsinki, Finland
| | - Olli Silvennoinen
- Institute of Biomedical Technology, University of Tampere, Tampere, Finland
- BioMediTech, Tampere, Finland
- Tampere University Hospital, Tampere, Finland
| | - Katriina Aalto-Setälä
- Institute of Biomedical Technology, University of Tampere, Tampere, Finland
- BioMediTech, Tampere, Finland
- Heart Center, Tampere, Finland
- * E-mail:
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Abstract
The late Na current is of pathophysiological importance for the heart. Ranolazine is an innovative anti-ischemic and antianginal agent that inhibits the late Na current, thereby reducing the Na-dependent Ca-overload, which improves diastolic tone and oxygen handling during myocardial ischemia. In addition, ranolazine seems to exert beneficial effects on diastolic cardiac function. Moreover, there are experimental and clinical data about its antiarrhythmic properties. A beneficial atrial selectivity of ranolazine has been suggested that may be helpful for the treatment of atrial fibrillation. The purpose of this review article is to discuss possible future clinical indications based on novel experimental and preclinical results and the significance of the available data.
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Affiliation(s)
- Lars S Maier
- Abteilung Kardiologie und Pneumologie/Herzzentrum, Deutsches Zentrum für Herzkreislaufforschung, Georg-August-Universität Göttingen, Robert-Koch-Strasse 40, 37075, Göttingen, Germany.
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86
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Roberts BN, Yang PC, Behrens SB, Moreno JD, Clancy CE. Computational approaches to understand cardiac electrophysiology and arrhythmias. Am J Physiol Heart Circ Physiol 2012; 303:H766-83. [PMID: 22886409 DOI: 10.1152/ajpheart.01081.2011] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Cardiac rhythms arise from electrical activity generated by precisely timed opening and closing of ion channels in individual cardiac myocytes. These impulses spread throughout the cardiac muscle to manifest as electrical waves in the whole heart. Regularity of electrical waves is critically important since they signal the heart muscle to contract, driving the primary function of the heart to act as a pump and deliver blood to the brain and vital organs. When electrical activity goes awry during a cardiac arrhythmia, the pump does not function, the brain does not receive oxygenated blood, and death ensues. For more than 50 years, mathematically based models of cardiac electrical activity have been used to improve understanding of basic mechanisms of normal and abnormal cardiac electrical function. Computer-based modeling approaches to understand cardiac activity are uniquely helpful because they allow for distillation of complex emergent behaviors into the key contributing components underlying them. Here we review the latest advances and novel concepts in the field as they relate to understanding the complex interplay between electrical, mechanical, structural, and genetic mechanisms during arrhythmia development at the level of ion channels, cells, and tissues. We also discuss the latest computational approaches to guiding arrhythmia therapy.
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Affiliation(s)
- Byron N Roberts
- Tri-Institutional MD-PhD Program, Physiology, Biophysics and Systems Biology Graduate Program, Weill Cornell Medical College/The Rockefeller University/Sloan-Kettering Cancer Institute, Weill Medical College of Cornell University, New York, New York, USA
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87
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Sovari AA, Dudley SC. Reactive oxygen species-targeted therapeutic interventions for atrial fibrillation. Front Physiol 2012; 3:311. [PMID: 22934062 PMCID: PMC3429082 DOI: 10.3389/fphys.2012.00311] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2012] [Accepted: 07/15/2012] [Indexed: 01/14/2023] Open
Abstract
Atrial fibrillation (AF) is the most common arrhythmia that requires medical attention, and its incidence is increasing. Current ion channel blockade therapies and catheter ablation have significant limitations in treatment of AF, mainly because they do not address the underlying pathophysiology of the disease. Oxidative stress has been implicated as a major underlying pathology that promotes AF; however, conventional antioxidants have not shown impressive therapeutic effects. A more careful design of antioxidant therapies and better selection of patients likely are required to treat effectively AF with antioxidant agents. Current evidence suggest inhibition of prominent cardiac sources of reactive oxygen species (ROS) such as nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and targeting subcellular compartments with the highest levels of ROS may prove to be effective therapies for AF. Increased serum markers of oxidative stress may be an important guide in selecting the AF patients who will most likely respond to antioxidant therapy.
