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Alhourani N, Wolfes J, Könemann H, Ellermann C, Frommeyer G, Güner F, Lange PS, Reinke F, Köbe J, Eckardt L. Relevance of mexiletine in the era of evolving antiarrhythmic therapy of ventricular arrhythmias. Clin Res Cardiol 2024; 113:791-800. [PMID: 38353682 PMCID: PMC11108884 DOI: 10.1007/s00392-024-02383-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/12/2023] [Accepted: 01/19/2024] [Indexed: 05/22/2024]
Abstract
Despite impressive developments in the field of ventricular arrhythmias, there is still a relevant number of patients with ventricular arrhythmias who require antiarrhythmic drug therapy and may, e.g., in otherwise drug and/or ablation refractory situations, benefit from agents known for decades, such as mexiletine. Through its capability of blocking fast sodium channels in cardiomyocytes, it has played a minor to moderate antiarrhythmic role throughout the recent decades. Nevertheless, certain patients with structural heart disease suffering from drug-refractory, i.e., mainly amiodarone refractory ventricular arrhythmias, as well as those with selected forms of congenital long QT syndrome (LQTS) may nowadays still benefit from mexiletine. Here, we outline mexiletine's cellular and clinical electrophysiological properties. In addition, the application of mexiletine may be accompanied by various potential side effects, e.g., nausea and tremor, and is limited by several drug-drug interactions. Thus, we shed light on the current therapeutic role of mexiletine for therapy of ventricular arrhythmias and discuss clinically relevant aspects of its indications based on current evidence.
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Affiliation(s)
- Nawar Alhourani
- Department of Cardiology II: Electrophysiology, University Hospital Münster, Münster, Germany.
| | - Julian Wolfes
- Department of Cardiology II: Electrophysiology, University Hospital Münster, Münster, Germany
| | - Hilke Könemann
- Department of Cardiology II: Electrophysiology, University Hospital Münster, Münster, Germany
| | - Christian Ellermann
- Department of Cardiology II: Electrophysiology, University Hospital Münster, Münster, Germany
| | - Gerrit Frommeyer
- Department of Cardiology II: Electrophysiology, University Hospital Münster, Münster, Germany
| | - Fatih Güner
- Department of Cardiology II: Electrophysiology, University Hospital Münster, Münster, Germany
| | - Philipp Sebastian Lange
- Department of Cardiology II: Electrophysiology, University Hospital Münster, Münster, Germany
| | - Florian Reinke
- Department of Cardiology II: Electrophysiology, University Hospital Münster, Münster, Germany
| | - Julia Köbe
- Department of Cardiology II: Electrophysiology, University Hospital Münster, Münster, Germany
| | - Lars Eckardt
- Department of Cardiology II: Electrophysiology, University Hospital Münster, Münster, Germany
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Könemann H, Güler-Eren S, Ellermann C, Frommeyer G, Eckardt L. Antiarrhythmic Treatment in Heart Failure. Curr Heart Fail Rep 2024; 21:22-32. [PMID: 38224446 PMCID: PMC10828006 DOI: 10.1007/s11897-023-00642-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 12/29/2023] [Indexed: 01/16/2024]
Abstract
PURPOSE OF REVIEW Arrhythmias are common in patients with heart failure (HF) and are associated with a significant risk of mortality and morbidity. Optimal antiarrhythmic treatment is therefore essential. Here, we review current approaches to antiarrhythmic treatment in patients with HF. RECENT FINDINGS In atrial fibrillation, rhythm control and ventricular rate control are accepted therapeutic strategies. In recent years, clinical trials have demonstrated a prognostic benefit of early rhythm control strategies and AF catheter ablation, especially in patients with HF with reduced ejection fraction. Prevention of sudden cardiac death with ICD therapy is essential, but optimal risk stratification is challenging. For ventricular tachycardias, recent data support early consideration of catheter ablation. Antiarrhythmic drug therapy is an adjunctive therapy in symptomatic patients but has no prognostic benefit and well-recognized (proarrhythmic) adverse effects. Antiarrhythmic therapy in HF requires a systematic, multimodal approach, starting with guideline-directed medical therapy for HF and integrating pharmacological, device, and interventional therapy.
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Affiliation(s)
- Hilke Könemann
- Department of Cardiology II: Electrophysiology, University Hospital Münster, Münster, Germany.
| | - Sati Güler-Eren
- Department of Cardiology II: Electrophysiology, University Hospital Münster, Münster, Germany
| | - Christian Ellermann
- Department of Cardiology II: Electrophysiology, University Hospital Münster, Münster, Germany
| | - Gerrit Frommeyer
- Department of Cardiology II: Electrophysiology, University Hospital Münster, Münster, Germany
| | - Lars Eckardt
- Department of Cardiology II: Electrophysiology, University Hospital Münster, Münster, Germany
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3
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Zaniboni M. The electrical restitution of the non-propagated cardiac ventricular action potential. Pflugers Arch 2024; 476:9-37. [PMID: 37783868 PMCID: PMC10758374 DOI: 10.1007/s00424-023-02866-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Revised: 08/19/2023] [Accepted: 09/21/2023] [Indexed: 10/04/2023]
Abstract
Sudden changes in pacing cycle length are frequently associated with repolarization abnormalities initiating cardiac arrhythmias, and physiologists have long been interested in measuring the likelihood of these events before their manifestation. A marker of repolarization stability has been found in the electrical restitution (ER), the response of the ventricular action potential duration to a pre- or post-mature stimulation, graphically represented by the so-called ER curve. According to the restitution hypothesis (ERH), the slope of this curve provides a quantitative discrimination between stable repolarization and proneness to arrhythmias. ER has been studied at the body surface, whole organ, and tissue level, and ERH has soon become a key reference point in theoretical, clinical, and pharmacological studies concerning arrhythmia development, and, despite criticisms, it is still widely adopted. The ionic mechanism of ER and cellular applications of ERH are covered in the present review. The main criticism on ERH concerns its dependence from the way ER is measured. Over the years, in fact, several different experimental protocols have been established to measure ER, which are also described in this article. In reviewing the state-of-the art on cardiac cellular ER, I have introduced a notation specifying protocols and graphical representations, with the aim of unifying a sometime confusing nomenclature, and providing a physiological tool, better defined in its scope and limitations, to meet the growing expectations of clinical and pharmacological research.
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Affiliation(s)
- Massimiliano Zaniboni
- Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma (Italy), Parco Area Delle Scienze, 11/A, 43124, Parma, Italy.
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Venkateshappa R, Hunter DV, Muralidharan P, Nagalingam RS, Huen G, Faizi S, Luthra S, Lin E, Cheng YM, Hughes J, Khelifi R, Dhunna DP, Johal R, Sergeev V, Shafaattalab S, Julian LM, Poburko DT, Laksman Z, Tibbits GF, Claydon TW. Targeted activation of human ether-à-go-go-related gene channels rescues electrical instability induced by the R56Q+/- long QT syndrome variant. Cardiovasc Res 2023; 119:2522-2535. [PMID: 37739930 PMCID: PMC10676460 DOI: 10.1093/cvr/cvad155] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Revised: 06/22/2023] [Accepted: 07/10/2023] [Indexed: 09/24/2023] Open
Abstract
AIMS Long QT syndrome type 2 (LQTS2) is associated with inherited variants in the cardiac human ether-à-go-go-related gene (hERG) K+ channel. However, the pathogenicity of hERG channel gene variants is often uncertain. Using CRISPR-Cas9 gene-edited hiPSC-derived cardiomyocytes (hiPSC-CMs), we investigated the pathogenic mechanism underlying the LQTS-associated hERG R56Q variant and its phenotypic rescue by using the Type 1 hERG activator, RPR260243. METHODS AND RESULTS The above approaches enable characterization of the unclear causative mechanism of arrhythmia in the R56Q variant (an N-terminal PAS domain mutation that primarily accelerates channel deactivation) and translational investigation of the potential for targeted pharmacologic manipulation of hERG deactivation. Using perforated patch clamp electrophysiology of single hiPSC-CMs, programmed electrical stimulation showed that the hERG R56Q variant does not significantly alter the mean action potential duration (APD90). However, the R56Q variant increases the beat-to-beat variability in APD90 during pacing at constant cycle lengths, enhances the variance of APD90 during rate transitions, and increases the incidence of 2:1 block. During paired S1-S2 stimulations measuring electrical restitution properties, the R56Q variant was also found to increase the variability in rise time and duration of the response to premature stimulations. Application of the hERG channel activator, RPR260243, reduces the APD variance in hERG R56Q hiPSC-CMs, reduces the variability in responses to premature stimulations, and increases the post-repolarization refractoriness. CONCLUSION Based on our findings, we propose that the hERG R56Q variant leads to heterogeneous APD dynamics, which could result in spatial dispersion of repolarization and increased risk for re-entry without significantly affecting the average APD90. Furthermore, our data highlight the antiarrhythmic potential of targeted slowing of hERG deactivation gating, which we demonstrate increases protection against premature action potentials and reduces electrical heterogeneity in hiPSC-CMs.
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Affiliation(s)
- Ravichandra Venkateshappa
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada V5A 1S6
| | - Diana V Hunter
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada V5A 1S6
| | - Priya Muralidharan
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada V5A 1S6
| | - Raghu S Nagalingam
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada V5A 1S6
- Cellular and Regenerative Medicine Centre, British Columbia Children’s Hospital Research Institute, 938 W 28th Ave, Vancouver, BC, Canada V5Z 4H4
| | - Galvin Huen
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada V5A 1S6
| | - Shoaib Faizi
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada V5A 1S6
| | - Shreya Luthra
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada V5A 1S6
| | - Eric Lin
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada V5A 1S6
| | - Yen May Cheng
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada V5A 1S6
| | - Julia Hughes
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada V5A 1S6
| | - Rania Khelifi
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada V5A 1S6
| | - Daman Parduman Dhunna
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada V5A 1S6
| | - Raj Johal
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada V5A 1S6
| | - Valentine Sergeev
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada V5A 1S6
| | - Sanam Shafaattalab
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada V5A 1S6
| | - Lisa M Julian
- Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada V5A 1S6
| | - Damon T Poburko
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada V5A 1S6
| | - Zachary Laksman
- Department of Medicine, School of Biomedical Engineering, University of British Columbia, 2194 Health Sciences Mall, Vancouver, BC, Canada V6T 1Z3
| | - Glen F Tibbits
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada V5A 1S6
- Cellular and Regenerative Medicine Centre, British Columbia Children’s Hospital Research Institute, 938 W 28th Ave, Vancouver, BC, Canada V5Z 4H4
- Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada V5A 1S6
| | - Tom W Claydon
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada V5A 1S6
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Gray RA, Franz MR. Amiodarone prevents wave front-tail interactions in patients with heart failure: an in silico study. Am J Physiol Heart Circ Physiol 2023; 325:H952-H964. [PMID: 37656133 PMCID: PMC10907032 DOI: 10.1152/ajpheart.00227.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Revised: 08/25/2023] [Accepted: 08/25/2023] [Indexed: 09/02/2023]
Abstract
Amiodarone (AM) is an antiarrhythmic drug whose chronic use has proved effective in preventing ventricular arrhythmias in a variety of patient populations, including those with heart failure (HF). AM has both class III [i.e., it prolongs the action potential duration (APD) via blocking potassium channels) and class I (i.e., it affects the rapid sodium channel) properties; however, the specific mechanism(s) by which it prevents reentry formation in patients with HF remains unknown. We tested the hypothesis that AM prevents reentry induction in HF during programmed electrical stimulation (PES) via its ability to induce postrepolarization refractoriness (PRR) via its class I effects on sodium channels. Here we extend our previous human action potential model to represent the effects of both HF and AM separately by calibrating to human tissue and clinical PES data, respectively. We then combine these models (HF + AM) to test our hypothesis. Results from simulations in cells and cables suggest that AM acts to increase PRR and decrease the elevation of takeoff potential. The ability of AM to prevent reentry was studied in silico in two-dimensional sheets in which a variety of APD gradients (ΔAPD) were imposed. Reentrant activity was induced in all HF simulations but was prevented in 23 of 24 HF + AM models. Eliminating the AM-induced slowing of the recovery of inactivation of the sodium channel restored the ability to induce reentry. In conclusion, in silico testing suggests that chronic AM treatment prevents reentry induction in patients with HF during PES via its class I effect to induce PRR.NEW & NOTEWORTHY This work presents a new model of the action potential of the human, which reproduces the complex dynamics during premature stimulation in heart failure patients with and without amiodarone. A specific mechanism of the ability of amiodarone to prevent reentrant arrhythmias is presented.
