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Burashnikov A, Di Diego JM, Patocskai B, Echt DS, Belardinelli L, Antzelevitch C. Effect of Flecainide and Ibutilide Alone and in Combination to Terminate and Prevent Recurrence of Atrial Fibrillation. Circ Arrhythm Electrophysiol 2024; 17:e012454. [PMID: 38146652 DOI: 10.1161/circep.123.012454] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/06/2023] [Accepted: 11/30/2023] [Indexed: 12/27/2023]
Abstract
BACKGROUND There is a need for improved approaches to rhythm control therapy of atrial fibrillation (AF). METHODS The effectiveness of flecainide (1.5 µmol/L) and ibutilide (20 nmol/L), alone and in combination, to cardiovert and prevent AF recurrence was studied in canine-isolated coronary-perfused right atrioventricular preparations. We also examined the safety of the combination of flecainide (1.5 µmol/L) and ibutilide (50 nmol/L) using canine left ventricular wedge preparations. RESULTS Sustained AF (>1 hour) was inducible in 100%, 60%, 20%, and 0% of atria in the presence of acetylcholine alone, acetylcholine+ibutilide, acetylcholine+flecainide, and acetylcholine+ibutilide+flecainide, respectively. When used alone, flecainide and ibutilide cardioverted sustained AF in 40% and 20% of atria, respectively, but in 100% of atria when used in combination. Ibutilide prolonged atrial and ventricular effective refractory period by 15% and 8%, respectively, at a cycle length of 500 ms (P<0.05 for both). Flecainide increased the effective refractory period in atria by 27% (P<0.01) but by only 2% in the ventricles. The combination of the 2 drugs lengthened the effective refractory period by 42% in atria (P<0.01) but by only 7% (P<0.05) in the ventricles. In left ventricular wedges, ibutilide prolonged QT and Tpeak-Tend intervals by 25 and 55%, respectively (P<0.05 for both; cycle length, 2000 ms). The addition of flecainide (1.5 µmol/L) partially reversed these effects (P<0.05 for both parameters versus ibutilide alone). Torsades de Pointes score was relatively high with ibutilide alone and low with the drug combination. CONCLUSIONS In our experimental model, a combination of flecainide and ibutilide significantly improves cardioversion and prevents the recurrence of AF compared with monotherapies with little to no risk for the development of long-QT-mediated ventricular proarrhythmia.
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Affiliation(s)
- Alexander Burashnikov
- Lankenau Institute for Medical Research, Wynnewood, PA (A.B., J.M.D.D., B.P., C.A.)
- Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA (A.B., C.A.)
| | - José M Di Diego
- Lankenau Institute for Medical Research, Wynnewood, PA (A.B., J.M.D.D., B.P., C.A.)
| | - Bence Patocskai
- Lankenau Institute for Medical Research, Wynnewood, PA (A.B., J.M.D.D., B.P., C.A.)
| | - Debra S Echt
- InCarda Therapeutics, Inc, Newark, CA (D.S.E., L.B.)
| | | | - Charles Antzelevitch
- Lankenau Institute for Medical Research, Wynnewood, PA (A.B., J.M.D.D., B.P., C.A.)
- Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA (A.B., C.A.)
- Lankenau Heart Institute, Main Line Health System, Wynnewood, PA (C.A.)
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Burashnikov A, Antzelevitch C. Mild elevation of extracellular potassium greatly potentiates the effect of sodium channel block to cardiovert atrial fibrillation: The Lankenau approach. Heart Rhythm 2023; 20:1257-1264. [PMID: 37169158 DOI: 10.1016/j.hrthm.2023.05.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Revised: 05/03/2023] [Accepted: 05/03/2023] [Indexed: 05/13/2023]
Abstract
BACKGROUND Cardioversion of atrial fibrillation (AF) is a common clinical necessity, and there is a need for more effective and safe options for acute cardioversion of AF. OBJECTIVE The purpose of this study was to test the hypothesis that the efficacy and time course of AF cardioversion by sodium channel current (INa) block can be improved by mild elevation of extracellular potassium ([K+]0). METHODS Using a canine acetylcholine (ACh)-mediated AF model (isolated coronary-perfused right atrial preparations with a rim of right ventricle), we evaluated the ability of flecainide to suppress AF in the presence of [K+]0 ranging from 3 to 8 mM. RESULTS At [K+]0 of 4 mM (baseline), persistent AF (>1 hour) was induced in 5 of 5 atria in the presence of 0.5 μM ACh. Flecainide alone (1.5 μM) cardioverted 3 of 6 atria at 4 mM [K+]0, 1 of 6 atria at 3 mM [K+]0, 5 of 5 atria at 5 mM and 6 mM [K+]0, and 4 of 4 atria at 8 mM [K+]0. In the absence of flecainide, an increase in [K+]0 from 4 mM to 5, 6, and 8 mM terminated AF in 0 of 5, 2 of 6, and 4 of 4 atria, respectively. The time to conversion was also abbreviated by elevation of [K+]0. After AF termination with flecainide plus elevated [K+]0, AF was either not inducible or brief (<100 seconds). Combined flecainide and elevated [K+]0 (6 mM) caused an atrial preferential depression of excitability. CONCLUSION Our findings suggest that a combination of INa block accompanied by mild elevation of serum potassium may be a novel approach to more effectively, rapidly, and safely cardiovert AF and prevent its recurrence in the short term.
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Affiliation(s)
- Alexander Burashnikov
- Lankenau Institute for Medical Research, Wynnewood, Pennsylvania; Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania.
| | - Charles Antzelevitch
- Lankenau Institute for Medical Research, Wynnewood, Pennsylvania; Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania; Lankenau Heart Institute, Main Line Health System, Wynnewood, Pennsylvania
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Hu D, Barajas-Martinez H, Zhang ZH, Duan HY, Zhao QY, Bao MW, Du YM, Burashnikov A, Monasky MM, Pappone C, Huang CX, Antzelevitch C, Jiang H. Advances in basic and translational research in atrial fibrillation. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220174. [PMID: 37122214 PMCID: PMC10150218 DOI: 10.1098/rstb.2022.0174] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2023] Open
Abstract
Atrial fibrillation (AF) is a very common cardiac arrhythmia with an estimated prevalence of 33.5 million patients globally. It is associated with an increased risk of death, stroke and peripheral embolism. Although genetic studies have identified a growing number of genes associated with AF, the definitive impact of these genetic findings is yet to be established. Several mechanisms, including electrical, structural and neural remodelling of atrial tissue, have been proposed to contribute to the development of AF. Despite over a century of exploration, the molecular and cellular mechanisms underlying AF have not been fully established. Current antiarrhythmic drugs are associated with a significant rate of adverse events and management of AF using ablation is not optimal, especially in cases of persistent AF. This review discusses recent advances in our understanding and management of AF, including new concepts of epidemiology, genetics and pathophysiological mechanisms. We review the current status of antiarrhythmic drug therapy for AF, new potential agents, as well as mechanism-based AF ablation. This article is part of the theme issue 'The heartbeat: its molecular basis and physiological mechanisms'.
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Affiliation(s)
- Dan Hu
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan 430060, People's Republic of China
- Cardiovascular Research Institute of Wuhan University, Wuhan 430060, People's Republic of China
- Hubei Key Laboratory of Cardiology, Wuhan 430060, People's Republic of China
| | - Hector Barajas-Martinez
- Lankenau Institute for Medical Research, and Lankenau Heart Institute, Wynnwood, PA 19096, USA
- Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA 19104, USA
| | - Zhong-He Zhang
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan 430060, People's Republic of China
- Cardiovascular Research Institute of Wuhan University, Wuhan 430060, People's Republic of China
- Hubei Key Laboratory of Cardiology, Wuhan 430060, People's Republic of China
| | - Hong-Yi Duan
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan 430060, People's Republic of China
- Cardiovascular Research Institute of Wuhan University, Wuhan 430060, People's Republic of China
- Hubei Key Laboratory of Cardiology, Wuhan 430060, People's Republic of China
| | - Qing-Yan Zhao
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan 430060, People's Republic of China
- Cardiovascular Research Institute of Wuhan University, Wuhan 430060, People's Republic of China
- Hubei Key Laboratory of Cardiology, Wuhan 430060, People's Republic of China
| | - Ming-Wei Bao
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan 430060, People's Republic of China
- Cardiovascular Research Institute of Wuhan University, Wuhan 430060, People's Republic of China
- Hubei Key Laboratory of Cardiology, Wuhan 430060, People's Republic of China
| | - Yi-Mei Du
- Department of Cardiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, People's Republic of China
| | - Alexander Burashnikov
- Lankenau Institute for Medical Research, and Lankenau Heart Institute, Wynnwood, PA 19096, USA
- Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA 19104, USA
| | - Michelle M Monasky
- Arrhythmology Department, IRCCS Policlinico San Donato, San Donato Milanese, Milan 20097, Italy
| | - Carlo Pappone
- Arrhythmology Department, IRCCS Policlinico San Donato, San Donato Milanese, Milan 20097, Italy
- Vita-Salute San Raffaele University, Milan 20132, Italy
- Institute of Molecular and Translational Cardiology (IMTC), San Donato Milanese, Milan 20097, Italy
| | - Cong-Xin Huang
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan 430060, People's Republic of China
- Cardiovascular Research Institute of Wuhan University, Wuhan 430060, People's Republic of China
- Hubei Key Laboratory of Cardiology, Wuhan 430060, People's Republic of China
| | - Charles Antzelevitch
- Lankenau Institute for Medical Research, and Lankenau Heart Institute, Wynnwood, PA 19096, USA
- Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA 19104, USA
| | - Hong Jiang
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan 430060, People's Republic of China
- Cardiovascular Research Institute of Wuhan University, Wuhan 430060, People's Republic of China
- Hubei Key Laboratory of Cardiology, Wuhan 430060, People's Republic of China
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Burashnikov A. Atrial Fibrillation Induced by Anticancer Drugs and Underling Mechanisms. J Cardiovasc Pharmacol 2022; 80:540-546. [PMID: 34803149 PMCID: PMC10566596 DOI: 10.1097/fjc.0000000000001182] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Accepted: 11/11/2021] [Indexed: 11/26/2022]
Abstract
ABSTRACT Cancer therapy has made major progress in the past several decades, but treatments are often accompanied by significant side effects. Arrhythmias are a widespread complication of some antineoplastic drugs, with atrial fibrillation (AF) being the most often encountered drug-associated arrhythmia. Preexisting AF risk factors are commonly present in cancer patients who develop drug-associated AF, and active cancer itself may cause or promote AF. Although anticancer drugs may induce AF in cancer patients without AF risk factors, it appears that most drug-associated AF develop when cancer drugs add or aggravate precancer-existing and/or cancer-related pro-AF factors/alterations, additively or synergistically producing AF. Abnormalities in intracellular calcium activity seem to be involved in the generation of anticancer drug-induced AF. In cancer survivors with cancer therapy-induced cardiomyopathy, AF often occurs, with most of the arrhythmias likely to develop secondary to the cardiomyopathy. AF may lead to modification or even cessation of cancer therapy. The management of AF in patients with cancer is currently conducted largely based on pragmatic assumptions. This review briefly discusses AF caused by anticancer drugs and the underlying mechanisms.
