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Huang JH, Lin YK, Hsieh MH, Chen SA, Chen YJ. Ventricular response as a predictor of the termination of sustained paroxysmal atrial fibrillation. Pacing Clin Electrophysiol 2024; 47:843-852. [PMID: 38630938 DOI: 10.1111/pace.14985] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Revised: 03/09/2024] [Accepted: 03/28/2024] [Indexed: 04/19/2024]
Abstract
BACKGROUND Atrial fibrillation (AF) is the most common sustained atrial arrhythmia. Accurate detection of the timing and possibility of AF termination is vital for optimizing rhythm and rate control strategies. The present study evaluated whether the ventricular response (VR) in AF offers a distinctive electrocardiographic indicator for predicting AF termination. METHODS Patients experiencing sustained paroxysmal AF for more than 3 h were observed using 24-h ambulatory Holter monitoring. VR within 5 min before AF termination (VR 0-5 min, BAFT) was compared with VR observed during the 60th to 65th min (VR 60-65 min, BAFT) and the 120th to 125th min (VR 120-125 min, BAFT) before AF termination. Maximum and minimum VRs were calculated on the basis of the average of the highest and lowest VRs across 10 consecutive heartbeats. RESULTS Data from 37 episodes of paroxysmal AF revealed that the minimum VR0-5 min, BAFT (64 ± 20 bpm) was significantly faster than both the minimum VR120-125 min, BAFT (56 ± 15 bpm) and the minimum VR60-65 min, BAFT (57 ± 16 bpm, p < .05). Similarly, the maximum VR0-5 min, BAFT (158 ± 49 bpm) was significantly faster than the maximum VR120-125 min, BAFT (148 ± 45 bpm, p < .05). In the daytime, the minimum VR0-5 min, BAFT (66 ± 20 bpm) was significantly faster than both the minimum VR60-65 min, BAFT (58 ± 17 bpm) and minimum VR120-125 min, BAFT (57 ± 15 bpm, p < .05). However, the mean and maximum VR0-5 min, BAFT in the daytime were similar to the mean and maximum VR120-125 min in the daytime, respectively. At night, the minimum, mean, and maximum VR0-5 min, BAFT were similar to the minimum, mean, and maximum VR120-125 min, respectively. CONCLUSIONS Elevated VR rates during AF episodes may be predictors for the termination of AF, especially during the daytime and in patients with nondilated left atria. These findings may guide the development of clinical approaches to rhythm control in AF.
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Affiliation(s)
- Jen-Hung Huang
- Division of Cardiovascular Medicine, Department of Internal Medicine, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan
- Department of Internal Medicine, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan
| | - Yung-Kuo Lin
- Division of Cardiovascular Medicine, Department of Internal Medicine, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan
- Department of Internal Medicine, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan
- Cardiovascular Research Center, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan
| | - Ming-Hsiung Hsieh
- Division of Cardiovascular Medicine, Department of Internal Medicine, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan
- Department of Internal Medicine, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan
- Cardiovascular Research Center, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan
| | - Shih-Ann Chen
- Division of Cardiology, Department of Medicine, Taipei Veterans General Hospital, Taipei, Taiwan
- Cardiovascular Center, Taichung Veterans General Hospital, Taipei, Taiwan
- Department of Post Baccalaureate Medicine, College of Medicine, National Chung Hsing University, Taipei, Taiwan
| | - Yi-Jen Chen
- Division of Cardiovascular Medicine, Department of Internal Medicine, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan
- Cardiovascular Research Center, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan
- Graduate Institute of Clinical Medicine, Taipei Medical University, Taipei, Taiwan
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Giommi A, Gurgel ARB, Smith GL, Workman AJ. Does the small conductance Ca 2+-activated K + current I SK flow under physiological conditions in rabbit and human atrial isolated cardiomyocytes? J Mol Cell Cardiol 2023; 183:70-80. [PMID: 37704101 DOI: 10.1016/j.yjmcc.2023.09.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Revised: 08/16/2023] [Accepted: 09/02/2023] [Indexed: 09/15/2023]
Abstract
BACKGROUND The small conductance Ca2+-activated K+ current (ISK) is a potential therapeutic target for treating atrial fibrillation. AIM To clarify, in rabbit and human atrial cardiomyocytes, the intracellular [Ca2+]-sensitivity of ISK, and its contribution to action potential (AP) repolarisation, under physiological conditions. METHODS Whole-cell-patch clamp, fluorescence microscopy: to record ion currents, APs and [Ca2+]i; 35-37°C. RESULTS In rabbit atrial myocytes, 0.5 mM Ba2+ (positive control) significantly decreased whole-cell current, from -12.8 to -4.9 pA/pF (P < 0.05, n = 17 cells, 8 rabbits). By contrast, the ISK blocker apamin (100 nM) had no effect on whole-cell current, at any set [Ca2+]i (∼100-450 nM). The ISK blocker ICAGEN (1 μM: ≥2 x IC50) also had no effect on current over this [Ca2+]i range. In human atrial myocytes, neither 1 μM ICAGEN (at [Ca2+]i ∼ 100-450 nM), nor 100 nM apamin ([Ca2+]i ∼ 250 nM) affected whole-cell current (5-10 cells, 3-5 patients/group). APs were significantly prolonged (at APD30 and APD70) by 2 mM 4-aminopyridine (positive control) in rabbit atrial myocytes, but 1 μM ICAGEN had no effect on APDs, versus either pre-ICAGEN or time-matched controls. High concentration (10 μM) ICAGEN (potentially ISK-non-selective) moderately increased APD70 and APD90, by 5 and 26 ms, respectively. In human atrial myocytes, 1 μM ICAGEN had no effect on APD30-90, whether stimulated at 1, 2 or 3 Hz (6-9 cells, 2-4 patients/rate). CONCLUSION ISK does not flow in human or rabbit atrial cardiomyocytes with [Ca2+]i set within the global average diastolic-systolic range, nor during APs stimulated at physiological or supra-physiological (≤3 Hz) rates.
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Affiliation(s)
- Alessandro Giommi
- School of Cardiovascular and Metabolic Health, University of Glasgow, Glasgow, UK
| | - Aline R B Gurgel
- School of Cardiovascular and Metabolic Health, University of Glasgow, Glasgow, UK
| | - Godfrey L Smith
- School of Cardiovascular and Metabolic Health, University of Glasgow, Glasgow, UK
| | - Antony J Workman
- School of Cardiovascular and Metabolic Health, University of Glasgow, Glasgow, UK.
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Gatta G, Sobota V, Citerni C, Diness JG, Sørensen US, Jespersen T, Bentzen BH, Zeemering S, Kuiper M, Verheule S, Schotten U, van Hunnik A. Effective termination of atrial fibrillation by SK channel inhibition is associated with a sudden organization of fibrillatory conduction. Europace 2021; 23:1847-1859. [PMID: 34080619 PMCID: PMC8576281 DOI: 10.1093/europace/euab125] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Accepted: 04/22/2021] [Indexed: 11/12/2022] Open
Abstract
AIMS Pharmacological termination of atrial fibrillation (AF) remains a challenge due to limited efficacy and potential ventricular proarrhythmic effects of antiarrhythmic drugs. SK channels are proposed as atrial-specific targets in the treatment of AF. Here, we investigated the effects of the new SK channel inhibitor AP14145. METHODS AND RESULTS Eight goats were implanted with pericardial electrodes for induction of AF (30 days). In an open-chest study, the atrial conduction velocity (CV) and effective refractory period (ERP) were measured during pacing. High-density mapping of both atrial free-walls was performed during AF and conduction properties were assessed. All measurements were performed at baseline and during AP14145 infusion [10 mg/kg/h (n = 1) or 20 mg/kg/h (n = 6)]. At an infusion rate of 20 mg/kg/h, AF terminated in five of six goats. AP14145 profoundly increased ERP and reduced CV during pacing. AP14145 increased spatiotemporal instability of conduction at short pacing cycle lengths. Atrial fibrillation cycle length and pathlength (AF cycle length × CV) underwent a strong dose-dependent prolongation. Conduction velocity during AF remained unchanged and conduction patterns remained complex until the last seconds before AF termination, during which a sudden and profound organization of fibrillatory conduction occurred. CONCLUSION AP14145 provided a successful therapy for termination of persistent AF in goats. During AF, AP14145 caused an ERP and AF cycle length prolongation. AP14145 slowed CV during fast pacing but did not lead to a further decrease during AF. Termination of AF was preceded by an abrupt organization of AF with a decline in the number of fibrillation waves.