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Affiliation(s)
- Richard A Gray
- Division of Biomedical Physics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, Food and Drug Administration, Silver Spring, Maryland, United States
| | - Michael R Franz
- Cardiology Division, Veteran Affairs Medical Center, Washington, District of Columbia, United States
- Department of Pharmacology, Georgetown University Medical Center, Washington, District of Columbia, United States
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Impact of Amiodarone Therapy on the Ablation Outcome of Ventricular Tachycardia in Arrhythmogenic Right Ventricular Cardiomyopathy. J Clin Med 2022; 11:jcm11247265. [PMID: 36555882 PMCID: PMC9787968 DOI: 10.3390/jcm11247265] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Revised: 12/04/2022] [Accepted: 12/05/2022] [Indexed: 12/13/2022] Open
Abstract
(1) Background: Catheter ablation (CA) is an accepted treatment option for drug-refractory ventricular tachycardia (VT) in patients with arrhythmogenic right ventricular cardiomyopathy (ARVC). This study investigates the effect of amiodarone on ablation outcomes in ARVC. (2) Methods: The study enrolled patients with ARVC undergoing CA of sustained VT. In all patients, substrate modification was performed to achieve non-inducible VT. The patients were categorized into two groups according to whether they had used amiodarone before CA. Baseline and electrophysiological characteristics, substrate, and outcomes were compared. (3) Results: A total of 72 ARVC patients were studied, including 29 (40.3%) "off" amiodarone and 43 (56.7%) "on" amiodarone. The scar area was similar between the two groups. Patients "off" amiodarone had smaller endocardial and epicardial areas with abnormal electrograms. Twenty of 43 patients (47.5%) "on" amiodarone discontinued it within 3 months after CA. During a mean follow-up period of 43.2 ± 29.5 months, higher VT recurrence was observed in patients "on" amiodarone. Patients "on" amiodarone who discontinued amiodarone after CA had a lower recurrence than those without. (4) Conclusions: Patients with ARVC "on" amiodarone before CA had distinct substrate characteristics and worse ablation outcomes than patients "off" amiodarone, especially in those who had used amiodarone continuously.
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Di Biase L, Romero J, Du X, Mohanty S, Trivedi C, Della Rocca DG, Patel K, Sanchez J, Yang R, Alviz I, Mohanty P, Gianni C, Tarantino N, Zhang XD, Horton R, Al-Ahmad A, Lakkireddy D, Burkhardt DJ, Chen M, Natale A. Catheter ablation of ventricular tachycardia in ischemic cardiomyopathy: Impact of concomitant amiodarone therapy on short- and long-term clinical outcomes. Heart Rhythm 2021; 18:885-893. [PMID: 33592323 DOI: 10.1016/j.hrthm.2021.02.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/22/2020] [Revised: 02/05/2021] [Accepted: 02/10/2021] [Indexed: 11/28/2022]
Abstract
BACKGROUND Substrate catheter ablation of scar-related ventricular tachycardia (VT) is a widely accepted therapeutic option for patients with ischemic cardiomyopathy (ICM). OBJECTIVE The purpose of this study was to investigate whether concomitant amiodarone therapy affects procedural outcomes. METHODS A total of 134 consecutive patients (89% male; age 66 ± 10 years) with ICM undergoing catheter ablation of VT were included in the study. Patients were sorted by amiodarone therapy before ablation. In all patients, a substrate-based catheter ablation (endocardial ± epicardial) in sinus rhythm abolishing all "abnormal" electrograms within the scar was performed. The endpoint of the procedure was VT noninducibility. After the ablation procedure, all antiarrhythmic medications were discontinued. All patients had an implantable cardioverter-defibrillator, and recurrences were analyzed through the device. RESULTS In 84 patients (63%), the ablation was performed on amiodarone; the remaining 50 patients (37%) were off amiodarone. Patients had comparable baseline characteristics. Mean scar size area was 143.6 ± 44.9 cm2 on amiodarone vs 139.2 ± 36.8 cm2 off amiodarone (P = .56). More radiofrequency time was necessary to achieve noninducibility in the off-amiodarone group compared to the on-amiodarone group (68.1 ± 20.1 minutes vs 51.5 ± 19.7 minutes; P <.001). In addition, due to persistent VT inducibility, more patients in the off-amiodarone group required epicardial ablation than in the on-amiodarone group (13/50 [26%] vs 5/84 [6%], respectively; P <.001). During mean follow-up of 23.9 ± 11.6 months, recurrence of any ventricular arrhythmias off antiarrhythmic drugs was 44% (37/84) in the on-amiodarone group vs 22% (11/50) in the off-amiodarone group (P = .013). CONCLUSION Albeit, VT noninducibility after substrate catheter ablation for scar related VT was achieved faster, with less radiofrequency time and less need for epicardial ablation in patients taking amiodarone, these patients had significantly higher VT recurrence at long-term follow-up when this medication was discontinued.
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Affiliation(s)
- Luigi Di Biase
- Cardiac Arrhythmia Center, Montefiore-Einstein Center for Heart and Vascular Care, Division of Cardiology, Department of Medicine, Albert Einstein College of Medicine, New York, New York; Texas Cardiac Arrhythmia Institute, St. David's Medical Center, Austin, Texas
| | - Jorge Romero
- Cardiac Arrhythmia Center, Montefiore-Einstein Center for Heart and Vascular Care, Division of Cardiology, Department of Medicine, Albert Einstein College of Medicine, New York, New York
| | - Xianfeng Du
- Cardiac Arrhythmia Center, Montefiore-Einstein Center for Heart and Vascular Care, Division of Cardiology, Department of Medicine, Albert Einstein College of Medicine, New York, New York; Arrhythmia Center of Cardiology Division, Ningbo First Hospital, Ningbo, China
| | - Sanghamitra Mohanty
- Texas Cardiac Arrhythmia Institute, St. David's Medical Center, Austin, Texas
| | - Chintan Trivedi
- Texas Cardiac Arrhythmia Institute, St. David's Medical Center, Austin, Texas
| | | | - Kavisha Patel
- Cardiac Arrhythmia Center, Montefiore-Einstein Center for Heart and Vascular Care, Division of Cardiology, Department of Medicine, Albert Einstein College of Medicine, New York, New York
| | - Javier Sanchez
- Texas Cardiac Arrhythmia Institute, St. David's Medical Center, Austin, Texas
| | - Ruike Yang
- Cardiac Arrhythmia Center, Montefiore-Einstein Center for Heart and Vascular Care, Division of Cardiology, Department of Medicine, Albert Einstein College of Medicine, New York, New York; Department of Cardiopulmonary Function, Henan Provincial People's Hospital, People's Hospital of Zhengzhou University, Zhengzhou, China
| | - Isabella Alviz
- Cardiac Arrhythmia Center, Montefiore-Einstein Center for Heart and Vascular Care, Division of Cardiology, Department of Medicine, Albert Einstein College of Medicine, New York, New York
| | - Prasant Mohanty
- Texas Cardiac Arrhythmia Institute, St. David's Medical Center, Austin, Texas
| | - Carola Gianni
- Texas Cardiac Arrhythmia Institute, St. David's Medical Center, Austin, Texas
| | - Nicola Tarantino
- Cardiac Arrhythmia Center, Montefiore-Einstein Center for Heart and Vascular Care, Division of Cardiology, Department of Medicine, Albert Einstein College of Medicine, New York, New York
| | - Xiao-Dong Zhang
- Cardiac Arrhythmia Center, Montefiore-Einstein Center for Heart and Vascular Care, Division of Cardiology, Department of Medicine, Albert Einstein College of Medicine, New York, New York
| | - Rodney Horton
- Texas Cardiac Arrhythmia Institute, St. David's Medical Center, Austin, Texas
| | - Amin Al-Ahmad
- Texas Cardiac Arrhythmia Institute, St. David's Medical Center, Austin, Texas
| | | | - David J Burkhardt
- Texas Cardiac Arrhythmia Institute, St. David's Medical Center, Austin, Texas
| | - Minglong Chen
- Cardiology Division, Jiangsu Province Hospital, Nanjing, China
| | - Andrea Natale
- Texas Cardiac Arrhythmia Institute, St. David's Medical Center, Austin, Texas.
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Aidonidis I, Simopoulos V, Stravela S, Dipla K, Stamatiou R, Hatziefthimiou A, Molyvdas PA. Ranolazine depresses conduction of rapid atrial depolarizations in a beating rabbit heart model. J Interv Card Electrophysiol 2020; 62:153-159. [PMID: 32996039 DOI: 10.1007/s10840-020-00865-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Accepted: 09/04/2020] [Indexed: 11/29/2022]
Abstract
PURPOSE Previous clinical studies have shown that ranolazine (RAN) added to amiodarone (AMIO) might accelerate the termination of recent-onset atrial fibrillation. This study was undertaken to delineate possible mechanisms that contribute to the enhancement of the antiarrhythmic efficacy of RAN-AMIO coadministration. METHODS Ten rabbits were anesthetized and two monophasic action potential (MAP) catheters were sequentially inserted into the right atrium. One MAP electrode was used to pace and record; the other electrode was used only for recording MAP from an adjacent atrial region. Intraatrial conduction time (IACT), 2:1 intraatrial conduction block (IACB), and atrial post-repolarization refractoriness (aPRR) were consecutively determined by high-rate atrial burst pacing and programmed stimulation, respectively. All parameters were evaluated during baseline and following AMIO (3 mg/kg iv) or AMIO+RAN (2.4 mg/kg iv bolus +0.134 mg/kg/min maintenance infusion). RESULTS The IACT remained unchanged post AMIO compared with baseline (37.6 ± 3.8 vs 36.4 ± 2.4 ms), whereas the addition of RAN to AMIO significantly prolonged IACT (50.4 ± 3.6 ms, p < .001). The pacing cycle length producing 2:1 IACB was 101.2 ± 21.7 ms at baseline , 117.5 ± 15 ms after AMIO (p = 0.265), and 150 ± 14 ms after AMIO+RAN (p < .001). Baseline aPRR was longer following AMIO treatment (35 ± 5 vs 50 ± 9 ms, p < .01) but remarkably prolonged with RAN supplementation (105 ± 11 ms, p < .001). CONCLUSIONS RAN significantly prolonged the propagation time of rapid atrial depolarizations and potentiated the AMIO-induced moderate increases in aPRR. These mechanisms possibly contribute to the earlier termination of atrial fibrillation when RAN is co-administered with AMIO.