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Affiliation(s)
- Ali A Sovari
- Section of Cardiology, Center for Cardiovascular Research, University of Illinois at Chicago Chicago, IL, USA
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88
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18β-Glycyrrhetinic acid preferentially blocks late Na current generated by ΔKPQ Nav1.5 channels. Acta Pharmacol Sin 2012; 33:752-60. [PMID: 22609834 DOI: 10.1038/aps.2012.22] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
AIM To compare the effects of two stereoisomeric forms of glycyrrhetinic acid on different components of Na(+) current, HERG and Kv1.5 channel currents. METHODS Wild-type (WT) and long QT syndrome type 3 (LQT-3) mutant ΔKPQ Nav1.5 channels, as well as HERG and Kv1.5 channels were expressed in Xenopus oocytes. In addition, isolated human atrial myocytes were used. Two-microelectrode voltage-clamp technique was used to record the voltage-activated currents. RESULTS Superfusion of 18β-glycyrrhetinic acid (18β-GA, 1-100 μmol/L) blocked both the peak current (I(Na,P)) and late current (I(Na,L)) generated by WT and ΔKPQ Nav1.5 channels in a concentration-dependent manner, while 18α-glycyrrhetinic acid (18α-GA) at the same concentrations had no effects. 18β-GA preferentially blocked I(Na,L) (IC(50)=37.2 ± 14.4 μmol/L) to I(Na,P) (IC(50)=100.4 ± 11.2 μmol/L) generated by ΔKPQ Nav1.5 channels. In human atrial myocytes, 18β-GA (30 μmol/L) inhibited 47% of I(Na,P) and 87% of I(Na,L) induced by Anemonia sulcata toxin (ATX-II, 30 nmol/L). Superfusion of 18β-GA (100 μmol/L) had no effects on HERG and Kv1.5 channel currents. CONCLUSION 18β-GA preferentially blocked the late Na current without affecting HERG and Kv1.5 channels.
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Tan VH, Yap J, Hsu, LF, Liew R. Catheter ablation of ventricular fibrillation triggers and electrical storm. Europace 2012; 14:1687-95. [DOI: 10.1093/europace/eus050] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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90
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Umar S, Lee JH, de Lange E, Iorga A, Partow-Navid R, Bapat A, van der Laarse A, Saggar R, Saggar R, Ypey DL, Karagueuzian HS, Eghbali M. Spontaneous ventricular fibrillation in right ventricular failure secondary to chronic pulmonary hypertension. Circ Arrhythm Electrophysiol 2011; 5:181-90. [PMID: 22199010 DOI: 10.1161/circep.111.967265] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
BACKGROUND Right ventricular failure (RVF) in pulmonary hypertension (PH) is associated with increased incidence of sudden death by a poorly explored mechanism. We test the hypothesis that PH promotes spontaneous ventricular fibrillation (VF) during a critical post-PH onset period characterized by a sudden increase in mortality. METHODS AND RESULTS Rats received either a single subcutaneous dose of monocrotaline (MCT, 60 mg/kg) to induce PH-associated RVF (PH, n=24) or saline (control, n=17). Activation pattern of the RV-epicardial surface was mapped using voltage-sensitive dye in isolated Langendorff-perfused hearts along with single glass-microelectrode and ECG-recordings. MCT-injected rats developed severe PH by day 21 and progressed to RVF by approximately day 30. Rats manifested increased mortality, and ≈30% rats died suddenly and precipitously during 23-32 days after MCT. This fatal period was associated with the initiation of spontaneous VF by a focal mechanism in the RV, which was subsequently maintained by both focal and incomplete reentrant wave fronts. Microelectrode recordings from the RV-epicardium at the onset of focal activity showed early afterdepolarization-mediated triggered activity that led to VF. The onset of the RV cellular triggered beats preceded left ventricular depolarizations by 23±8 ms. The RV but not the left ventricular cardiomyocytes isolated during this fatal period manifested significant action potential duration prolongation, dispersion, and an increased susceptibility to depolarization-induced repetitive activity. No spontaneous VF was observed in any of the control hearts. RVF was associated with significantly reduced RV ejection fraction (P<0.001), RV hypertrophy (P<0.001), and RV fibrosis (P<0.01). The hemodynamic function of the LV and its structure were preserved. CONCLUSIONS PH-induced RVF is associated with a distinct phase of increased mortality characterized by spontaneous VF arising from the RV by an early afterdepolarization-mediated triggered activity.