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Affiliation(s)
- Giulia Gatta
- Department of Physiology, Maastricht University, P.O. Box 616, 6200 MD Maastricht, The Netherlands
| | - Vladimir Sobota
- Department of Physiology, Maastricht University, P.O. Box 616, 6200 MD Maastricht, The Netherlands
| | - Carlotta Citerni
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | | | | | - Thomas Jespersen
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Bo Hjorth Bentzen
- Acesion Pharma, Copenhagen, Denmark.,Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Stef Zeemering
- Department of Physiology, Maastricht University, P.O. Box 616, 6200 MD Maastricht, The Netherlands
| | - Marion Kuiper
- Department of Physiology, Maastricht University, P.O. Box 616, 6200 MD Maastricht, The Netherlands
| | - Sander Verheule
- Department of Physiology, Maastricht University, P.O. Box 616, 6200 MD Maastricht, The Netherlands
| | - Ulrich Schotten
- Department of Physiology, Maastricht University, P.O. Box 616, 6200 MD Maastricht, The Netherlands
| | - Arne van Hunnik
- Department of Physiology, Maastricht University, P.O. Box 616, 6200 MD Maastricht, The Netherlands
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Citerni C, Kirchhoff J, Olsen LH, Sattler SM, Grunnet M, Edvardsson N, Bentzen BH, Diness JG. Inhibition of K Ca2 and K v11.1 Channels in Pigs With Left Ventricular Dysfunction. Front Pharmacol 2020; 11:556. [PMID: 32435191 PMCID: PMC7219273 DOI: 10.3389/fphar.2020.00556] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Accepted: 04/14/2020] [Indexed: 12/17/2022] Open
Abstract
Background Inhibition of KCa2 channels, conducting IKCa, can convert atrial fibrillation (AF) to sinus rhythm and protect against its induction. IKCa inhibition has been shown to possess functional atrial selectivity with minor effects on ventricles. Under pathophysiological conditions with ventricular remodeling, however, inhibiting IKCa can exhibit both proarrhythmic and antiarrhythmic ventricular effects. The aim of this study was to evaluate the effects of the IKCa inhibitor AP14145, when given before or after the IKr blocker dofetilide, on cardiac function and ventricular proarrhythmia markers in pigs with or without left ventricular dysfunction (LVD). Methods Landrace pigs were randomized into an AF group (n = 6) and two control groups: SHAM1 (n = 8) and SHAM2 (n = 4). AF pigs were atrially tachypaced (A-TP) for 43 ± 4 days until sustained AF and LVD developed. A-TP and SHAM1 pigs received 20 mg/kg AP14145 followed by 100 µg/kg dofetilide whereas SHAM2 pigs received the same drugs in the opposite order. Proarrhythmic markers such as short-term variability of QT (STVQT) and RR (STVRR) intervals, and the number of premature ventricular complexes (PVCs) were measured at baseline and after administration of drugs. The influence on cardiac function was assessed by measuring cardiac output, stroke volume, and relevant echocardiographic parameters. Results IKCa inhibition by AP14145 did not increase STVQT or STVRR in any of the pigs. IKr inhibition by dofetilide markedly increased STVQT in the A-TP pigs, but not in SHAM operated pigs. Upon infusion of AP14145 the number of PVCs decreased or remained unchanged both when AP14145 was infused after baseline and after dofetilide. Conversely, the number of PVCs increased or remained unchanged upon dofetilide infusion. Neither AP14145 nor dofetilide affected relevant echocardiographic parameters, cardiac output, or stroke volume in any of the groups. Conclusion IKCa inhibition with AP14145 was not proarrhythmic in healthy pigs, or in the presence of LVD resulting from A-TP. In pigs already challenged with 100 µg/kg dofetilide there were no signs of proarrhythmia when 20 mg/kg AP14145 were infused. KCa2 channel inhibition did not affect cardiac function, implying that KCa2 inhibitors can be administered safely also in the presence of LV dysfunction.
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Affiliation(s)
- Carlotta Citerni
- Biomedical Institute, University of Copenhagen, Copenhagen, Denmark.,Acesion Pharma, Copenhagen, Denmark
| | | | - Lisbeth Høier Olsen
- Department of Veterinary Disease Biology, University of Copenhagen, Frederiksberg, Denmark
| | - Stefan Michael Sattler
- Biomedical Institute, University of Copenhagen, Copenhagen, Denmark.,Department of Cardiology, Heart Center, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark
| | | | - Nils Edvardsson
- Acesion Pharma, Copenhagen, Denmark.,Department of Molecular and Clinical Medicine, Sahlgrenska Academy at Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Bo Hjorth Bentzen
- Biomedical Institute, University of Copenhagen, Copenhagen, Denmark.,Acesion Pharma, Copenhagen, Denmark
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Kosiuk J, Langenhan K, Stegmann C, Uhe T, Dagres N, Dinov B, Kircher S, Richter S, Sommer P, Bertagnolli L, Bollmann A, Hindricks G. Effect of remote ischemic preconditioning on electrophysiological parameters in nonvalvular paroxysmal atrial fibrillation: The RIPPAF Randomized Clinical Trial. Heart Rhythm 2019; 17:3-9. [PMID: 31356986 DOI: 10.1016/j.hrthm.2019.07.026] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Indexed: 11/18/2022]
Abstract
BACKGROUND Atrial fibrillation (AF) remains the most relevant arrhythmia with a prevalence of 2%. The treatment options are either highly invasive and cost-intensive or limited by potential side effects or insufficient efficacy. However, no direct means of prevention that could reduce the burden of AF have been tested. OBJECTIVE The purpose of this study was to determine whether remote ischemic preconditioning (RIPC) has an impact on inducibility and sustainability of AF. METHODS A total of 146 patients with paroxysmal AF undergoing electrophysiology study were randomized to receive either RIPC, performed by short episodes of forearm ischemia, or sham intervention (clinicaltrials.gov identifier: NCT02779660). Effective refractory periods, conduction times, velocities, and conduction delays measured were analyzed by pacing from the coronary sinus (CS). End points of the study were the inducibility and sustainability of AF after prespecified rapid pacing sequences. RESULTS RIPC significantly reduces the inducibility (odds ratio 0.35; 95% confidence interval 0.17-0.71; P = .003) and sustainability (odds ratio 0.36; 95% confidence interval 0.16-0.81; P = .01) of AF. Furthermore, it decreased dispersion of atrial refractory periods (16.0 ± 14.0 ms vs 22.7 ± 19.0 ms; P = .021) as well as atrial conduction delays (49.2 ± 19.6 ms vs 56.2 ± 22.5 ms; P = .049 for proximal CS and 42.4 ± 16.6 ms vs 49.8 ± 22.2 ms; P = .029 for distal CS). In the whole cohort, longer atrial conduction delay (57.6 ± 22.2 ms vs 50.0 ± 20.5 ms; P = .044) and slower conduction velocity (1.74 ± 0.3 mm/ms vs 1.93 ± 0.5 mm/ms; P = .006) were associated with inducibility of AF whereas a wider dispersion of effective refractory periods (25.9 ± 18.3 ms vs 15.7 ± 11.6 ms; P = .028) maintained AF episodes. CONCLUSION RIPC reduces the inducibility and sustainability of AF, which is possibly mediated by changes in electrophysiological properties of the atria. It may be used as a simple noninvasive procedure to reduce AF burden.