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Affiliation(s)
- I Aidonidis
- Department of Physiology, Faculty of Medicine, University of Thessaly, Larissa, Greece.
| | - V Simopoulos
- Department of Cardiac & Thoracic Surgery, University Hospital of Larissa, Faculty of Medicine, University of Thessaly, Larissa, Greece
| | - S Stravela
- Department of Cardiac & Thoracic Surgery, University Hospital of Larissa, Faculty of Medicine, University of Thessaly, Larissa, Greece
| | - K Dipla
- Department of Sport Sciences at Serres, Aristotle University of Thessaloniki, Thessaloniki, Greece
| | - R Stamatiou
- Department of Physiology, Faculty of Medicine, University of Thessaly, Larissa, Greece
| | - A Hatziefthimiou
- Department of Physiology, Faculty of Medicine, University of Thessaly, Larissa, Greece
| | - P-A Molyvdas
- Department of Physiology, Faculty of Medicine, University of Thessaly, Larissa, Greece
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Kuzmin VS, Abramov AA, Egorov YV, Rosenshtraukh LV. Hypothermia-Induced Postrepolarization Refractoriness Is the Reason of the Atrial Myocardium Tolerance to the Bioelectrical Activity Disorders in the Hibernating and Active Ground Squirrel Citellus undulatus. DOKLADY BIOLOGICAL SCIENCES : PROCEEDINGS OF THE ACADEMY OF SCIENCES OF THE USSR, BIOLOGICAL SCIENCES SECTIONS 2019; 486:63-68. [PMID: 31317446 DOI: 10.1134/s0012496619030050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Revised: 03/18/2019] [Accepted: 03/18/2019] [Indexed: 11/23/2022]
Abstract
The electrophysiological mechanism of the atrial myocardium resistance to the cold-induced arrhythmias was studied in the hibernating ground squirrel Citellus undulatus. The atrial action potentials (APs) and refractoriness were recorded with microelectrodes in isolated multicellular preparations of the atrial myocardium taken from the hibernating and summer active ground squirrels (HS and SAS, respectively) at 37, 27, and 17°С to estimate the AP and refractoriness durations. In both HS and SAS, hypothermia increased the duration of the AP and refractoriness period (APD and RD, respectively), and in both animal groups RD was longer than APD under hypothermia but not at 37°С. This last observation can be a result of the postrepolarization refractoriness (PRR), which seems to contribute substantially to the atrial myocardium tolerance of the hibernating animals to the hypothermia-induced arrhythmias because it prevents afterdepolarizations.
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Affiliation(s)
- V S Kuzmin
- Institute of Experimental Cardiology, Russian Research and Production Cardiological Complex, Ministry of Health, 121552, Moscow, Russia.
| | - A A Abramov
- Institute of Experimental Cardiology, Russian Research and Production Cardiological Complex, Ministry of Health, 121552, Moscow, Russia
| | - Yu V Egorov
- Institute of Experimental Cardiology, Russian Research and Production Cardiological Complex, Ministry of Health, 121552, Moscow, Russia
| | - L V Rosenshtraukh
- Institute of Experimental Cardiology, Russian Research and Production Cardiological Complex, Ministry of Health, 121552, Moscow, Russia
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da Rocha AM, Campbell K, Mironov S, Jiang J, Mundada L, Guerrero-Serna G, Jalife J, Herron TJ. hiPSC-CM Monolayer Maturation State Determines Drug Responsiveness in High Throughput Pro-Arrhythmia Screen. Sci Rep 2017; 7:13834. [PMID: 29061979 PMCID: PMC5653750 DOI: 10.1038/s41598-017-13590-y] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Accepted: 09/25/2017] [Indexed: 01/26/2023] Open
Abstract
Human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CMs) offer a novel in vitro platform for pre-clinical cardiotoxicity and pro-arrhythmia screening of drugs in development. To date hiPSC-CMs used for cardiotoxicity testing display an immature, fetal-like cardiomyocyte structural and electrophysiological phenotype which has called into question the applicability of hiPSC-CM findings to the adult heart. The aim of the current work was to determine the effect of cardiomyocyte maturation state on hiPSC-CM drug responsiveness. To this end, here we developed a high content pro-arrhythmia screening platform consisting of either fetal-like or mature hiPSC-CM monolayers. Compounds tested in the screen were selected based on the pro-arrhythmia risk classification (Low risk, Intermediate risk, or High risk) established recently by the FDA and major stakeholders in the Drug Discovery field for the validation of the Comprehensive In vitro Pro-Arrhythmia Assay (CiPA). Here we show that maturation state of hiPSC-CMs determines the absolute pro-arrhythmia risk score calculated for these compounds. Thus, the maturation state of hiPSC-CMs should be considered prior to pro-arrhythmia and cardiotoxicity screening in drug discovery programs.
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Affiliation(s)
- André Monteiro da Rocha
- University of Michigan, Internal Medicine-Cardiology, Center for Arrhythmia Research, Ann Arbor, MI, 48109, USA.,Frankel Cardiovascular Center, Cardiovascular Regeneration Core Laboratory, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Katherine Campbell
- University of Michigan, Internal Medicine-Cardiology, Center for Arrhythmia Research, Ann Arbor, MI, 48109, USA
| | - Sergey Mironov
- University of Michigan, Internal Medicine-Cardiology, Center for Arrhythmia Research, Ann Arbor, MI, 48109, USA
| | - Jiang Jiang
- University of Michigan, Internal Medicine-Cardiology, Center for Arrhythmia Research, Ann Arbor, MI, 48109, USA
| | - Lakshmi Mundada
- University of Michigan, Internal Medicine-Cardiology, Center for Arrhythmia Research, Ann Arbor, MI, 48109, USA
| | - Guadalupe Guerrero-Serna
- University of Michigan, Internal Medicine-Cardiology, Center for Arrhythmia Research, Ann Arbor, MI, 48109, USA
| | - José Jalife
- University of Michigan, Internal Medicine-Cardiology, Center for Arrhythmia Research, Ann Arbor, MI, 48109, USA.,Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), 28029, Madrid, Spain.,CIBER of Cardiovascular Diseases (CIBERCV), ISCIII, Madrid, Spain
| | - Todd J Herron
- University of Michigan, Internal Medicine-Cardiology, Center for Arrhythmia Research, Ann Arbor, MI, 48109, USA. .,Frankel Cardiovascular Center, Cardiovascular Regeneration Core Laboratory, University of Michigan, Ann Arbor, MI, 48109, USA.
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11
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Osadchii OE. Role of abnormal repolarization in the mechanism of cardiac arrhythmia. Acta Physiol (Oxf) 2017; 220 Suppl 712:1-71. [PMID: 28707396 DOI: 10.1111/apha.12902] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
In cardiac patients, life-threatening tachyarrhythmia is often precipitated by abnormal changes in ventricular repolarization and refractoriness. Repolarization abnormalities typically evolve as a consequence of impaired function of outward K+ currents in cardiac myocytes, which may be caused by genetic defects or result from various acquired pathophysiological conditions, including electrical remodelling in cardiac disease, ion channel modulation by clinically used pharmacological agents, and systemic electrolyte disorders seen in heart failure, such as hypokalaemia. Cardiac electrical instability attributed to abnormal repolarization relies on the complex interplay between a provocative arrhythmic trigger and vulnerable arrhythmic substrate, with a central role played by the excessive prolongation of ventricular action potential duration, impaired intracellular Ca2+ handling, and slowed impulse conduction. This review outlines the electrical activity of ventricular myocytes in normal conditions and cardiac disease, describes classical electrophysiological mechanisms of cardiac arrhythmia, and provides an update on repolarization-related surrogates currently used to assess arrhythmic propensity, including spatial dispersion of repolarization, activation-repolarization coupling, electrical restitution, TRIaD (triangulation, reverse use dependence, instability, and dispersion), and the electromechanical window. This is followed by a discussion of the mechanisms that account for the dependence of arrhythmic vulnerability on the location of the ventricular pacing site. Finally, the review clarifies the electrophysiological basis for cardiac arrhythmia produced by hypokalaemia, and gives insight into the clinical importance and pathophysiology of drug-induced arrhythmia, with particular focus on class Ia (quinidine, procainamide) and Ic (flecainide) Na+ channel blockers, and class III antiarrhythmic agents that block the delayed rectifier K+ channel (dofetilide).
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Affiliation(s)
- O. E. Osadchii
- Department of Health Science and Technology; University of Aalborg; Aalborg Denmark
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12
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Saengklub N, Limprasutr V, Sawangkoon S, Hamlin RL, Kijtawornrat A. Dronedarone attenuates the duration of atrial fibrillation in a dog model of sustained atrial fibrillation. Exp Anim 2017; 66:251-258. [PMID: 28381818 PMCID: PMC5543246 DOI: 10.1538/expanim.17-0002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Atrial fibrillation (AF) is a supraventricular arrhythmia that leads to a decrease in
cardiac output and impairs cardiac function and quality of life. Dronedarone has an
atrial-selective property and has been used for management of AF in humans, but limited
information is available in dogs. This study was designed to evaluate efficacy of
dronedarone in attenuating the duration of AF in dog model of sustained AF. Six beagle
dogs were anesthetized with isoflurane and instrumented to measure atrial action potential
duration (aAPD) and atrial effective refractory period (AERP). Then AF was induced by
rapid right atrial pacing (20 V, 40 Hz) simultaneously with infusion of phenylephrine (2
µg/kg/min, intravenously) for 20 min. The duration of sustained AF was
recorded, and the animals were allowed to recover. Dronedarone was given at a dose of 20
mg/kg, BID, orally for 7 days. On the last day, the dogs were anesthetized again to record
aAPD and AERP, and AF was induced with the same procedure as described above. The results
showed that after dronedarone administration the aAPD was lengthened significantly from
76.4 ± 4.2 ms to 91.2 ± 3.9 ms (P<0.05) and AERP was prolonged
significantly from 97.5 ± 2.8 ms to 120 ± 4.8 ms (P<0.05). The
duration of sustained AF was also significantly attenuated after receipt of dronedarone
(P<0.05). It can be suggested that oral dronedarone attenuates the
duration of sustained AF in a dog model of AF by extending the AERP more than the aAPD,
causing post-repolarization refractoriness. Hence, dronedarone may be useful for
management of AF in dogs.
