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Nascimento LV, Neto FL, Ribeiro Moreira DA, Cerutti VB, Thurow HS, Bastos GM, Ferreira EB, Crespo Hirata RD, Hirata MH. Influence of antidepressant drugs on DNA methylation of ion channels genes in blood cells of psychiatric patients. Epigenomics 2022; 14:851-864. [PMID: 35818955 DOI: 10.2217/epi-2022-0089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Aim: This study investigated the influence of antidepressant drugs on methylation status of KCNE1, KCNH2 and SCN5A promoters and ECG parameters in adult psychiatric patients. Materials & methods: Electrocardiographic evaluation (24 h) and blood samples were obtained from 34 psychiatric patients before and after 30 days of antidepressant therapy. Methylation of promoter CpG sites of KCNE1, KCNH2 and SCN5A was analyzed by pyrosequencing. Results: Three CpG and four CpG sites of KCNE1 and SCN5A, respectively, had increased % methylation after treatment. Principal component analysis showed correlations of the methylation status with electrocardiographic variables, antidepressant doses and patient age. Conclusion: Short-term treatment with antidepressant drugs increase DNA methylation in KCNE1 and SCN5A promoters, which may induce ECG alterations in psychiatric patients.
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Affiliation(s)
- Larissa Vilela Nascimento
- Department of Clinical e Toxicological Analyses, School of Pharmaceutical Sciences, University of Sao Paulo, Sao Paulo, 05508-000, Brazil
| | - Francisco Lotufo Neto
- Institute of Psychiatry, School of Medicine, University of Sao Paulo, Sao Paulo, 01246-903, Brazil
| | - Dalmo Antonio Ribeiro Moreira
- Department of Electrophysiology & Cardiac Arrhythmias, Institute Dante Pazzanese of Cardiology, Sao Paulo, 04012-909, Brazil
| | - Virginia Braga Cerutti
- Department of Electrophysiology & Cardiac Arrhythmias, Institute Dante Pazzanese of Cardiology, Sao Paulo, 04012-909, Brazil
| | - Helena Strelow Thurow
- Department of Teaching & Research, Real e Benemerita Associação Portuguesa de Beneficiência, Sao Paulo, 01323-001, Brazil
| | - Gisele Medeiros Bastos
- Department of Teaching & Research, Real e Benemerita Associação Portuguesa de Beneficiência, Sao Paulo, 01323-001, Brazil
| | - Eric Batista Ferreira
- Institute of Exact Sciences, Federal University of Alfenas, Alfenas, 37130-001, Brazil
| | - Rosario Dominguez Crespo Hirata
- Department of Clinical e Toxicological Analyses, School of Pharmaceutical Sciences, University of Sao Paulo, Sao Paulo, 05508-000, Brazil
| | - Mario Hiroyuki Hirata
- Department of Clinical e Toxicological Analyses, School of Pharmaceutical Sciences, University of Sao Paulo, Sao Paulo, 05508-000, Brazil
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Smoczyńska A, Loen V, Sprenkeler DJ, Tuinenburg AE, Ritsema van Eck HJ, Malik M, Schmidt G, Meine M, Vos MA. Short-Term Variability of the QT Interval Can be Used for the Prediction of Imminent Ventricular Arrhythmias in Patients With Primary Prophylactic Implantable Cardioverter Defibrillators. J Am Heart Assoc 2020; 9:e018133. [PMID: 33215550 PMCID: PMC7763775 DOI: 10.1161/jaha.120.018133] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Background Short‐term variability of the QT interval (STVQT) has been proposed as a novel electrophysiological marker for the prediction of imminent ventricular arrhythmias in animal models. Our aim is to study whether STVQT can predict imminent ventricular arrhythmias in patients. Methods and Results In 2331 patients with primary prophylactic implantable cardioverter defibrillators, 24‐hour ECG Holter recordings were obtained as part of the EU‐CERT‐ICD (European Comparative Effectiveness Research to Assess the Use of Primary Prophylactic Implantable Cardioverter Defibrillators) study. ECG Holter recordings showing ventricular arrhythmias of >4 consecutive complexes were selected for the arrhythmic groups (n=170), whereas a control group was randomly selected from the remaining Holter recordings (n=37). STVQT was determined from 31 beats with fiducial segment averaging and calculated as ∑Dn+1‐Dn/30×2, where Dn represents the QT interval. STVQT was determined before the ventricular arrhythmia or 8:00 am in the control group and between 1:30 and 4:30 am as baseline. STVQT at baseline was 0.84±0.47 ms and increased to 1.18±0.74 ms (P<0.05) before the ventricular arrhythmia, whereas the STVQT in the control group remained unchanged. The arrhythmic patients were divided into three groups based on the severity of the arrhythmia: (1) nonsustained ventricular arrhythmia (n=32), (2) nonsustained ventricular tachycardia (n=134), (3) sustained ventricular tachycardia (n=4). STVQT increased before nonsustained ventricular arrhythmia, nonsustained ventricular tachycardia, and sustained ventricular tachycardia from 0.80±0.43 ms to 1.18±0.78 ms (P<0.05), from 0.90±0.49 ms to 1.14±0.70 ms (P<0.05), and from 1.05±0.22 ms to 2.33±1.25 ms (P<0.05). This rise in STVQT was significantly higher in sustained ventricular tachycardia compared with nonsustained ventricular arrhythmia (+1.28±1.05 ms versus +0.24±0.57 ms [P<0.05]) and compared with nonsustained ventricular arrhythmia (+0.34±0.87 ms [P<0.05]). Conclusions STVQT increases before imminent ventricular arrhythmias in patients, and the extent of the increase is associated with the severity of the ventricular arrhythmia.
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Affiliation(s)
- Agnieszka Smoczyńska
- Department of Medical Physiology University Medical Center Utrecht Utrecht The Netherlands
| | - Vera Loen
- Department of Medical Physiology University Medical Center Utrecht Utrecht The Netherlands
| | - David J Sprenkeler
- Department of Medical Physiology University Medical Center Utrecht Utrecht The Netherlands
| | - Anton E Tuinenburg
- Department of Cardiology University Medical Center Utrecht Utrecht The Netherlands
| | - Henk J Ritsema van Eck
- Department of Medical Informatics Erasmus University Medical Center Rotterdam The Netherlands
| | - Marek Malik
- National Heart and Lung InstituteImperial College London London United Kingdom
| | - Georg Schmidt
- Medical Klinik und Poliklinik I Technische Universität MünchenKlinikum rechts der Isar Münich Germany
| | - Mathias Meine
- Department of Cardiology University Medical Center Utrecht Utrecht The Netherlands
| | - Marc A Vos
- Department of Medical Physiology University Medical Center Utrecht Utrecht The Netherlands
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Baczkó I, Hornyik T, Brunner M, Koren G, Odening KE. Transgenic Rabbit Models in Proarrhythmia Research. Front Pharmacol 2020; 11:853. [PMID: 32581808 PMCID: PMC7291951 DOI: 10.3389/fphar.2020.00853] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Accepted: 05/22/2020] [Indexed: 12/23/2022] Open
Abstract
Drug-induced proarrhythmia constitutes a potentially lethal side effect of various drugs. Most often, this proarrhythmia is mechanistically linked to the drug's potential to interact with repolarizing cardiac ion channels causing a prolongation of the QT interval in the ECG. Despite sophisticated screening approaches during drug development, reliable prediction of proarrhythmia remains very challenging. Although drug-induced long-QT-related proarrhythmia is often favored by conditions or diseases that impair the individual's repolarization reserve, most cellular, tissue, and whole animal model systems used for drug safety screening are based on normal, healthy models. In recent years, several transgenic rabbit models for different types of long QT syndromes (LQTS) with differences in the extent of impairment in repolarization reserve have been generated. These might be useful for screening/prediction of a drug's potential for long-QT-related proarrhythmia, particularly as different repolarizing cardiac ion channels are impaired in the different models. In this review, we summarize the electrophysiological characteristics of the available transgenic LQTS rabbit models, and the pharmacological proof-of-principle studies that have been performed with these models—highlighting the advantages and disadvantages of LQTS models for proarrhythmia research. In the end, we give an outlook on potential future directions and novel models.
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Affiliation(s)
- István Baczkó
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary
| | - Tibor Hornyik
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary.,Department of Cardiology and Angiology I, Heart Center, University of Freiburg, Freiburg, Germany.,Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Michael Brunner
- Department of Cardiology and Angiology I, Heart Center, University of Freiburg, Freiburg, Germany.,Faculty of Medicine, University of Freiburg, Freiburg, Germany.,Department of Cardiology and Medical Intensive Care, St. Josefskrankenhaus, Freiburg, Germany
| | - Gideon Koren
- Cardiovascular Research Center, Division of Cardiology, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, RI, United States
| | - Katja E Odening
- Department of Cardiology and Angiology I, Heart Center, University of Freiburg, Freiburg, Germany.,Faculty of Medicine, University of Freiburg, Freiburg, Germany.,Translational Cardiology, Department of Cardiology, Inselspital, Bern University Hospital, Bern, Switzerland.,Institute of Physiology, University of Bern, Bern, Switzerland
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4
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Duijvenboden SV, Porter B, Pueyo E, Sampedro-Puente DA, Fernandez-Bes J, Sidhu B, Gould J, Orini M, Bishop MJ, Hanson B, Lambiase P, Razavi R, Rinaldi CA, Gill JS, Taggart P. Complex Interaction Between Low-Frequency APD Oscillations and Beat-to-Beat APD Variability in Humans Is Governed by the Sympathetic Nervous System. Front Physiol 2020; 10:1582. [PMID: 32038279 PMCID: PMC6987475 DOI: 10.3389/fphys.2019.01582] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Accepted: 12/17/2019] [Indexed: 02/03/2023] Open
Abstract
BACKGROUND Recent clinical, experimental and modeling studies link oscillations of ventricular repolarization in the low frequency (LF) (approx. 0.1 Hz) to arrhythmogenesis. Sympathetic provocation has been shown to enhance both LF oscillations of action potential duration (APD) and beat-to-beat variability (BVR) in humans. We hypothesized that beta-adrenergic blockade would reduce LF oscillations of APD and BVR of APD in humans and that the two processes might be linked. METHODS AND RESULTS Twelve patients with normal ventricles were studied during routine electrophysiological procedures. Activation-recovery intervals (ARI) as a conventional surrogate for APD were recorded from 10 left and 10 right ventricular endocardial sites before and after acute beta-adrenergic adrenergic blockade. Cycle length was maintained constant with right ventricular pacing. Oscillatory behavior of ARI was quantified by spectral analysis and BVR as the short-term variability. Beta-adrenergic blockade reduced LF ARI oscillations (8.6 ± 4.5 ms2 vs. 5.5 ± 3.5 ms2, p = 0.027). A significant correlation was present between the initial control values and reduction seen following beta-adrenergic blockade in LF ARI (r s = 0.62, p = 0.037) such that when initial values are high the effect is greater. A similar relationship was also seen in the beat-to beat variability of ARI (r s = 0.74, p = 0.008). There was a significant correlation between the beta-adrenergic blockade induced reduction in LF power of ARI and the witnessed reduction of beat-to-beat variability of ARI (r s = 0.74, p = 0.01). These clinical results accord with recent computational modeling studies which provide mechanistic insight into the interactions of LF oscillations and beat-to-beat variability of APD at the cellular level. CONCLUSION Beta-adrenergic blockade reduces LF oscillatory behavior of APD (ARI) in humans in vivo. Our results support the importance of LF oscillations in modulating the response of BVR to beta-adrenergic blockers, suggesting that LF oscillations may play role in modulating beta-adrenergic mechanisms underlying BVR.