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Affiliation(s)
- Alexander Burashnikov
- Lankenau Institute for Medical Research, Wynnewood, PA; and
- Sidney Kimmel College of Medicine, Thomas Jefferson University, Philadelphia, PA
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Burashnikov A. Depolarization of the atrial resting membrane potential as an approach to enhance the anti-atrial fibrillation efficacy of sodium channel blockers. Heart Rhythm 2021; 18:1221-1222. [PMID: 33785461 DOI: 10.1016/j.hrthm.2021.03.039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Accepted: 03/25/2021] [Indexed: 10/21/2022]
Affiliation(s)
- Alexander Burashnikov
- Lankenau Institute for Medical Research, Wynnewood, Pennsylvania, and Sidney Kimmel College of Medicine, Thomas Jefferson University, Philadelphia, Pennsylvania.
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Affiliation(s)
- Alexander Burashnikov
- From the Lankenau Institute for Medical Research (A.B., C.A.), Lankenau Heart Institute (C.A.), Wynnewood, PA; and Sidney Kimmel Medical College of Thomas Jefferson University, Philadelphia, PA (A.B.)
| | - Charles Antzelevitch
- From the Lankenau Institute for Medical Research (A.B., C.A.), Lankenau Heart Institute (C.A.), Wynnewood, PA; and Sidney Kimmel Medical College of Thomas Jefferson University, Philadelphia, PA (A.B.).
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Burashnikov A, Antzelevitch C. Is extensive atrial fibrosis in the setting of heart failure associated with a reduced atrial fibrillation burden? Pacing Clin Electrophysiol 2018; 41:1289-1297. [PMID: 30152017 DOI: 10.1111/pace.13474] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Revised: 08/07/2018] [Accepted: 08/16/2018] [Indexed: 01/30/2023]
Abstract
Atrial fibrillation (AF) affects 10-50% of patients with chronic heart failure (HF) and is associated with poor long-term prognosis. AF is commonly associated with atrial structural remodeling (ASR), principally characterized by atrial dilatation and fibrosis. However, the occurrence of AF in the full spectrum of ASR encountered in patients with HF is poorly defined. Experimental studies have presented evidence that extensive ASR can be accompanied with a reduced burden of AF, secondary to a prominent depression of atrial excitability. This reduction in AF burden is associated with severe atrial fibrosis rather than with dilatation. Clinical studies of patients with HF point to the possibility that advanced ASR is associated with a less frequent AF occurrence than moderate ASR. Our goal in this review is to introduce the hypothesis that AF is less likely to occur in severe versus moderate atrial ASR in the setting of HF and that it is severe atrial fibrosis-associated depression of atrial excitability that reduces AF burden.
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Affiliation(s)
- Alexander Burashnikov
- Lankenau Institute for Medical Research, Wynnewood, PA, USA.,Sidney Kimmel Medical College of Thomas Jefferson University, Philadelphia, PA, USA
| | - Charles Antzelevitch
- Lankenau Institute for Medical Research, Wynnewood, PA, USA.,Sidney Kimmel Medical College of Thomas Jefferson University, Philadelphia, PA, USA.,Lankenau Heart Institute, Main Line Health, Wynnewood, PA, USA
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Hu D, Barajas-Martínez H, Burashnikov A, Panama BK, Cordeiro JM, Antzelevitch C. Mechanisms underlying atrial-selective block of sodium channels by Wenxin Keli: Experimental and theoretical analysis. Int J Cardiol 2016; 207:326-34. [PMID: 26820362 DOI: 10.1016/j.ijcard.2016.01.016] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Revised: 12/29/2015] [Accepted: 01/01/2016] [Indexed: 12/19/2022]
Abstract
INTRODUCTION Atrial-selective inhibition of cardiac sodium channel current (INa) and INa-dependent parameters has been shown to contribute to the safe and effective management of atrial fibrillation. The present study was designed to examine the basis for the atrial-selective actions of Wenxin Keli. METHODS Whole cell INa was recorded at room temperature in canine atrial and ventricular myocytes. Trains of 40 pulses were elicited over a range of pulse durations and interpulse intervals to determine tonic and use-dependent block. A Markovian model for INa that incorporates interaction of Wenxin Keli with different states of the channel was developed to examine the basis for atrial selectivity of the drug. RESULTS Our data indicate that Wenxin Keli does not bind significantly to either closed or open states of the sodium channel, but binds very rapidly to the inactivated state of the channel and dissociates rapidly from the closed state. Action potentials recorded from atrial and ventricular preparations in the presence of 5g/L Wenxin Keli were introduced into the computer model in current clamp mode to simulate the effects on maximum upstroke velocity (Vmax). The model predicted much greater inhibition of Vmax in atrial vs. ventricular cells at rapid stimulation rates. CONCLUSION Our findings suggest that atrial selectivity of Wenxin Keli to block INa is due to more negative steady-state inactivation, less negative resting membrane potential, and shorter diastolic intervals in atrial vs. ventricular cells at rapid activation rates. These actions of Wenxin Keli account for its relatively safe and effective suppression of atrial fibrillation.
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Affiliation(s)
- Dan Hu
- Masonic Medical Research Laboratory, Utica, NY, United States
| | | | | | - Brian K Panama
- Masonic Medical Research Laboratory, Utica, NY, United States
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Burashnikov A, Di Diego JM, Goodrow RJ, Belardinelli L, Antzelevitch C. Atria are More Sensitive Than Ventricles to GS-458967-Induced Inhibition of Late Sodium Current. J Cardiovasc Pharmacol Ther 2015; 20:501-8. [PMID: 25652294 DOI: 10.1177/1074248415570636] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/07/2014] [Accepted: 12/12/2014] [Indexed: 01/06/2023]
Abstract
INTRODUCTION The differential response of atrial and ventricular cells to late sodium channel current (late INa) inhibition has not been thoroughly investigated. The aim of the present study was to compare the atrioventricular differences in electrophysiological actions of GS-458967, a potent late INa blocker. METHODS AND MATERIALS Canine coronary-perfused atrial and ventricular preparations and isolated ventricular myocytes were used. Transmembrane action potentials were recorded using standard microelectrode recording techniques. RESULTS In coronary-perfused preparations paced at a cycle length (CL) of 500 ms, GS-458967 (100-300 nmol/L) significantly abbreviated action potential duration at 50% to 90% (APD50-90) in atria but not in the ventricles. GS-458967 (≥100 nmol/L) prolonged the effective refractory period (ERP) in atria due to the development of postrepolarization refractoriness (PRR) but did not alter ERP in the ventricles. The maximum rate of rise in the action potential upstroke (Vmax) was significantly reduced at concentrations ≥100 nmol/L in atria but not in the ventricles (CL = 300 ms). At slower pacing rates (CL = 2000 ms) and higher concentrations, GS-458967 (100-1000 nmol/L) still failed to abbreviate ventricular APD. However, when APD was prolonged by the rapidly activating delayed rectifier potassium channel blocker E-4031 (1 µmol/L), addition of 1 μmol/L GS-458967 abbreviated APD in the ventricles at slow rates. In contrast, GS-458967 (300 nmol/L) consistently abbreviated APD in untreated isolated ventricular myocytes. CONCLUSION In canine coronary-perfused preparations, GS-458967 abbreviates APD, induces PRR, and reduces Vmax in atria but has no significant effect on these parameters in the ventricles, indicating an atrial-selective effect of GS-458967 on both peak and late INa-mediated parameters. In multicellular preparations, GS-458967 abbreviated ventricular APD only under long QT conditions, suggesting a pathology-specific action of GS-458967 in canine ventricular myocardium.
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Affiliation(s)
- Alexander Burashnikov
- Department of Experimental Cardiology, Masonic Medical Research Laboratory, Utica, NY, USA
| | - José M Di Diego
- Department of Experimental Cardiology, Masonic Medical Research Laboratory, Utica, NY, USA
| | - Robert J Goodrow
- Department of Experimental Cardiology, Masonic Medical Research Laboratory, Utica, NY, USA
| | - Luiz Belardinelli
- Department of Cardiovascular Therapeutics, Gilead Sciences, Inc, Foster City, CA, USA
| | - Charles Antzelevitch
- Department of Experimental Cardiology, Masonic Medical Research Laboratory, Utica, NY, USA
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Burashnikov A, Belardinelli L, Antzelevitch C. Inhibition of IKr potentiates development of atrial-selective INa block leading to effective suppression of atrial fibrillation. Heart Rhythm 2014; 12:836-44. [PMID: 25546810 DOI: 10.1016/j.hrthm.2014.12.033] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/22/2014] [Indexed: 12/19/2022]
Abstract
BACKGROUND The availability of safe and effective drugs for the management of atrial fibrillation (AF) remains an unmet medical need. OBJECTIVES The purpose of this study was to test the hypothesis that the inhibition of the rapidly activating delayed rectifier potassium current (IKr) greatly potentiates the development of atrial-selective sodium channel current (INa) block, leading to more effective suppression of AF. METHODS Electrophysiological and anti-AF effects of highly selective INa and IKr blockers (lidocaine and E-4031) individually and in combination were determined in canine coronary-perfused atrial and ventricular preparations. Acetylcholine (1 µM) was used to induce persistent AF. RESULTS Lidocaine (10 µM) caused a relatively small abbreviation of the action potential duration measured at 90% repolarization in both atria and ventricles, but caused atrial-selective prolongation of the effective refractory period owing to the induction of post-repolarization refractoriness. Lidocaine also caused modest atrial-selective depression of other INa-mediated parameters including excitability, maximum rate of rise of the action potential upstroke, and conduction time. E-4031 (1 µM) prolonged the action potential duration measured at 90% repolarization and effective refractory period in an atrial-predominant manner. A combination of lidocaine and E-4031 caused a greater atrial-selective depression of INa-mediated parameters. Persistent acetylcholine-mediated AF developed in 100% of atria under control conditions, in 80% (4 of 5) after pretreatment with lidocaine (10 µM), in 100% (4 of 4) after E-4031 (1 µM), and in only 14% (1 of 7) after the combination of lidocaine and E-4031. CONCLUSION Our results provide a proof of concept that IKr block greatly potentiates the effects of rapidly dissociating INa blockers to depress sodium channel-dependent parameters in the canine atria but not in the ventricles, thus contributing significantly to suppression of AF.