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Affiliation(s)
- Jedrzej Kosiuk
- Department of Electrophysiology, Heart Center Leipzig, University of Leipzig, Leipzig, Germany.
| | - Katharina Langenhan
- Department of Electrophysiology, Heart Center Leipzig, University of Leipzig, Leipzig, Germany
| | - Clara Stegmann
- Department of Electrophysiology, Heart Center Leipzig, University of Leipzig, Leipzig, Germany
| | - Tobias Uhe
- Department of Electrophysiology, Heart Center Leipzig, University of Leipzig, Leipzig, Germany; Department IV Cardiology, Division of Internal Medicine, Neurology and Dermatology, University of Leipzig, Leipzig, Germany
| | - Nikolaos Dagres
- Department of Electrophysiology, Heart Center Leipzig, University of Leipzig, Leipzig, Germany
| | - Borislav Dinov
- Department of Electrophysiology, Heart Center Leipzig, University of Leipzig, Leipzig, Germany
| | - Simon Kircher
- Department of Electrophysiology, Heart Center Leipzig, University of Leipzig, Leipzig, Germany
| | - Sergio Richter
- Department of Electrophysiology, Heart Center Leipzig, University of Leipzig, Leipzig, Germany
| | - Philipp Sommer
- Department of Electrophysiology, Heart Center Leipzig, University of Leipzig, Leipzig, Germany; Department of Electrophysiology, Heart and Diabetes Center NRW, University Hospital of the Ruhr University of Bochum, Bad Oeynhausen, Germany
| | - Livio Bertagnolli
- Department of Electrophysiology, Heart Center Leipzig, University of Leipzig, Leipzig, Germany
| | - Andreas Bollmann
- Department of Electrophysiology, Heart Center Leipzig, University of Leipzig, Leipzig, Germany
| | - Gerhard Hindricks
- Department of Electrophysiology, Heart Center Leipzig, University of Leipzig, Leipzig, Germany
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6
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Kettlewell S, Saxena P, Dempster J, Colman MA, Myles RC, Smith GL, Workman AJ. Dynamic clamping human and rabbit atrial calcium current: narrowing I CaL window abolishes early afterdepolarizations. J Physiol 2019; 597:3619-3638. [PMID: 31093979 PMCID: PMC6767690 DOI: 10.1113/jp277827] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Accepted: 05/13/2019] [Indexed: 11/08/2022] Open
Abstract
Key points Early‐afterdepolarizations (EADs) are abnormal action potential oscillations and a known cause of cardiac arrhythmias. Ventricular EADs involve reactivation of a Ca2+ current (ICaL) in its ‘window region’ voltage range. However, electrical mechanisms of atrial EADs, a potential cause of atrial fibrillation, are poorly understood. Atrial cells were obtained from consenting patients undergoing heart surgery, as well as from rabbits. ICaL was blocked with nifedipine and then a hybrid patch clamp/mathematical‐modelling technique, ‘dynamic clamping’, was used to record action potentials at the same time as injecting an artificial, modifiable, ICaL (ICaL,D‐C). Progressively widening the ICaL,D‐C window region produced EADs of various types, dependent on window width. EAD production was strongest upon moving the activation (vs. inactivation) side of the window. EADs were then induced by a different method: increasing ICaL,D‐C amplitude and/or K+ channel‐blockade (4‐aminopyridine). Narrowing of the ICaL,D‐C window by ∼10 mV abolished these EADs. Atrial ICaL window narrowing is worthy of further testing as a potential anti‐atrial fibrillation drug mechanism.
Abstract Atrial early‐afterdepolarizations (EADs) may contribute to atrial fibrillation (AF), perhaps involving reactivation of L‐type Ca2+ current (ICaL) in its window region voltage range. The present study aimed (i) to validate the dynamic clamp technique for modifying the ICaL contribution to atrial action potential (AP) waveform; (ii) to investigate the effects of widening the window ICaL on EAD‐propensity; and (iii) to test whether EADs from increased ICaL and AP duration are supressed by narrowing the window ICaL. ICaL and APs were recorded from rabbit and human atrial myocytes by whole‐cell‐patch clamp. During AP recording, ICaL was inhibited (3 µm nifedipine) and replaced by a dynamic clamp model current, ICaL,D‐C (tuned to native ICaL characteristics), computed in real‐time (every 50 µs) based on myocyte membrane potential. ICaL,D‐C‐injection restored the nifedipine‐suppressed AP plateau. Widening the window ICaL,D‐C, symmetrically by stepwise simultaneous equal shifts of half‐voltages (V0.5) of ICaL,D‐C activation (negatively) and inactivation (positively), generated EADs (single, multiple or preceding repolarization failure) in a window width‐dependent manner, as well as AP alternans. A stronger EAD‐generating effect resulted from independently shifting activation V0.5 (asymmetrical widening) than inactivation V0.5; for example, a 15 mV activation shift produced EADs in nine of 17 (53%) human atrial myocytes vs. 0 of 18 from inactivation shift (P < 0.05). In 11 rabbit atrial myocytes in which EADs were generated either by increasing the conductance of normal window width ICaL,D‐C or subsequent 4‐aminopyridine (2 mm), window ICaL,D‐C narrowing (10 mV) abolished EADs of all types (P < 0.05). The present study validated the dynamic clamp for ICaL, which is novel in atrial cardiomyocytes, and showed that EADs of various types are generated by widening (particularly asymmetrically) the window ICaL, as well as abolished by narrowing it. Window ICaL narrowing is a potential therapeutic mechanism worth pursuing in the search for improved anti‐AF drugs. Early‐afterdepolarizations (EADs) are abnormal action potential oscillations and a known cause of cardiac arrhythmias. Ventricular EADs involve reactivation of a Ca2+ current (ICaL) in its ‘window region’ voltage range. However, electrical mechanisms of atrial EADs, a potential cause of atrial fibrillation, are poorly understood. Atrial cells were obtained from consenting patients undergoing heart surgery, as well as from rabbits. ICaL was blocked with nifedipine and then a hybrid patch clamp/mathematical‐modelling technique, ‘dynamic clamping’, was used to record action potentials at the same time as injecting an artificial, modifiable, ICaL (ICaL,D‐C). Progressively widening the ICaL,D‐C window region produced EADs of various types, dependent on window width. EAD production was strongest upon moving the activation (vs. inactivation) side of the window. EADs were then induced by a different method: increasing ICaL,D‐C amplitude and/or K+ channel‐blockade (4‐aminopyridine). Narrowing of the ICaL,D‐C window by ∼10 mV abolished these EADs. Atrial ICaL window narrowing is worthy of further testing as a potential anti‐atrial fibrillation drug mechanism.