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Affiliation(s)
| | - Bradley Porter
- School of Imaging Sciences and Biomedical Engineering, King’s College London, London, United Kingdom
| | - Esther Pueyo
- BSICOS Group, I3A, IIS Aragón, University of Zaragoza, Zaragoza, Spain
- CIBER-BBN, Madrid, Spain
| | | | | | - Baldeep Sidhu
- School of Imaging Sciences and Biomedical Engineering, King’s College London, London, United Kingdom
| | - Justin Gould
- School of Imaging Sciences and Biomedical Engineering, King’s College London, London, United Kingdom
| | - Michele Orini
- Department of Clinical Pharmacology, Queen Mary University of London, London, United Kingdom
| | - Martin J. Bishop
- School of Imaging Sciences and Biomedical Engineering, King’s College London, London, United Kingdom
| | - Ben Hanson
- Department of Mechanical Engineering, University College London, London, United Kingdom
| | - Pier Lambiase
- Institute of Cardiovascular Science, University College London, London, United Kingdom
| | - Reza Razavi
- School of Imaging Sciences and Biomedical Engineering, King’s College London, London, United Kingdom
| | | | | | - Peter Taggart
- Institute of Cardiovascular Science, University College London, London, United Kingdom
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Nánási PP, Szabó Z, Kistamás K, Horváth B, Virág L, Jost N, Bányász T, Almássy J, Varró A. Implication of frequency-dependent protocols in antiarrhythmic and proarrhythmic drug testing. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2019; 157:76-83. [PMID: 31726065 DOI: 10.1016/j.pbiomolbio.2019.11.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Revised: 10/30/2019] [Accepted: 11/01/2019] [Indexed: 01/20/2023]
Abstract
It has long been known that the electrophysiological effects of many cardioactive drugs strongly depend on the rate dependent frequency. This was recognized first for class I antiarrhythmic agents: their Vmax suppressive effect was attenuated at long cycle lengths. Later many Ca2+ channel blockers were also found to follow such kinetics. The explanation was provided by the modulated and the guarded receptor theories. Regarding the duration of cardiac action potentials (APD) an opposite frequency-dependence was observed, i.e. the drug-induced changes in APD were proportional with the cycle length of stimulation, therefore it was referred as "reverse rate-dependency". The beat-to-beat, or short term variability of APD (SV) has been recognized as an important proarrhythmic mechanism, its magnitude can be used as an arrhythmia predictor. SV is modulated by several cardioactive agents, however, these drugs modify also APD itself. In order to clear the drug-specific effects on SV from the concomitant unspecific APD-change related ones, the term of "relative variability" was introduced. Relative variability is increased by ion channel blockers that decrease the negative feedback control of APD (i.e. blockers of ICa, IKr and IKs) and also by elevation of cytosolic Ca2+. Cardiac arrhythmias are also often categorized according to the characteristic heart rate (tachy- and bradyarrhythmias). Tachycardia is proarrhythmic primarily due to the concomitant Ca2+ overload causing delayed afterdepolarizations. Early afterdepolarizations (EADs) are complications of the bradycardic heart. What is common in the reverse rate-dependent nature of drug action on APD, increased SV and EAD incidence associated with bradycardia.
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Affiliation(s)
- Péter P Nánási
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary; Department of Dental Physiology, Faculty of Dentistry, University of Debrecen, Debrecen, Hungary
| | - Zoltán Szabó
- Department of Emergency Medicine, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Kornél Kistamás
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Balázs Horváth
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - László Virág
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary; Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of Szeged, Szeged, Hungary
| | - Norbert Jost
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary; Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of Szeged, Szeged, Hungary; MTA-SZTE Research Group for Cardiovascular Pharmacology, Szeged, Hungary
| | - Tamás Bányász
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - János Almássy
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - András Varró
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary; Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of Szeged, Szeged, Hungary; MTA-SZTE Research Group for Cardiovascular Pharmacology, Szeged, Hungary.
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Porter B, Bishop MJ, Claridge S, Child N, Van Duijvenboden S, Bostock J, Sieniewicz BJ, Gould J, Sidhu B, Hanson B, Chen Z, Rinaldi CA, Taggart P, Gill JS. Left ventricular activation-recovery interval variability predicts spontaneous ventricular tachyarrhythmia in patients with heart failure. Heart Rhythm 2019; 16:702-709. [DOI: 10.1016/j.hrthm.2018.11.013] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Indexed: 01/01/2023]
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7
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Asahi Y, Hamada T, Hattori A, Matsuura K, Odaka M, Nomura F, Kaneko T, Abe Y, Takasuna K, Sanbuissho A, Yasuda K. On-chip spatiotemporal electrophysiological analysis of human stem cell derived cardiomyocytes enables quantitative assessment of proarrhythmia in drug development. Sci Rep 2018; 8:14536. [PMID: 30266924 PMCID: PMC6162288 DOI: 10.1038/s41598-018-32921-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Accepted: 09/17/2018] [Indexed: 12/17/2022] Open
Abstract
We examined a simultaneous combined spatiotemporal field potential duration (FPD) and cell-to-cell conduction time (CT) in lined-up shaped human embryonic stem cell-derived cardiomyocytes (hESC-CMs) using an on-chip multielectrode array (MEA) system to evaluate two origins of lethal arrhythmia, repolarization and depolarization. The repolarization index, FPD, was prolonged by E-4031 and astemizole, and shortened by verapamil, flecainide and terfenadine at 10 times higher than therapeutic plasma concentrations of each drug, but it did not change after lidocaine treatment up to 100 μM. CT was increased by astemizol, flecainide, terfenadine, and lidocaine at equivalent concentrations of Nav1.5 IC50, suggesting that CT may be an index of cardiac depolarization because the increase in CT (i.e., decrease in cell-to-cell conduction speed) was relevant to Nav1.5 inhibition. Fluctuations (short-term variability; STV) of FPD and CT, STVFPD and STVCT also discriminated between torsadogenic and non-torsadogenic compounds with significant increases in their fluctuation values, enabling precise prediction of arrhythmogenic risk as potential new indices.
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Affiliation(s)
- Yumiko Asahi
- Medicinal Safety Research Laboratories, Kasai R&D Center, Daiichi-Sankyo Co. Ltd., Edogawa, Tokyo, 134-8630, Japan
| | - Tomoyo Hamada
- Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, 2-3-10 Kanda-Surugadai, Chiyoda, Tokyo, 101-0062, Japan
- Chiome Bioscience Inc. Shibuya, Tokyo, 151-0071, Japan
| | - Akihiro Hattori
- Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, 2-3-10 Kanda-Surugadai, Chiyoda, Tokyo, 101-0062, Japan
- Organization for University Research Initiatives, Waseda University, 3-14-9 Ookubo, Shinjuku, Tokyo, 169-0072, Japan
- Waseda Bioscience Research Institute in Singapore (WABOIS), Helios, 11 Biopolis Way, 138667, Singapore
| | - Kenji Matsuura
- Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, 2-3-10 Kanda-Surugadai, Chiyoda, Tokyo, 101-0062, Japan
- Organization for University Research Initiatives, Waseda University, 3-14-9 Ookubo, Shinjuku, Tokyo, 169-0072, Japan
- Waseda Bioscience Research Institute in Singapore (WABOIS), Helios, 11 Biopolis Way, 138667, Singapore
| | - Masao Odaka
- Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, 2-3-10 Kanda-Surugadai, Chiyoda, Tokyo, 101-0062, Japan
- Organization for University Research Initiatives, Waseda University, 3-14-9 Ookubo, Shinjuku, Tokyo, 169-0072, Japan
- Waseda Bioscience Research Institute in Singapore (WABOIS), Helios, 11 Biopolis Way, 138667, Singapore
| | - Fumimasa Nomura
- Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, 2-3-10 Kanda-Surugadai, Chiyoda, Tokyo, 101-0062, Japan
| | - Tomoyuki Kaneko
- Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, 2-3-10 Kanda-Surugadai, Chiyoda, Tokyo, 101-0062, Japan
- Department of Frontier Bioscience, Hosei Univ., Koganei, Tokyo, 184-8584, Japan
| | - Yasuyuki Abe
- Medicinal Safety Research Laboratories, Kasai R&D Center, Daiichi-Sankyo Co. Ltd., Edogawa, Tokyo, 134-8630, Japan
| | - Kiyoshi Takasuna
- Medicinal Safety Research Laboratories, Kasai R&D Center, Daiichi-Sankyo Co. Ltd., Edogawa, Tokyo, 134-8630, Japan
| | - Atsushi Sanbuissho
- Medicinal Safety Research Laboratories, Kasai R&D Center, Daiichi-Sankyo Co. Ltd., Edogawa, Tokyo, 134-8630, Japan
| | - Kenji Yasuda
- Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, 2-3-10 Kanda-Surugadai, Chiyoda, Tokyo, 101-0062, Japan.
- Organization for University Research Initiatives, Waseda University, 3-14-9 Ookubo, Shinjuku, Tokyo, 169-0072, Japan.
- Waseda Bioscience Research Institute in Singapore (WABOIS), Helios, 11 Biopolis Way, 138667, Singapore.
- Department of Pure and Applied Physics, Graduate School of Advanced Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo, 169-8555, Japan.
- Department of Physics, School of Advanced Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo, 169-8555, Japan.