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Burashnikov A, Di Diego JM, Barajas-Martínez H, Hu D, Zygmunt AC, Cordeiro JM, Moise NS, Kornreich BG, Belardinelli L, Antzelevitch C. Ranolazine effectively suppresses atrial fibrillation in the setting of heart failure. Circ Heart Fail 2014; 7:627-33. [PMID: 24874201 DOI: 10.1161/circheartfailure.114.001129] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
BACKGROUND There is a critical need for safer and more effective pharmacological management of atrial fibrillation (AF) in the setting of heart failure (HF). METHODS AND RESULTS This study investigates the electrophysiological, antiarrhythmic, and proarrhythmic effects of a clinically relevant concentration of ranolazine (5 μmol/L) in coronary-perfused right atrial and left ventricular preparations isolated from the hearts of HF dogs. HF was induced by ventricular tachypacing (2-6 weeks at 200-240 beats per minute; n=17). Transmembrane action potentials were recorded using standard microelectrode techniques. In atria, ranolazine slightly prolonged action potential duration but significantly depressed sodium channel current-dependent parameters causing a reduction of maximum rate of rise of the action potential upstroke, a prolongation of the effective refractory period secondary to the development of postrepolarization refractoriness, and an increase in diastolic threshold of excitation and atrial conduction time. Ranolazine did not significantly alter these parameters or promote arrhythmias in the ventricles. Ranolazine produced greater inhibition of peak sodium channel current in atrial cells isolated from HF versus normal dogs. A single premature beat reproducibly induced self-terminating AF in 10 of 17 atria. Ranolazine (5 μmol/L) suppressed induction of AF in 7 of 10 (70%) atria. In the remaining 3 atria, ranolazine reduced frequency and duration of AF. CONCLUSIONS Our results demonstrate more potent suppression of AF by ranolazine in the setting of HF than previously demonstrated in nonfailing hearts and absence of ventricular proarrhythmia. The data suggest that ranolazine may be of benefit as an alternative to amiodarone and dofetilide in the management of AF in patients with HF.
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Affiliation(s)
- Alexander Burashnikov
- From the Masonic Medical Research Laboratory, Utica, NY (A.B., J.M.D.D., H.B.-M., D.H., A.C.Z., J.M.C., C.A.); Department of Clinical and Biological Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY (N.S.M., B.G.K.); and Gilead Sciences, Foster City, CA (L.B.).
| | - José M Di Diego
- From the Masonic Medical Research Laboratory, Utica, NY (A.B., J.M.D.D., H.B.-M., D.H., A.C.Z., J.M.C., C.A.); Department of Clinical and Biological Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY (N.S.M., B.G.K.); and Gilead Sciences, Foster City, CA (L.B.)
| | - Hector Barajas-Martínez
- From the Masonic Medical Research Laboratory, Utica, NY (A.B., J.M.D.D., H.B.-M., D.H., A.C.Z., J.M.C., C.A.); Department of Clinical and Biological Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY (N.S.M., B.G.K.); and Gilead Sciences, Foster City, CA (L.B.)
| | - Dan Hu
- From the Masonic Medical Research Laboratory, Utica, NY (A.B., J.M.D.D., H.B.-M., D.H., A.C.Z., J.M.C., C.A.); Department of Clinical and Biological Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY (N.S.M., B.G.K.); and Gilead Sciences, Foster City, CA (L.B.)
| | - Andrew C Zygmunt
- From the Masonic Medical Research Laboratory, Utica, NY (A.B., J.M.D.D., H.B.-M., D.H., A.C.Z., J.M.C., C.A.); Department of Clinical and Biological Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY (N.S.M., B.G.K.); and Gilead Sciences, Foster City, CA (L.B.)
| | - Jonathan M Cordeiro
- From the Masonic Medical Research Laboratory, Utica, NY (A.B., J.M.D.D., H.B.-M., D.H., A.C.Z., J.M.C., C.A.); Department of Clinical and Biological Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY (N.S.M., B.G.K.); and Gilead Sciences, Foster City, CA (L.B.)
| | - N Sydney Moise
- From the Masonic Medical Research Laboratory, Utica, NY (A.B., J.M.D.D., H.B.-M., D.H., A.C.Z., J.M.C., C.A.); Department of Clinical and Biological Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY (N.S.M., B.G.K.); and Gilead Sciences, Foster City, CA (L.B.)
| | - Bruce G Kornreich
- From the Masonic Medical Research Laboratory, Utica, NY (A.B., J.M.D.D., H.B.-M., D.H., A.C.Z., J.M.C., C.A.); Department of Clinical and Biological Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY (N.S.M., B.G.K.); and Gilead Sciences, Foster City, CA (L.B.)
| | - Luiz Belardinelli
- From the Masonic Medical Research Laboratory, Utica, NY (A.B., J.M.D.D., H.B.-M., D.H., A.C.Z., J.M.C., C.A.); Department of Clinical and Biological Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY (N.S.M., B.G.K.); and Gilead Sciences, Foster City, CA (L.B.)
| | - Charles Antzelevitch
- From the Masonic Medical Research Laboratory, Utica, NY (A.B., J.M.D.D., H.B.-M., D.H., A.C.Z., J.M.C., C.A.); Department of Clinical and Biological Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY (N.S.M., B.G.K.); and Gilead Sciences, Foster City, CA (L.B.).
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Burashnikov A, Di Diego JM, Sicouri S, Doss MX, Sachinidis A, Barajas-Martínez H, Hu D, Minoura Y, Sydney Moise N, Kornreich BG, Chi L, Belardinelli L, Antzelevitch C. A temporal window of vulnerability for development of atrial fibrillation with advancing heart failure. Eur J Heart Fail 2014; 16:271-80. [PMID: 24464846 DOI: 10.1002/ejhf.28] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/10/2013] [Revised: 09/18/2013] [Accepted: 10/04/2013] [Indexed: 12/11/2022] Open
Abstract
AIMS Heart failure (HF) is associated with development of AF and life-threatening ventricular tachycardia and fibrillation (VT/VF). Vulnerability to development of AF and VT/VF at different stages of HF and the underlying pathophysiological mechanisms are poorly defined. The present study was designed to determine the time-course of development of electrical and structural remodelling of the atria and ventricles, and their contribution to induction of AF and VT/VF in a canine model of HF. METHODS AND RESULTS Dogs were ventricular tachypaced (VTP) for 2-3 weeks or 5-6 weeks ('early' and 'late' HF, respectively). Electrophysiological studies were performed in isolated atrial and ventricular preparations and correlated with cardiac dimensions and haemodynamic parameters recorded in vivo. Vulnerability to programmed electrical stimulation-induced AF was greater in early vs. late stages of HF (78% vs. 38%). In contrast, VT/VF was inducible in late but not in early stages of HF (38% vs. 0%). The temporal distinction in atrial and ventricular arrhythmia susceptibility was associated with a much more rapid development of electrical and structural remodelling in atria. Vulnerability to AF developed following moderate electro-structural remodelling and waned with further progression to severe remodelling, which averted rapid atrial activation. CONCLUSIONS A temporal window of vulnerability for AF appears relatively early during development of VTP-induced HF in dogs, whereas VT/VF vulnerability is observed at more advanced stages of HF. These findings, if confirmed in humans, may have clinical implications with regard to prognosis and approach to therapy of patients with HF.
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Cordeiro JM, Panama BK, Goodrow R, Zygmunt AC, White C, Treat JA, Zeina T, Nesterenko VV, Di Diego JM, Burashnikov A, Antzelevitch C. Developmental changes in expression and biophysics of ion channels in the canine ventricle. J Mol Cell Cardiol 2013; 64:79-89. [PMID: 24035801 DOI: 10.1016/j.yjmcc.2013.09.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/02/2013] [Revised: 08/12/2013] [Accepted: 09/02/2013] [Indexed: 11/17/2022]
Abstract
BACKGROUND Developmental changes in the electrical characteristics of the ventricular myocardium are not well defined. This study examines the contribution of inwardly rectifying K(+) current (IK1), transient outward K(+) current (Ito), delayed rectifier K(+) currents (IKr and IKs) and sodium channel current (INa) to repolarization in the canine neonate myocardium. METHODS Single myocytes isolated from the left ventricle of 2-3week old canine neonate hearts were studied using patch-clamp techniques. RESULTS Neonate cells were ~6-fold smaller than those of adults (28.8±8.8 vs. 176±6.7pF). IK1 was larger in neonate myocytes and displayed a substantial inward component and an outward component with negative slope conductance, peaking at -60mV (4.13 pA/pF). IKr tail currents (at -40mV), were small (<20pA). IKs could not be detected, even after exposure to isoproterenol (100nM). Ito was also absent in the neonate, consistent with the absence of a phase 1 in the action potential. Peak INa, late INa and ICa were smaller in the neonate compared with adults. KCND3, KCNIP2 and KCNQ1 mRNA expression was half, while KCNH2 was equal and KCNJ2 was greater in the neonate when compared with adults. CONCLUSIONS Two major repolarizing K(+) currents (IKs and Ito) present in adult ventricular cells are absent in the 2week old neonate. Peak and late INa are significantly smaller in the neonate. Our results suggest that the absence of these two currents in the neonate heart may increase the susceptibility to arrhythmias under certain long QT conditions.
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Affiliation(s)
- Jonathan M Cordeiro
- Department of Experimental Cardiology, Masonic Medical Research Laboratory, 2150 Bleecker St., Utica, NY 13501, USA.