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Affiliation(s)
- Nakkawee Saengklub
- Animal Physiology Program, Faculty of Veterinary Science, Chulalongkorn University, 39 Henri Dunant Road, Pathumwan, Bangkok 10330, Thailand
| | - Vudhiporn Limprasutr
- Department of Physiology, Faculty of Veterinary Science, Chulalongkorn University, 39 Henri Dunant Road, Pathumwan, Bangkok 10330, Thailand
| | - Suwanakiet Sawangkoon
- Department of Physiology, Faculty of Veterinary Science, Chulalongkorn University, 39 Henri Dunant Road, Pathumwan, Bangkok 10330, Thailand
| | - Robert L Hamlin
- QTest Labs, Ltd., 6456 Fiesta Drive, Columbus, Ohio 43235, USA
| | - Anusak Kijtawornrat
- Department of Physiology, Faculty of Veterinary Science, Chulalongkorn University, 39 Henri Dunant Road, Pathumwan, Bangkok 10330, Thailand.,Research clusters: research study and testing of drug's effect related to cardiovascular system in laboratory animal, Chulalongkorn University, 39 Henri Dunant Road, Pathumwan, Bangkok 10330, Thailand
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13
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Reduction of atrial fibrillation by Tanshinone IIA in chronic heart failure. Biomed Pharmacother 2016; 84:1760-1767. [DOI: 10.1016/j.biopha.2016.10.110] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2016] [Revised: 10/25/2016] [Accepted: 10/30/2016] [Indexed: 11/30/2022] Open
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14
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Syeda F, Holmes AP, Yu TY, Tull S, Kuhlmann SM, Pavlovic D, Betney D, Riley G, Kucera JP, Jousset F, de Groot JR, Rohr S, Brown NA, Fabritz L, Kirchhof P. PITX2 Modulates Atrial Membrane Potential and the Antiarrhythmic Effects of Sodium-Channel Blockers. J Am Coll Cardiol 2016; 68:1881-1894. [PMID: 27765191 PMCID: PMC5075046 DOI: 10.1016/j.jacc.2016.07.766] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Revised: 07/05/2016] [Accepted: 07/20/2016] [Indexed: 12/19/2022]
Abstract
BACKGROUND Antiarrhythmic drugs are widely used to treat patients with atrial fibrillation (AF), but the mechanisms conveying their variable effectiveness are not known. Recent data suggested that paired like homeodomain-2 transcription factor (PITX2) might play an important role in regulating gene expression and electrical function of the adult left atrium (LA). OBJECTIVES After determining LA PITX2 expression in AF patients requiring rhythm control therapy, the authors assessed the effects of Pitx2c on LA electrophysiology and the effect of antiarrhythmic drugs. METHODS LA PITX2 messenger ribonucleic acid (mRNA) levels were measured in 95 patients undergoing thoracoscopic AF ablation. The effects of flecainide, a sodium (Na+)-channel blocker, and d,l-sotalol, a potassium channel blocker, were studied in littermate mice with normal and reduced Pitx2c mRNA by electrophysiological study, optical mapping, and patch clamp studies. PITX2-dependent mechanisms of antiarrhythmic drug action were studied in human embryonic kidney (HEK) cells expressing human Na channels and by modeling human action potentials. RESULTS Flecainide 1 μmol/l was more effective in suppressing atrial arrhythmias in atria with reduced Pitx2c mRNA levels (Pitx2c+/-). Resting membrane potential was more depolarized in Pitx2c+/- atria, and TWIK-related acid-sensitive K+ channel 2 (TASK-2) gene and protein expression were decreased. This resulted in enhanced post-repolarization refractoriness and more effective Na-channel inhibition. Defined holding potentials eliminated differences in flecainide's effects between wild-type and Pitx2c+/- atrial cardiomyocytes. More positive holding potentials replicated the increased effectiveness of flecainide in blocking human Nav1.5 channels in HEK293 cells. Computer modeling reproduced an enhanced effectiveness of Na-channel block when resting membrane potential was slightly depolarized. CONCLUSIONS PITX2 mRNA modulates atrial resting membrane potential and thereby alters the effectiveness of Na-channel blockers. PITX2 and ion channels regulating the resting membrane potential may provide novel targets for antiarrhythmic drug development and companion therapeutics in AF.
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Affiliation(s)
- Fahima Syeda
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Andrew P Holmes
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Ting Y Yu
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, United Kingdom; Physical Sciences of Imaging in the Biomedical Sciences, School of Chemistry, University of Birmingham, Birmingham, United Kingdom
| | - Samantha Tull
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, United Kingdom
| | | | - Davor Pavlovic
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Daniel Betney
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Genna Riley
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Jan P Kucera
- Department of Physiology, University of Bern, Bern, Switzerland
| | - Florian Jousset
- Department of Physiology, University of Bern, Bern, Switzerland
| | - Joris R de Groot
- Heart Center, Department of Cardiology, Academisch Medisch Centrum, Amsterdam, the Netherlands
| | - Stephan Rohr
- Department of Physiology, University of Bern, Bern, Switzerland
| | - Nigel A Brown
- St. George's Hospital Medical School, University of London, London, United Kingdom
| | - Larissa Fabritz
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, United Kingdom; Department of Cardiovascular Medicine, University Hospital Muenster, Muenster, Germany; Atrial Fibrillation NETwork, Muenster, Germany; University Hospitals Birmingham NHS Foundation Trust, Birmingham, United Kingdom
| | - Paulus Kirchhof
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, United Kingdom; Department of Cardiovascular Medicine, University Hospital Muenster, Muenster, Germany; Atrial Fibrillation NETwork, Muenster, Germany; University Hospitals Birmingham NHS Foundation Trust, Birmingham, United Kingdom; Sandwell and West Birmingham Hospitals NHS Trust, Birmingham, United Kingdom.
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15
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Franz MR, Gray RA, Karasik P, Moore HJ, Singh SN. Drug-induced post-repolarization refractoriness as an antiarrhythmic principle and its underlying mechanism. Europace 2014; 16 Suppl 4:iv39-iv45. [DOI: 10.1093/europace/euu274] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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16
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Gemmell P, Burrage K, Rodriguez B, Quinn TA. Population of computational rabbit-specific ventricular action potential models for investigating sources of variability in cellular repolarisation. PLoS One 2014; 9:e90112. [PMID: 24587229 PMCID: PMC3938586 DOI: 10.1371/journal.pone.0090112] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Accepted: 01/29/2014] [Indexed: 11/18/2022] Open
Abstract
Variability is observed at all levels of cardiac electrophysiology. Yet, the underlying causes and importance of this variability are generally unknown, and difficult to investigate with current experimental techniques. The aim of the present study was to generate populations of computational ventricular action potential models that reproduce experimentally observed intercellular variability of repolarisation (represented by action potential duration) and to identify its potential causes. A systematic exploration of the effects of simultaneously varying the magnitude of six transmembrane current conductances (transient outward, rapid and slow delayed rectifier K+, inward rectifying K+, L-type Ca2+, and Na+/K+ pump currents) in two rabbit-specific ventricular action potential models (Shannon et al. and Mahajan et al.) at multiple cycle lengths (400, 600, 1,000 ms) was performed. This was accomplished with distributed computing software specialised for multi-dimensional parameter sweeps and grid execution. An initial population of 15,625 parameter sets was generated for both models at each cycle length. Action potential durations of these populations were compared to experimentally derived ranges for rabbit ventricular myocytes. 1,352 parameter sets for the Shannon model and 779 parameter sets for the Mahajan model yielded action potential duration within the experimental range, demonstrating that a wide array of ionic conductance values can be used to simulate a physiological rabbit ventricular action potential. Furthermore, by using clutter-based dimension reordering, a technique that allows visualisation of multi-dimensional spaces in two dimensions, the interaction of current conductances and their relative importance to the ventricular action potential at different cycle lengths were revealed. Overall, this work represents an important step towards a better understanding of the role that variability in current conductances may play in experimentally observed intercellular variability of rabbit ventricular action potential repolarisation.
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Affiliation(s)
- Philip Gemmell
- Department of Computer Science, University of Oxford, Oxford, United Kingdom
| | - Kevin Burrage
- Department of Computer Science, University of Oxford, Oxford, United Kingdom
- School of Mathematical Sciences, Queensland University of Technology, Brisbane, Australia
| | - Blanca Rodriguez
- Department of Computer Science, University of Oxford, Oxford, United Kingdom
| | - T. Alexander Quinn
- Department of Physiology and Biophysics, Dalhousie University, Halifax, NS, Canada
- * E-mail:
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17
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Frommeyer G, Milberg P, Witte P, Stypmann J, Koopmann M, Lücke M, Osada N, Breithardt G, Fehr M, Eckardt L. A new mechanism preventing proarrhythmia in chronic heart failure: rapid phase-III repolarization explains the low proarrhythmic potential of amiodarone in contrast to sotalol in a model of pacing-induced heart failure. Eur J Heart Fail 2014; 13:1060-9. [DOI: 10.1093/eurjhf/hfr107] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- Gerrit Frommeyer
- Department of Cardiology and Angiology; Hospital of the Westfälische Wilhelms-University; Münster Germany
| | - Peter Milberg
- Department of Cardiology and Angiology; Hospital of the Westfälische Wilhelms-University; Münster Germany
| | - Patricia Witte
- Department of Cardiology and Angiology; Hospital of the Westfälische Wilhelms-University; Münster Germany
| | - Jörg Stypmann
- Department of Cardiology and Angiology; Hospital of the Westfälische Wilhelms-University; Münster Germany
| | - Matthias Koopmann
- Department of Cardiology and Angiology; Hospital of the Westfälische Wilhelms-University; Münster Germany
| | - Martin Lücke
- Experimental Animal Research Centre; Medical Faculty of the Westfälische Wilhelms-University; Münster Germany
| | - Nani Osada
- Department of Medical Informatics and Biomathematics; University of Münster; Münster Germany
| | - Günter Breithardt
- Department of Cardiology and Angiology; Hospital of the Westfälische Wilhelms-University; Münster Germany
| | - Michael Fehr
- Clinic of Exotic Pets, Reptiles, Exotic and Feral Birds; University of Hanover; Hanover Germany
| | - Lars Eckardt
- Department of Cardiology and Angiology; Hospital of the Westfälische Wilhelms-University; Münster Germany
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18
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Frommeyer G, Schmidt M, Clauß C, Kaese S, Stypmann J, Pott C, Eckardt L, Milberg P. Further insights into the underlying electrophysiological mechanisms for reduction of atrial fibrillation by ranolazine in an experimental model of chronic heart failure. Eur J Heart Fail 2014; 14:1322-31. [DOI: 10.1093/eurjhf/hfs163] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Affiliation(s)
- Gerrit Frommeyer
- Division of Electrophysiology, Department of Cardiovascular Medicine; University Hospital of Münster; Germany
| | - Marco Schmidt
- Division of Electrophysiology, Department of Cardiovascular Medicine; University Hospital of Münster; Germany
| | - Catharina Clauß
- Division of Electrophysiology, Department of Cardiovascular Medicine; University Hospital of Münster; Germany
| | - Sven Kaese
- Division of Electrophysiology, Department of Cardiovascular Medicine; University Hospital of Münster; Germany
| | - Jörg Stypmann
- Division of Cardiology, Department of Cardiovascular Medicine; University Hospital of Münster; Germany
| | - Christian Pott
- Division of Electrophysiology, Department of Cardiovascular Medicine; University Hospital of Münster; Germany
| | - Lars Eckardt
- Division of Electrophysiology, Department of Cardiovascular Medicine; University Hospital of Münster; Germany
| | - Peter Milberg
- Division of Electrophysiology, Department of Cardiovascular Medicine; University Hospital of Münster; Germany
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19
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Milberg P, Frommeyer G, Ghezelbash S, Rajamani S, Osada N, Razvan R, Belardinelli L, Breithardt G, Eckardt L. Sodium channel block by ranolazine in an experimental model of stretch-related atrial fibrillation: prolongation of interatrial conduction time and increase in post-repolarization refractoriness. ACTA ACUST UNITED AC 2013; 15:761-9. [DOI: 10.1093/europace/eus399] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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20
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Frommeyer G, Rajamani S, Grundmann F, Stypmann J, Osada N, Breithardt G, Belardinelli L, Eckardt L, Milberg P. New Insights into the Beneficial Electrophysiologic Profile of Ranolazine in Heart Failure: Prevention of Ventricular Fibrillation With Increased Postrepolarization Refractoriness and Without Drug-Induced Proarrhythmia. J Card Fail 2012. [DOI: 10.1016/j.cardfail.2012.10.017] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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21
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Bonny A, De Sisti A, Márquez MF, Megbemado R, Hidden-Lucet F, Fontaine G. Low doses of intravenous epinephrine for refractory sustained monomorphic ventricular tachycardia. World J Cardiol 2012; 4:296-301. [PMID: 23110246 PMCID: PMC3482623 DOI: 10.4330/wjc.v4.i10.296] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/18/2012] [Revised: 09/25/2012] [Accepted: 10/02/2012] [Indexed: 02/06/2023] Open
Abstract
We report three cases of sustained monomorphic ventricular tachycardia (VT) in the setting of coronary artery disease, resistant to beta-blockers in two patients and to amiodarone in all, successfully terminated by low doses of intravenous (IV) epinephrine. VT was the first manifestation of coronary artery disease in one patient, whereas the other two patients had a previous history of myocardial infarction and were recipients of an implantable cardioverter-defibrillator (ICD). One of these two patients experienced an arrhythmic storm. All had hemodynamic instability at the time of epinephrine administration. A single slow administration of IV epinephrine (0.5 to 1 mg administered over 30 to 60 s) restored sinus rhythm after 30-90 s with only minor side effects. In the ICD patient with recurrent VT and several cardioversions due to transformation of VT to ventricular fibrillation, epinephrine injection led to the avoidance of further shocks. Although potentially harmful, low doses of IV epinephrine used alone or in combination with beta-blocker treatment and electrical cardioversion may be an alternative effective therapy for sustained monomorphic VT refractory to amiodarone. The role of epinephrine in the termination of VT should be studied further, especially in patients pre-treated with amiodarone in combination with beta-blockers.