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Affiliation(s)
- Soban Umar
- Department of Anesthesiology, UCLA School of Medicine, BH-160CHS, 650 Charles Young Dr, Los Angeles, CA 90095-7115, USA.
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91
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Sossalla S, Maier LS. Role of ranolazine in angina, heart failure, arrhythmias, and diabetes. Pharmacol Ther 2011; 133:311-23. [PMID: 22133843 DOI: 10.1016/j.pharmthera.2011.11.003] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2011] [Accepted: 11/14/2011] [Indexed: 02/07/2023]
Abstract
Ranolazine which is currently approved as an antianginal agent reduces the Na-dependent Ca overload via inhibition of the late sodium current (late I(Na)) and thus improves diastolic tone and oxygen handling during myocardial ischemia. According to accumulating evidence ranolazine also exerts beneficial effects on diastolic and systolic heart failure where late I(Na) was also found to be elevated. Moreover, late I(Na) plays a crucial role as an arrhythmic substrate. Ranolazine has been described to have antiarrhythmic effects on ventricular as well as atrial arrhythmias without any proarrythmia or severe organ toxicity as it is common for several antiarrhythmic drugs. In patients with diabetes, treatment with ranolazine led to a significant improvement of glycemic control. In this article possible new clinical indications of the late I(Na)-inhibitor ranolazine are reviewed. We summarize novel experimental and clinical studies and discuss the significance of the available data.
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Affiliation(s)
- Samuel Sossalla
- Department of Cardiology & Pneumology, Georg-August-University Göttingen, Germany.
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92
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Sovari AA, Bonini MG, Dudley SC. Effective antioxidant therapy for the management of arrhythmia. Expert Rev Cardiovasc Ther 2011; 9:797-800. [PMID: 21809958 DOI: 10.1586/erc.11.85] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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93
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Tamargo J, Caballero R, Delpón E. Ranolazine: an antianginal drug with antiarrhythmic properties. Expert Rev Cardiovasc Ther 2011; 9:815-27. [PMID: 21809962 DOI: 10.1586/erc.11.91] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Ranolazine is an agent approved for the symptomatic treatment of chronic stable angina that inhibits the late inward sodium current (I(NaL)). I(NaL) amplitude is increased under several pathological conditions, including increased oxidative stress, myocardial ischemia, cardiac hypertrophy, heart failure, long-QT syndrome variant 3 and atrial fibrillation. Experimental and preliminary clinical evidence suggests that ranolazine may represent a new therapeutic strategy in the treatment of a broad spectrum of cardiac arrhythmias. This article reviews the role of the I(NaL) and provides an update on experimental and clinical evidence supporting the efficacy and safety of ranolazine across a broad spectrum of arrhythmias.
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Affiliation(s)
- Juan Tamargo
- Department of Pharmacology, School of Medicine, Universidad Complutense, 28040 Madrid, Spain.