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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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Burashnikov A, Di Diego J, Moise N, Kornreich B, Belardinelli L, Antzelevitch C. Ranolazine Causes Atrial-Selective Electrophysiological Effects and Suppresses the Induction of Atrial Fibrillation in a Canine Model of Heart Failure. Heart Rhythm 2012. [DOI: 10.1016/j.hrthm.2012.09.103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Abstract
Postoperative atrial fibrillation (AF) is a major complication of cardiothoracic surgery, leading to significant consequences, including a higher rate of stroke, longer hospital stays and increased costs. Amiodarone is among the most widely used agents for prevention of postoperative AF. Ranolazine, a US FDA-approved antianginal agent, has been shown to effectively, safely prevent and terminate nonpostoperative AF in both experimental and clinical studies. In a recent publication, Miles and colleagues directly compared the efficacy and safety of amiodarone and ranolazine for prevention of postoperative AF in 393 patients. The patients were pretreated with amiodarone and ranolaizne for >1 week and 1 day, respectively, and the treatment continued for 10-14 days after surgery. Following coronary artery bypass grafting (CABG), AF occurred in 26.5% of patients taking amiodarone and in 17.5% of patients taking ranolazine (34% reduction; p < 0.035). No differences in adverse events between the two groups of patients were recorded. The results of this retrospective nonrandomized single-center study indicate that ranolazine may be used to effectively and safely prevent postoperative AF. These results need to be confirmed in a larger randomized study. If confirmed, ranolazine may be a good choice for preventing AF in patients undergoing CABG.
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Affiliation(s)
- Alexander Burashnikov
- Gordon K Moe Scholar, Masonic Medical Research Laboratory, 2150 Bleecker St, Utica, NY 13501, USA
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Burashnikov A, Pourrier M, Gibson JK, Lynch JJ, Antzelevitch C. Rate-dependent effects of vernakalant in the isolated non-remodeled canine left atria are primarily due to block of the sodium channel: comparison with ranolazine and dl-sotalol. Circ Arrhythm Electrophysiol 2012; 5:400-8. [PMID: 22322366 DOI: 10.1161/circep.111.968305] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
BACKGROUND Several clinical trials have shown that vernakalant is effective in terminating recent onset atrial fibrillation (AF). The electrophysiological actions of vernakalant are not fully understood. METHODS AND RESULTS Here we report the results of a blinded study comparing the in vitro canine atrial electrophysiological effects of vernakalant, ranolazine, and dl-sotalol. Action potential durations (APD(50,75,90)), effective refractory period (ERP), post repolarization refractoriness (PRR), maximum rate of rise of the action potential (AP) upstroke (V(max)), diastolic threshold of excitation (DTE), conduction time (CT), and the shortest S(1)-S(1) permitting 1:1 activation (S(1)-S(1)) were measured using standard stimulation and microelectrode recording techniques in isolated normal, non-remodeled canine arterially perfused left atrial preparations. Vernakalant caused variable but slight prolongation of APD(90) (P=not significant), but significant prolongation of APD(50) at 30 μmol/L and rapid rates. In contrast, ranolazine and dl-sotalol produced consistent concentration- and reverse rate-dependent prolongation of APD(90). Vernakalant and ranolazine caused rate-dependent, whereas dl-sotalol caused reverse rate-dependent, prolongation of ERP. Significant rate-dependent PRR developed with vernakalant and ranolazine, but not with dl-sotalol. Other sodium channel-mediated parameters (ie, V(max), CT, DTE, and S(1)-S(1)) also were depressed significantly by vernakalant and ranolazine, but not by dl-sotalol. Only vernakalant elevated AP plateau voltage, consistent with blockade of ultrarapid delayed rectified potassium current and transient outward potassium current. CONCLUSIONS In isolated canine left atria, the effects of vernakalant and ranolazine were characterized by use-dependent inhibition of sodium channel-mediated parameters, and those of dl-sotalol by reverse rate-dependent prolongation of APD(90) and ERP. This suggests that during the rapid activation rates of AF, the I(Na) blocking action of the mixed ion channel blocker vernakalant takes prominence. This mechanism may explain vernakalant's anti-AF efficacy.
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Burashnikov A, Antzelevitch C. Novel pharmacological targets for the rhythm control management of atrial fibrillation. Pharmacol Ther 2011; 132:300-13. [PMID: 21867730 PMCID: PMC3205214 DOI: 10.1016/j.pharmthera.2011.08.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2011] [Accepted: 08/05/2011] [Indexed: 12/19/2022]
Abstract
Atrial fibrillation (AF) is a growing clinical problem associated with increased morbidity and mortality. Development of safe and effective pharmacological treatments for AF is one of the greatest unmet medical needs facing our society. In spite of significant progress in non-pharmacological AF treatments (largely due to the use of catheter ablation techniques), anti-arrhythmic agents (AADs) remain first line therapy for rhythm control management of AF for most AF patients. When considering efficacy, safety and tolerability, currently available AADs for rhythm control of AF are less than optimal. Ion channel inhibition remains the principal strategy for termination of AF and prevention of its recurrence. Practical clinical experience indicates that multi-ion channel blockers are generally more optimal for rhythm control of AF compared to ion channel-selective blockers. Recent studies suggest that atrial-selective sodium channel block can lead to safe and effective suppression of AF and that concurrent inhibition of potassium ion channels may potentiate this effect. An important limitation of the ion channel block approach for AF treatment is that non-electrical factors (largely structural remodeling) may importantly determine the generation of AF, so that "upstream therapy", aimed at preventing or reversing structural remodeling, may be required for effective rhythm control management. This review focuses on novel pharmacological targets for the rhythm control management of AF.
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Burashnikov A, Belardinelli L, Antzelevitch C. Atrial-selective sodium channel block strategy to suppress atrial fibrillation: ranolazine versus propafenone. J Pharmacol Exp Ther 2011; 340:161-8. [PMID: 22005044 DOI: 10.1124/jpet.111.186395] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Ranolazine has been shown to produce atrial-selective depression of sodium channel-dependent parameters and suppress atrial fibrillation (AF) in a variety of experimental models. The present study contrasts the effects of ranolazine and those of a clinically used anti-AF class IC agent, propafenone. Electrophysiological and anti-AF effects of propafenone and ranolazine were compared at clinically relevant concentrations (i.e., 0.3-1.5 and 1-10 μM, respectively) in canine isolated coronary-perfused atrial and ventricular preparations. Transmembrane action potential and pseudo-ECG were recorded. Both ranolazine and propafenone produced atrial-selective prolongation of action potential duration. Propafenone depressed sodium channel-mediated parameters [maximum rate of rise of the action potential upstroke (V(max)), conduction time, and diastolic threshold of excitation] and induced postrepolarization refractoriness to a greater degree than ranolazine, and these effects, unlike those induced by ranolazine, were not or only mildly atrial-selective at normal rates (cycle length 500 ms). At fast pacing rates, however, the effects of propafenone on V(max) and conduction time became atrial-selective, because of the elimination of diastolic interval in atria, but not in ventricles. Propafenone (1.5 μM) and ranolazine (10.0 μM) were effective in preventing the initiation of persistent acetylcholine-mediated AF (6/7 and 9/11 atria, respectively), its termination (8/10 and 8/12 atria, respectively), and subsequent reinduction (8/8 and 7/8 atria, respectively). Thus, propafenone and ranolazine both suppress AF, but ranolazine, unlike propafenone, does it with minimal effects on ventricular myocardium, suggesting a reduced potential for promoting ventricular arrhythmias.
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Burashnikov A, Petroski A, Hu D, Barajas-Martinez H, Antzelevitch C. Atrial-selective inhibition of sodium-channel current by Wenxin Keli is effective in suppressing atrial fibrillation. Heart Rhythm 2011; 9:125-31. [PMID: 21884675 DOI: 10.1016/j.hrthm.2011.08.027] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2011] [Accepted: 08/28/2011] [Indexed: 11/17/2022]
Abstract
BACKGROUND Wenxin Keli is a Chinese herb extract reported to be of benefit in the treatment of cardiac arrhythmias, cardiac inflammation, and heart failure. METHODS AND RESULTS We evaluated the electrophysiologic effects of Wenxin Keli in isolated canine arterially perfused right atrial preparations with a rim of right ventricular tissue (n = 11). Transmembrane action potentials and a pseudoelectrocardiogram were simultaneously recorded. Acetylcholine (1 μM) was used to induce atrial fibrillation (AF) and to test the anti-AF potential of Wenxin Keli (5 g/L). Wenxin Keli produced preferential abbreviation of action potential duration measured at 90% repolarization (APD(90)) in atria, but caused atrial-selective prolongation of the effective refractory period, due to the development of postrepolarization refractoriness. The maximum rate of rise of the action potential upstroke was preferentially reduced in atria. The diastolic threshold of excitation increased in both atria and ventricles, but much more in atria. The duration of the "P wave" (index of atrial conduction time) was prolonged to a much greater extent than the duration of the "QRS complex" (index of ventricular conduction time). Wenxin Keli significantly reduced I(Na) and shifted steady-state inactivation to more negative potentials in HEK293 cells stably expressing SCN5A. Wenxin Keli prevented the induction of persistent AF in 100% atria (6/6) and, in another experimental series, was found to terminate persistent acetylcholine-mediated AF in 100% of atria (3/3). CONCLUSION Wenxin Keli produces atrial-selective depression of I(Na)-dependent parameters in canine isolated coronary-perfused preparations via a unique mechanism and is effective in suppressing AF and preventing its induction, with minimal effects on the ventricular electrophysiology.