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Affiliation(s)
- Aimé Bonny
- Aimé Bonny, Antonio De Sisti, Françoise Hidden-Lucet, Guy Fontaine, Hôpital Pitié-Salpêtrière, Unité de Rythmologie, 47-83 Boulevard de l'Hôpital, 75651 Paris, France
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22
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Frommeyer G, Kaiser D, Uphaus T, Kaese S, Osada N, Rajamani S, Belardinelli L, Breithardt G, Eckardt L, Milberg P. Effect of ranolazine on ventricular repolarization in class III antiarrhythmic drug-treated rabbits. Heart Rhythm 2012; 9:2051-8. [PMID: 23044390 DOI: 10.1016/j.hrthm.2012.08.029] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2012] [Indexed: 11/16/2022]
Abstract
BACKGROUND Ranolazine exhibits a synergistic effect in combination with class III drugs to suppress atrial fibrillation. OBJECTIVE To investigate whether a combination therapy affects repolarization and provokes ventricular tachyarrhythmias (VT) in a sensitive model of proarrhythmia. METHODS Thirty-seven rabbits were assigned to 3 groups and fed with amiodarone (50 mg/kg/d; n = 10) or dronedarone (50 mg/kg/d; n = 10) over a period of 6 weeks. A third group was used as control (n = 17). After obtaining baseline data in Langendorff-perfused control hearts, sotalol (100 μM) was administered in this group. Thereafter, ranolazine (10 μM) was additionally infused on top of amiodarone, dronedarone, or sotalol. RESULTS Chronic treatment with amiodarone or dronedarone as well as sotalol significantly increased action potential duration at 90% repolarization (APD(90)). Additional treatment with ranolazine further increased APD(90) in amiodarone- and dronedarone-pretreated hearts but not in sotalol-treated hearts. Ranolazine increased postrepolarization refractoriness as compared with amiodarone or dronedarone alone owing to a marked effect on the refractory period. In contrast to amiodarone and dronedarone, acute application of sotalol increased dispersion of repolarization (P < .05). Additional treatment with ranolazine did not further increase spatial or temporal dispersion. After lowering extracellular [K(+)] in bradycardic hearts, no proarrhythmia occurred in amiodarone- or dronedarone-treated hearts whereas 11 of 17 sotalol-treated hearts showed early afterdepolarizations and subsequent polymorphic VT. Additional treatment with ranolazine reduced the number of VT episodes in sotalol-treated hearts and did not cause proarrhythmia in combination with amiodarone or dronedarone. CONCLUSIONS Application of ranolazine on top of class III drugs does not cause proarrhythmia despite a marked effect on ventricular repolarization. The effect of ranolazine on the repolarization reserve is associated with the lack of effect on early afterdepolarizations and dispersion of repolarization.
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Affiliation(s)
- Gerrit Frommeyer
- Division of Electrophysiology, Department of Cardiovascular Medicine, University of Münster, Münster, Germany
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23
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Aidonidis I, Doulas K, Hatziefthimiou A, Tagarakis G, Simopoulos V, Rizos I, Tsilimingas N, Molyvdas PA. Ranolazine-Induced Postrepolarization Refractoriness Suppresses Induction of Atrial Flutter and Fibrillation in Anesthetized Rabbits. J Cardiovasc Pharmacol Ther 2012; 18:94-101. [DOI: 10.1177/1074248412453874] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Ranolazine (Ran) is a novel anti-ischemic agent with electrophysiologic properties mainly attributed to the inhibition of late Na+ current and atrial-selective early Na+ current. However, there are only limited data regarding its efficacy and mechanism of action against atrial flutter (Afl) and atrial fibrillation (AF) in intact animals. Therefore, we aimed to investigate the electrophysiologic mechanism of Ran in a rabbit model of inducible atrial tachyarrhythmias elicited by acetylcholine (ACh). Arrhythmias were produced in 19 rabbits by rapid atrial burst pacing during control, after intravenous ACh and after Ran + ACh administration. Recording of right atrial monophasic action potentials (MAPs) and programmed stimulation were utilized to determine the duration of atrial repolarization at various cycle lengths and voltage levels of action potential, including 75% of total MAP duration (MAPD75), effective refractory period (ERP), and postrepolarization refractoriness (PRR = ERP − MAPD75) prior to and after Ran. Control stimulation yielded no arrhythmias or maximal nonsustained runs of Afl/AF. Upon ACh, 17 of 19 rabbits exhibited sustained Afl and AF as well as mixed forms of Afl/AF, while 2 animals revealed none or short runs of nonsustained arrhythmias and were excluded from the study. High-frequency burst pacing during the first 30 minutes after Ran + ACh failed to induce any arrhythmia in 13 of 17 rabbits (76%), while 2 animals displayed sustained Afl/AF and 2 other animals nonsustained Afl/AF. At basic stimulation cycle length of 250 milliseconds, Ran prolonged baseline atrial ERP (80 ± 8 vs 120 ± 9 milliseconds, P < .001) much more than MAPD75 (65 ± 7 vs 85 ± 7 milliseconds, P < .001), leading to atrial PRR which was more pronounced after Ran compared with control measurements (35 ± 11 vs 15 ± 10 milliseconds, P < .001). This in vivo study demonstrates that Ran exerts antiarrhythmic activity by suppressing inducibility of ACh-mediated Afl/AF in intact rabbits. Its action may predominantly be related to a significant increase in atrial PRR, resulting in depressed electrical excitability and impediment of arrhythmia initiation.
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Affiliation(s)
- Isaac Aidonidis
- Department of Physiology, Medical School of Larissa & Thoracic and Cardiovascular Surgery of the University Hospital of Larissa, University of Thessaly, Larissa, Greece
| | - Konstantinos Doulas
- Department of Physiology, Medical School of Larissa & Thoracic and Cardiovascular Surgery of the University Hospital of Larissa, University of Thessaly, Larissa, Greece
| | - Apostolia Hatziefthimiou
- Department of Physiology, Medical School of Larissa & Thoracic and Cardiovascular Surgery of the University Hospital of Larissa, University of Thessaly, Larissa, Greece
| | - Georgios Tagarakis
- Department of Physiology, Medical School of Larissa & Thoracic and Cardiovascular Surgery of the University Hospital of Larissa, University of Thessaly, Larissa, Greece
| | - Vassilios Simopoulos
- Department of Physiology, Medical School of Larissa & Thoracic and Cardiovascular Surgery of the University Hospital of Larissa, University of Thessaly, Larissa, Greece
| | - Ioannis Rizos
- Department of Cardiology, Attikon University Hospital of Athens, Greece
| | - Nikolaos Tsilimingas
- Department of Physiology, Medical School of Larissa & Thoracic and Cardiovascular Surgery of the University Hospital of Larissa, University of Thessaly, Larissa, Greece
| | - Paschalis-Adam Molyvdas
- Department of Physiology, Medical School of Larissa & Thoracic and Cardiovascular Surgery of the University Hospital of Larissa, University of Thessaly, Larissa, Greece
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Postrepolarization refractoriness in acute ischemia and after antiarrhythmic drug administration: Action potential duration is not always an index of the refractory period. Heart Rhythm 2012; 9:977-82. [DOI: 10.1016/j.hrthm.2012.01.021] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2011] [Indexed: 11/17/2022]
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Zhou SX, Fang C, Zheng SX, Zhang YL, Lei J, Wang JF. Effect of amiodarone on dispersion of ventricular repolarization in a canine congestive heart failure model. Clin Exp Pharmacol Physiol 2012; 39:241-6. [PMID: 22229329 DOI: 10.1111/j.1440-1681.2012.05667.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The effects of amiodarone on ventricular electrophysiological parameters, especially the dispersion of ventricular repolarization, were investigated in a canine model of congestive heart failure (CHF). Dogs were randomized to either a control, amiodarone, CHF, or CHF+amiodarone group. Dogs in the CHF and CHF+amiodarone groups underwent 4-5 weeks of rapid ventricular pacing; dogs in the control and amiodarone groups underwent sham operation only. Amiodarone (20 mg/kg per day) was administered orally, beginning on postoperative Day 1, in the treatment groups; ventricular electrophysiological variables were evaluated 4-5 weeks after rapid pacing or sham operation. In CHF dogs, the transmural dispersion ventricular repolarization time (TDVRT) increased significantly. Amiodarone significantly decreased the TDVRT in CHF dogs. The ventricular fibrillation threshold (VFT) decreased in the CHF group. Amiodarone increased the VFT in CHF dogs. The TDVRT increased in CHF dogs, but amiodarone decreased TDVRT and increased VFT in these dogs. These results suggest a beneficial effect of amiodarone on malignant arrhythmias and may provide the basis for its use in CHF patients.
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Affiliation(s)
- Shu-Xian Zhou
- Division of Cardiology, Department of Internal Medicine, Sun Yat-Sen Memorial Hospital of Sun Yat-Sen University, Guangzhou, China.