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Hemmeryckx B, Feng Y, Frederix L, Lox M, Trenson S, Vreeken R, Lu HR, Gallacher D, Ni Y, Lijnen HR. Evaluation of cardiac arrhythmic risks using a rabbit model of left ventricular systolic dysfunction. Eur J Pharmacol 2018; 832:145-155. [PMID: 29782862 DOI: 10.1016/j.ejphar.2018.05.026] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Revised: 05/17/2018] [Accepted: 05/17/2018] [Indexed: 12/13/2022]
Abstract
Patients with heart disease have a higher risk to develop cardiac arrhythmias, either spontaneously or drug-induced. In this study, we have used a rabbit model of myocardial infarction (MI) with severe left ventricular systolic dysfunction (LVSD) to study potential drug-induced cardiac risks with N-(piperidin-2-ylmethyl)-2,5-bis(2,2,2-trifluoroethoxy)benzamide (flecainide). Upon ligation of the left circumflex arteries, male New Zealand White rabbits developed a large MI and moderate or severe LVSD 7 weeks after surgery, in comparison to SHAM-operated animals. Subsequently, animals were exposed to escalating doses of flecainide (0.25-4 mg/kg) or solvent. Electrocardiograms (ECG) were recorded before surgery, 1 and 7 weeks after surgery and continuously during the drug protocol. The ECG biomarker iCEB (index of Cardio-Electrophysiological Balance = QT/QRS ratio) was calculated. During the ECG recording at week 1 and week 7 post MI, rabbits had no spontaneous cardiac arrhythmias. When rabbits were exposed to escalating doses of flecainide, 2 out of 5 rabbits with MI and moderate LVSD versus 0 out of 5 solvent-treated rabbits developed arrhythmias, such as ventricular tachycardia/ventricular fibrillation. These were preceded by a marked decrease of iCEB just before the onset (from 4.09 to 2.42 and from 5.56 to 2.25, respectively). Furthermore, 1 out of 5 MI rabbits with moderate LVSD and 1 out of 7 MI rabbits with severe LVSD developed total atrioventricular block after flecainide infusion and died. This rabbit model of MI and severe LVSD may be useful for preclinical evaluation of drug (similar mechanism as flecainide)-induced arrhythmic risks, which might be predicted by iCEB.
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Affiliation(s)
- Bianca Hemmeryckx
- Center for Molecular and Vascular Biology, Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium.
| | - Yuanbo Feng
- Radiology, Department of Imaging and Pathology, KU Leuven, Leuven, Belgium.
| | - Liesbeth Frederix
- Center for Molecular and Vascular Biology, Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium.
| | - Marleen Lox
- Center for Molecular and Vascular Biology, Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium.
| | - Sander Trenson
- Cardiology, Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium.
| | - Rob Vreeken
- Metabolomics, Pharmacokinetics, Dynamics and Metabolism Discovery Sciences, Janssen Pharmaceutical NV, Beerse, Belgium.
| | - Hua Rong Lu
- Translational Sciences, Safety Pharmacology Research, Janssen Research & Development, Janssen Pharmaceutical NV, Beerse, Belgium.
| | - David Gallacher
- Translational Sciences, Safety Pharmacology Research, Janssen Research & Development, Janssen Pharmaceutical NV, Beerse, Belgium.
| | - Yicheng Ni
- Radiology, Department of Imaging and Pathology, KU Leuven, Leuven, Belgium.
| | - H Roger Lijnen
- Center for Molecular and Vascular Biology, Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium.
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9
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Porter B, van Duijvenboden S, Bishop MJ, Orini M, Claridge S, Gould J, Sieniewicz BJ, Sidhu B, Razavi R, Rinaldi CA, Gill JS, Taggart P. Beat-to-Beat Variability of Ventricular Action Potential Duration Oscillates at Low Frequency During Sympathetic Provocation in Humans. Front Physiol 2018; 9:147. [PMID: 29670531 PMCID: PMC5893843 DOI: 10.3389/fphys.2018.00147] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2017] [Accepted: 02/13/2018] [Indexed: 01/22/2023] Open
Abstract
Background: The temporal pattern of ventricular repolarization is of critical importance in arrhythmogenesis. Enhanced beat-to-beat variability (BBV) of ventricular action potential duration (APD) is pro-arrhythmic and is increased during sympathetic provocation. Since sympathetic nerve activity characteristically exhibits burst patterning in the low frequency range, we hypothesized that physiologically enhanced sympathetic activity may not only increase BBV of left ventricular APD but also impose a low frequency oscillation which further increases repolarization instability in humans. Methods and Results: Heart failure patients with cardiac resynchronization therapy defibrillator devices (n = 11) had activation recovery intervals (ARI, surrogate for APD) recorded from left ventricular epicardial electrodes alongside simultaneous non-invasive blood pressure and respiratory recordings. Fixed cycle length was achieved by right ventricular pacing. Recordings took place during resting conditions and following an autonomic stimulus (Valsalva). The variability of ARI and the normalized variability of ARI showed significant increases post Valsalva when compared to control (p = 0.019 and p = 0.032, respectively). The oscillatory behavior was quantified by spectral analysis. Significant increases in low frequency (LF) power (p = 0.002) and normalized LF power (p = 0.019) of ARI were seen following Valsalva. The Valsalva did not induce changes in conduction variability nor the LF oscillatory behavior of conduction. However, increases in the LF power of ARI were accompanied by increases in the LF power of systolic blood pressure (SBP) and the rate of systolic pressure increase (dP/dtmax). Positive correlations were found between LF-SBP and LF-dP/dtmax (rs = 0.933, p < 0.001), LF-ARI and LF-SBP (rs = 0.681, p = 0.001) and between LF-ARI and LF-dP/dtmax (rs = 0.623, p = 0.004). There was a strong positive correlation between the variability of ARI and LF power of ARI (rs = 0.679, p < 0.001). Conclusions: In heart failure patients, physiological sympathetic provocation induced low frequency oscillation (~0.1 Hz) of left ventricular APD with a strong positive correlation between the LF power of APD and the BBV of APD. These findings may be of importance in mechanisms underlying stability/instability of repolarization and arrhythmogenesis in humans.
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Affiliation(s)
- Bradley Porter
- Department of Imaging Sciences and Biomedical Engineering, Kings College London, London, United Kingdom
| | | | - Martin J. Bishop
- Department of Imaging Sciences and Biomedical Engineering, Kings College London, London, United Kingdom
| | - Michele Orini
- Guy's and St Thomas' Hospital, London, United Kingdom
| | - Simon Claridge
- Department of Imaging Sciences and Biomedical Engineering, Kings College London, London, United Kingdom
| | - Justin Gould
- Department of Imaging Sciences and Biomedical Engineering, Kings College London, London, United Kingdom
| | - Benjamin J. Sieniewicz
- Department of Imaging Sciences and Biomedical Engineering, Kings College London, London, United Kingdom
| | - Baldeep Sidhu
- Department of Imaging Sciences and Biomedical Engineering, Kings College London, London, United Kingdom
| | - Reza Razavi
- Department of Imaging Sciences and Biomedical Engineering, Kings College London, London, United Kingdom
| | - Christopher A. Rinaldi
- Department of Cardiovascular Sciences, University College London, London, United Kingdom
| | - Jaswinder S. Gill
- Department of Cardiovascular Sciences, University College London, London, United Kingdom
| | - Peter Taggart
- Guy's and St Thomas' Hospital, London, United Kingdom
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10
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Limprasutr V, Pirintr P, Kijtawornrat A, Hamlin RL. An increasing electromechanical window is a predictive marker of ventricular fibrillation in anesthetized rabbit with ischemic heart. Exp Anim 2017; 67:175-183. [PMID: 29162767 PMCID: PMC5955749 DOI: 10.1538/expanim.17-0100] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The QTc interval is widely used in Safety Pharmacological studies to predict arrhythmia
risk, and the electromechanical window (EMW) and short-term variability of QT intervals
(STVQT) have been studied as new biomarkers for drug-induced Torsades de
Pointes (TdP). However, the use of EMW and STVQT to predict ventricular
fibrillation (VF) has not been elucidated. This study aimed to evaluate EMW and
STVQT to predict VF in anesthetized rabbit model of VF. VF was induced by
ligation of the left anterior descending and a descending branch of the left circumflex
coronary arteries in a sample population of rabbits (n=18). VF was developed 55.6%
(10/18). In rabbit with VF, the EMW was significantly higher than in rabbits without VF
(96.3 ± 15.6 ms and 49.5 ± 5.6 ms, respectively, P<0.05).
STVQT had significantly increased before the onset of VF in rabbits that
experienced VF, but not in rabbits that did not experience VF (11.7 ± 1.8 ms and 3.7 ± 0.4
ms, respectively, P<0.05). The EMW and STVQT had better
predictive power for VF with higher sensitivity and specificity than the QTc measure. The
result suggested that the increasing of EMW, as well as the elevation of STVQT,
can potentially be used as biomarkers for predicting of VF.
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Affiliation(s)
- Vudhiporn Limprasutr
- Department of Physiology, Faculty of Veterinary Science, Chulalongkorn University, 39 Henri Dunant Road, Wang Mai, Pathumwan, Bangkok 10330, Thailand
| | - Prapawadee Pirintr
- Department of Physiology, Faculty of Veterinary Science, Chulalongkorn University, 39 Henri Dunant Road, Wang Mai, Pathumwan, Bangkok 10330, Thailand.,Department of Veterinary Biosciences and Veterinary Public Health, Faculty of Veterinary Medicine, Chiang Mai University, 155 Tumbon Mae Hiae, Muang, Chiang Mai 50100, Thailand
| | - Anusak Kijtawornrat
- Department of Physiology, Faculty of Veterinary Science, Chulalongkorn University, 39 Henri Dunant Road, Wang Mai, Pathumwan, Bangkok 10330, Thailand.,Research clusters: research study and testing of drug's effect related to cardiovascular system in laboratory animals, Chulalongkorn University, 39 Henri Dunant Road, Wang Mai, Pathumwan, Bangkok 10330, Thailand
| | - Robert L Hamlin
- QTest Labs, LLC. 6456 Fiesta Drive, Columbus, Ohio 43235, USA
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11
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Pastarapatee N, Kijtawornrat A, Buranakarl C. Imbalance of autonomic nervous systems involved in ventricular arrhythmia after splenectomy in dogs. J Vet Med Sci 2017; 79:2002-2010. [PMID: 29070771 PMCID: PMC5745180 DOI: 10.1292/jvms.17-0482] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The role of cardiac autonomic modulation on ventricular arrhythmia, known as ventricular premature complexes (VPC), after splenectomy was investigated. Twelve dogs undergoing splenectomy were divided into 2 groups: low VPC (<1,000/day, n=6) and high VPC groups (≥1,000/day, n=6). Electrocardiograph recording was performed prior to (D0), during the first three days (D1-3) and on day 9 (D9) after surgery. Arrhythmic indices, Tpeak-Tend, corrected QT interval and short-term variability of QT interval as well as heart rate variability (HRV) were evaluated. Plasma concentrations of norepinephrine (NE) and epinephrine (E) were measured. In the high VPC group, the occurrences of VPC were significantly increased (P<0.05) after surgery, and reached the levels higher than those in the low VPC group. For the arrhythmic indices, only Tp-Te in the high VPC group increased significantly (P<0.05) after surgery. For HRV analysis, enhancement of both time and frequency domains were found postoperatively in both groups. On D2, however, the high VPC group showed significantly lower total power and high frequency with higher low to high frequency ratio (P<0.05) than the low VPC group. Plasma NE concentration significantly increased in the high VPC group after surgery. Dogs in the high VPC group had shorter survival time than those in the low VPC group. In conclusion, dogs with imbalance cardiac autonomic modulation accompanied with high circulating NE concentration after splenectomy are prone to ventricular arrhythmia, which leads to short survival time.