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Affiliation(s)
- Sarah Kettlewell
- Institute of Cardiovascular & Medical Sciences, University of Glasgow, Glasgow, UK
| | - Priyanka Saxena
- Institute of Cardiovascular & Medical Sciences, University of Glasgow, Glasgow, UK
| | - John Dempster
- Strathclyde Institute of Pharmacy & Biomedical Sciences, University of Strathclyde, Glasgow, UK
| | | | - Rachel C Myles
- Institute of Cardiovascular & Medical Sciences, University of Glasgow, Glasgow, UK
| | - Godfrey L Smith
- Institute of Cardiovascular & Medical Sciences, University of Glasgow, Glasgow, UK
| | - Antony J Workman
- Institute of Cardiovascular & Medical Sciences, University of Glasgow, Glasgow, UK
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Whittaker DG, Hancox JC, Zhang H. In silico Assessment of Pharmacotherapy for Human Atrial Patho-Electrophysiology Associated With hERG-Linked Short QT Syndrome. Front Physiol 2019; 9:1888. [PMID: 30687112 PMCID: PMC6336736 DOI: 10.3389/fphys.2018.01888] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Accepted: 12/12/2018] [Indexed: 12/19/2022] Open
Abstract
Short QT syndrome variant 1 (SQT1) arises due to gain-of-function mutations to the human Ether-à-go-go-Related Gene (hERG), which encodes the α subunit of channels carrying rapid delayed rectifier potassium current, IKr. In addition to QT interval shortening and ventricular arrhythmias, SQT1 is associated with increased risk of atrial fibrillation (AF), which is often the only clinical presentation. However, the underlying basis of AF and its pharmacological treatment remain incompletely understood in the context of SQT1. In this study, computational modeling was used to investigate mechanisms of human atrial arrhythmogenesis consequent to a SQT1 mutation, as well as pharmacotherapeutic effects of selected class I drugs–disopyramide, quinidine, and propafenone. A Markov chain formulation describing wild type (WT) and N588K-hERG mutant IKr was incorporated into a contemporary human atrial action potential (AP) model, which was integrated into one-dimensional (1D) tissue strands, idealized 2D sheets, and a 3D heterogeneous, anatomical human atria model. Multi-channel pharmacological effects of disopyramide, quinidine, and propafenone, including binding kinetics for IKr/hERG and sodium current, INa, were considered. Heterozygous and homozygous formulations of the N588K-hERG mutation shortened the AP duration (APD) by 53 and 86 ms, respectively, which abbreviated the effective refractory period (ERP) and excitation wavelength in tissue, increasing the lifespan and dominant frequency (DF) of scroll waves in the 3D anatomical human atria. At the concentrations tested in this study, quinidine most effectively prolonged the APD and ERP in the setting of SQT1, followed by disopyramide and propafenone. In 2D simulations, disopyramide and quinidine promoted re-entry termination by increasing the re-entry wavelength, whereas propafenone induced secondary waves which destabilized the re-entrant circuit. In 3D simulations, the DF of re-entry was reduced in a dose-dependent manner for disopyramide and quinidine, and propafenone to a lesser extent. All of the anti-arrhythmic agents promoted pharmacological conversion, most frequently terminating re-entry in the order quinidine > propafenone = disopyramide. Our findings provide further insight into mechanisms of SQT1-related AF and a rational basis for the pursuit of combined IKr and INa block based pharmacological strategies in the treatment of SQT1-linked AF.
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Affiliation(s)
- Dominic G Whittaker
- Faculty of Biological Sciences, School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom.,Biological Physics Group, School of Physics and Astronomy, The University of Manchester, Manchester, United Kingdom
| | - Jules C Hancox
- Biological Physics Group, School of Physics and Astronomy, The University of Manchester, Manchester, United Kingdom.,Cardiovascular Research Laboratories, Department of Physiology, Pharmacology and Neuroscience, School of Medical Sciences, University of Bristol, Bristol, United Kingdom
| | - Henggui Zhang
- Biological Physics Group, School of Physics and Astronomy, The University of Manchester, Manchester, United Kingdom.,School of Computer Science and Technology, Harbin Institute of Technology, Harbin, China.,Space Institute of Southern China, Shenzhen, China.,Key Laboratory of Medical Electrophysiology of Ministry of Education and Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, China
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8
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Ma J, Yin C, Ma S, Qiu H, Zheng C, Chen Q, Ding C, Lv W. Shensong Yangxin capsule reduces atrial fibrillation susceptibility by inhibiting atrial fibrosis in rats with post-myocardial infarction heart failure. DRUG DESIGN DEVELOPMENT AND THERAPY 2018; 12:3407-3418. [PMID: 30349194 PMCID: PMC6186904 DOI: 10.2147/dddt.s182834] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Purpose Shensong Yangxin (SSYX) capsule is a traditional Chinese medicine that has been used widely to treat cardiac arrhythmia. This study aimed to assess whether SSYX prevents atrial fibrillation (AF) after chronic myocardial infarction (MI)-induced heart failure and to determine the underlying mechanisms. Materials and methods The study included 45 male Sprague Dawley rats. The rats underwent MI induction or sham surgery. One week after MI induction surgery, we performed serial echocardiography and administered SSYX capsule to some rats that experienced MI. After 4 weeks of treatment, AF inducibility was assessed with transesophageal programmed electrical stimulation technology. Additionally, multielectrode array assessment, histological analysis, and Western blot analysis were performed. Results AF inducibility was significantly lower in SSYX rats than in MI rats (33.3% vs 73.3%, P<0.05). Additionally, conduction velocities in the left atrium were greater in SSYX rats than in MI rats. Moreover, SSYX decreased left atrial fibrosis, downregulated TGF-β1, MMP-9, TIMP-I, and type I and III collagen expressions, and inhibited the differentiation of cardiac fibroblasts to myofibroblasts. Conclusion SSYX reduces AF inducibility after MI by improving left atrial conduction function via the inhibition of left atrial fibrosis. It prevents the development of an MI-induced vulnerable substrate for AF.
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Affiliation(s)
- Jin Ma
- Heart Center, Guangdong Provincial Hospital of Chinese Medicine, 2nd Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou 510006, China, ,
| | - Chunxia Yin
- Heart Center, Guangdong Provincial Hospital of Chinese Medicine, 2nd Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou 510006, China, ,
| | - Shiyu Ma
- Department of Critical-Care Medicine, Guangdong Provincial Hospital of Chinese Medicine, 2nd Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou 510006, China
| | - Huiliang Qiu
- Heart Center, Guangdong Provincial Hospital of Chinese Medicine, 2nd Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou 510006, China, ,
| | - Chaoyang Zheng
- Heart Center, Guangdong Provincial Hospital of Chinese Medicine, 2nd Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou 510006, China, ,
| | - Qiuxiong Chen
- Heart Center, Guangdong Provincial Hospital of Chinese Medicine, 2nd Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou 510006, China, ,
| | - Chunhua Ding
- Heart Center, Guangdong Provincial Hospital of Chinese Medicine, 2nd Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou 510006, China, , .,Cardiac Department, Aerospace Center Hospital, Peking University Aerospace Clinical College of Medicine, Beijing 100049, China,
| | - Weihui Lv
- Heart Center, Guangdong Provincial Hospital of Chinese Medicine, 2nd Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou 510006, China, ,
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Ji Y, Veldhuis MG, Zandvoort J, Romunde FL, Houtman MJC, Duran K, van Haaften G, Zangerl-Plessl EM, Takanari H, Stary-Weinzinger A, van der Heyden MAG. PA-6 inhibits inward rectifier currents carried by V93I and D172N gain-of-function K IR2.1 channels, but increases channel protein expression. J Biomed Sci 2017; 24:44. [PMID: 28711067 PMCID: PMC5513211 DOI: 10.1186/s12929-017-0352-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Accepted: 07/11/2017] [Indexed: 01/23/2023] Open
Abstract
BACKGROUND The inward rectifier potassium current IK1 contributes to a stable resting membrane potential and phase 3 repolarization of the cardiac action potential. KCNJ2 gain-of-function mutations V93I and D172N associate with increased IK1, short QT syndrome type 3 and congenital atrial fibrillation. Pentamidine-Analogue 6 (PA-6) is an efficient (IC50 = 14 nM with inside-out patch clamp methodology) and specific IK1 inhibitor that interacts with the cytoplasmic pore region of the KIR2.1 ion channel, encoded by KCNJ2. At 10 μM, PA-6 increases wild-type (WT) KIR2.1 expression in HEK293T cells upon chronic treatment. We hypothesized that PA-6 will interact with and inhibit V93I and D172N KIR2.1 channels, whereas impact on channel expression at the plasma membrane requires higher concentrations. METHODS Molecular modelling was performed with the human KIR2.1 closed state homology model using FlexX. WT and mutant KIR2.1 channels were expressed in HEK293 cells. Patch-clamp single cell electrophysiology measurements were performed in the whole cell and inside-out mode of the patch clamp method. KIR2.1 expression level and localization were determined by western blot analysis and immunofluorescence microscopy, respectively. RESULTS PA-6 docking in the V93I/D172N double mutant homology model of KIR2.1 demonstrated that mutations and drug-binding site are >30 Å apart. PA-6 inhibited WT and V93I outward currents with similar potency (IC50 = 35.5 and 43.6 nM at +50 mV for WT and V93I), whereas D172N currents were less sensitive (IC50 = 128.9 nM at +50 mV) using inside-out patch-clamp electrophysiology. In whole cell mode, 1 μM of PA-6 inhibited outward IK1 at -50 mV by 28 ± 36%, 18 ± 20% and 10 ± 6%, for WT, V93I and D172N channels respectively. Western blot analysis demonstrated that PA-6 (5 μM, 24 h) increased KIR2.1 expression levels of WT (6.3 ± 1.5 fold), and V93I (3.9 ± 0.9) and D172N (4.8 ± 2.0) mutants. Immunofluorescent microscopy demonstrated dose-dependent intracellular KIR2.1 accumulation following chronic PA-6 application (24 h, 1 and 5 μM). CONCLUSIONS 1) KCNJ2 gain-of-function mutations V93I and D172N in the KIR2.1 ion channel do not impair PA-6 mediated inhibition of IK1, 2) PA-6 elevates KIR2.1 protein expression and induces intracellular KIR2.1 accumulation, 3) PA-6 is a strong candidate for further preclinical evaluation in treatment of congenital SQT3 and AF.