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Franz MR, Singh SN. Comparative pharmacophysiology of vernakalant, ranolazine, and d-sotalol in canine pulmonary vein sleeve preparations: new flavors or same old taste? Heart Rhythm 2012; 9:430-1. [DOI: 10.1016/j.hrthm.2011.10.030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/25/2011] [Indexed: 10/15/2022]
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Burashnikov A, Antzelevitch C. Ranolazine versus amiodarone for prevention of postoperative atrial fibrillation. Future Cardiol 2011; 7:733-7. [PMID: 22050058 PMCID: PMC4737707 DOI: 10.2217/fca.11.67] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
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
| | - Charles Antzelevitch
- Gordon K Moe Scholar, Masonic Medical Research Laboratory, 2150 Bleecker St, Utica, NY 13501, USA
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OSAKA TOSHIYUKI, YOKOYAMA ERIKO, HASEBE HIDEYUKI, KODAMA ITSUO. Effects of Chronic Amiodarone on the Electrical Restitution in the Human Ventricle With Reference to Its Antiarrhythmic Efficacy. J Cardiovasc Electrophysiol 2011; 22:669-76. [DOI: 10.1111/j.1540-8167.2010.01990.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Dautova Y, Zhang Y, Grace AA, Huang CLH. Experimental Physiology -Research Paper: Atrial arrhythmogenic properties in wild-type andScn5a+/− murine hearts. Exp Physiol 2010; 95:994-1007. [DOI: 10.1113/expphysiol.2010.053868] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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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] [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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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] [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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Faria DM, Viviane AG, Galvão KM, Caricati-Neto A, Godoy CMG. Influence of age on inducibility and cholinergic modulation of arrhythmia in isolated rat right atria. AGE (DORDRECHT, NETHERLANDS) 2009; 31:51-58. [PMID: 19234768 PMCID: PMC2645994 DOI: 10.1007/s11357-008-9080-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2008] [Accepted: 10/03/2008] [Indexed: 05/27/2023]
Abstract
The effects of carbachol and atropine on the number of trains (NT) and on the train stimulus strength (SS) necessary to induce arrhythmia were studied in isolated right atria of infant, young, adult and mature rats submitted to electric field stimulation (66.7 Hz, 5 ms pulse-duration, 250 pulses). Carbachol (1 microM) decreased NT from four (control) to two in all ages tested. Atropine (1 microM) prevented tachyarrhythmia induction in tissue of all ages, even with NT equal to 12, except for mature rats (typically four trains). The SS decreases from infant to adult age [5- to 2-fold atrial threshold (AT)] and increases in mature animals (5-fold AT). Carbachol changes this result only for mature rats (5- to 2-fold AT). The SS was decreased by carbachol (1 microM) from 5- to 3-fold AT in mature rats, but atropine did not modify SS in this age. These results indicate that inducibility and cholinergic modulation of atrial tachyarrhythmia is influenced by age.
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Affiliation(s)
- D. M. Faria
- Núcleo de Pesquisas Tecnológicas, University of Mogi das Cruzes (UMC), Avenida Dr. Cândido Xavier de Almeida e Souza, 200, Centro Cívico, Mogi das Cruzes, SP 08780-911 Brazil
| | - A. G. Viviane
- Núcleo de Pesquisas Tecnológicas, University of Mogi das Cruzes (UMC), Avenida Dr. Cândido Xavier de Almeida e Souza, 200, Centro Cívico, Mogi das Cruzes, SP 08780-911 Brazil
| | - K. M. Galvão
- Department of Pharmacology, Escola Paulista de Medicina (UNIFESP/EPM), Federal University of São Paulo, São Paulo, SP Brazil
| | - A. Caricati-Neto
- Department of Pharmacology, Escola Paulista de Medicina (UNIFESP/EPM), Federal University of São Paulo, São Paulo, SP Brazil
| | - C. M. G. Godoy
- Núcleo de Pesquisas Tecnológicas, University of Mogi das Cruzes (UMC), Avenida Dr. Cândido Xavier de Almeida e Souza, 200, Centro Cívico, Mogi das Cruzes, SP 08780-911 Brazil
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Sicouri S, Belardinelli L, Carlsson L, Antzelevitch C. Potent antiarrhythmic effects of chronic amiodarone in canine pulmonary vein sleeve preparations. J Cardiovasc Electrophysiol 2009; 20:803-10. [PMID: 19298559 DOI: 10.1111/j.1540-8167.2009.01449.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
OBJECTIVES To examine the effects of chronic amiodarone on the electrophysiology of canine pulmonary vein (PV) sleeve preparations and left ventricular wedge preparation. BACKGROUND Amiodarone is commonly used for the treatment of ventricular and supraventricular arrhythmias. Ectopic activity arising from the PV plays a prominent role in the development of atrial fibrillation (AF). METHODS Standard microelectrode techniques were used to evaluate the electrophysiological characteristics of superfused PV sleeve (left superior or inferior) and arterially perfused left ventricular (LV) wedge preparations isolated from untreated and chronic amiodarone-treated dogs (amiodarone, 40 mg/kg daily for 6 weeks). RESULTS In PV sleeves, chronic amiodarone (n = 6) induced a significant increase in action potential duration at 90% repolarization (APD90) and a significant use-dependent reduction in Vmax leading to 1:1 activation failure at long cycle lengths (basic cycle length of 124 +/- 15 ms in control vs 420 +/- 320 ms after chronic amiodarone [P < 0.01]). Diastolic threshold of excitation increased from 0.3 +/- 0.2 to 1.8 +/- 0.7 mA (P < 0.01). Delayed and late phase 3 early afterdepolarizations and triggered activity could be induced in PV sleeve preparations using acetylcholine (ACh, 1 microM), high calcium ([Ca2+]o = 5.4 mM), isoproterenol (Iso, 1 microM), or their combination in 6 of 6 untreated PV sleeves, but in only 1 of 5 chronic amiodarone-treated PV sleeve preparations. Vmax, conduction velocity, and 1:1 activation failure were much more affected in PV sleeves versus LV wedge preparations isolated from amiodarone-treated animals. CONCLUSIONS The results point to potent effects of chronic amiodarone to preferentially suppress arrhythmogenic substrates and triggers arising from the PV sleeves of the dog.
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Affiliation(s)
- Serge Sicouri
- Masonic Medical Research Laboratory, Utica, New York 13501, USA
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Dautova Y, Zhang Y, Sabir I, Grace AA, Huang CLH. Atrial arrhythmogenesis in wild-type and Scn5a+/delta murine hearts modelling LQT3 syndrome. Pflugers Arch 2009; 458:443-57. [PMID: 19184093 PMCID: PMC2691533 DOI: 10.1007/s00424-008-0633-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2008] [Accepted: 12/25/2008] [Indexed: 01/02/2023]
Abstract
Long QT(3) (LQT3) syndrome is associated with abnormal repolarisation kinetics, prolonged action potential durations (APD) and QT intervals and may lead to life-threatening ventricular arrhythmias. However, there have been few physiological studies of its effects on atrial electrophysiology. Programmed electrical stimulation and burst pacing induced atrial arrhythmic episodes in 16 out of 16 (16/16) wild-type (WT) and 7/16 genetically modified Scn5a+/Δ (KPQ) Langendorff-perfused murine hearts modelling LQT3 (P < 0.001 for both), and in 14/16 WT and 1/16 KPQ hearts (P < 0.001 for both; Fisher’s exact test), respectively. The arrhythmogenic WT hearts had significantly larger positive critical intervals (CI), given by the difference between atrial effective refractory periods (AERPs) and action potential durations at 90% recovery (APD90), compared to KPQ hearts (8.1 and 3.2 ms, respectively, P < 0.001). Flecainide prevented atrial arrhythmias in all arrhythmogenic WT (P < 0.001) and KPQ hearts (P < 0.05). It prolonged the AERP to a larger extent than it did the APD90 in both WT and KPQ groups, giving negative CIs. Quinidine similarly exerted anti-arrhythmic effects, prolonged AERP over corresponding APD90 in both WT and KPQ groups. These findings, thus, demonstrate, for the first time, inhibitory effects of the KPQ mutation on atrial arrhythmogenesis and its modification by flecainide and quinidine. They attribute these findings to differences in the CI between WT and mutant hearts, in the presence or absence of these drugs. Thus, prolongation of APD90 over AERP gave positive CI values and increased atrial arrhythmogenicity whereas lengthening of AERP over APD90 reduced such CI values and produced the opposite effect.
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Affiliation(s)
- Yana Dautova
- Cardiovascular Biology Group, Physiological Laboratory, University of Cambridge, Cambridge, UK
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Harada M, Osaka T, Yokoyama E, Takemoto Y, Ito A, Kodama I. Action Potential Characteristics in the Sinus Venosa of Patients With and Without Atrial Flutter. Circ J 2009; 73:647-53. [DOI: 10.1253/circj.cj-08-0748] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Masahide Harada
- Division of Arrhythmia and Electrophysiology, Shizuoka Saiseikai General Hospital
- Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University
| | - Toshiyuki Osaka
- Division of Arrhythmia and Electrophysiology, Shizuoka Saiseikai General Hospital
| | - Eriko Yokoyama
- Division of Arrhythmia and Electrophysiology, Shizuoka Saiseikai General Hospital
| | - Yoshio Takemoto
- Division of Arrhythmia and Electrophysiology, Shizuoka Saiseikai General Hospital
| | - Atsushi Ito
- Division of Arrhythmia and Electrophysiology, Shizuoka Saiseikai General Hospital
| | - Itsuo Kodama
- Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University
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Does the postrepolarization refractoriness play a role in amiodarone's antiarrhythmic efficacy? Heart Rhythm 2008; 5:1743-4. [PMID: 19084814 DOI: 10.1016/j.hrthm.2008.09.032] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/26/2008] [Indexed: 11/20/2022]
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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] [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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Guo D, Zhou J, Zhao X, Gupta P, Kowey PR, Martin J, Wu Y, Liu T, Yan GX. L-type calcium current recovery versus ventricular repolarization: preserved membrane-stabilizing mechanism for different QT intervals across species. Heart Rhythm 2007; 5:271-9. [PMID: 18242553 DOI: 10.1016/j.hrthm.2007.09.025] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/29/2007] [Accepted: 09/22/2007] [Indexed: 11/27/2022]
Abstract
BACKGROUND Long QT syndrome is associated with early after-depolarization (EAD) that may result in torsade de pointes (TdP). Interestingly, the corrected QT interval seems to be proportional to body mass across species under physiologic conditions. OBJECTIVE The purpose of this study was to test whether recovery of L-type calcium current (I(Ca,L)), the primary charge carrier for EADs, from its inactivated state matches ventricular repolarization time and whether impairment of this relationship leads to development of EAD and TdP. METHODS Transmembrane action potentials from the epicardium, endocardium, or subendocardium were recorded simultaneously with a transmural ECG in arterially perfused left ventricular wedges isolated from cow, dog, rabbit, and guinea pig hearts. I(Ca,L) recovery was examined using action potential stimulation in isolated left ventricular myocytes. RESULTS The ventricular repolarization time (action potential duration at 90% repolarization [APD(90)]), ranging from 194.7 +/- 1.8 ms in guinea pig to 370.2 +/- 9.9 ms in cows, was linearly related to the thickness of the left ventricular wall among the species studied. The time constants (tau) of I(Ca,L) recovery were proportional to APD(90), making the ratios of tau to APD(90) fall into a relatively narrow range among these species despite markedly different ventricular repolarization time. Drugs with risk for TdP in humans were shown to impair this intrinsic balance by either prolongation of the repolarization time and/or acceleration of I(Ca,L) recovery, leading to the appearance of EADs capable of initiating TdP. CONCLUSION An adequate balance between I(Ca,L) recovery and ventricular repolarization serves as a "physiologic stabilizer" of ventricular action potentials in repolarization phases.