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Affiliation(s)
- Nuttika Pastarapatee
- Department of Physiology, Faculty of Veterinary Science, Chulalongkorn University, Henri Dunant Rd., Pathumwan, Bangkok 10330, Thailand
| | - Anusak Kijtawornrat
- Department of Physiology, Faculty of Veterinary Science, Chulalongkorn University, Henri Dunant Rd., Pathumwan, Bangkok 10330, Thailand
| | - Chollada Buranakarl
- Department of Physiology, Faculty of Veterinary Science, Chulalongkorn University, Henri Dunant Rd., Pathumwan, Bangkok 10330, Thailand
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12
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Nánási PP, Magyar J, Varró A, Ördög B. Beat-to-beat variability of cardiac action potential duration: underlying mechanism and clinical implications. Can J Physiol Pharmacol 2017; 95:1230-1235. [PMID: 28746810 DOI: 10.1139/cjpp-2016-0597] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Beat-to-beat variability of cardiac action potential duration (short-term variability, SV) is a common feature of various cardiac preparations, including the human heart. Although it is believed to be one of the best arrhythmia predictors, the underlying mechanisms are not fully understood at present. The magnitude of SV is basically determined by the intensity of cell-to-cell coupling in multicellular preparations and by the duration of the action potential (APD). To compensate for the APD-dependent nature of SV, the concept of relative SV (RSV) has been introduced by normalizing the changes of SV to the concomitant changes in APD. RSV is reduced by ICa, IKr, and IKs while increased by INa, suggesting that ion currents involved in the negative feedback regulation of APD tend to keep RSV at a low level. RSV is also influenced by intracellular calcium concentration and tissue redox potential. The clinical implications of APD variability is discussed in detail.
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Affiliation(s)
- Péter P Nánási
- a Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.,b Department of Dental Physiology and Pharmacology, Faculty of Dentistry, University of Debrecen, Debrecen, Hungary
| | - János Magyar
- a Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - András Varró
- c Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary
| | - Balázs Ördög
- c Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary
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13
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Electrocardiographic Predictors of Torsadogenic Risk During Dofetilide or Sotalol Initiation: Utility of a Novel T Wave Analysis Program. Cardiovasc Drugs Ther 2016; 29:433-41. [PMID: 26411977 DOI: 10.1007/s10557-015-6619-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
INTRODUCTION Initiation of class III anti-arrhythmic medications requires telemetric monitoring for ventricular arrhythmias and QT prolongation to reduce the risk of torsades de pointes (TdP). Heart rate-corrected QT interval (QTc) is an indicator of risk, however it is imperfect, and subtle abnormalities of repolarization have been linked with arrhythmogenesis. PURPOSE Identification of electrocardiographic predictors of torsadogenic risk through the application of a novel T wave analysis tool. METHODS Among all patients admitted to Mayo Clinic for initiation of dofetilide or sotalol, we identified 13 cases who developed drug-induced TdP and 26 age and sex matched controls that did not develop TdP. The immediate pre-TdP ECG of those with TdP was compared to the last ECG performed prior to hospital discharge in controls using a novel T wave program that quantified subtle changes in T wave morphology. RESULTS The QTc and 12 T wave parameters successfully distinguished TdP cases from controls. The top performing parameters were the QTc in lead V3 (mean case vs control 480 vs 420 msec, p < 0.001, r = 0.72) and T wave right slope in lead I (mean case vs control -840.29 vs -1668.71 mV/s, p = 0.002, r = 0.45). The addition of T wave right slope to QTc improved prediction accuracy from 79 to 88 %. CONCLUSION Our data demonstrate that, in addition to QTc, the T wave right slope is correlated strongly with TdP risk. This suggests that a computer-based repolarization measurement tool that integrates additional data beyond the QTc may identify patients with the greatest torsadogenic potential.
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14
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Lang CN, Koren G, Odening KE. Transgenic rabbit models to investigate the cardiac ion channel disease long QT syndrome. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2016; 121:142-56. [PMID: 27210307 DOI: 10.1016/j.pbiomolbio.2016.05.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Accepted: 05/01/2016] [Indexed: 12/13/2022]
Abstract
Long QT syndrome (LQTS) is a rare inherited channelopathy caused mainly by different mutations in genes encoding for cardiac K(+) or Na(+) channels, but can also be caused by commonly used ion-channel-blocking and QT-prolonging drugs, thus affecting a much larger population. To develop novel diagnostic and therapeutic strategies to improve the clinical management of these patients, a thorough understanding of the pathophysiological mechanisms of arrhythmogenesis and potential pharmacological targets is needed. Drug-induced and genetic animal models of various species have been generated and have been instrumental for identifying pro-arrhythmic triggers and important characteristics of the arrhythmogenic substrate in LQTS. However, due to species differences in features of cardiac electrical function, these different models do not entirely recapitulate all aspects of the human disease. In this review, we summarize advantages and shortcomings of different drug-induced and genetically mediated LQTS animal models - focusing on mouse and rabbit models since these represent the most commonly used small animal models for LQTS that can be subjected to genetic manipulation. In particular, we highlight the different aspects of arrhythmogenic mechanisms, pro-arrhythmic triggering factors, anti-arrhythmic agents, and electro-mechanical dysfunction investigated in transgenic LQTS rabbit models and their translational application for the clinical management of LQTS patients in detail. Transgenic LQTS rabbits have been instrumental to increase our understanding of the role of spatial and temporal dispersion of repolarization to provide an arrhythmogenic substrate, genotype-differences in the mechanisms for early afterdepolarization formation and arrhythmia maintenance, mechanisms of hormonal modification of arrhythmogenesis and regional heterogeneities in electro-mechanical dysfunction in LQTS.
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Affiliation(s)
- C N Lang
- Department of Cardiology and Angiology I, University Heart Center Freiburg, Medical Center - University of Freiburg, Germany; Faculty of Medicine, University of Freiburg, Germany
| | - G Koren
- Cardiovascular Research Center, Division of Cardiology, Rhode Island Hospital, Warren Alpert Medical School of Brown University, Providence, RI, USA
| | - K E Odening
- Department of Cardiology and Angiology I, University Heart Center Freiburg, Medical Center - University of Freiburg, Germany; Faculty of Medicine, University of Freiburg, Germany.
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15
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Baczkó I, Jost N, Virág L, Bősze Z, Varró A. Rabbit models as tools for preclinical cardiac electrophysiological safety testing: Importance of repolarization reserve. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2016; 121:157-68. [PMID: 27208697 DOI: 10.1016/j.pbiomolbio.2016.05.002] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Accepted: 05/01/2016] [Indexed: 01/26/2023]
Abstract
It is essential to more reliably assess the pro-arrhythmic liability of compounds in development. Current guidelines for pre-clinical and clinical testing of drug candidates advocate the use of healthy animals/tissues and healthy individuals and focus on the test compound's ability to block the hERG current and prolong cardiac ventricular repolarization. Also, pre-clinical safety tests utilize several species commonly used in cardiac electrophysiological studies. In this review, important species differences in cardiac ventricular repolarizing ion currents are considered, followed by the discussion on electrical remodeling associated with chronic cardiovascular diseases that leads to altered ion channel and transporter expression and densities in pathological settings. We argue that the choice of species strongly influences experimental outcome and extrapolation of results to human clinical settings. We suggest that based on cardiac cellular electrophysiology, the rabbit is a useful species for pharmacological pro-arrhythmic investigations. In addition to healthy animals and tissues, the use of animal models (e.g. those with impaired repolarization reserve) is suggested that more closely resemble subsets of patients exhibiting increased vulnerability towards the development of ventricular arrhythmias and sudden cardiac death.
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Affiliation(s)
- István Baczkó
- Department of Pharmacology & Pharmacotherapy, University of Szeged, Dóm tér 12., 6720 Szeged, Hungary.
| | - Norbert Jost
- Department of Pharmacology & Pharmacotherapy, University of Szeged, Dóm tér 12., 6720 Szeged, Hungary; MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, Dóm tér 12., 6720 Szeged, Hungary
| | - László Virág
- Department of Pharmacology & Pharmacotherapy, University of Szeged, Dóm tér 12., 6720 Szeged, Hungary
| | - Zsuzsanna Bősze
- Rabbit Genome and Biomodel Group, NARIC-Agricultural Biotechnology Institute, 2100 Gödöllő, Hungary
| | - András Varró
- Department of Pharmacology & Pharmacotherapy, University of Szeged, Dóm tér 12., 6720 Szeged, Hungary; MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, Dóm tér 12., 6720 Szeged, Hungary
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16
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Stams TR, Oosterhoff P, Heijdel A, Dunnink A, Beekman JD, van der Nagel R, van Rijen HV, van der Heyden MA, Vos MA. Beat-to-Beat Variability in Preload Unmasks Latent Risk of Torsade de Pointes in Anesthetized Chronic Atrioventricular Block Dogs. Circ J 2016; 80:1336-45. [PMID: 27151565 DOI: 10.1253/circj.cj-15-1335] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
BACKGROUND Beat-to-beat variability in ventricular repolarization (BVR) associates with increased arrhythmic risk. Proarrhythmic remodeling in the dog with chronic AV-block (CAVB) compromises repolarization reserve and associates with increased BVR, which further increases upon dofetilide infusion and correlates with Torsade de Pointes (TdP) arrhythmias. It was hypothesized that these pro-arrhythmia-associated increases in BVR are induced by beat-to-beat variability in preload. METHODS AND RESULTS Left ventricular monophasic action potential duration (LVMAPD) was recorded in acute (AAVB) and CAVB dogs, before and after dofetilide infusion. BVR was quantified as short-term variability of LVMAPD. The PQ-interval was controlled by pacing: either a constant or an alternating preload pattern was established, verified by PV-loop. The effect of the stretch-activated channel blocker, streptomycin, on BVR was evaluated in a second CAVB group. At alternating preload only, BVR was increased after proarrhythmic remodeling (0.45±0.14 ms AAVB vs. 2.2±1.1 ms CAVB, P<0.01). At CAVB, but not at AAVB, dofetilide induced significant proarrhythmia. Preload variability augmented the dofetilide-induced BVR increase at CAVB (+1.5±0.8 ms vs. +0.9±0.9 ms, P=0.058). In the second group, the increase in baseline BVR by alternating preload (0.3±0.03 ms to 1.0±0.8 ms, P<0.01) was abolished by streptomycin (0.5±0.2 ms, P<0.05). CONCLUSIONS In CAVB dogs, the inverse relation between BVR and repolarization reserve originates from an augmented sensitivity of ventricular repolarization to beat-to-beat preload changes. Stretch-activated channels appear to be involved in the mechanism of BVR. (Circ J 2016; 80: 1336-1345).