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Affiliation(s)
- Yuan Ji
- Department of Medical Physiology, Division of Heart and Lungs, University Medical Center Utrecht, Yalelaan 50, 3584 CM Utrecht, The Netherlands
| | - Marlieke G. Veldhuis
- Department of Medical Physiology, Division of Heart and Lungs, University Medical Center Utrecht, Yalelaan 50, 3584 CM Utrecht, The Netherlands
| | - Jantien Zandvoort
- Department of Medical Physiology, Division of Heart and Lungs, University Medical Center Utrecht, Yalelaan 50, 3584 CM Utrecht, The Netherlands
| | - Fee L. Romunde
- Department of Medical Physiology, Division of Heart and Lungs, University Medical Center Utrecht, Yalelaan 50, 3584 CM Utrecht, The Netherlands
| | - Marien J. C. Houtman
- Department of Medical Physiology, Division of Heart and Lungs, University Medical Center Utrecht, Yalelaan 50, 3584 CM Utrecht, The Netherlands
| | - Karen Duran
- Center for Molecular Medicine, Department of Medical Genetics, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Gijs van Haaften
- Center for Molecular Medicine, Department of Medical Genetics, University Medical Center Utrecht, Utrecht, The Netherlands
| | | | - Hiroki Takanari
- Department of Medical Physiology, Division of Heart and Lungs, University Medical Center Utrecht, Yalelaan 50, 3584 CM Utrecht, The Netherlands
| | | | - Marcel A. G. van der Heyden
- Department of Medical Physiology, Division of Heart and Lungs, University Medical Center Utrecht, Yalelaan 50, 3584 CM Utrecht, The Netherlands
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Atrial-ventricular differences in rabbit cardiac voltage-gated Na + currents: Basis for atrial-selective block by ranolazine. Heart Rhythm 2017; 14:1657-1664. [PMID: 28610990 PMCID: PMC5666337 DOI: 10.1016/j.hrthm.2017.06.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Indexed: 01/15/2023]
Abstract
Background Class 1 antiarrhythmic drugs are highly effective in restoring and maintaining sinus rhythm in atrial fibrillation patients but carry a risk of ventricular tachyarrhythmia. The antianginal agent ranolazine is a prototypic atrial-selective voltage-gated Na+ channel blocker but the mechanisms underlying its atrial-selective action remain unclear. Objective The present study examined the mechanisms underlying the atrial-selective action of ranolazine. Methods Whole-cell voltage-gated Na+ currents (INa) were recorded at room temperature (∼22°C) from rabbit isolated left atrial and right ventricular myocytes. Results INa conductance density was ∼1.8-fold greater in atrial than in ventricular cells. Atrial INa was activated at command potentials ∼7 mV more negative and inactivated at conditioning potentials ∼11 mV more negative than ventricular INa. The onset of inactivation of INa was faster in atrial cells than in ventricular myocytes. Ranolazine (30 μM) inhibited INa in atrial and ventricular myocytes in a use-dependent manner consistent with preferential activated/inactivated state block. Ranolazine caused a significantly greater negative shift in voltage of half-maximal inactivation in atrial cells than in ventricular cells, the recovery from inactivation of INa was slowed by ranolazine to a greater extent in atrial myocytes than in ventricular cells, and ranolazine produced an instantaneous block that showed marked voltage dependence in atrial cells. Conclusion Differences exist between rabbit atrial and ventricular myocytes in the biophysical properties of INa. The more negative voltage dependence of INa activation and inactivation, together with trapping of the drug in the inactivated channel, underlies an atrial-selective action of ranolazine.
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Dong Z, Yao H, Miao Z, Wang H, Xie R, Wang Y, Shang Y, Gong C, Liang Z. Pretreatment with intravenous amiodarone improves the efficacy of ibutilide treatment on cardioversion rate and maintenance time of sinus rhythm in patients with persistent atrial fibrillation. Biomed Rep 2017; 6:686-690. [PMID: 28584642 DOI: 10.3892/br.2017.896] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Accepted: 03/17/2017] [Indexed: 11/06/2022] Open
Abstract
The aim of the present study was to assess the efficacy and safety of the pharmacological conversion of persistent atrial fibrillation (AF) using amiodarone or/and ibutilide. Seventy-nine consecutive patients (48 males and 31 females; mean age, 64.6±11.2 years; range, 40-80 years) with non-valvular chronic AF lasting >7 days (range, 7-97 days) that were admitted to hospital for elective pharmacological cardioversion were randomly assigned to receive treatment with intravenous ibutilide (1 mg plus an additional 1 mg if required; n=39) or intravenous amiodarone (300 mg) plus intravenous ibutilide (1 mg; n=40). Success rates of cardioversion were 51.3% (20/39 patients) for ibutilide alone and 71.8% (28/39 patients) for amiodarone + ibutilide (P<0.05). A comparable increase in the QTc interval was observed in the two groups. It was observed that the co-administration of amiodarone and ibutilide was safer than ibutilide alone with regard to the risk of ventricular arrhythmia. Forty-eight patients of successful cardioversion were personally contacted for follow-up. The result indicated that the sinus rhythm maintenance time of the amiodarone + ibutilide group (4.36±2.44 months) was significantly higher than that of the ibutilide group (2.34±1.75 months; P<0.01). In conclusion, pretreatment with intravenous amiodarone + ibutilide for pharmacological cardioversion of persistent AF is considered to be more effective and safer than treatment with ibutilide alone.