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Affiliation(s)
- Donglin Guo
- Main Line Health Heart Center, Wynnewood, Pennsylvania 19096, USA
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Killeen MJ, Gurung IS, Thomas G, Stokoe KS, Grace AA, Huang CLH. Separation of early afterdepolarizations from arrhythmogenic substrate in the isolated perfused hypokalaemic murine heart through modifiers of calcium homeostasis. Acta Physiol (Oxf) 2007; 191:43-58. [PMID: 17524066 PMCID: PMC2040229 DOI: 10.1111/j.1748-1716.2007.01715.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
AIMS We resolved roles for early afterdepolarizations (EADs) and transmural gradients of repolarization in arrhythmogenesis in Langendorff-perfused hypokalaemic murine hearts paced from the right ventricular epicardium. METHODS Left ventricular epicardial and endocardial monophasic action potentials (MAPs) and arrhythmogenic tendency were compared in the presence and absence of the L-type Ca(2+) channel blocker nifedipine (10 nm-1 microm) and the calmodulin kinase type II inhibitor KN-93 (2 microm). RESULTS All the hypokalaemic hearts studied showed prolonged epicardial and endocardial MAPs, decreased epicardial-endocardial APD(90) difference, EADs, triggered beats and ventricular tachycardia (VT) (n = 6). In all spontaneously beating hearts, 100 (but not 10) nm nifedipine reduced both the incidence of EADs and triggered beats from 66.9 +/- 15.7% to 28.3 +/- 8.7% and episodes of VT from 10.8 +/- 6.3% to 1.2 +/- 0.7% of MAPs (n = 6 hearts, P < 0.05); 1 microm nifedipine abolished all these phenomena (n = 6). In contrast programmed electrical stimulation (PES) still triggered VT in six of six hearts with 0, 10 and 100 nm but not 1 microm nifedipine. 1 microm nifedipine selectively reduced epicardial (from 66.1 +/- 3.4 to 46.2 +/- 2.5 ms) but not endocardial APD(90), thereby restoring DeltaAPD(90) from -5.9 +/- 2.5 to 15.5 +/- 3.2 ms, close to normokalaemic values. KN-93 similarly reduced EADs, triggered beats and VT in spontaneously beating hearts to 29.6 +/- 8.9% and 1.7 +/- 1.1% respectively (n = 6) yet permitted PES-induced VT (n = 6), in the presence of a persistently negative DeltaAPD(90). CONCLUSIONS These findings empirically implicate both EADs and triggered beats alongside arrhythmogenic substrate of DeltaAPD(90) in VT pathogenesis at the whole heart level.
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Affiliation(s)
- M J Killeen
- Physiological Laboratory, University of Cambridge, Cambridge, UK.
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Sabir IN, Fraser JA, Cass TR, Grace AA, Huang CLH. A quantitative analysis of the effect of cycle length on arrhythmogenicity in hypokalaemic Langendorff-perfused murine hearts. Pflugers Arch 2007; 454:925-36. [PMID: 17437126 PMCID: PMC2627988 DOI: 10.1007/s00424-007-0255-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2007] [Accepted: 03/13/2007] [Indexed: 11/09/2022]
Abstract
The clinically established proarrhythmic effect of bradycardia and antiarrhythmic effect of lidocaine (10 μM) were reproduced in hypokalaemic (3.0 mM K+) Langendorff-perfused murine hearts paced over a range (80–180 ms) of baseline cycle lengths (BCLs). Action potential durations (at 90% repolarization, APD90s), transmural conduction times and ventricular effective refractory periods (VERPs) were then determined from monophasic action potential records obtained during a programmed electrical stimulation procedure in which extrasystolic stimuli were interposed following regular stimuli at successively decreasing coupling intervals. A novel graphical analysis of epicardial and endocardial, local and transmural relationships between APD90, corrected for transmural conduction time where appropriate, and VERP yielded predictions in precise agreement with the arrhythmogenic findings obtained over the entire range of BCLs studied. Thus, in normokalaemic (5.2 mM K+) hearts a statistical analysis confirmed that all four relationships were described by straight lines of gradients not significantly (P > 0.05) different from unity that passed through the origin and thus subtended constant critical angles, θ with the abscissa (45.8° ± 0.9°, 46.6° ± 0.5°, 47.6° ± 0.5° and 44.9° ± 0.8°, respectively). Hypokalaemia shifted all points to the left of these reference lines, significantly (P < 0.05) increasing θ at BCLs of 80–120 ms where arrhythmic activity was not observed (∼63°, ∼54°, ∼55° and ∼58°, respectively) and further significantly (P < 0.05) increasing θ at BCLs of 140–180 ms where arrhythmic activity was observed (∼68°, ∼60°, ∼61° and ∼65°, respectively). In contrast, the antiarrhythmic effect of lidocaine treatment was accompanied by a significant (P < 0.05) disruption of this linear relationship and decreases in θ in both normokalaemic (∼40°, ∼33°, ∼39° and ∼41°, respectively) and hypokalaemic (∼40°, ∼44°, ∼50° and ∼48°, respectively) hearts. This extended a previous approach that had correlated alterations in transmural repolarization gradients with arrhythmogenicity in murine models of the congenital long QT syndrome type 3 and hypokalaemia at a single BCL. Thus, the analysis in terms of APD90 and VERP provided a more sensitive indication of the effect of lidocaine than one only considering transmural repolarization gradients and may be particularly applicable in physiological and pharmacological situations in which these parameters diverge.
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Affiliation(s)
- Ian N. Sabir
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge, CB2 3EG UK
| | - James A. Fraser
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge, CB2 3EG UK
| | - Thomas R. Cass
- Statistical Laboratory, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge, CB3 0WB UK
| | - Andrew A. Grace
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QW UK
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Selvaraj RJ, Picton P, Nanthakumar K, Chauhan VS. Steeper restitution slopes across right ventricular endocardium in patients with cardiomyopathy at high risk of ventricular arrhythmias. Am J Physiol Heart Circ Physiol 2007; 292:H1262-8. [PMID: 17098829 DOI: 10.1152/ajpheart.00913.2006] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Steep action potential duration (APD) restitution slopes (>1) and spatial APD restitution heterogeneity provide the substrate for ventricular fibrillation in computational models and experimental studies. Their relationship to ventricular arrhythmia vulnerability in human cardiomyopathy has not been defined. Patients with cardiomyopathy [left ventricular (LV) ejection fraction <40%] and no history of ventricular arrhythmias underwent risk stratification with programmed electrical stimulation or T wave alternans (TWA). Low-risk patients ( n = 10) had no inducible ventricular tachycardia (VT) or negative TWA, while high-risk patients ( n = 8) had inducible VT or positive TWA. Activation recovery interval (ARI) restitution slopes were measured simultaneously from 10 right ventricular (RV) endocardial sites during an S1-S2 pacing protocol. ARI restitution slope heterogeneity was defined as the coefficient of variation of slopes. Mean ARI restitution slope was significantly steeper in the high-risk group compared with the low-risk group [1.16 (SD 0.31) vs. 0.59 (SD 0.19), P = 0.0002]. The proportion of endocardial recording sites with a slope >1 was significantly larger in the high-risk patients [47% (SD 35) vs. 13% (SD 21), P = 0.022]. Spatial heterogeneity of ARI restitution slopes was similar between the two groups [29% (SD 16) vs. 39% (SD 34), P = 0.48]. There was an inverse linear relationship between the ARI restitution slope and the minimum diastolic interval ( P < 0.001). In cardiomyopathic patients at high risk of ventricular arrhythmias, ARI restitution slopes along the RV endocardium are steeper, but restitution slope heterogeneity is similar compared with those at low risk. Steeper ARI restitution slopes may increase the propensity for ventricular arrhythmias in patients with impaired left ventricular function.
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Affiliation(s)
- Raja J Selvaraj
- Division of Cardiology, University Health Network and Mount Sinai Hospital, Toronto, Ontario, Canada
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Sabir IN, Killeen MJ, Goddard CA, Thomas G, Gray S, Grace AA, Huang CLH. Transient alterations in transmural repolarization gradients and arrhythmogenicity in hypokalaemic Langendorff-perfused murine hearts. J Physiol 2007; 581:277-89. [PMID: 17331992 PMCID: PMC2075225 DOI: 10.1113/jphysiol.2007.128637] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Clinical hypokalaemia is associated with acquired electrocardiographic QT prolongation and arrhythmic activity initiated by premature ventricular depolarizations and suppressed by lidocaine (lignocaine). Nevertheless, regular (S1) pacing at a 125 ms interstimulus interval resulted in stable waveforms and rhythm studied using epicardial and endocardial monophasic action potential (MAP) electrodes in Langendorff-perfused murine hearts whether under normokalaemic (5.2 mM K+) or hypokalaemic (3.0 mM K+) conditions, in both the presence and absence of lidocaine (10 microM). Furthermore, the transmural gradient in repolarization time, known to be altered in the congenital long-QT syndromes, and reflected in the difference between endocardial and epicardial MAP duration at 90% repolarization (DeltaAPD(90)), did not differ significantly (P > 0.05) between normokalaemic (5.5 +/- 4.5 ms, n = 8, five hearts), hypokalaemic (n = 8, five hearts), or lidocaine-treated normokalaemic (n = 8, five hearts) or hypokalaemic (n = 8, five hearts) hearts. However, premature ventricular depolarizations occurring in response to extrasystolic (S2) stimulation delivered at S1S2 intervals between 0 and 22 +/- 6 ms following recovery from refractoriness initiated arrhythmic activity specifically in hypokalaemic (n = 8, five hearts) as opposed to normokalaemic (n = 25, 14 hearts), or lidocaine-treated hypokalaemic (n = 8, five hearts) or normokalaemic hearts (n = 8, five hearts). This was associated with sharp but transient reversals in DeltaAPD(90) in MAPs initiated within the 250 ms interval directly succeeding premature ventricular depolarizations, from 3.3 +/- 5.6 ms to -31.8 +/- 11.8 ms (P < 0.05) when they were initiated immediately after recovery from refractoriness. In contrast the corresponding latency differences consistently remained close to the normokalaemic value (-1.6 +/- 1.4 ms, P > 0.05). These findings empirically associate arrhythmogenesis in hypokalaemic hearts with transient alterations in transmural repolarization gradients resulting from premature ventricular depolarizations. This is in contrast to sustained alterations in transmural repolarization gradients present on regular stimulation in long-QT syndrome models.
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Affiliation(s)
- Ian N Sabir
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK
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Killeen MJ, Thomas G, Gurung IS, Goddard CA, Fraser JA, Mahaut-Smith MP, Colledge WH, Grace AA, Huang CLH. Arrhythmogenic mechanisms in the isolated perfused hypokalaemic murine heart. Acta Physiol (Oxf) 2007; 189:33-46. [PMID: 17280555 PMCID: PMC1859975 DOI: 10.1111/j.1748-1716.2006.01643.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Aim Hypokalaemia is associated with a lethal form of ventricular tachycardia (VT), torsade de pointes, through pathophysiological mechanisms requiring clarification. Methods Left ventricular endocardial and epicardial monophasic action potentials were compared in isolated mouse hearts paced from the right ventricular epicardium perfused with hypokalaemic (3 and 4 mm [K+]o) solutions. Corresponding K+ currents were compared in whole-cell patch-clamped epicardial and endocardial myocytes. Results Hypokalaemia prolonged epicardial action potential durations (APD) from mean APD90s of 37.2 ± 1.7 ms (n = 7) to 58.4 ± 4.1 ms (n =7) and 66.7 ± 2.1 ms (n = 11) at 5.2, 4 and 3 mm [K+]o respectively. Endocardial APD90s correspondingly increased from 51.6 ± 1.9 ms (n = 7) to 62.8 ± 2.8 ms (n = 7) and 62.9 ± 5.9 ms (n = 11) giving reductions in endocardial–epicardial differences, ΔAPD90, from 14.4 ± 2.6 to 4.4 ± 5.0 and −3.4 ± 6.0 ms respectively. Early afterdepolarizations (EADs) occurred in epicardia in three of seven spontaneously beating hearts at 4 mm [K+]o with triggered beats followed by episodes of non-sustained VT in nine of 11 preparations at 3 mm. Programmed electrical stimulation never induced arrhythmic events in preparations perfused with normokalemic solutions yet induced VT in two of seven and nine of 11 preparations at 4 and 3 mm [K+]o respectively. Early outward K+ current correspondingly fell from 73.46 ± 8.45 to 61.16±6.14 pA/pF in isolated epicardial but not endocardial myocytes (n = 9) (3 mm [K+]o). Conclusions Hypokalaemic mouse hearts recapitulate the clinical arrhythmogenic phenotype, demonstrating EADs and triggered beats that might initiate VT on the one hand and reduced transmural dispersion of repolarization reflected in ΔAPD90 suggesting arrhythmogenic substrate on the other.