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Affiliation(s)
- Thom Rg Stams
- Department of Medical Physiology, Division of Heart and Lungs, University Medical Center
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17
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Odening KE, Kohl P. Editorial to "Disturbances of cardiac wavelength and repolarization precede torsade de pointes and ventricular fibrillation in langendorff perfused rabbit hearts" by Luc Hondeghem: It is difficult to make predictions, especially about the future∗: Thoughts about forecasting cardiotoxicity of pharmacological interventions. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2016; 121:1-2. [PMID: 27137834 DOI: 10.1016/j.pbiomolbio.2016.04.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Affiliation(s)
- Katja E Odening
- Department of Cardiology and Angiology I, University Heart Center Freiburg - Bad Krozingen, Medical Center - University of Freiburg, Germany; Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg - Bad Krozingen, Medical Center - University of Freiburg, Germany; Faculty of Medicine, University of Freiburg, Germany.
| | - Peter Kohl
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg - Bad Krozingen, Medical Center - University of Freiburg, Germany; Faculty of Medicine, University of Freiburg, Germany; Cardiac Biophysics and Systems Biology, National Heart and Lung Institute, London, UK
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18
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Davies MR, Wang K, Mirams GR, Caruso A, Noble D, Walz A, Lavé T, Schuler F, Singer T, Polonchuk L. Recent developments in using mechanistic cardiac modelling for drug safety evaluation. Drug Discov Today 2016; 21:924-38. [PMID: 26891981 PMCID: PMC4909717 DOI: 10.1016/j.drudis.2016.02.003] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Revised: 01/13/2016] [Accepted: 02/05/2016] [Indexed: 01/21/2023]
Abstract
Modelling and simulation can streamline decision making in drug safety testing. Computational cardiac electrophysiology is a mature technology with a long heritage. There are many challenges and opportunities in using in silico techniques in future. We discuss how models can be used at different stages of drug discovery. CiPA will combine screening platforms, human cell assays and in silico predictions.
On the tenth anniversary of two key International Conference on Harmonisation (ICH) guidelines relating to cardiac proarrhythmic safety, an initiative aims to consider the implementation of a new paradigm that combines in vitro and in silico technologies to improve risk assessment. The Comprehensive In Vitro Proarrhythmia Assay (CiPA) initiative (co-sponsored by the Cardiac Safety Research Consortium, Health and Environmental Sciences Institute, Safety Pharmacology Society and FDA) is a bold and welcome step in using computational tools for regulatory decision making. This review compares and contrasts the state-of-the-art tools from empirical to mechanistic models of cardiac electrophysiology, and how they can and should be used in combination with experimental tests for compound decision making.
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Affiliation(s)
| | - Ken Wang
- Roche Pharmaceutical Research and Early Development, Pharmaceutical Sciences, Roche Innovation Center Basel, Switzerland
| | - Gary R Mirams
- Computational Biology, Department of Computer Science, University of Oxford, OX1 3QD, UK
| | - Antonello Caruso
- Roche Pharmaceutical Research and Early Development, Pharmaceutical Sciences, Roche Innovation Center Basel, Switzerland
| | - Denis Noble
- Department of Physiology, Anatomy & Genetics, University of Oxford, OX1 3PT, UK
| | - Antje Walz
- Roche Pharmaceutical Research and Early Development, Pharmaceutical Sciences, Roche Innovation Center Basel, Switzerland
| | - Thierry Lavé
- Roche Pharmaceutical Research and Early Development, Pharmaceutical Sciences, Roche Innovation Center Basel, Switzerland
| | - Franz Schuler
- Roche Pharmaceutical Research and Early Development, Pharmaceutical Sciences, Roche Innovation Center Basel, Switzerland
| | - Thomas Singer
- Roche Pharmaceutical Research and Early Development, Pharmaceutical Sciences, Roche Innovation Center Basel, Switzerland
| | - Liudmila Polonchuk
- Roche Pharmaceutical Research and Early Development, Pharmaceutical Sciences, Roche Innovation Center Basel, Switzerland
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19
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Abstract
Ventricular repolarization is a complex electrical phenomenon which represents a crucial stage in electrical cardiac activity. It is expressed on the surface electrocardiogram by the interval between the start of the QRS complex and the end of the T wave or U wave (QT). Several physiological, pathological and iatrogenic factors can influence ventricular repolarization. It has been demonstrated that small perturbations in this process can be a potential trigger of malignant arrhythmias, therefore the analysis of ventricular repolarization represents an interesting tool to implement risk stratification of arrhythmic events in different clinical settings. The aim of this review is to critically revise the traditional methods of static analysis of ventricular repolarization as well as those for dynamic evaluation, their prognostic significance and the possible application in daily clinical practice.
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20
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Monitillo F, Leone M, Rizzo C, Passantino A, Iacoviello M. Ventricular repolarization measures for arrhythmic risk stratification. World J Cardiol 2016; 8:57-73. [PMID: 26839657 PMCID: PMC4728107 DOI: 10.4330/wjc.v8.i1.57] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/30/2015] [Revised: 09/04/2015] [Accepted: 11/04/2015] [Indexed: 02/06/2023] Open
Abstract
Ventricular repolarization is a complex electrical phenomenon which represents a crucial stage in electrical cardiac activity. It is expressed on the surface electrocardiogram by the interval between the start of the QRS complex and the end of the T wave or U wave (QT). Several physiological, pathological and iatrogenic factors can influence ventricular repolarization. It has been demonstrated that small perturbations in this process can be a potential trigger of malignant arrhythmias, therefore the analysis of ventricular repolarization represents an interesting tool to implement risk stratification of arrhythmic events in different clinical settings. The aim of this review is to critically revise the traditional methods of static analysis of ventricular repolarization as well as those for dynamic evaluation, their prognostic significance and the possible application in daily clinical practice.
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21
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Jones DK, Liu F, Dombrowski N, Joshi S, Robertson GA. Dominant negative consequences of a hERG 1b-specific mutation associated with intrauterine fetal death. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2016; 120:67-76. [PMID: 26772437 DOI: 10.1016/j.pbiomolbio.2016.01.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2015] [Revised: 12/07/2015] [Accepted: 01/04/2016] [Indexed: 12/16/2022]
Abstract
The human ether-a-go-go related gene (hERG) encodes two subunits, hERG 1a and hERG 1b, that combine in vivo to conduct the rapid delayed rectifier potassium current (IKr). Reduced IKr slows cardiac action potential (AP) repolarization and is an underlying cause of cardiac arrhythmias associated with long QT syndrome (LQTS). Although the physiological importance of hERG 1b has been elucidated, the effects of hERG 1b disease mutations on cardiac IKr and AP behavior have not been described. To explore the disease mechanism of a 1b-specific mutation associated with a case of intrauterine fetal death, we examined the effects of the 1b-R25W mutation on total protein, trafficking and membrane current levels in HEK293 cells at physiological temperatures. By all measures the 1b-R25W mutation conferred diminished expression, and exerted a temperature-sensitive, dominant-negative effect over the WT hERG 1a protein with which it was co-expressed. Membrane currents were reduced by 60% with no apparent effect on voltage dependence or deactivation kinetics. The dominant-negative effects of R25W were demonstrated in iPSC-CMs, where 1b-R25W transfection diminished native IKr compared to controls. R25W also slowed AP repolarization, and increased AP triangulation and variability in iPSC-CMs, reflecting cellular manifestations of pro-arrhythmia. These data demonstrate that R25W is a dominant-negative mutation with significant pathophysiological consequences, and provide the first direct link between hERG 1b mutation and cardiomyocyte dysfunction.
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Affiliation(s)
- David K Jones
- Dept. of Neuroscience, University of Wisconsin School of Medicine and Public Health, 1111 Highland Avenue, Madison WI 53705, USA
| | - Fang Liu
- Dept. of Neuroscience, University of Wisconsin School of Medicine and Public Health, 1111 Highland Avenue, Madison WI 53705, USA
| | - Natasha Dombrowski
- Dept. of Neuroscience, University of Wisconsin School of Medicine and Public Health, 1111 Highland Avenue, Madison WI 53705, USA
| | - Sunita Joshi
- Dept. of Neuroscience, University of Wisconsin School of Medicine and Public Health, 1111 Highland Avenue, Madison WI 53705, USA
| | - Gail A Robertson
- Dept. of Neuroscience, University of Wisconsin School of Medicine and Public Health, 1111 Highland Avenue, Madison WI 53705, USA.
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22
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Kistamás K, Hegyi B, Váczi K, Horváth B, Bányász T, Magyar J, Szentandrássy N, Nánási PP. Oxidative shift in tissue redox potential increases beat-to-beat variability of action potential duration. Can J Physiol Pharmacol 2015; 93:563-8. [DOI: 10.1139/cjpp-2014-0531] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Profound changes in tissue redox potential occur in the heart under conditions of oxidative stress frequently associated with cardiac arrhythmias. Since beat-to-beat variability (short term variability, SV) of action potential duration (APD) is a good indicator of arrhythmia incidence, the aim of this work was to study the influence of redox changes on SV in isolated canine ventricular cardiomyocytes using a conventional microelectrode technique. The redox potential was shifted toward a reduced state using a reductive cocktail (containing dithiothreitol, glutathione, and ascorbic acid) while oxidative changes were initiated by superfusion with H2O2. Redox effects were evaluated as changes in “relative SV” determined by comparing SV changes with the concomitant APD changes. Exposure of myocytes to the reductive cocktail decreased SV significantly without any detectable effect on APD. Application of H2O2 increased both SV and APD, but the enhancement of SV was the greater, so relative SV increased. Longer exposure to H2O2 resulted in the development of early afterdepolarizations accompanied by tremendously increased SV. Pretreatment with the reductive cocktail prevented both elevation in relative SV and the development of afterdepolarizations. The results suggest that the increased beat-to-beat variability during an oxidative stress contributes to the generation of cardiac arrhythmias.