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Affiliation(s)
- Zengxiang Dong
- Department of Cardiology, The First Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang 150001, P.R. China
| | - Hong Yao
- Department of Cardiology, The First Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang 150001, P.R. China
| | - Zhuangzhuang Miao
- Department of Cardiology, The First Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang 150001, P.R. China
| | - Hao Wang
- Department of Cardiology, The First Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang 150001, P.R. China
| | - Rongsheng Xie
- Department of Cardiology, The First Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang 150001, P.R. China
| | - Ye Wang
- Department of Cardiology, The First Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang 150001, P.R. China
| | - Yingfang Shang
- Department of Cardiology, The First Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang 150001, P.R. China
| | - Chunlin Gong
- Department of Cardiology, The First Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang 150001, P.R. China
| | - Zhaoguang Liang
- Department of Cardiology, The First Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang 150001, P.R. China
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Xu X, Alida CT, Yu B. Administration of antiarrhythmic drugs to maintain sinus rhythm after catheter ablation for atrial fibrillation: a meta-analysis. Cardiovasc Ther 2016; 33:242-6. [PMID: 26031448 DOI: 10.1111/1755-5922.12133] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND Whether the short-term administration of antiarrhythmic drugs (AADs) to maintain sinus rhythm following catheter ablation (CA) for atrial fibrillation (AF) can prevent the recurrence of AF is still a matter of debate. We searched the PubMed database and the Cochrane Library, and compiled a list of retrieved articles. We included only randomised controlled trials(RCTs) that compared any AADs against control (placebo or no treatment) or other AADs following CA for AF. Statistical analysis of the odds ratio (OR) and corresponding 95% confidence interval (CI) were used to determine the overall effect of both outcomes. The Mantel-Haenszel method was used to pool data of the outcomes of AF recurrence into fixed effect model meta-analyses. AIMS We performed a systematic review to determine the effectiveness of short-term treatment with AADs on the recurrence of AF after CA. RESULTS Six RCTs were included in this study, with a total of 814 patients. Post-procedural temporary administration of AADs in patients after CA for AF reduced the early recurrence of AF (antiarrhythmic drug 103 patients [25.3%], control 162 patients [39.8%]; OR 0.47 [95% CI 0.34-0.64]; χ(2) = 3.77; P = 0.58; I(2) = 0%). No significant difference in patients after CA for AF in the late recurrence of AF (antiarrhythmic drug 148 patients [36.5%], control 171 patients [42.5%]; OR 0.77 [95% CI 0.57-1.03]; χ(2) = 3.15; P = 0.68; I(2) = 0%). The heterogeneity was zero in both analyses. CONCLUSION Although the continued administration of AADs after CA for AF can decrease early atrial tachycardias (ATa), this treatment does not prevent late ATa.
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Affiliation(s)
- Xiuli Xu
- Department of Cardiology, The First Hospital Affiliated to China Medical University, Shenyang, Liaoning, China
| | - Choumi T Alida
- Department of Cardiology, The First Hospital Affiliated to China Medical University, Shenyang, Liaoning, China
| | - Bo Yu
- Department of Cardiology, The First Hospital Affiliated to China Medical University, Shenyang, Liaoning, China
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Hancox JC, James AF, Marrion NV, Zhang H, Thomas D. Novel ion channel targets in atrial fibrillation. Expert Opin Ther Targets 2016; 20:947-58. [DOI: 10.1517/14728222.2016.1159300] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
- Jules C. Hancox
- School of Physiology, Pharmacology and Neuroscience, University Walk, Bristol, UK
| | - Andrew F. James
- School of Physiology, Pharmacology and Neuroscience, University Walk, Bristol, UK
| | - Neil V. Marrion
- School of Physiology, Pharmacology and Neuroscience, University Walk, Bristol, UK
| | - Henggui Zhang
- Biological Physics Group, School of Physics and Astronomy, University of Manchester, Manchester, United Kingdom
| | - Dierk Thomas
- Department of Cardiology, University of Heidelberg, Heidelberg, Germany
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van der Heyden MA, Jespersen T. Pharmacological exploration of the resting membrane potential reserve: Impact on atrial fibrillation. Eur J Pharmacol 2016; 771:56-64. [DOI: 10.1016/j.ejphar.2015.11.026] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Revised: 11/06/2015] [Accepted: 11/16/2015] [Indexed: 12/24/2022]
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Hancock JM, Weatherall KL, Choisy SC, James AF, Hancox JC, Marrion NV. Selective activation of heteromeric SK channels contributes to action potential repolarization in mouse atrial myocytes. Heart Rhythm 2015; 12:1003-15. [PMID: 25620048 DOI: 10.1016/j.hrthm.2015.01.027] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/04/2014] [Indexed: 11/15/2022]
Abstract
BACKGROUND Activation of small conductance calcium-activated potassium (SK) channels is proposed to contribute to repolarization of the action potential in atrial myocytes. This role is controversial, as these cardiac SK channels appear to exhibit an uncharacteristic pharmacology. OBJECTIVES The objectives of this study were to resolve whether activation of SK channels contributes to atrial action potential repolarization and to determine the likely subunit composition of the channel. METHODS The effect of 2 SK channel inhibitors was assessed on outward current evoked in voltage clamp and on action potential duration in perforated patch and whole-cell current clamp recording from acutely isolated mouse atrial myocytes. The presence of SK channel subunits was assessed using immunocytochemistry. RESULTS A significant component of outward current was reduced by the SK channel blockers apamin and UCL1684. Block by apamin displayed a sensitivity indicating that this current was carried by homomeric SK2 channels. Action potential duration was significantly prolonged by UCL1684, but not by apamin. This effect was accompanied by an increase in beat-to-beat variability and action potential triangulation. This pharmacology was matched by that of expressed heteromeric SK2-SK3 channels in HEK293 cells. Immunocytochemistry showed that atrial myocytes express both SK2 and SK3 channels with an overlapping expression pattern. CONCLUSION Only proposed heteromeric SK2-SK3 channels are physiologically activated to contribute to action potential repolarization, which is indicated by the difference in pharmacology of evoked outward current and prolongation of atrial action potential duration. The effect of blocking this channel on the action potential suggests that SK channel inhibition during cardiac function has the potential to be proarrhythmic.
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Affiliation(s)
- Jane M Hancock
- School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom
| | - Kate L Weatherall
- School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom
| | - Stéphanie C Choisy
- School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom
| | - Andrew F James
- School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom
| | - Jules C Hancox
- School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom
| | - Neil V Marrion
- School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom.
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Colman MA, Varela M, Hancox JC, Zhang H, Aslanidi OV. Evolution and pharmacological modulation of the arrhythmogenic wave dynamics in canine pulmonary vein model. Europace 2014; 16:416-23. [PMID: 24569896 PMCID: PMC3934846 DOI: 10.1093/europace/eut349] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
Aims Atrial fibrillation (AF), the commonest cardiac arrhythmia, has been strongly linked with arrhythmogenic sources near the pulmonary veins (PVs), but underlying mechanisms are not fully understood. We aim to study the generation and sustenance of wave sources in a model of the PV tissue. Methods and results A previously developed biophysically detailed three-dimensional canine atrial model is applied. Effects of AF-induced electrical remodelling are introduced based on published experimental data, as changes of ion channel currents (ICaL, IK1, Ito, and IKur), the action potential (AP) and cell-to-cell coupling levels. Pharmacological effects are introduced by blocking specific ion channel currents. A combination of electrical heterogeneity (AP tissue gradients of 5–12 ms) and anisotropy (conduction velocities of 0.75–1.25 and 0.21–0.31 m/s along and transverse to atrial fibres) can results in the generation of wave breaks in the PV region. However, a long wavelength (171 mm) prevents the wave breaks from developing into re-entry. Electrical remodelling leads to decreases in the AP duration, conduction velocity and wavelength (to 49 mm), such that re-entry becomes sustained. Pharmacological effects on the tissue heterogeneity and vulnerability (to wave breaks and re-entry) are quantified to show that drugs that increase the wavelength and stop re-entry (IK1 and IKur blockers) can also increase the heterogeneity (AP gradients of 26–27 ms) and the likelihood of wave breaks. Conclusion Biophysical modelling reveals large conduction block areas near the PVs, which are due to discontinuous fibre arrangement enhanced by electrical heterogeneity. Vulnerability to re-entry in such areas can be modulated by pharmacological interventions.