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94
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BUNCH TJARED, MAHAPATRA SRIJOY, MURDOCK DAVID, MOLDEN JAMIE, WEISS JPETER, MAY HEIDIT, BAIR TAMIL, MADER KATYM, CRANDALL BRIANG, DAY JOHND, OSBORN JEFFREYS, MUHLESTEIN JOSEPHB, LAPPE DONALDL, ANDERSON JEFFREYL. Ranolazine Reduces Ventricular Tachycardia Burden and ICD Shocks in Patients with Drug-Refractory ICD Shocks. PACING AND CLINICAL ELECTROPHYSIOLOGY: PACE 2011; 34:1600-6. [DOI: 10.1111/j.1540-8159.2011.03208.x] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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95
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Biary N, Xie C, Kauffman J, Akar FG. Biophysical properties and functional consequences of reactive oxygen species (ROS)-induced ROS release in intact myocardium. J Physiol 2011; 589:5167-79. [PMID: 21825030 DOI: 10.1113/jphysiol.2011.214239] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Reactive oxygen species (ROS)-induced ROS release (RIRR) is a fundamental mechanism by which cardiac mitochondria respond to elevated ROS levels by stimulating endogenous ROS production in a regenerative, autocatalytic process that ultimately results in global oxidative stress (OS), cellular dysfunction and death. Despite elegant studies describing the phenomenon of RIRR under artificial conditions such as photo-induced oxidation of discrete regions within cardiomyocytes, the existence, biophysical properties and functional consequences of RIRR in intact myocardium remain unclear. Here, we used a semi-quantitative approach of optical superoxide (O(2)(-)) mapping using dihydroethidium (DHE) fluorescence to explore RIRR, its arrhythmic consequences and underlying mechanisms in intact myocardium. Initially, perfusion of rat hearts with 200 μM H(2)O(2) for 40 min (n = 4) elicited two distinct O(2)(-) peaks that were readily distinguished by their timing and amplitude. The first peak (P1), which was generated rapidly (within 5-8 min of H(2)O(2) perfusion) was associated with a relatively limited (10 ± 2%) rise in normalized O(2)(-) levels relative to baseline. In contrast, the second peak (P2) occurred 19-26 min following onset of H(2)O(2) perfusion and was associated with a significantly greater amplitude compared to P1. Spatio-temporal ROS mapping during P2 revealed active O(2)(-) propagation across the myocardium at a velocity of ~20 μm s(-1). Exposure of hearts (n = 18) to a short (10 min) episode of H(2)O(2) perfusion revealed consistent generation of P2 by high (≥200 μM, 8/8) but not lower (≤100 μM, 3/8) H(2)O(2) concentrations (P < 0.03). In these hearts, onset of P2 occurred following, not during, the 10 min OS protocol, consistent with RIRR. Importantly, P2 (+) hearts exhibited a markedly greater (by 3.8-fold, P < 0.001) arrhythmia score compared to P2 (-) hearts. To explore the mechanism underlying RIRR in intact myocardium, hearts were perfused with either cyclosporin A (CsA) or 4-chlorodiazepam (4-Cl-DZP) to inhibit the mitochondrial permeability transition pore (mPTP) or the inner membrane anion channel (IMAC), respectively. Surprisingly, perfusion with CsA failed to suppress (P = 0.75, n.s.) or even delay H(2)O(2)-induced P2 or the incidence of arrhythmias compared to untreated hearts. In sharp contrast, perfusion with 4-Cl-DZP markedly blunted O(2)(-) levels during P2, and suppressed the incidence of sustained ventricular tachycardia or ventricular fibrillation (VT/VF). Finally, perfusion of hearts with the synthetic superoxide dismutase/catalase mimetic EUK-134 completely abolished the H(2)O(2)-mediated RIRR response as well as the incidence of arrhythmias. These findings extend the concept of RIRR to the level of the intact heart, establish regenerative O(2)(-) production as the mediator of RIRR-related arrhythmias and reveal their strong dependence on IMAC and not the mPTP in this acute model of OS.