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Affiliation(s)
- Kornél Kistamás
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, P.O. Box 22, Hungary
| | - Bence Hegyi
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, P.O. Box 22, Hungary
| | - Krisztina Váczi
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, P.O. Box 22, Hungary
| | - Balázs Horváth
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, P.O. Box 22, Hungary
- Faculty of Pharmacy, University of Debrecen, H-4012 Debrecen, P.O. Box 22, Hungary
| | - Tamás Bányász
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, P.O. Box 22, Hungary
| | - János Magyar
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, P.O. Box 22, Hungary
- Division of Sport Physiology, Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, P.O. Box 22, Hungary
| | - Norbert Szentandrássy
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, P.O. Box 22, Hungary
- Department of Dental Physiology, Faculty of Dentistry, University of Debrecen, H-4012 Debrecen, P.O. Box 22, Hungary
| | - Péter P. Nánási
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, P.O. Box 22, Hungary
- Department of Dental Physiology, Faculty of Dentistry, University of Debrecen, H-4012 Debrecen, P.O. Box 22, Hungary
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Dumotier BM. Republished: A straightforward guide to the basic science behind arrhythmogenesis. Postgrad Med J 2015; 91:221-9. [DOI: 10.1136/postgradmedj-2014-305647rep] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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Abstract
The human ether-à-go-go-related gene (hERG; or KCNH2) encodes the voltage-gated potassium channel underlying IKr, a repolarizing current in the heart. Mutations in KCNH2 or pharmacological agents that reduce IKr slow action potential (AP) repolarization and can trigger cardiac arrhythmias associated with long QT syndrome. Two channel-forming subunits encoded by KCNH2 (hERG 1a and 1b) are expressed in cardiac tissue. In heterologous expression systems, these subunits avidly coassemble and exhibit biophysical and pharmacological properties distinct from those of homomeric hERG 1a channels. Despite these findings, adoption of hERG 1a/1b heteromeric channels as a model for cardiac IKr has been hampered by the lack of evidence for a direct functional role for the 1b subunit in native tissue. In this study, we measured IKr and APs at physiological temperature in cardiomyocytes derived from human induced pluripotent stem cells (iPSC-CMs). We found that specific knockdown of the 1b subunit using shRNA caused reductions in 1b mRNA, 1b protein levels, and IKr magnitude by roughly one-half. AP duration was increased and AP variability was enhanced relative to controls. Early afterdepolarizations, considered cellular substrates for arrhythmia, were also observed in cells with reduced 1b expression. Similar behavior was elicited when channels were effectively converted from heteromers to 1a homomers by expressing a fragment corresponding to the 1a-specific N-terminal Per-Arnt-Sim domain, which is omitted from hERG 1b by alternate transcription. These findings establish that hERG 1b is critical for normal repolarization and that loss of 1b is proarrhythmic in human cardiac cells.
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VARKEVISSER ROSANNE, VOS MARCA, BEEKMAN JETD, TIELAND RALPHG, VAN DER HEYDEN MARCELA. AV-Block and Conduction Slowing Prevail Over TdP Arrhythmias in the Methoxamine-Sensitized Pro-Arrhythmic Rabbit Model. J Cardiovasc Electrophysiol 2014; 26:82-9. [DOI: 10.1111/jce.12533] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Revised: 08/14/2014] [Accepted: 08/19/2014] [Indexed: 11/27/2022]
Affiliation(s)
- ROSANNE VARKEVISSER
- Department of Medical Physiology; Division Heart & Lungs University Medical Center Utrecht; Utrecht The Netherlands
| | - MARC A. VOS
- Department of Medical Physiology; Division Heart & Lungs University Medical Center Utrecht; Utrecht The Netherlands
| | - JET D. BEEKMAN
- Department of Medical Physiology; Division Heart & Lungs University Medical Center Utrecht; Utrecht The Netherlands
| | - RALPH G. TIELAND
- Department of Medical Physiology; Division Heart & Lungs University Medical Center Utrecht; Utrecht The Netherlands
| | - MARCEL A. VAN DER HEYDEN
- Department of Medical Physiology; Division Heart & Lungs University Medical Center Utrecht; Utrecht The Netherlands
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Niemeijer MN, van den Berg ME, Eijgelsheim M, van Herpen G, Stricker BH, Kors JA, Rijnbeek PR. Short-term QT variability markers for the prediction of ventricular arrhythmias and sudden cardiac death: a systematic review. Heart 2014; 100:1831-6. [PMID: 25092875 DOI: 10.1136/heartjnl-2014-305671] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Sudden cardiac death (SCD) is a major health burden and is primarily caused by ventricular arrhythmias. Currently, the most well-known marker for the risk of ventricular arrhythmias is QT/QTc prolongation. Animal studies indicate that QT variability might be a better indicator. Our objective was to give an overview of the literature on QT variability in humans, therefore we performed a free-text search in PubMed and Embase from inception through February 2013. We identified nine QT variability markers in 109 studies reporting on QT variability markers, measured on the surface ECG. QT variability can be distinguished using two characteristics: heart rate normalisation and whether QT interval is measured on consecutive beats. Most study populations were small (median 48 subjects, range 1-805) and different methods, time intervals and leads for measurement were used. QT variability markers were determinants for the risk of ventricular arrhythmias, (sudden) cardiac death and total mortality. Few studies compared the predictive value of QT variability with that of QT/QTc prolongation. A study comparing all different QT variability markers is lacking. In conclusion, QT variability markers are potential determinants of ventricular arrhythmias and cardiac mortality. However, it is unclear which marker and methodology are clinically most useful as well as what reference values are reliable. More studies on larger datasets are needed to find the most accurate marker for the prediction of arrhythmias and SCD to assess its value in addition to QT/QTc duration and its role in drug-induced arrhythmia and sudden death.
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Affiliation(s)
- Maartje N Niemeijer
- Department of Epidemiology, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Marten E van den Berg
- Department of Medical Informatics, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Mark Eijgelsheim
- Department of Epidemiology, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands Department of Internal Medicine, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Gerard van Herpen
- Department of Medical Informatics, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Bruno H Stricker
- Department of Epidemiology, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands Department of Internal Medicine, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands Inspectorate of Health Care, The Hague, The Netherlands
| | - Jan A Kors
- Department of Medical Informatics, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Peter R Rijnbeek
- Department of Medical Informatics, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
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Contribution of ion currents to beat-to-beat variability of action potential duration in canine ventricular myocytes. Pflugers Arch 2014; 467:1431-1443. [DOI: 10.1007/s00424-014-1581-4] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2014] [Revised: 07/11/2014] [Accepted: 07/14/2014] [Indexed: 12/19/2022]
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Staikou C, Stamelos M, Stavroulakis E. Impact of anaesthetic drugs and adjuvants on ECG markers of torsadogenicity. Br J Anaesth 2014; 112:217-230. [DOI: 10.1093/bja/aet412] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/30/2023] Open
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Townsend C, Brown BS. Predicting drug-induced QT prolongation and torsades de pointes: a review of preclinical endpoint measures. ACTA ACUST UNITED AC 2013; Chapter 10:Unit 10.16. [PMID: 23744708 DOI: 10.1002/0471141755.ph1016s61] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Compound-induced prolongation of the cardiac QT interval is a major concern in drug development and this unit discusses approaches that can predict QT effects prior to undertaking clinical trials. The majority of compounds that prolong the QT interval block the cardiac rapid delayed rectifier potassium current, IKr (hERG). Described in this overview are different ways to measure hERG, from recent advances in automated electrophysiology to the quantification of channel protein trafficking and binding. The contribution of other cardiac ion channels to hERG data interpretation is also discussed. In addition, endpoint measures of the integrated activity of cardiac ion channels at the single-cell, tissue, and whole-animal level, including for example the well-established action potential to the more recent beat-to-beat variability, transmural dispersion of repolarization, and field potential duration, are described in the context of their ability to predict QT prolongation and torsadogenicity in humans.
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Affiliation(s)
- Claire Townsend
- GlaxoSmithKline Biological Reagents and Assay Development, Research Triangle Park, NC, USA
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Meng J, Shi C, Li L, Du Y, Xu Y. Compound ICA-105574 prevents arrhythmias induced by cardiac delayed repolarization. Eur J Pharmacol 2013; 718:87-97. [PMID: 24041920 DOI: 10.1016/j.ejphar.2013.09.011] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2013] [Revised: 08/27/2013] [Accepted: 09/04/2013] [Indexed: 01/14/2023]
Abstract
Impaired ventricular repolarization can lead to long QT syndrome (LQT), a proarrhythmic disease with high risk of developing lethal ventricular tachyarrhythmias. The compound ICA-105574 is a recently developed hERG activator and it enhances IKr current with very high potency by removing the channel inactivation. The present study was designed to investigate antiarrhythmic properties of ICA-105574. For comparison, the effects of another compound NS1643 was in-parallel assessed, which also acts primarily to attenuate channel inactivation with moderate potency. We found that both ICA-105574 and NS1643 concentration-dependently shortened action potential duration (APD) in ventricular myocytes, and QT/QTc intervals in isolated guinea-pig hearts. ICA-105574, but not NS1643, completely prevented ventricular arrhythmias in intact guinea-pig hearts caused by IKr and IKs inhibitors, although both ICA-105574 and NS1643 could reverse the drug-induced prolongation of APD in ventricular myocytes. Reversing prolongation of QT/QTc intervals and antagonizing the increases in transmural dispersion of repolarization and instability of the QT interval induced by IKr and IKs inhibitors contributed to antiarrhythmic effect of ICA-105574. Meanwhile, ICA-105574 at higher concentrations showed a potential proarrhythmic risk in normal hearts. Our results suggest that ICA-105574 has more efficient antiarrhythmic activity than NS1643. However, its potential proarrhythmic risk implies that benefits and risks should be seriously taken into consideration for further developing this type of hERG activators.
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Affiliation(s)
- Jing Meng
- The Key Laboratory of Neural and Vascular Biology, Ministry of Education; The Key Laboratory of New Drug Pharmacology and Toxicology, Department of Pharmacology, Hebei Medical University, Hebei Province, Shijiazhuang 050017, China; Department of Pharmaceutical Chemistry, Hebei Medical University, Shijiazhuang, China
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Dealing with global safety issues : was the response to QT-liability of non-cardiac drugs well coordinated? Drug Saf 2013; 36:167-82. [PMID: 23417505 DOI: 10.1007/s40264-013-0016-z] [Citation(s) in RCA: 120] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Drug-induced torsade de pointes (TdP) is a potentially fatal iatrogenic entity. Its reporting rate in association with non-cardiac drugs increased exponentially from the early 1990s and was associated with an increasing number of new non-cardiac drugs whose proarrhythmic liability was not appreciated pre-marketing. This epidemic provoked a comprehensive global response from drug regulators, drug developers and academia, which resulted in stabilization of the reporting rate of TdP. This commentary reviews the chronology and nature of, and the reasons for, this response, examines its adequacy, and proposes future strategies for dealing with such iatrogenic epidemics more effectively. It is concluded that the response was piecemeal and lacked direction. No one entity was responsible, with the result that important contributions from regulators, industry and academia lacked coordination. While the process of dealing with QT crisis seemed to have worked reasonably well in this instance, it does not seem wise to expect the next crisis in drug development to be managed as well. Future crises will need better management and the challenge is to implement a system set up to respond globally and efficiently to a perceived drug-related hazard. In this regard, we discuss the roles of new tools the legislation has provided to the regulators and the value of an integrated expert assessment of all pre-approval data that may signal a potential safety issue in the postmarketing period. We also discuss the roles of other bodies such as the WHO Collaborating Centre for International Drug Monitoring, CIOMS and the International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH).