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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: 177] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [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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Burashnikov A, Antzelevitch C. Advances in the Pharmacologic Management of Atrial Fibrillation. Card Electrophysiol Clin 2011; 3:157-167. [PMID: 21731596 PMCID: PMC3125069 DOI: 10.1016/j.ccep.2010.10.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
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Burashnikov A, Sicouri S, Di Diego JM, Belardinelli L, Antzelevitch C. Synergistic Effect of the Combination of Dronedarone and Ranolazine to Suppress Atrial Fibrillation. Heart Rhythm 2010. [DOI: 10.1016/j.hrthm.2010.09.022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Burashnikov A, Sicouri S, Di Diego JM, Belardinelli L, Antzelevitch C. Synergistic effect of the combination of ranolazine and dronedarone to suppress atrial fibrillation. J Am Coll Cardiol 2010; 56:1216-24. [PMID: 20883928 DOI: 10.1016/j.jacc.2010.08.600] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/07/2010] [Revised: 08/12/2010] [Accepted: 08/17/2010] [Indexed: 12/19/2022]
Abstract
OBJECTIVES The aim of this study was to evaluate the effectiveness of a combination of dronedarone and ranolazine in suppression of atrial fibrillation (AF). BACKGROUND Safe and effective pharmacological management of AF remains one of the greatest unmet medical needs. METHODS The electrophysiological effects of dronedarone (10 μmol/l) and a relatively low concentration of ranolazine (5 μmol/l) separately and in combination were evaluated in canine isolated coronary-perfused right and left atrial and left ventricular preparations as well as in pulmonary vein preparations. RESULTS Ranolazine caused moderate atrial-selective prolongation of action potential duration and atrial-selective depression of sodium channel-mediated parameters, including maximal rate of rise of the action potential upstroke, leading to the development of atrial-specific post-repolarization refractoriness. Dronedarone caused little or no change in electrophysiological parameters in both atrial and ventricular preparations. The combination of dronedarone and ranolazine caused little change in action potential duration in either chamber but induced potent use-dependent atrial-selective depression of the sodium channel-mediated parameters (maximal rate of rise of the action potential upstroke, diastolic threshold of excitation, and the shortest cycle length permitting a 1:1 response) and considerable post-repolarization refractoriness. Separately, dronedarone or a low concentration of ranolazine prevented the induction of AF in 17% and 29% of preparations, respectively. In combination, the 2 drugs suppressed AF and triggered activity and prevented the induction of AF in 9 of 10 preparations (90%). CONCLUSIONS Low concentrations of ranolazine and dronedarone produce relatively weak electrophysiological effects and weak suppression of AF when used separately but when combined exert potent synergistic effects, resulting in atrial-selective depression of sodium channel-dependent parameters and effective suppression of AF.
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Burashnikov A, Belardinelli L, Antzelevitch C. Acute dronedarone is inferior to amiodarone in terminating and preventing atrial fibrillation in canine atria. Heart Rhythm 2010; 7:1273-9. [PMID: 20478403 DOI: 10.1016/j.hrthm.2010.05.019] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/12/2010] [Accepted: 05/08/2010] [Indexed: 11/16/2022]
Abstract
BACKGROUND Dronedarone is approved by the U.S. Food and Drug Administration for the treatment of patients with atrial fibrillation (AF) as a safe alternative to amiodarone. There are no full-length published reports describing the effectiveness of acute dronedarone use against AF in experimental or clinical studies. OBJECTIVE The purpose of this study was to determine the effect of acute dronedarone and amiodarone on electrophysiological parameters, and their anti-AF efficacy in canine isolated arterially perfused right atria. METHODS Transmembrane action potentials and pseudoelectrocardiograms were recorded. Acetylcholine (ACh, 1.0 muM) was used to induce persistent AF. RESULTS Amiodarone-induced changes were much more pronounced than those of dronedarone on (1) action potential duration (DeltaAPD(90), +51 +/- 17 ms vs. 4 +/- 6 ms, P >.01), (2) effective refractory period (DeltaERP, +84 +/- 23 ms vs. 18 +/- 9 ms, P <.001), (3) diastolic threshold of excitation (DeltaDTE, +0.32 +/- 0.11 mA vs. 0.03 +/- 0.02 mA, P <.001), and (4) V(max) (DeltaV(max), -43 +/- 14% vs. -11 +/- 4%, P <.01, n = 5 to 6; all recorded at 10 muM, cycle length = 500 ms). Persistent AF was induced in 10 of 10 atria exposed to ACh alone; subsequent addition of dronedarone or amiodarone terminated AF in 1 of 7 and 4 of 5 atria, respectively. Persistent ACh-mediated AF was induced in 5 of 6 and 0 of 5 atria pretreated with dronedarone and amiodarone, respectively. CONCLUSION The electrophysiological effects and anti-AF efficacy of acute dronedarone are much weaker than those of amiodarone in a canine model of AF. The efficacy of acute dronedarone to prevent induction of acetylcholine-mediated AF as well as to terminate persistent AF in canine right atria is relatively poor. Our data suggest that acute dronedarone is a poor substitute for amiodarone for acute cardioversion of AF or prevention of AF recurrence.
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Abstract
Safe and effective pharmacologic management of atrial fibrillation (AF) is one of the greatest challenges facing an aging society. Currently available pharmacologic strategies for rhythm control of AF are associated with ventricular arrhythmias and in some cases multi-organ toxicity. Consequently, drug development has focused on atrial-selective agents such as IKur blockers. Recent studies suggest that IKur block alone may be ineffective for suppression of AF and may promote AF in healthy hearts. Recent experimental studies have demonstrated other important electrophysiologic differences between atrial and ventricular cells, particularly with respect to sodium channel function, and have identified sodium channel blockers that exploit these electrophysiologic distinctions. Atrial-selective sodium channel blockers, such as ranolazine and amiodarone, effectively suppress and/or prevent the induction of AF in experimental models, while producing little to no effect on ventricular myocardium. These findings suggest that atrial-selective sodium channel block may be a fruitful new strategy for the management of AF.
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Burashnikov A, Antzelevitch C. Advances in the Pharmacological Treatment of Atrial Fibrillation. Curr Med Lit Cardiol 2010; 29:1-5. [PMID: 21152111 PMCID: PMC2997698] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Grants] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
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Sicouri S, Burashnikov A, Belardinelli L, Antzelevitch C. Synergistic electrophysiologic and antiarrhythmic effects of the combination of ranolazine and chronic amiodarone in canine atria. Circ Arrhythm Electrophysiol 2009; 3:88-95. [PMID: 19952329 DOI: 10.1161/circep.109.886275] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
BACKGROUND Amiodarone and ranolazine have been characterized as inactivated- and activated-state blockers of cardiac sodium channel current (I(Na)), respectively, and shown to cause atrial-selective depression of I(Na)-related parameters. This study tests the hypothesis that their combined actions synergistically depress I(Na)-dependent parameters in atria but not ventricles. METHODS AND RESULTS The effects of acute ranolazine (5 to 10 micromol/L) were studied in coronary-perfused right atrial and left ventricular wedge preparations and superfused left atrial pulmonary vein sleeves isolated from chronic amiodarone-treated (40 mg/kg daily for 6 weeks) and untreated dogs. Floating and standard microelectrode techniques were used to record transmembrane action potentials. When studied separately, acute ranolazine and chronic amiodarone caused atrial-predominant depression of I(Na)-dependent parameters. Ranolazine produced a much greater reduction in V(max) and much greater increase in diastolic threshold of excitation and effective refractory period in atrial preparations isolated from amiodarone-treated versus untreated dogs, leading to a marked increase in postrepolarization refractoriness. The drug combination effectively suppressed triggered activity in pulmonary vein sleeves but produced relatively small changes in I(Na)-dependent parameters in the ventricle. Acetylcholine (0.5 micromol/L) and burst pacing induced atrial fibrillation in 100% of control atria, 75% of ranolazine-treated (5 micromol/L) atria, 16% of atria from amiodarone-treated dogs, and in 0% of atria from amiodarone-treated dogs exposed to 5 micromol/L ranolazine. CONCLUSIONS The combination of chronic amiodarone and acute ranolazine produces a synergistic use-dependent depression of I(Na)-dependent parameters in isolated canine atria, leading to a potent effect of the drug combination to prevent the induction of atrial fibrillation.
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Burashnikov A, Di Diego JM, Linhardt G, Carlsson L, Antzelevitch C. AZD1305 has Atrial-Predominant Electrophysiologic Actions and is Effective in Suppressing Atrial Fibrillation in the Dog. Heart Rhythm 2009. [DOI: 10.1016/j.hrthm.2009.09.029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Abstract
Atrial fibrillation (AF) is a growing clinical problem, increasing in prevalence as the population of the United States and countries around the world ages. Intensive research aimed at improving prevention, diagnosis, and treatment of AF is ongoing. Although the use and efficacy of catheter ablation-based approaches in AF treatment have increased significantly in the last decade, pharmacological agents remain the first-line therapy for rhythm management of AF. Currently available anti-AF agents are generally only moderately effective and associated with extracardiac toxicity and/or a risk for development of life-threatening ventricular arrhythmias. Included among current investigational strategies for improving the effectiveness and safety of anti-AF drugs is the development of (1) Agents that produce atrial-specific or predominant inhibition of I(Kur), I(K-ACh), or I(Na); (2) "Upstream therapies" that effect nonion channel targets that reduce atrial structural remodeling, hypertrophy, dilatation, inflammation, oxidative injury, etc; (3) Derivatives of "old" anti-AF drugs with an improved safety pharmacological profile; and (4) Gap junction therapy aimed at improving conduction without affecting sodium channels. This review focuses on new pharmacological approaches under investigation for the treatment of AF.
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Burashnikov A, Shimizu W, Antzelevitch C. Fever accentuates transmural dispersion of repolarization and facilitates development of early afterdepolarizations and torsade de pointes under long-QT Conditions. Circ Arrhythm Electrophysiol 2009; 1:202-8. [PMID: 19649147 DOI: 10.1161/circep.107.691931] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
BACKGROUND The arrhythmogenic effects of hyperthermia have been highlighted in the Brugada syndrome but remain largely unexplored in other arrhythmic syndromes. The present study examines the effect of hyperthermia on transmural dispersion of action potential duration (TD-APD), early afterdepolarization (EAD) activity, and torsade de pointes (TdP) under long-QT conditions. METHODS AND RESULTS Standard and floating glass microelectrodes were used to record action potentials from epicardial, M cell, and endocardial regions of the arterially perfused left ventricle wedge, from tissue slices isolated from these regions, and from isolated Purkinje fibers. A transmural ECG was simultaneously recorded across the wedge. Under baseline conditions and in the presence of I(Ks) block (chromanol 293B), hyperthermia (39 degrees C to 40 degrees C) abbreviated APD in tissue slices from all 3 regions. In the presence of I(Kr) block (E-4031), hyperthermia prolonged APD and induced or augmented EADs in M cell and Purkinje preparations at pacing cycle lengths > or = 800 ms but abbreviated APD in epicardium and endocardium, resulting in a marked accentuation of TD-APD. Ryanodine prevented the hyperthermia- induced EAD. In perfused wedge preparations, hyperthermia abbreviated APD throughout both in the absence or presence of I(Kr) or I(Ks) block and did not induce EADs or TdP. Combined I(Kr) and I(Ks) block increased TD-APD and induced EADs (4/12) and spontaneous TdP (3/12) at 36 degrees C to 37 degrees C; hyperthermia (39 degrees C to 40 degrees C) further accentuated TD-APD and facilitated the development of EAD activity (9/12) and TdP (6/12). CONCLUSIONS Our findings suggest that hyperthermia can be associated with an increased arrhythmic risk when the repolarization reserve of the myocardium is compromised.