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Affiliation(s)
- Nora Biary
- Cardiovascular Institute, Department of Medicine, Mount Sinai School of Medicine, New York, NY 10029, USA
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96
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Karagueuzian HS. Targeting cardiac fibrosis: a new frontier in antiarrhythmic therapy? AMERICAN JOURNAL OF CARDIOVASCULAR DISEASE 2011; 1:101-109. [PMID: 22254191 PMCID: PMC3253497] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 05/12/2011] [Accepted: 05/29/2011] [Indexed: 05/31/2023]
Abstract
Cardiac fibrosis is known to alter cardiac conduction and promote reentry. Recent evidence indicates that fibrosis characterized by increased interstitial collagen accumulation and increased myofibroblast proliferation also promotes enhanced automaticity and early afterdepolarizations (EADs) causing triggered activity. Fibrosis then becomes an effective therapeutic target for the management of lethal cardiac arrhythmias. While oxidative stress with hydrogen peroxide (H(2)O(2)) is shown to readily promote EADs and triggered activity in isolated rat and rabbit ventricular myocytes however, this same stress fails to cause EADs in well-coupled, non-fibrotic hearts due to source-to-sink mismatches arising from cell-to-cell coupling. The triggered activity in the aged fibrotic hearts causes focal ventricular tachycardia (VT) that degenerates within seconds to ventricular fibrillation (VF) after the emergence of spatially discordant action potential duration alternans leading to wavebreak, reentry and VF. Computer simulations in 2D tissue incorporating variable degrees of fibrosis showed that intermediate (but not mild or very severe) fibrosis promoted EADs and TA. Human studies have shown that myocardial fibrosis was an independent predictor for arrhythmias including sustained VT and VF. A variety of drug classes including, torsemide, a loop diuretic, that inhibits the enzyme involved in the myocardial extracellular generation of collagen type I molecules and the inhibitors of the renin-angiotensin-aldosterone system (RAAS), the mineralocorticoid receptors and endothelin receptors reduce cardiac fibrosis with reduction of myocardial stiffness and improved ventricular function. It is hoped that in the near future effective antifibrotic drug regimen would be developed to reduce the risk of fibrosis related VT and VF.
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Affiliation(s)
- Hrayr S Karagueuzian
- Translational Arrhythmia Research Section, UCLA Cardiovascular Research Laboratory and the Division of Cardiology, Departments of Medicine, David Geffen School of Medicine at UCLA Los Angeles, California, USA
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97
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Morita N, Lee JH, Bapat A, Fishbein MC, Mandel WJ, Chen PS, Weiss JN, Karagueuzian HS. Glycolytic inhibition causes spontaneous ventricular fibrillation in aged hearts. Am J Physiol Heart Circ Physiol 2011; 301:H180-91. [PMID: 21478408 DOI: 10.1152/ajpheart.00128.2011] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Selective glycolytic inhibition (GI) promotes electromechanical alternans and triggered beats in isolated cardiac myocytes. We sought to determine whether GI promotes triggered activity by early afterdepolarization (EAD) or delayed afterdepolarizations in intact hearts isolated from adult and aged rats. Dual voltage and intracellular calcium ion (Ca(i)(2+)) fluorescent optical maps and single cell glass microelectrode recordings were made from the left ventricular (LV) epicardium of isolated Langendorff-perfused adult (∼4 mo) and aged (∼24 mo) rat hearts. GI was induced by replacing glucose with 10 mM pyruvate in oxygenated Tyrode's. Within 20 min, GI slowed Ca(i)(2+) transient decline rate and shortened action potential duration in both groups. These changes were associated with ventricular fibrillation (VF) in the aged hearts (64 out of 66) but not in adult hearts (0 out of 18; P < 0.001). VF was preceded by a transient period of focal ventricular tachycardia caused by EAD-mediated triggered activity leading to VF within seconds. The VF was suppressed by the ATP-sensitive K (K(ATP)) channel blocker glibenclamide (1 μM) but not (0 out of 7) by mitochondrial K(ATP) block. The Ca-calmodulin-dependent protein kinase II (CaMKII) blocker KN-93 (1 μM) prevented GI-mediated VF (P < 0.05). Block of Na-Ca exchanger (NCX) by SEA0400 (2 μM) prevented GI-mediated VF (3 out of 6), provided significant bradycardia did not occur. Aged hearts had significantly greater LV fibrosis and reduced connexin 43 than adult hearts (P < 0.05). We conclude that in aged fibrotic unlike in adult rat hearts, GI promotes EADs, triggered activity, and VF by activation of K(ATP) channels CaMKII and NCX.