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Heijman J, Zaza A, Johnson DM, Rudy Y, Peeters RLM, Volders PGA, Westra RL. Determinants of beat-to-beat variability of repolarization duration in the canine ventricular myocyte: a computational analysis. PLoS Comput Biol 2013; 9:e1003202. [PMID: 23990775 PMCID: PMC3749940 DOI: 10.1371/journal.pcbi.1003202] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2013] [Accepted: 06/10/2013] [Indexed: 12/26/2022] Open
Abstract
Beat-to-beat variability of repolarization duration (BVR) is an intrinsic characteristic of cardiac function and a better marker of proarrhythmia than repolarization prolongation alone. The ionic mechanisms underlying baseline BVR in physiological conditions, its rate dependence, and the factors contributing to increased BVR in pathologies remain incompletely understood. Here, we employed computer modeling to provide novel insights into the subcellular mechanisms of BVR under physiological conditions and during simulated drug-induced repolarization prolongation, mimicking long-QT syndromes type 1, 2, and 3. We developed stochastic implementations of 13 major ionic currents and fluxes in a model of canine ventricular-myocyte electrophysiology. Combined stochastic gating of these components resulted in short- and long-term variability, consistent with experimental data from isolated canine ventricular myocytes. The model indicated that the magnitude of stochastic fluctuations is rate dependent due to the rate dependence of action-potential (AP) duration (APD). This process (the “active” component) and the intrinsic nonlinear relationship between membrane current and APD (“intrinsic component”) contribute to the rate dependence of BVR. We identified a major role in physiological BVR for stochastic gating of the persistent Na+ current (INa) and rapidly activating delayed-rectifier K+ current (IKr). Inhibition of IKr or augmentation of INa significantly increased BVR, whereas subsequent β-adrenergic receptor stimulation reduced it, similar to experimental findings in isolated myocytes. In contrast, β-adrenergic stimulation increased BVR in simulated long-QT syndrome type 1. In addition to stochastic channel gating, AP morphology, APD, and beat-to-beat variations in Ca2+ were found to modulate single-cell BVR. Cell-to-cell coupling decreased BVR and this was more pronounced when a model cell with increased BVR was coupled to a model cell with normal BVR. In conclusion, our results provide new insights into the ionic mechanisms underlying BVR and suggest that BVR reflects multiple potentially proarrhythmic parameters, including increased ion-channel stochasticity, prolonged APD, and abnormal Ca2+ handling. Every heartbeat has an electrical recovery (repolarization) interval that varies in duration from beat to beat. Excessive beat-to-beat variability of repolarization duration has been shown to be a risk marker of potentially fatal heart-rhythm disorders, but the contributing subcellular mechanisms remain incompletely understood. Computational models have greatly enhanced our understanding of several basic electrophysiological mechanisms. We developed a detailed computer model of the ventricular myocyte that can simulate beat-to-beat changes in repolarization duration by taking into account stochastic changes in the opening and closing of individual ion channels responsible for all main ion currents. The model accurately reproduced experimental data from isolated myocytes under both physiological and pathological conditions. Using the model, we identified several mechanisms contributing to repolarization variability, including stochastic gating of ion channels, duration and morphology of the repolarization phase, and intracellular calcium handling, thereby providing insights into its basis as a proarrhythmic marker. Our computer model provides a detailed framework to study the dynamics of cardiac electrophysiology and arrhythmias.
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Affiliation(s)
- Jordi Heijman
- Department of Knowledge Engineering, Maastricht University, Maastricht, The Netherlands
- Department of Cardiology, Cardiovascular Research Institute Maastricht, Maastricht University Medical Centre, Maastricht, The Netherlands
- Institute of Pharmacology, Faculty of Medicine, University Duisburg-Essen, Essen, Germany
| | - Antonio Zaza
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Milano, Italy
| | - Daniel M. Johnson
- Department of Cardiology, Cardiovascular Research Institute Maastricht, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Yoram Rudy
- Cardiac Bioelectricity and Arrhythmia Center, Washington University in St. Louis, St. Louis, Missouri, United States of America
| | - Ralf L. M. Peeters
- Department of Knowledge Engineering, Maastricht University, Maastricht, The Netherlands
| | - Paul G. A. Volders
- Department of Cardiology, Cardiovascular Research Institute Maastricht, Maastricht University Medical Centre, Maastricht, The Netherlands
- * E-mail: (PGAV); (RLW)
| | - Ronald L. Westra
- Department of Knowledge Engineering, Maastricht University, Maastricht, The Netherlands
- * E-mail: (PGAV); (RLW)
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Vahedi F, Diamant UB, Lundahl G, Bergqvist G, Gransberg L, Jensen SM, Bergfeldt L. Instability of repolarization in LQTS mutation carriers compared to healthy control subjects assessed by vectorcardiography. Heart Rhythm 2013; 10:1169-75. [PMID: 23643511 DOI: 10.1016/j.hrthm.2013.05.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/18/2013] [Indexed: 11/18/2022]
Abstract
BACKGROUND Potassium channel dysfunction in congenital and acquired forms of long QT syndrome types 1 and 2 (LQT1 and LQT2) increases the beat-to-beat variability of the QT interval. OBJECTIVE To study about the little known variability (instability) of other aspects of ventricular repolarization (VR) in humans by using vectorcardiography. METHODS Beat-to-beat analysis was performed regarding vectorcardiography derived RR, QRS, and QT intervals, as well as T vector- and T vector loop-based parameters during 1-minute recordings of uninterrupted sinus rhythm at rest in 41 adult LQT1 (n = 31) and LQT2 (n = 10) mutation carriers and 41 age- and sex-matched control subjects. The short-term variability for each parameter, describing the mean orthogonal distance to the line of identity on the Poincaré plot, was calculated. RESULTS Mutation carriers showed significantly larger (by a factor 2) instability in most VR parameters compared to controls despite higher instantaneous heart rate variability (STVRR) in the control group. The longer the QT interval, the greater was its instability, and the instability of VR dispersion measures. CONCLUSIONS A greater instability of most aspects of VR already at rest seems to be a salient feature in both LQT1 and LQT2, which might pave the way for early afterdepolarizations and torsades de pointes ventricular tachycardia. In contrast, no signs of increased VR dispersion per se were observed in mutation carriers.
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Affiliation(s)
- Farzad Vahedi
- Department of Molecular and Clinical Medicine/Cardiology, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
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Kaye AD, Volpi-Abadie J, Bensler JM, Kaye AM, Diaz JH. QT interval abnormalities: risk factors and perioperative management in long QT syndromes and Torsades de Pointes. J Anesth 2013; 27:575-87. [PMID: 23412014 DOI: 10.1007/s00540-013-1564-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2012] [Accepted: 01/21/2013] [Indexed: 01/08/2023]
Abstract
Electrophysiological abnormalities of the QT interval of the standard electrocardiogram are not uncommon. Congenital long QT syndrome is due to mutations of several possible genes (genotype) that result in prolongation of the corrected QT interval (phenotype). Abnormalities of the QT interval can be acquired and are often drug-induced. Torsades de Pointes (TP) is an arrhythmia that is a result of aberrant repolarization/QT abnormalities. If not recognized and corrected quickly, QT interval abnormalities may precipitate potentially fatal ventricular dysrhythmias. The main mechanism responsible for the development of QT prolongation is blockade of the rapid component of the delayed rectifier potassium current (I kr), encoded for by the human-ether-a-go-go-related gene (hERG). The objectives of this review were (1) to describe the electrical pathophysiology of QT interval abnormalities, (2) to differentiate congenital from acquired QT interval abnormalities, (3) to describe the currently known risk factors for QT interval abnormalities, (4) to identify current drug-induced causes of acquired QT interval abnormalities, and (5) to recommend immediate and effective management strategies to prevent unanticipated dysrhythmias and deaths from QT abnormalities in the perioperative period.
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Affiliation(s)
- Alan David Kaye
- Department of Anesthesiology, LSU School of Medicine, New Orleans, LA 70112, USA.
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Lu HR, Yan GX, Gallacher DJ. A new biomarker--index of cardiac electrophysiological balance (iCEB)--plays an important role in drug-induced cardiac arrhythmias: beyond QT-prolongation and Torsades de Pointes (TdPs). J Pharmacol Toxicol Methods 2013; 68:250-259. [PMID: 23337247 DOI: 10.1016/j.vascn.2013.01.003] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2012] [Revised: 01/02/2013] [Accepted: 01/05/2013] [Indexed: 12/15/2022]
Abstract
INTRODUCTION In the present study, we investigated whether a new biomarker - index of cardiac electrophysiological balance (iCEB=QT/QRS) - could predict drug-induced cardiac arrhythmias (CAs), including ventricular tachycardia/ventricular fibrillation (VT/VF) and Torsades de Pointes (TdPs). METHODS The rabbit left ventricular arterially-perfused-wedge was used to investigate whether the simple iCEB measured from the ECG is reflective of the more difficult measurement of λ (effective refractory period×conduction velocity) for predicting CAs induced by a number of drugs. RESULTS Dofetilide concentration-dependently increased iCEB and λ, predicting potential risk of drug-induced incidence of early afterdepolarizations (EADs) starting at 0.01μM. Digoxin (1 and 5μM), encainide (5 and 20μM) and propoxyphene (10 and 100μM) markedly reduced both iCEB and λ, predicting their ability to induce non-TdP-like VT/VF. At 10μM, both NS1643 and levcromakalim significantly decreased λ and iCEB, which was preceded with presence of non-TdP-like VT/VF. Isoprenaline (0.05 to 0.5μM) significantly reduced both λ and iCEB, which was associated with a high incidence of non-TdP-like VT/VF in most preparations. Other biomarkers (i.e. transmural dispersion of T-wave and instability of the QT interval) predicted only dofetilide-induced long QT and EADs, but did not predict drug-induced risk of non-TdP-like VT/VF. DISCUSSION Our data from 7 reference drugs of known pro-arrhythmic effects suggests that 1) this non-invasive iCEB predicts potential risk of drug-induced CAs beyond long QT and TdP; 2) iCEB is more useful than the current biomarkers (i.e. transmural dispersion and instability) in predicting potential risks for drug-induced non-TdP-like VT/VF.