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Nof E, Burashnikov A, Antzelevitch C. Cellular basis for atrial fibrillation in an experimental model of short QT1: implications for a pharmacological approach to therapy. Heart Rhythm 2009; 7:251-7. [PMID: 20042373 DOI: 10.1016/j.hrthm.2009.10.017] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/30/2009] [Accepted: 10/14/2009] [Indexed: 11/16/2022]
Abstract
BACKGROUND Short QT (SQT) syndrome (SQT) 1 is an inherited sudden death syndrome often associated with atrial fibrillation (AF). We examined the cellular basis for AF in a newly developed experimental atrial model of SQT1. METHODS Action potentials (APs) were recorded from the pectinate muscle (PM) and crista terminalis (CT) regions of coronary-perfused canine right atrial preparations, together with a pseudoelectrocardiogram. The I(Kr) agonist PD-118057 (20 microM) was used to mimic the gain of function in I(Kr) known to underlie SQT1. RESULTS The I(Kr) agonist significantly abbreviated the AP duration (APD) of CT and PM and of the effective refractory period (ERP) measured in PM (n = 28). Spatial dispersion of repolarization (SDR), defined as inter-regional differences of APD, increased from 27 +/- 17 ms to 51 +/- 32 ms (P = .002; n = 28). AF could be induced by a single premature stimulus after but not before exposure to PD-118057 in 26/28 (93%) preparations. Quinidine (10 microM), which prolonged APD and ERP, but not lidocaine (20 microM) or E-4031 (5 microM), which prolonged only ERP or APD, respectively, was effective in preventing the PD-118057-mediated AF. In the presence of PD-118057, isoproterenol (100 nM) further abbreviated both APD and ERP and facilitated induction of sustained AF in five of six preparations. CONCLUSIONS The I(Kr) agonist recapitulates the electrophysiologic and arrhythmic manifestations of SQT1. Abbreviation of APD and ERP and amplification of SDR predispose to the development of AF by creating the substrate for reentry. Quinidine, but not E-4031 or lidocaine, was effective in preventing AF in this setting.
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Affiliation(s)
- Eyal Nof
- Masonic Medical Research Laboratory, Utica, NY, USA
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Abstract
The pharmacological approach to therapy of atrial fibrillation (AF) is often associated with adverse effects resulting in the development of ventricular arrhythmias. As a consequence, much of the focus in recent years has been on development of atrial-selective agents. Atrial-selective sodium channel blockers have recently been shown to exist and be useful in the management of AF. This review summarizes the available data relative to current therapies, focusing on our understanding of the actions of atrial selective sodium channel blockers in suppressing and preventing the induction of AF and electrophysiological properties that confer atrial-selectivity to these antifibrillatory drugs.
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Affiliation(s)
- Alexander Burashnikov
- Research Scientist Masonic Medical Research Laboratory, 2150 Bleecker Street, Utica, NY 13501, USA
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Antzelevitch C, Burashnikov A. Atrial-selective sodium channel block as a novel strategy for the management of atrial fibrillation. J Electrocardiol 2009; 42:543-8. [PMID: 19698954 DOI: 10.1016/j.jelectrocard.2009.07.007] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2009] [Indexed: 12/19/2022]
Abstract
Pharmacological management of atrial fibrillation (AF) remains an important unmet medical need. Because available drugs for rhythm control of AF are often associated with a significant risk for development of ventricular arrhythmias or extracardiac toxicity, recent drug development has focused on agents that are atrial selective. Inhibition of the ultrarapid delayed rectifier potassium current (I(Kur)), a current exclusive to atria, is an example of an atrial-selective approach. Recent studies, however, have shown that loss-of-function mutations in KCNA5, the gene that encodes K(V)1.5, the alpha subunit of the I(Kur) channel, is associated with the development of AF and that inhibition of I(Kur) can promote the induction of AF in experimental models. Another potential atrial-selective approach has recently been identified. Experimental studies have demonstrated important atrioventricular differences in the biophysical properties of the sodium channel and have identified sodium channel blockers that can exploit electrophysiological distinctions between atria and ventricles. Atrial-selective/predominant sodium channel blockers such as ranolazine effectively suppress AF in experimental models involving canine-isolated right atrial preparations at concentrations that produce little to no effect on electrophysiological parameters in ventricular myocardium. Chronic administration of amiodarone was also found to exert atrial-selective depression of I(Na)-dependent parameters and thus to prevent the induction of AF. Ranolazine and amiodarone have in common the ability to rapidly dissociate from the sodium channel and to prolong the atrial action potential duration via inhibition of I(Kr). Our observations suggest that atrial-selective sodium channel block may be a fruitful strategy for the management of AF.
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Burashnikov A, Di Diego JM, Sicouri S, Ferreiro M, Carlsson L, Antzelevitch C. Atrial-selective effects of chronic amiodarone in the management of atrial fibrillation. Heart Rhythm 2008; 5:1735-42. [PMID: 19084813 DOI: 10.1016/j.hrthm.2008.09.015] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/16/2008] [Accepted: 09/13/2008] [Indexed: 12/19/2022]
Abstract
BACKGROUND Although amiodarone is one of the most effective pharmacologic agents used in clinical management of atrial fibrillation (AF), little is known about its differential effects in atrial and ventricular myocardium. OBJECTIVES This study sought to compare the electrophysiological effects of chronic amiodarone in atria and ventricles. METHODS We compared the electrophysiological characteristics of coronary-perfused atrial and ventricular wedge preparations isolated from untreated and chronic amiodarone-treated dogs (amiodarone, 40 mg/kg/day for 6 weeks, n = 12). RESULTS Chronic amiodarone prolonged action potential duration (APD(90)) predominantly in atria compared to ventricles and prolonged the effective refractory period (ERP) more than APD(90) in both ventricular and atrial preparations (particularly in the latter) due to the development of postrepolarization refractoriness. Amiodarone reduced dispersion of APD(90) in both atria and ventricles. Although the maximum rate of increase of the action potential upstroke (V(max)) was significantly lower in both atria and ventricles of amiodarone-treated hearts versus untreated controls, the reduction of V(max) was much more pronounced in atria. Amiodarone prolonged P-wave duration more significantly than QRS duration, reflecting greater slowing of conduction in atria versus ventricles. These atrioventricular distinctions were significantly accentuated at faster activation rates. Persistent acetylcholine-mediated AF could be induced in only 1 of 6 atria from amiodarone-treated versus 10 of 10 untreated dogs. CONCLUSION Our results indicate that under the conditions studied, chronic amiodarone has potent atrial-predominant effects to depress sodium channel-mediated parameters and that this action of the drug is greatly potentiated by its ability to prolong APD predominantly in the atria, thus contributing to its effectiveness to suppress AF.
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Burashnikov A, Di Diego JM, Zygmunt AC, Belardinelli L, Antzelevitch C. Atrial-selective sodium channel block as a strategy for suppression of atrial fibrillation. Ann N Y Acad Sci 2008; 1123:105-12. [PMID: 18375582 DOI: 10.1196/annals.1420.012] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
UNLABELLED Antiarrhythmic drug therapy remains the principal approach for suppression of atrial fibrillation (AF) and flutter (AFl) and prevention of their recurrence. Among the current strategies for suppression of AF/AFl is the development of antiarrhythmic agents that preferentially affect atrial, rather than ventricular electrical parameters. Inhibition of the ultrarapid delayed rectifier potassium current (IKur), present in the atria, but not in the ventricles, is an example of an atrial-selective approach. Our recent study examined the hypothesis that sodium channel characteristics differ between atrial and ventricular cells and that atrial-selective sodium channel block is another effective strategy for the management of AF. We have demonstrated very significant differences in the inactivation characteristics of atrial versus ventricular sodium channels and a striking atrial selectivity for the action of ranolazine, an inactivated-state sodium channel blocker, to produce use-dependent block of the sodium channels, leading to depression of excitability, development of post-repolarization refractoriness (PRR), and suppression of AF. Lidocaine and chronic amiodarone, both predominantly inactivated-state sodium channel blockers, also produced a preferential depression of sodium channel-dependent parameters (VMax conduction velocity, diastolic threshold of excitation, and PRR) in the atria. Propafenone, a predominantly open-state sodium channel blocker, produced similar changes of electrophysiological parameters, which were was not atrial-selective. The ability of ranolazine, chronic amiodarone, and propafenone to prolong the atrial action potential potentiated their ability to suppress AF in coronary-perfused canine atrial preparations. IN CONCLUSION Our data demonstrate important differences in the inactivation characteristics of atrial versus ventricular sodium channels and a striking atrial selectivity for the action of agents like ranolazine to produce use-dependent block of sodium channels leading to suppression of AF. Our findings suggest that atrial-selective sodium channel block may be a valuable strategy to combat AF.