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Affiliation(s)
- Michael A Colman
- Biological Physics Group, School of Physics & Astronomy, University of Manchester, Manchester M13 9PL, UK
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Kharche SR, Stary T, Colman MA, Biktasheva IV, Workman AJ, Rankin AC, Holden AV, Zhang H. Effects of human atrial ionic remodelling by β-blocker therapy on mechanisms of atrial fibrillation: a computer simulation. Europace 2014; 16:1524-33. [PMID: 25085203 DOI: 10.1093/europace/euu084] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
AIMS Atrial anti-arrhythmic effects of β-adrenoceptor antagonists (β-blockers) may involve both a suppression of pro-arrhythmic effects of catecholamines, and an adaptational electrophysiological response to chronic β-blocker use; so-called 'pharmacological remodelling'. In human atrium, such remodelling decreases the transient outward (Ito) and inward rectifier (IK1) K(+) currents, and increases the cellular action potential duration (APD) and effective refractory period (ERP). However, the consequences of these changes on mechanisms of genesis and maintenance of atrial fibrillation (AF) are unknown. Using mathematical modelling, we tested the hypothesis that the long-term adaptational decrease in human atrial Ito and IK1 caused by chronic β-blocker therapy, i.e. independent of acute electrophysiological effects of β-blockers, in an otherwise un-remodelled atrium, could suppress AF. METHODS AND RESULTS Contemporarily, biophysically detailed human atrial cell and tissue models were used to investigate effects of the β-blocker-based pharmacological remodelling. Chronic β-blockade remodelling prolonged atrial cell APD and ERP. The incidence of small amplitude APD alternans in the CRN model was reduced. At the 1D tissue level, β-blocker remodelling decreased the maximum pacing rate at which APs could be conducted. At the three-dimensional organ level, β-blocker remodelling reduced the life span of re-entry scroll waves. CONCLUSION This study improves our understanding of the electrophysiological mechanisms of AF suppression by chronic β-blocker therapy. Atrial fibrillation suppression may involve a reduced propensity for maintenance of re-entrant excitation waves, as a consequence of increased APD and ERP.
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Affiliation(s)
- Sanjay R Kharche
- College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, EX4 4QF, UK Biological Physics Group, School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK
| | - Tomas Stary
- College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, EX4 4QF, UK
| | - Michael A Colman
- Biological Physics Group, School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK
| | - Irina V Biktasheva
- Department of Computer Sciences, University of Liverpool, Liverpool, L69 3BX, UK
| | - Antony J Workman
- Institute of Cardiovascular and Medical Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, 126 University Place, Glasgow G12 8TA, UK
| | - Andrew C Rankin
- School of Medicine, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Arun V Holden
- School of Biomedical Sciences, University of Leeds, Leeds, LS6 9JT, UK
| | - Henggui Zhang
- Biological Physics Group, School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK
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Atrial fibrillation: A progressive atrial myopathy or a distinct disease? Int J Cardiol 2014; 171:126-33. [DOI: 10.1016/j.ijcard.2013.12.009] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Revised: 10/09/2013] [Accepted: 12/10/2013] [Indexed: 02/06/2023]
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Spector P. Principles of cardiac electric propagation and their implications for re-entrant arrhythmias. Circ Arrhythm Electrophysiol 2013; 6:655-61. [PMID: 23778249 DOI: 10.1161/circep.113.000311] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Peter Spector
- University of Vermont College of Medicine, Burlington, VT 05401, USA.
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Kettlewell S, Burton FL, Smith GL, Workman AJ. Chronic myocardial infarction promotes atrial action potential alternans, afterdepolarizations, and fibrillation. Cardiovasc Res 2013; 99:215-24. [PMID: 23568957 PMCID: PMC3687753 DOI: 10.1093/cvr/cvt087] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Aims Atrial fibrillation (AF) is increased in patients with heart failure resulting from myocardial infarction (MI). We aimed to determine the effects of chronic ventricular MI in rabbits on the susceptibility to AF, and underlying atrial electrophysiological and Ca2+-handling mechanisms. Methods and results In Langendorff-perfused rabbit hearts, under β-adrenergic stimulation with isoproterenol (ISO; 1 µM), 8 weeks MI decreased AF threshold, indicating increased AF susceptibility. This was associated with increased atrial action potential duration (APD)-alternans at 90% repolarization, by 147%, and no significant change in the mean APD or atrial global conduction velocity (CV; n = 6–13 non-MI hearts, 5–12 MI). In atrial isolated myocytes, also under β-stimulation, L-type Ca2+ current (ICaL) density and intracellular Ca2+-transient amplitude were decreased by MI, by 35 and 41%, respectively, and the frequency of spontaneous depolarizations (SDs) was substantially increased. MI increased atrial myocyte size and capacity, and markedly decreased transverse-tubule density. In non-MI hearts perfused with ISO, the ICaL-blocker nifedipine, at a concentration (0.02 µM) causing an equivalent ICaL reduction (35%) to that from the MI, did not affect AF susceptibility, and decreased APD. Conclusion Chronic MI in rabbits remodels atrial structure, electrophysiology, and intracellular Ca2+ handling. Increased susceptibility to AF by MI, under β-adrenergic stimulation, may result from associated production of atrial APD alternans and SDs, since steady-state APD and global CV were unchanged under these conditions, and may be unrelated to the associated reduction in whole-cell ICaL. Future studies may clarify potential contributions of local conduction changes, and cellular and subcellular mechanisms of alternans, to the increased AF susceptibility.
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Affiliation(s)
- Sarah Kettlewell
- Institute of Cardiovascular and Medical Sciences, University of Glasgow, 126 University Place, Glasgow G128TA, UK
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Abstract
The anti-arrhythmic efficacy of the late sodium channel current (late I(Na)) inhibition has been convincingly demonstrated in the ventricles, particularly under conditions of prolonged ventricular repolarization. The value of late I(Na) block in the setting of atrial fibrillation (AF) remains poorly investigated. All sodium channel blockers inhibit both peak and late I(Na) and are generally more potent in inhibiting late vs. early I(Na). Selective late I(Na) block does not prolong the effective refractory period (ERP), a feature common to practically all anti-AF agents. Although the late I(Na) blocker ranolazine has been shown to be effective in suppression of AF, it is noteworthy that at concentrations at which it blocks late I(Na) in the ventricles, it also potently blocks peak I(Na) in the atria, thus causing rate-dependent prolongation of ERP due to development of post-repolarization refractoriness. Late I(Na) inhibition in atria is thought to suppress intracellular calcium (Ca(i))-mediated triggered activity, secondary to a reduction in intracellular sodium (Na(i)). However, agents that block late I(Na) (ranolazine, amiodarone, vernakalant, etc) are also potent atrial-selective peak I(Na) blockers, so that the reduction of Na(i) loading in atrial cells by these agents can be in large part due to the block of peak I(Na). The impact of late I(Na) inhibition is reduced by the abbreviation of the action potential that occurs in AF patients secondary to electrical remodeling. It stands to reason that selective late I(Na) block may contribute more to inhibition of Ca(i)-mediated triggered activity responsible for initiation of AF in clinical pathologies associated with a prolonged atrial APD (such as long QT syndrome). Additional studies are clearly needed to test this hypothesis.
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Current world literature. Curr Opin Cardiol 2012. [PMID: 23207493 DOI: 10.1097/hco.0b013e32835c1388] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Durukan AB, Erdem B, Durukan E, Sevim H, Karaduman T, Gurbuz HA, Gurpinar A, Yorgancioglu C. May toxicity of amiodarone be prevented by antioxidants? A cell-culture study. J Cardiothorac Surg 2012; 7:61. [PMID: 22741616 PMCID: PMC3410766 DOI: 10.1186/1749-8090-7-61] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2012] [Accepted: 06/28/2012] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND Atrial Fibrillation is the most common arrhythmia encountered following cardiac surgery. The most commonly administered drug used in treatment and prophylaxis is amiodarone which has several toxic effects on major organ functions. There are few clinical data concerning prevention of toxic effects and there is no routinely suggested agent. The aim of this study is to document the cytotoxic effects of amiodarone on cell culture media and compare the cytoprotective effects of commonly used antioxidant agents. METHODS L929 mouse fibroblast cell line was cultured and 100,000 cells/well-plate were obtained. First group of cells were treated with increasing concentrations of amiodarone (20 to 180 μM) alone. Second and third group of cells were incubated with one-fold equimolar dose of vitamin C and N-acetyl cysteine prior to amiodarone exposure. The viability of cells were measured by MTT assay and the cytoprotective effect of each agent was compared. RESULTS The cytotoxicity of amiodarone was significant with concentrations of 100 μM and more. The viabilities of both vitamin C and N-acetyl cysteine treated cells were higher compared to untreated cells. CONCLUSIONS Vitamin C and N-acetyl cysteine are commonly used in the clinical setting for different purposes in context of their known antioxidant actions. Their role in prevention of amiodarone induced cytotoxicity is not fully documented. The study fully demonstrates the cytoprotective role of both agents in amiodarone induced cytotoxicity on cell culture media; more pronounced with vitamin C in some concentrations. The findings may be projectile for further clinical studies.