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Affiliation(s)
- M J Killeen
- Physiological Laboratory, University of Cambridge, Cambridge, UK.
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Thomsen MB, Matz J, Volders PGA, Vos MA. Assessing the proarrhythmic potential of drugs: current status of models and surrogate parameters of torsades de pointes arrhythmias. Pharmacol Ther 2006; 112:150-70. [PMID: 16714061 DOI: 10.1016/j.pharmthera.2005.04.009] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2005] [Accepted: 04/06/2005] [Indexed: 02/08/2023]
Abstract
Torsades de pointes (TdP) is a potentially lethal cardiac arrhythmia that can occur as an unwanted adverse effect of various pharmacological therapies. Before a drug is approved for marketing, its effects on cardiac repolarisation are examined clinically and experimentally. This paper expresses the opinion that effects on repolarisation duration cannot directly be translated to risk of proarrhythmia. Current safety assessments of drugs only involve repolarisation assays, however the proarrhythmic profile can only be determined in the predisposed model. The availability of these proarrhythmic animal models is emphasised in the present paper. It is feasible for the pharmaceutical industry to establish one or more of these proarrhythmic animal models and large benefits are potentially available if pharmaceutical industries and patient-care authorities embraced these models. Furthermore, suggested surrogate parameters possessing predictive power of TdP arrhythmia are reviewed. As these parameters are not developed to finalisation, any meaningful study of the proarrhythmic potential of a new drug will include evaluation in an integrated model of TdP arrhythmia.
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Affiliation(s)
- Morten B Thomsen
- Department of Medical Physiology, Heart Lung Centre Utrecht, University Medical Centre Utrecht, Yalelaan 50, NL-3584 CM Utrecht, Netherlands.
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Kirchhof P, Fetsch T, Hanrath P, Meinertz T, Steinbeck G, Lehmacher W, Breithardt G. Targeted pharmacological reversal of electrical remodeling after cardioversion--rationale and design of the Flecainide Short-Long (Flec-SL) trial. Am Heart J 2005; 150:899. [PMID: 16290956 DOI: 10.1016/j.ahj.2005.07.020] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2005] [Accepted: 07/12/2005] [Indexed: 11/28/2022]
Abstract
Persistent atrial fibrillation (AF) causes relevant mortality and cardiovascular and noncardiovascular morbidity. Therefore, maintenance of sinus rhythm is an important clinical goal, especially when the patient is symptomatic, despite the fact that current treatment strategies are not sufficient to completely prevent recurrent AF. In addition to underlying atrial disease that predisposes to AF, AF in itself induces structural and electrical adaptations ("electrical remodeling" and "structural remodeling"). Underlying disease processes and parts of structural remodeling are not always reversible. Electrical remodeling, in contrast, is reversed by a few weeks of maintenance of sinus rhythm under experimental conditions. This corresponds to the period when most of the recurrent episodes of AF occur after cardioversion. Antiarrhythmic drugs that prolong the atrial action potential can assist in the prevention of recurrent AF by promoting the reversal of electrical remodeling. Such drugs, which are currently used over long periods after cardioversion, may only be needed until the physiological action potential duration is restored, for example, during the first few weeks after cardioversion of persistent AF. This treatment concept that we call "targeted pharmacological reversal of electrical remodeling" would limit both cost and drug-induced side effects of antiarrhythmic drug therapy after cardioversion. The Flec-SL trial, ISECTN62728743, therefore tests the main hypothesis that targeted pharmacological reversal of electrical remodeling by short-term antiarrhythmic drug therapy for 4 weeks after cardioversion is not inferior to standard long-term antiarrhythmic drug therapy for the prevention of recurrent AF after cardioversion in a parallel group, randomized, multicenter, open, blinded end point analysis design. Based on its effectiveness and pharmacokinetic profile, flecainide is used to test the study hypothesis. The trial uses daily transtelephonic electrocardiographic monitoring for all patients and will be conducted within the German Atrial Fibrillation Competence NETwork (AFNET) to facilitate inclusion of patients from electrophysiologically oriented cardiology centers, ordinary hospitals, and office-based physicians.
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Affiliation(s)
- Paulus Kirchhof
- Department of Cardiology and Angiology, Hospital of the University of Münster, Germany.
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Kirchhof P, Engelen M, Franz MR, Ribbing M, Wasmer K, Breithardt G, Haverkamp W, Eckardt L. Electrophysiological effects of flecainide and sotalol in the human atrium during persistent atrial fibrillation. Basic Res Cardiol 2005; 100:112-21. [PMID: 15696400 DOI: 10.1007/s00395-005-0513-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/28/2004] [Revised: 12/14/2004] [Accepted: 12/16/2004] [Indexed: 11/24/2022]
Abstract
AIMS Atrial fibrillation (AF) shortens the atrial action potential and the atrial refractory period. These changes promote persistence of AF. Pharmacological prolongation of atrial action potential duration (APD) may therefore help to prevent recurrent AF. In addition to prolonging APD, sodium channel blockers may prevent AF by inducing post-repolarization refractoriness (PRR). We studied whether two antiarrhythmic drugs (sotalol, flecainide) prolong APD or induce PRR in the fibrillating human atrium. METHODS In 12 patients with persistent AF (11 male, 58 +/- 5 yrs, 27 +/- 7 months duration of AF), we recorded monophasic action potentials from the right atrial appendage and inferior right atrium at baseline and 15 minutes after intravenous administration of sotalol (1.5 mg/kg) or flecainide (2 mg/kg). APD and effective refractory periods (ERP) were determined. RESULTS Both drugs prolonged APD90 during AF (flecainide from 109 +/- 7 ms to 137 +/- 10 ms, sotalol from 108 +/- 6 ms to 131 +/- 8 ms, both p < 0.05 vs. baseline). Sotalol prolonged ERP in parallel to APD (from 119 +/- 8 ms to 139 +/- 8 ms, p < 0.05). Flecainide induced PRR by prolonging ERP more than APD90 (from 134 +/- 9 ms to 197 +/- 28 ms, p < 0.05 vs. baseline and vs. sotalol). CONCLUSIONS Flecainide and sotalol prolong the atrial action potential during atrial fibrillation in humans. In addition, flecainide induces atrial PRR. These electrophysiological effects may reduce AF recurrences and prevent their persistence.
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Affiliation(s)
- Paulus Kirchhof
- Medizinische Klinik und Poliklinik C Kardiologie und Angiologie, Universitätsklinikum Münster, Münster, Germany.
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Milberg P, Ramtin S, Mönnig G, Osada N, Wasmer K, Breithardt G, Haverkamp W, Eckardt L. Comparison of the in vitro electrophysiologic and proarrhythmic effects of amiodarone and sotalol in a rabbit model of acute atrioventricular block. J Cardiovasc Pharmacol 2005; 44:278-86. [PMID: 15475823 DOI: 10.1097/01.fjc.0000129581.81508.78] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The mechanisms for the different proarrhythmic potential of antiarrhythmic drugs in the presence of comparable QT prolongation are not completely understood. The reasons for the lower proarrhythmic potential of amiodarone as compared with other class-III antiarrhythmic drugs such as sotalol, a fact that has been well established for years, is insufficiently known. Therefore, the aim of our study was to assess the different electrophysiologic effects of amiodarone and sotalol in a previously developed experimental model of proarrhythmia. In eight male rabbits, amiodarone (280-340 mg/d) was fed over a period of six weeks. Hearts were excised and retrogradely perfused. Up to eight simultaneous epi- and endocardial monophasic action potentials (MAP) were recorded. Results were compared with sotalol-treated (10-50-100 microM) hearts (n = 13). Amiodarone and sotalol (50 microM and 100 microM) led to a significant increase in QT interval (mean increase: amiodarone: 31 +/- 6 ms; sotalol: 41 +/- 4 ms and 61 +/- 9 ms) and MAP-duration (mean increase-MAP90: amiodarone: 20 +/- 5 ms; sotalol: 17 +/- 5 ms and 25 +/- 8 ms) (P < 0.01). In bradycardic (AV-blocked) hearts, MAP-recordings demonstrated reverse-use dependence and a significant increase in dispersion of repolarization (MAP90) in the presence of sotalol (P < 0.01), but not in amiodarone-treated hearts (10%; p = ns). Sotalol led to early afterdepolarizations (EAD) and torsade de pointes (TdP) after lowering of potassium concentration (6 of 13 hearts). In amiodarone-treated, hypokalemic hearts, no EAD or TdP occurred. Sotalol changed the MAP configuration to a triangular pattern (ratio-MAP90/50: 1.52 as compared with 1.36 at baseline) whereas amiodarone caused a rectangular pattern of MAP prolongation (ratio-MAP90/50: 1.36). In conclusion, these results show no direct correlation between the occurrence of TdP and the degree of QT prolongation. Several factors including reverse-use dependence, dispersion of repolarization, and the propensity to induce early afterdepolarizations but also differences in the action potential configuration may help to understand proarrhythmic side effects of drugs.
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Affiliation(s)
- Peter Milberg
- Hospital of the Westfälische Wilhelms-University, Department of Cardiology and Angiology and Institute for Arteriosclerosis Research, Münster, Germany.
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Abstract
The electrical restitution curve (ERC) traditionally describes the recovery of action potential duration (APD) as a function of the interbeat interval or, more correctly, the diastolic interval (DI). Often overlooked in modeling studies, the normal ventricular ERC is triphasic, starting with a steep initial recovery at the shortest DIs, a transient decline, and a final asymptotic rise to a plateau phase reached at long DIs. Recent studies have proposed that it would be advantageous to lower the slope of the ERC by drug intervention, as this might reduce the potential for electrical alternans and ventricular fibrillation. This review discusses the pros and cons of a flat versus steep slope of the ERC and draws attention to mechanisms thatjustify the (physiologically) steep slope, rather than a flat slope, as a better design against arrhythmias. Five potential mechanisms are discussed, which allows for a different interpretation of the effect of the slope on arrhythmogenicity. The most important appears to be the physiologic rate adaptive shortening of APD that, by reciprocal lengthening of the DI, allows the subsequent APD to move more quickly from the steep initial ERC phase onto the flat phase. A less steep initial ERC phase would protract the transition toward more fully recovered APD and, in fact, may perpetuate electrical alternans. The triphasic ERC time course in normal myocardium cannot be explained by or fitted to single exponentials or single ion channel recovery kinetics. A simple tri-ionic model is suggested that may help explain the shape of the ERC at various repolarization levels and place APD recovery into perspective with intracellular calcium recycling and recovery of contractile force.
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Affiliation(s)
- Michael R Franz
- Cardiology Division, Veteran Affairs Medical Center, Washington, DC 20422, USA.
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