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Abstract
BACKGROUND Block of ultrarapid delayed rectified potassium current (I(Kur)), present in atria but not in ventricles, is thought to be a promising approach for atrial-specific therapy of atrial fibrillation (AF). However, it has been shown that I(Kur) block may abbreviate atrial repolarization and that loss-of-function mutations in KCNA5, which encodes K(v) 1.5 channels responsible for I(Kur), is associated with familial AF. OBJECTIVE Our objective in this study was to use low concentrations of 4-aminopyridine (4-AP, 10 to 50 microM), known to selectively block I(Kur), to assess the proarrhythmic and antiarrhythmic effects of I(Kur) block in healthy and remodeled atria. METHODS Isolated canine coronary-perfused right atrial preparations were used. Acetylcholine or ischemia/reperfusion was used to acutely remodel the atria. Transmembrane action potentials and a pseudo-electrocardiogram were simultaneously recorded. RESULTS Normal (healthy) atria typically displayed action potentials (AP) with a prominent plateau, whereas remodeled atria displayed triangular-shaped APs (remodeled). In healthy atria, in which AF could not be induced with programmed stimulation, 4-AP abbreviated action potential measured at 90% repolarization (APD(90)) and effective refractory period (ERP), permitting the induction of AF in 4 of 12 preparations (33%). In remodeled atria, 4-AP produced little (50 microM) to no (10 to 25 microM) prolongation of APD(90) or ERP and was either ineffective or poorly effective in terminating AF or preventing its induction. CONCLUSION Our findings suggest that block of I(Kur) can provide the substrate for development of AF in healthy canine atria, presumably via abbreviation of APD and ERP.
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Abstract
The risk of developing severe ventricular arrhythmias and/or organ toxicity by currently available drugs used to treat atrial fibrillation (AF) has prompted the development of atrial-selective antiarrhythmic agents. Until recently the principal focus has been on development of agents that selectively inhibit the ultra-rapid delayed rectifier outward potassium channels (I Kur), taking advantage of the presence of these channels in atria but not ventricles. Recent experimental studies have demonstrated important atrioventricular differences in biophysical properties of the sodium channel and have identified sodium channel blockers such as ranolazine and chronic amiodarone that appear to take advantage of these electrophysiologic distinctions and act to specifically or predominantly depress sodium channel-mediated parameters in "healthy" canine atria versus ventricles. Atrial-selective/predominant sodium channel blockers such as ranolazine effectively suppress AF in experimental models of AF involving canine isolated right atrial preparations at concentrations that produce little to no effect on ventricular electrophysiologic parameters. These findings point to atrial-selective sodium channel block as a new strategy for the management of AF. The present review examines our current understanding of atrioventricular distinctions between atrial and ventricular sodium channels and our understanding of the basis for atrial selectively of the sodium channel blockers. A major focus will be on the ability of the atrial-selective sodium channel blocking properties of these agents, possibly in conjunction with I Kur and/or I Kr blocking properties, to suppress and prevent the reinduction of AF.
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Burashnikov A, Antzelevitch C. How Do Atrial-Selective Drugs Differ From Antiarrhythmic Drugs Currently Used in the Treatment of Atrial Fibrillation? J Atr Fibrillation 2008; 1:98-107. [PMID: 21057583 DOI: 10.4022/jafib.v1i1.400] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Current pharmacologic strategies for the management of Atrial fibrillation (AF) include use of 1) sodium channel blockers, which are contraindicated in patients with coronary artery or structural heart disease because of their potent effect to slow conduction in the ventricles, 2) potassium channel blockers, which predispose to acquired long QT and Torsade de Pointes arrhythmias because of their potent effect to prolong ventricular repolarization, and 3) mixed ion channel blockers such as amiodarone, which are associated with multi-organ toxicity. Accordingly, recent studies have focused on agents that selectively affect the atria but not the ventricles. Several Atrial-selective approaches have been proposed for the management of AF, including inhibition of the Atrial-specific ultra rapid delayed rectified potassium current (IKur), acetylcholine-regulated inward rectifying potassium current (IK-ACh), or connexin-40 (Cx40). All three are largely exclusive to atria. Recent studies have proposed that an Atrial-selective depression of sodium channel-dependent parameters with agents such as ranolazine may be an alternative approach capable of effectively suppressing AF without increasing susceptibility to ventricular arrhythmias. Clinical evidence for Cx40 modulation or IK-ACh inhibition are lacking at this time. The available data suggest that Atrial-selective approaches involving a combination of INa, IKur, IKr, and, perhaps, Ito block may be more effective in the management of AF than pure IKur or INa block. The anti-AF efficacy of the Atrial-selective/predominant agents appears to be similar to that of conventionally used anti-AF agents, with the major apparent difference being that the latter are associated with ventricular arrhythmogenesis and extra cardiac toxicity.
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Burashnikov A, Di Diego JM, Zygmunt AC, Belardinelli L, Antzelevitch C. Atrium-selective sodium channel block as a strategy for suppression of atrial fibrillation: differences in sodium channel inactivation between atria and ventricles and the role of ranolazine. Circulation 2007; 116:1449-57. [PMID: 17785620 PMCID: PMC2566303 DOI: 10.1161/circulationaha.107.704890] [Citation(s) in RCA: 316] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
BACKGROUND The development of selective atrial antiarrhythmic agents is a current strategy for suppression of atrial fibrillation (AF). METHODS AND RESULTS Whole-cell patch clamp techniques were used to evaluate inactivation of peak sodium channel current (I(Na)) in myocytes isolated from canine atria and ventricles. The electrophysiological effects of therapeutic concentrations of ranolazine (1 to 10 micromol/L) and lidocaine (2.1 to 21 micromol/L) were evaluated in canine isolated coronary-perfused atrial and ventricular preparations. Half-inactivation voltage of I(Na) was approximately 15 mV more negative in atrial versus ventricular cells under control conditions; this difference increased after exposure to ranolazine. Ranolazine produced a marked use-dependent depression of sodium channel parameters, including the maximum rate of rise of the action potential upstroke, conduction velocity, and diastolic threshold of excitation, and induced postrepolarization refractoriness in atria but not in ventricles. Lidocaine also preferentially suppressed these parameters in atria versus ventricles, but to a much lesser extent than ranolazine. Ranolazine produced a prolongation of action potential duration (APD90) in atria, no effect on APD90 in ventricular myocardium, and an abbreviation of APD90 in Purkinje fibers. Lidocaine abbreviated both atrial and ventricular APD90. Ranolazine was more effective than lidocaine in terminating persistent AF and in preventing the induction of AF. CONCLUSIONS Our study demonstrates important differences in the inactivation characteristics of atrial versus ventricular sodium channels and a striking atrial selectivity for the action of ranolazine to produce use-dependent block of sodium channels, leading to suppression of AF. Our results point to atrium-selective sodium channel block as a novel strategy for the management of AF.
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Antzelevitch C, Viskin S, Shimizu W, Yan GX, Kowey P, Zhang L, Sicouri S, Di Diego JM, Burashnikov A. Does Tpeak-Tend provide an index of transmural dispersion of repolarization? Heart Rhythm 2007; 4:1114-6; author reply 1116-9. [PMID: 17675094 PMCID: PMC1994816 DOI: 10.1016/j.hrthm.2007.05.028] [Citation(s) in RCA: 206] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/13/2007] [Indexed: 01/11/2023]
Affiliation(s)
| | - Sami Viskin
- Department of Cardiology, Tel-Aviv Sourasky Medical Center, and Sackler School of Medicine, Tel-Aviv University, Israel
| | - Wataru Shimizu
- Division of Cardiology, Department of Internal Medicine, National Cardiovascular Center, Suita, Osaka, Japan
| | - Gan-Xin Yan
- Main Line Health Heart Center, Wynnewood, PA and Jefferson Medical College of Thomas Jefferson University, Philadelphia, PA
| | - Peter Kowey
- Main Line Health Heart Center, Wynnewood, PA and Jefferson Medical College of Thomas Jefferson University, Philadelphia, PA
| | - Li Zhang
- Department of Cardiology LDS Hospital, Intermountain Healthcare, University of Utah School of Medicine, Salt Lake City, UT
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Abstract
Early (EAD) and delayed (DAD) afterdepolarizations-induced triggered activity is capable of initiating and maintaining cardiac arrhythmias. EAD-induced triggered responses are traditionally thought to be involved in the generation of ventricular arrhythmias under long QT conditions and are precipitated by bradycardia or long pauses. In contrast, DAD-induced triggered activity commonly underlies arrhythmias precipitated by tachycardia. Spontaneous release of calcium from the sarcoplasmic reticulum (SR) secondary to cellular calcium overload induces DADs and some forms of EADs. Recent studies from our laboratory have uncovered a novel mechanism giving rise to triggered activity, termed "late-phase 3 EAD," which combines properties of both EAD and DAD, but has its own unique character. Late-phase 3 EAD-induced triggered extrasystoles represent a new concept of arrhythmogenesis in which abbreviated repolarization permits "normal SR calcium release" to induce an EAD-mediated closely coupled triggered response, particularly under conditions permitting intracellular calcium loading. This review briefly describes the mechanisms and properties of late-phase 3 EADs, how they differ from conventional EADs and DADs, as well as their role in the initiation of cardiac arrhythmias, such as atrial fibrillation.
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Abstract
INTRODUCTION Although the role of action potential duration restitution (APD-R) in the initiation and maintenance of ventricular fibrillation (VF) has been the subject of numerous investigations, its role in the generation of atrial fibrillation (AF) is less well studied. The cellular and ionic basis for coarse versus fine AF is not well delineated. METHODS AND RESULTS We measured APD-R during acetylcholine-mediated AF as well as during pacing (standard and dynamic protocols) in crista teriminalis, pectinate muscle, superior vena cava, and appendage of isolated canine arterially perfused right atria (n = 15). Transmembrane action potential (TAP), pseudo-ECG, and isometric tension development were simultaneously recorded. Acetylcholine flattened APD-R measured by both standard and dynamic protocols, but promoted induction of AF. AF was initially coarse, converting to fine within 3-15 minutes of AF. Coarse, but not fine AF was associated with dramatic fluctuations in tension development, reflecting wide variations in intracellular calcium activity ([Ca(2+)](i)). During coarse AF, APD-R data displayed a cloud-like distribution pattern, with a wide range of maximum APD-R slope (from 1.21 to 0.35). A maximum APD-R slope >1 was observed only in crista terminalis (3/10). The APD-R relationship was relatively linear and flat during fine AF. Reduction of [Ca(2+)](i) was associated with fine AF whereas augmentation of [Ca(2+)](i) with coarse AF. CONCLUSIONS Our data indicate that while APD-R may have a limited role in the maintenance of coarse AF, it is unlikely to contribute to the maintenance of fine AF and that [Ca(2+)](i) dynamics determine the degree to which AF is coarse or fine.