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Affiliation(s)
- Hua Rong Lu
- Janssen Research and Development, Janssen Pharmaceutica NV, Belgium.
| | - Gan-Xin Yan
- Main Line Health Heart Center and Lankenau Institute for Medical Research, Wynnewood, PA, USA
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Johnson DM, Heijman J, Bode EF, Greensmith DJ, van der Linde H, Abi-Gerges N, Eisner DA, Trafford AW, Volders PGA. Diastolic spontaneous calcium release from the sarcoplasmic reticulum increases beat-to-beat variability of repolarization in canine ventricular myocytes after β-adrenergic stimulation. Circ Res 2012; 112:246-56. [PMID: 23149594 DOI: 10.1161/circresaha.112.275735] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
RATIONALE Spontaneous Ca(2+) release (SCR) from the sarcoplasmic reticulum can cause delayed afterdepolarizations and triggered activity, contributing to arrhythmogenesis during β-adrenergic stimulation. Excessive beat-to-beat variability of repolarization duration (BVR) is a proarrhythmic marker. Previous research has shown that BVR is increased during intense β-adrenergic stimulation, leading to SCR. OBJECTIVE We aimed to determine ionic mechanisms controlling BVR under these conditions. METHODS AND RESULTS Membrane potentials and cell shortening or Ca(2+) transients were recorded from isolated canine left ventricular myocytes in the presence of isoproterenol. Action-potential (AP) durations after delayed afterdepolarizations were significantly prolonged. Addition of slowly activating delayed rectifier K(+) current (I(Ks)) blockade led to further AP prolongation after SCR, and this strongly correlated with exaggerated BVR. Suppressing SCR via inhibition of ryanodine receptors, Ca(2+)/calmodulin-dependent protein kinase II inhibition, or by using Mg(2+) or flecainide eliminated delayed afterdepolarizations and decreased BVR independent of effects on AP duration. Computational analyses and voltage-clamp experiments measuring L-type Ca(2+) current (I(CaL)) with and without previous SCR indicated that I(CaL) was increased during Ca(2+)-induced Ca(2+) release after SCR, and this contributes to AP prolongation. Prolongation of QT, T(peak)-T(end) intervals, and left ventricular monophasic AP duration of beats after aftercontractions occurred before torsades de pointes in an in vivo dog model of drug-induced long-QT1 syndrome. CONCLUSIONS SCR contributes to increased BVR by interspersed prolongation of AP duration, which is exacerbated during I(Ks) blockade. Attenuation of Ca(2+)-induced Ca(2+) release by SCR underlies AP prolongation via increased I(CaL.) These data provide novel insights into arrhythmogenic mechanisms during β-adrenergic stimulation besides triggered activity and illustrate the importance of I(Ks) function in preventing excessive BVR.
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Affiliation(s)
- Daniel M Johnson
- Department of Cardiology, Cardiovascular Research Institute Maastricht, Maastricht University Medical Center, Maastricht, The Netherlands
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Mirams GR, Davies MR, Cui Y, Kohl P, Noble D. Application of cardiac electrophysiology simulations to pro-arrhythmic safety testing. Br J Pharmacol 2012; 167:932-45. [PMID: 22568589 PMCID: PMC3492977 DOI: 10.1111/j.1476-5381.2012.02020.x] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2011] [Revised: 03/23/2012] [Accepted: 04/26/2012] [Indexed: 12/19/2022] Open
Abstract
Concerns over cardiac side effects are the largest single cause of compound attrition during pharmaceutical drug development. For a number of years, biophysically detailed mathematical models of cardiac electrical activity have been used to explore how a compound, interfering with specific ion-channel function, may explain effects at the cell-, tissue- and organ-scales. With the advent of high-throughput screening of multiple ion channels in the wet-lab, and improvements in computational modelling of their effects on cardiac cell activity, more reliable prediction of pro-arrhythmic risk is becoming possible at the earliest stages of drug development. In this paper, we review the current use of biophysically detailed mathematical models of cardiac myocyte electrical activity in drug safety testing, and suggest future directions to employ the full potential of this approach.
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Affiliation(s)
- Gary R Mirams
- Computational Biology, Department of Computer Science, University of OxfordOxford, UK
| | - Mark R Davies
- Computational Biology, Discovery SciencesAstraZeneca, Alderley Park, UK
| | - Yi Cui
- Safety Pharmacology, Safety Assessment, GlaxoSmithKline, R&D WareUK
| | - Peter Kohl
- Computational Biology, Department of Computer Science, University of OxfordOxford, UK
- National Heart and Lung Institute, Imperial College LondonLondon, UK
| | - Denis Noble
- Computational Biology, Department of Computer Science, University of OxfordOxford, UK
- Department of Physiology, Anatomy & Genetics, University of OxfordOxford, UK
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Beat-to-beat variability of repolarization as a new biomarker for proarrhythmia in vivo. Heart Rhythm 2012; 9:1718-26. [DOI: 10.1016/j.hrthm.2012.05.016] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/03/2011] [Indexed: 11/20/2022]
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Tang YQ, Yu P, Zhao N, Yang Q, Yin YM, Le XY, Guo X, Wang MH, Zhong H, You QD. The Multiple Ion Channel Blocker CPUY11018 Prevents Aconitine-Induced Arrhythmias. Drug Dev Res 2012. [DOI: 10.1002/ddr.21009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Yi-Qun Tang
- Research Division of Pharmacology; China Pharmaceutical University; Nanjing; China
| | - Peng Yu
- Research Division of Pharmacology; China Pharmaceutical University; Nanjing; China
| | - Na Zhao
- Research Division of Pharmacology; China Pharmaceutical University; Nanjing; China
| | - Qian Yang
- Department of Medicinal Chemistry; China Pharmaceutical University; Nanjing; China
| | - Yue-Miao Yin
- Research Division of Pharmacology; China Pharmaceutical University; Nanjing; China
| | - Xiao-Yong Le
- Research Division of Pharmacology; China Pharmaceutical University; Nanjing; China
| | - Xiang Guo
- Research Division of Pharmacology; China Pharmaceutical University; Nanjing; China
| | - Min-Hui Wang
- Research Division of Pharmacology; China Pharmaceutical University; Nanjing; China
| | - Hao Zhong
- Research Division of Pharmacology; China Pharmaceutical University; Nanjing; China
| | - Qi-Dong You
- Department of Medicinal Chemistry; China Pharmaceutical University; Nanjing; China
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Johnson DM, Hussein L, Spätjens RL, Valentin J, Volders PG, Abi‐Gerges N. Measurement of Action Potential Generation in Isolated Canine Left Ventricular Midmyocardial Myocytes. ACTA ACUST UNITED AC 2011; Chapter 10:Unit 10.14.1-23. [DOI: 10.1002/0471141755.ph1014s55] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Daniel M. Johnson
- Cardiovascular Research Institute Maastricht, Maastricht University Medical Centre Maastricht The Netherlands
| | - Leyla Hussein
- Safety Assessment UK, AstraZeneca R&D, Macclesfield Cheshire United Kingdom
| | - Roel L.H.M.G. Spätjens
- Cardiovascular Research Institute Maastricht, Maastricht University Medical Centre Maastricht The Netherlands
| | | | - Paul G.A. Volders
- Cardiovascular Research Institute Maastricht, Maastricht University Medical Centre Maastricht The Netherlands
| | - Najah Abi‐Gerges
- Safety Assessment UK, AstraZeneca R&D, Macclesfield Cheshire United Kingdom
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Johnson DM, de Jong MMJ, Crijns HJGM, Carlsson LG, Volders PGA. Reduced ventricular proarrhythmic potential of the novel combined ion-channel blocker AZD1305 versus dofetilide in dogs with remodeled hearts. Circ Arrhythm Electrophysiol 2011; 5:201-9. [PMID: 22080293 DOI: 10.1161/circep.111.963025] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND AZD1305 is an investigational antiarrhythmic agent for management of atrial fibrillation. It blocks various cardiac ion currents at different potencies and has atrial-predominant electrophysiological effects. We investigated the electrophysiological and proarrhythmic effects of AZD1305 versus dofetilide in dogs with chronic complete atrioventricular block and myocardial hypertrophic remodeling. METHODS AND RESULTS AZD1305 was administered to anesthetized mongrel dogs before and >2 weeks after the induction of atrioventricular block and ventricular and atrial electrophysiological parameters were assessed. In all dogs, the selective I(Kr) blocker dofetilide was used to examine susceptibility to acquired torsades de pointes in chronic atrioventricular block and for comparison. At normal sinus rhythm, AZD1305 increased QT and RR intervals from 290±7 to 397±15 ms (+37%, P<0.0001) and from 603±22 to 778±32 ms (+29%, P=0.002), respectively. In the same animals at chronic atrioventricular block, AZD1305 increased the QT interval from 535±28 to 747±36 ms (+40%, P<0.0001), similar to the QT prolongation by dofetilide (511±22 to 703±45 ms [+38%, P<0.0001]). AZD1305 slightly slowed the idioventricular rhythm. Whereas all (n=14) chronic atrioventricular block animals exhibited torsades de pointes on dofetilide, the arrhythmia was induced in only 4 of 11 dogs after AZD1305. Beat-to-beat variability of left-ventricular monophasic-action-potential duration increased after dofetilide (2.3±0.2 to 6.3±0.7 ms; P<0.0001) but not after AZD1305 (2.8±0.3 to 3.7±0.3 ms; P=0.20) despite similar left-ventricular monophasic-action-potential duration prolongations. CONCLUSIONS Despite causing similar degrees of repolarization delay as the selective I(Kr) blocker dofetilide, the combined ion-channel blocker AZD1305 induces less repolarization instability and has a lower ventricular proarrhythmic potential in the remodeled dog heart.
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Affiliation(s)
- Daniel M Johnson
- Department of Cardiology, Cardiovascular Research Institute Maastricht, Maastricht University Medical Centre, Maastricht, The Netherlands
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Oosterhoff P, Tereshchenko LG, van der Heyden MA, Ghanem RN, Fetics BJ, Berger RD, Vos MA. Short-term variability of repolarization predicts ventricular tachycardia and sudden cardiac death in patients with structural heart disease: A comparison with QT variability index. Heart Rhythm 2011; 8:1584-90. [DOI: 10.1016/j.hrthm.2011.04.033] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2011] [Accepted: 04/29/2011] [Indexed: 10/18/2022]
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Supplemental Studies for Cardiovascular Risk Assessment in Safety Pharmacology: A Critical Overview. Cardiovasc Toxicol 2011; 11:285-307. [DOI: 10.1007/s12012-011-9133-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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Floré V, Claus P, Antoons G, Oosterhoff P, Holemans P, Vos MA, Sipido KR, Willems R. Microvolt T-wave alternans and beat-to-beat variability of repolarization during early postischemic remodeling in a pig heart. Heart Rhythm 2011; 8:1050-7. [DOI: 10.1016/j.hrthm.2011.02.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/06/2010] [Accepted: 02/11/2011] [Indexed: 10/18/2022]
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