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Affiliation(s)
- Ahmet Baris Durukan
- Department of Cardiovascular Surgery, Medicana International Ankara Hospital, Eskisehir Yolu Uzeri, Sogutozu, Ankara, 06520, Turkey
| | - Beril Erdem
- Department Of Biology, Hacettepe University, Faculty Of Science, Beytepe, Ankara, 06800, Turkey
| | - Elif Durukan
- Department Of Public Health, Baskent University Medical Faculty, 79.sokak 7/6 Bahcelievler, Ankara, 06490, Turkey
| | - Handan Sevim
- Department Of Biology, Hacettepe University, Faculty Of Science, Beytepe, Ankara, 06800, Turkey
| | - Tugce Karaduman
- Department Of Biology, Hacettepe University, Faculty Of Science, Beytepe, Ankara, 06800, Turkey
| | - Hasan Alper Gurbuz
- Department of Cardiovascular Surgery, Medicana International Ankara Hospital, Eskisehir Yolu Uzeri, Sogutozu, Ankara, 06520, Turkey
| | - Aylin Gurpinar
- Department Of Biology, Hacettepe University, Faculty Of Science, Beytepe, Ankara, 06800, Turkey
| | - Cem Yorgancioglu
- Department of Cardiovascular Surgery, Medicana International Ankara Hospital, Eskisehir Yolu Uzeri, Sogutozu, Ankara, 06520, Turkey
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Workman AJ, Marshall GE, Rankin AC, Smith GL, Dempster J. Transient outward K+ current reduction prolongs action potentials and promotes afterdepolarisations: a dynamic-clamp study in human and rabbit cardiac atrial myocytes. J Physiol 2012; 590:4289-305. [PMID: 22733660 DOI: 10.1113/jphysiol.2012.235986] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Human atrial transient outward K(+) current (I(TO)) is decreased in a variety of cardiac pathologies, but how I(TO) reduction alters action potentials (APs) and arrhythmia mechanisms is poorly understood, owing to non-selectivity of I(TO) blockers. The aim of this study was to investigate effects of selective I(TO) changes on AP shape and duration (APD), and on afterdepolarisations or abnormal automaticity with β-adrenergic-stimulation, using the dynamic-clamp technique in atrial cells. Human and rabbit atrial cells were isolated by enzymatic dissociation, and electrical activity recorded by whole-cell-patch clamp (35-37°C). Dynamic-clamp-simulated I(TO) reduction or block slowed AP phase 1 and elevated the plateau, significantly prolonging APD, in both species. In human atrial cells, I(TO) block (100% I(TO) subtraction) increased APD(50) by 31%, APD(90) by 17%, and APD(-61 mV) (reflecting cellular effective refractory period) by 22% (P < 0.05 for each). Interrupting I(TO) block at various time points during repolarisation revealed that the APD(90) increase resulted mainly from plateau-elevation, rather than from phase 1-slowing or any residual I(TO). In rabbit atrial cells, partial I(TO) block (∼40% I(TO) subtraction) reversibly increased the incidence of cellular arrhythmic depolarisations (CADs; afterdepolarisations and/or abnormal automaticity) in the presence of the β-agonist isoproterenol (0.1 μm; ISO), from 0% to 64% (P < 0.05). ISO-induced CADs were significantly suppressed by dynamic-clamp increase in I(TO) (∼40% I(TO) addition). ISO+I(TO) decrease-induced CADs were abolished by β(1)-antagonism with atenolol at therapeutic concentration (1 μm). Atrial cell action potential changes from selective I(TO) modulation, shown for the first time using dynamic-clamp, have the potential to influence reentrant and non-reentrant arrhythmia mechanisms, with implications for both the development and treatment of atrial fibrillation.
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Affiliation(s)
- A J Workman
- Institute of Cardiovascular and Medical Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, 126 University Place, Glasgow G12 8TA, UK.
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Grandi E, Workman AJ, Pandit SV. Altered Excitation-Contraction Coupling in Human Chronic Atrial Fibrillation. J Atr Fibrillation 2012; 4:495. [PMID: 28496736 DOI: 10.4022/jafib.495] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2011] [Revised: 02/10/2012] [Accepted: 03/19/2012] [Indexed: 12/19/2022]
Abstract
This review focuses on the (mal)adaptive processes in atrial excitation-contraction coupling occurring in patients with chronic atrial fibrillation. Cellular remodeling includes shortening of the atrial action potential duration and effective refractory period, depressed intracellular Ca2+ transient, and reduced myocyte contractility. Here we summarize the current knowledge of the ionic bases underlying these changes. Understanding the molecular mechanisms of excitation-contraction-coupling remodeling in the fibrillating human atria is important to identify new potential targets for AF therapy.
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Affiliation(s)
- Eleonora Grandi
- Department of Pharmacology, University of California at Davis, Davis, CA, USA
| | - Antony J Workman
- Institute of Cardiovascular and Medical Sciences, University of Glasgow, UK
| | - Sandeep V Pandit
- Center for Arrhythmia Research, University of Michigan, Ann Arbor, MI, USA
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Remodelling of human atrial K+ currents but not ion channel expression by chronic β-blockade. Pflugers Arch 2011; 463:537-48. [PMID: 22160437 DOI: 10.1007/s00424-011-1061-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2011] [Revised: 11/11/2011] [Accepted: 11/14/2011] [Indexed: 10/14/2022]
Abstract
Chronic β-adrenoceptor antagonist (β-blocker) treatment in patients is associated with a potentially anti-arrhythmic prolongation of the atrial action potential duration (APD), which may involve remodelling of repolarising K(+) currents. The aim of this study was to investigate the effects of chronic β-blockade on transient outward, sustained and inward rectifier K(+) currents (I(TO), I(KSUS) and I(K1)) in human atrial myocytes and on the expression of underlying ion channel subunits. Ion currents were recorded from human right atrial isolated myocytes using the whole-cell-patch clamp technique. Tissue mRNA and protein levels were measured using real time RT-PCR and Western blotting. Chronic β-blockade was associated with a 41% reduction in I(TO) density: 9.3 ± 0.8 (30 myocytes, 15 patients) vs 15.7 ± 1.1 pA/pF (32, 14), p < 0.05; without affecting its voltage-, time- or rate dependence. I(K1) was reduced by 34% at -120 mV (p < 0.05). Neither I(KSUS), nor its increase by acute β-stimulation with isoprenaline, was affected by chronic β-blockade. Mathematical modelling suggested that the combination of I(TO)- and I(K1)-decrease could result in a 28% increase in APD(90). Chronic β-blockade did not alter mRNA or protein expression of the I(TO) pore-forming subunit, Kv4.3, or mRNA expression of the accessory subunits KChIP2, KChAP, Kvβ1, Kvβ2 or frequenin. There was no reduction in mRNA expression of Kir2.1 or TWIK to account for the reduction in I(K1). A reduction in atrial I(TO) and I(K1) associated with chronic β-blocker treatment in patients may contribute to the associated action potential prolongation, and this cannot be explained by a reduction in expression of associated ion channel subunits.
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