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Affiliation(s)
- Norishige Morita
- Translational Arrhythmia Research Section, Cardiovascular Research Laboratory, David Geffen School of Medicine at UCLA, 675 Charles E. Young Dr. South, MRL 3645 Mail Code: 176022, Los Angeles, CA 90095, USA
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98
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Antzelevitch C, Burashnikov A, Sicouri S, Belardinelli L. Electrophysiologic basis for the antiarrhythmic actions of ranolazine. Heart Rhythm 2011; 8:1281-90. [PMID: 21421082 DOI: 10.1016/j.hrthm.2011.03.045] [Citation(s) in RCA: 178] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/23/2011] [Accepted: 03/11/2011] [Indexed: 12/19/2022]
Abstract
Ranolazine is a Food and Drug Administration-approved antianginal agent. Experimental and clinical studies have shown that ranolazine has antiarrhythmic effects in both ventricles and atria. In the ventricles, ranolazine can suppress arrhythmias associated with acute coronary syndrome, long QT syndrome, heart failure, ischemia, and reperfusion. In atria, ranolazine effectively suppresses atrial tachyarrhythmias and atrial fibrillation (AF). Recent studies have shown that the drug may be effective and safe in suppressing AF when used as a pill-in-the pocket approach, even in patients with structurally compromised hearts, warranting further study. The principal mechanism underlying ranolazine's antiarrhythmic actions is thought to be primarily via inhibition of late I(Na) in the ventricles and via use-dependent inhibition of peak I(Na) and I(Kr) in the atria. Short- and long-term safety of ranolazine has been demonstrated in the clinic, even in patients with structural heart disease. This review summarizes the available data regarding the electrophysiologic actions and antiarrhythmic properties of ranolazine in preclinical and clinical studies.
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99
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Antifibrillatory effect of ranolazine during severe coronary stenosis in the intact porcine model. Heart Rhythm 2010; 8:608-14. [PMID: 21094698 DOI: 10.1016/j.hrthm.2010.11.029] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/26/2010] [Accepted: 11/16/2010] [Indexed: 11/23/2022]
Abstract
BACKGROUND Clinical evidence suggests that the antianginal agent ranolazine has antiarrhythmic properties, but its effects on vulnerability to ventricular fibrillation (VF) and T-wave alternans (TWA) during coronary artery stenosis have not been measured. OBJECTIVE We investigated whether the antiarrhythmic effect of ranolazine during acute coronary stenosis could be quantified by measuring VF threshold and TWA magnitude. METHODS Electrode catheters placed in the left ventricular apex were used to determine VF threshold during ventricular pacing at 130 beats/min, and TWA was quantified from epicardial electrograms using modified moving average method (N = 18). Left anterior descending coronary flow was reduced with a balloon occluder by 75% for 10 minutes. The I(Kr) blocker E-4031 was used to distinguish effects of late I(Na) and I(Kr) inhibition by ranolazine. RESULTS Before stenosis, ranolazine and E-4031 increased VF threshold from 32 ± 4 mA to 46 ± 4 mA (mean ± SEM), P = .02, and from 33 ± 5 mA to 40 ± 9 mA, P = .02, respectively. During stenosis, ranolazine increased VF threshold from 19 ± 2 mA to 33 ± 3 mA (P = .02), whereas E-4031 decreased VF threshold from 21 ± 3 mA to 15 ± 3 mA (P = .02). The ischemia-induced increase in TWA was suppressed by ranolazine but not by E-4031, consistent with effects of these agents on VF threshold. CONCLUSION Ranolazine exerts significant antifibrillatory effects during coronary stenosis through direct effects on cardiac electrical properties independent of coronary flow. Ranolazine's antifibrillatory action during myocardial ischemia does not appear to be mediated by blockade of I(Kr) but rather by inhibition of late I(Na). TWA changes paralleled vulnerability to VF as indicated by VF threshold testing.
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