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Antzelevitch C, Belardinelli L, Wu L, Fraser H, Zygmunt AC, Burashnikov A, Di Diego JM, Fish JM, Cordeiro JM, Goodrow RJ, Scornik F, Perez G. Electrophysiologic properties and antiarrhythmic actions of a novel antianginal agent. J Cardiovasc Pharmacol Ther 2005; 9 Suppl 1:S65-83. [PMID: 15378132 DOI: 10.1177/107424840400900106] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Ranolazine is a novel antianginal agent capable of producing anti-ischemic effects at plasma concentrations of 2 to 6 microM without a significant reduction of heart rate or blood pressure. This review summarizes the electrophysiologic properties of ranolazine. Ranolazine significantly blocks I(Kr) (IC(50) = 12 microM), late I(Na), late I(Ca), peak I(Ca), I(Na-Ca) (IC(50) = 5.9, 50, 296, and 91 microM, respectively) and I(Ks) (17% at 30 microM), but causes little or no inhibition of I(to) or I(K1). In left ventricular tissue and wedge preparations, ranolazine produces a concentration-dependent prolongation of action potential duration (APD) in epicardium, but abbreviation of APD of M cells, leading to either no change or a reduction in transmural dispersion of repolarization (TDR). The result is a modest prolongation of the QT interval. Prolongation of APD and QT by ranolazine is fundamentally different from that of other drugs that block I(Kr) and induce torsade de pointes in that APD prolongation is rate-independent (ie, does not display reverse rate-dependent prolongation of APD) and is not associated with early after depolarizations, triggered activity, increased spatial dispersion of repolarization, or polymorphic ventricular tachycardia. Torsade de pointes arrhythmias were not observed spontaneously nor could they be induced with programmed electrical stimulation in the presence of ranolazine at concentrations as high as 100 microM. Indeed, ranolazine was found to possess significant antiarrhythmic activity, acting to suppress the arrhythmogenic effects of other QT-prolonging drugs. Ranolazine produces ion channel effects similar to those observed after chronic exposure to amiodarone (reduced late I(Na), I(Kr), I(Ks), and I(Ca)). Ranolazine's actions to reduce TDR and suppress early after depolarization suggest that in addition to its anti-anginal actions, the drug possesses antiarrhythmic activity.
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Abstract
BACKGROUND Mutations in the ryanodine 2 receptor (RyR2) gene have been identified in patients with catecholaminergic polymorphic ventricular tachycardia. We examined the cellular basis for the ECG features and arrhythmia mechanisms using low-dose caffeine to mimic the defective calcium homeostasis encountered under these conditions. METHODS AND RESULTS A transmural ECG and action potentials were recorded simultaneously from epicardial, M, and endocardial cells in arterially perfused canine ventricular wedge preparations. Caffeine alone produced no change (10 to 100 micromol/L) or a slight abbreviation (300 micromol/L) of the QT interval and no change in transmural dispersion of repolarization. Isoproterenol (100 nmol/L) alone induced sustained monomorphic ventricular tachycardia (VT) that originated in the epicardium in 3 of 14 wedge preparations. Isoproterenol in the presence of caffeine (100 to 300 micromol/L) induced epicardial VT in 9 of 16 wedge preparations. Delayed afterdepolarization-induced triggered beats that originated in the epicardium were associated with an increased Tpeak-Tend interval and transmural dispersion of repolarization. Bidirectional VT developed in 11 of 16 wedge preparations as a consequence of alternation in the origin of ectopic activity between endocardial, M, and epicardial regions. Single extrastimuli delivered during sustained epicardial VT induced a rapid polymorphic VT/ventricular fibrillation (VF) in 3 of 9 wedges. Spontaneous polymorphic VT was observed in 3 of 16 preparations. Propranolol (1.0 micromol/L) or verapamil (1.0 micromol/L) completely suppressed ectopic activity that arose from the epicardium and prevented induction of polymorphic VT. CONCLUSIONS Our data suggest delayed afterdepolarization-induced extrasystolic activity serves to trigger catecholamine-induced VT/VF under conditions of defective calcium handling. Epicardial origin of the ectopic beats increases transmural dispersion of repolarization, thus providing the substrate for the development of reentrant tachyarrhythmias that underlie rapid polymorphic VT/VF.
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Affiliation(s)
- Gi-Byoung Nam
- Masonic Medical Research Laboratory, 2150 Bleecker St, Utica, NY 13501-1787, USA
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Antzelevitch C, Belardinelli L, Zygmunt AC, Burashnikov A, Di Diego JM, Fish JM, Cordeiro JM, Thomas G. Electrophysiological effects of ranolazine, a novel antianginal agent with antiarrhythmic properties. Circulation 2004; 110:904-10. [PMID: 15302796 PMCID: PMC1513623 DOI: 10.1161/01.cir.0000139333.83620.5d] [Citation(s) in RCA: 536] [Impact Index Per Article: 26.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Ranolazine is a novel antianginal agent capable of producing antiischemic effects at plasma concentrations of 2 to 6 micromol/L without reducing heart rate or blood pressure. The present study examines its electrophysiological effects in isolated canine ventricular myocytes, tissues, and arterially perfused left ventricular wedge preparations. METHODS AND RESULTS Transmembrane action potentials (APs) from epicardial and midmyocardial (M) regions and a pseudo-ECG were recorded simultaneously from wedge preparations. APs were also recorded from epicardial and M tissues. Whole-cell currents were recorded from epicardial and M myocytes. Ranolazine inhibited I(Kr) (IC50=11.5 micromol/L), late I(Na), late I(Ca), peak I(Ca), and I(Na-Ca) (IC50=5.9, 50, 296, and 91 micromol/L, respectively) and I(Ks) (17% at 30 micromol/L), but caused little or no inhibition of I(to) or I(K1). In tissues and wedge preparations, ranolazine produced a concentration-dependent prolongation of AP duration of epicardial but abbreviation of that of M cells, leading to reduction or no change in transmural dispersion of repolarization (TDR). At [K+]o=4 mmol/L, 10 micromol/L ranolazine prolonged QT interval by 20 ms but did not increase TDR. Extrasystolic activity and spontaneous torsade de pointes (TdP) were never observed, and stimulation-induced TdP could not be induced at any concentration of ranolazine, either in normal or low [K+]o. Ranolazine (5 to 20 micromol/L) suppressed early afterdepolarizations (EADs) and reduced the increase in TDR induced by the selective I(Kr) blocker d-sotalol. CONCLUSIONS Ranolazine produces ion channel effects similar to those observed after chronic amiodarone (reduced I(Kr), I(Ks), late I(Na), and I(Ca)). The actions of ranolazine to suppress EADs and reduce TDR suggest that, in addition to its antianginal actions, the drug may possess antiarrhythmic activity.
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Burashnikov A, Mannava S, Antzelevitch C. Transmembrane action potential heterogeneity in the canine isolated arterially perfused right atrium: effect of IKr and IKur/Ito block. Am J Physiol Heart Circ Physiol 2004; 286:H2393-400. [PMID: 15148061 DOI: 10.1152/ajpheart.01242.2003] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The role of electrical heterogeneity in development of cardiac arrhythmias is well recognized. The extent to which transmembrane action potential (TAP) heterogeneity contributes to the normal electrophysiology of well-oxygenated atria is not well defined. The principal objective of the present study was to define regional and transmural differences in characteristics of the TAP in isolated superfused and arterially perfused canine right atrial (RA) preparations under baseline, rapidly activating delayed rectifier K(+) current (I(Kr)) block, and combined block of ultrarapid delayed rectifier and transient outward K(+) current (I(Kur)/I(to) block). Superfused preparations that survived generally displayed a triangle-shaped TAP. Exceptions included cells from the crista terminalis, where TAPs with a normal plateau could be recorded. In contrast, most TAPs recorded from throughout the perfused RA displayed a spike-and-dome and/or plateau morphology. The perfused RA displayed a heterogeneous distribution of repolarization, V(max), and spike-and-dome morphology along the epicardial and endocardial surfaces as well as transmurally, in the region of the upper crista terminalis. I(Kr) block with E-4031 prolonged repolarization homogeneously in the perfused RA, whereas I(Kur)/I(to) block using low concentrations of 4-aminopyridine abbreviated action potential duration at 90% repolarization heterogeneously, leading to a reduction in dispersion of repolarization. Our data indicate that the electrical heterogeneities, previously described for the canine ventricle, also exist within the atria and that I(Kr) block does not accentuate and I(Kur)/I(to) block reduces RA dispersion of repolarization. Our study also points to major differences in the transmembrane activity recorded using superfused vs. arterially perfused atrial preparations.
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Burashnikov A, Antzelevitch C. Reinduction of atrial fibrillation immediately after termination of the arrhythmia is mediated by late phase 3 early afterdepolarization-induced triggered activity. Circulation 2003; 107:2355-60. [PMID: 12695296 DOI: 10.1161/01.cir.0000065578.00869.7c] [Citation(s) in RCA: 250] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Atrial fibrillation (AF) at times recurs immediately after termination of the arrhythmia. The mechanism(s) responsible for the extrasystole that reinduces AF is largely unknown. We hypothesized that abbreviation of action potential duration (APD) would permit very rapid rates of excitation, known to induce intracellular calcium loading, which in turn could promote delayed and/or early afterdepolarizations (EADs). METHODS AND RESULTS Acetylcholine (ACh, 1 micromol/L) was used to abbreviate atrial APD and permit rapid-pacing induction of AF in isolated coronary-perfused canine right atria. Transmembrane action potentials, pseudo-ECG, and tension development were recorded. AF or rapid pacing was associated with an increase in tonic tension. Termination of AF or rapid pacing (cycle length, 150 to 80 ms) resulted in a dramatic rise of phasic tension, prolongation of repolarization of the initial beats at the regular rate (cycle length, 700 ms), and the development of late phase 3 EADs and extrasystoles. These extrasystoles initiated AF in 15 cases (involving 9 right atria) within the first 11 seconds after termination of AF or rapid pacing. This novel EAD mechanism is observed only in association with marked APD abbreviation. The calcium channel blocker nifedipine reduced, and the sarcoplasmic reticulum calcium release blocker ryanodine eliminated, the post-rapid pacing-induced increase in phasic tension, late phase 3 EADs, and extrasystoles that initiate AF. CONCLUSIONS These data suggest that calcium overload conditions present after termination of vagally mediated AF contribute to the development of late phase 3 EAD-induced triggered activity and that this mechanism may be responsible for the extrasystolic activity that reinitiates AF.
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