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E-cigarettes and their lone constituents induce cardiac arrhythmia and conduction defects in mice. Nat Commun 2022; 13:6088. [PMID: 36284091 PMCID: PMC9596490 DOI: 10.1038/s41467-022-33203-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Accepted: 08/24/2022] [Indexed: 01/11/2023] Open
Abstract
E-cigarette use has surged, but the long-term health effects remain unknown. E-cigarette aerosols containing nicotine and acrolein, a combustion and e-cigarette byproduct, may impair cardiac electrophysiology through autonomic imbalance. Here we show in mouse electrocardiograms that acute inhalation of e-cigarette aerosols disturbs cardiac conduction, in part through parasympathetic modulation. We demonstrate that, similar to acrolein or combustible cigarette smoke, aerosols from e-cigarette solvents (vegetable glycerin and propylene glycol) induce bradycardia, bradyarrhythmias, and elevations in heart rate variability during inhalation exposure, with inverse post-exposure effects. These effects are slighter with tobacco- or menthol-flavored aerosols containing nicotine, and in female mice. Yet, menthol-flavored and PG aerosols also increase ventricular arrhythmias and augment early ventricular repolarization (J amplitude), while menthol uniquely alters atrial and atrioventricular conduction. Exposure to e-cigarette aerosols from vegetable glycerin and its byproduct, acrolein, diminish heart rate and early repolarization. The pro-arrhythmic effects of solvent aerosols on ventricular repolarization and heart rate variability depend partly on parasympathetic modulation, whereas ventricular arrhythmias positively associate with early repolarization dependent on the presence of nicotine. Our study indicates that chemical constituents of e-cigarettes could contribute to cardiac risk by provoking pro-arrhythmic changes and stimulating autonomic reflexes.
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Tse G, Zhang N, Song W, Letsas KP, Ngarmukos T, Jeevaratnam K, Liu T. Editorial: Risk Stratification Strategies for Cardiac Rhythm Abnormalities. Front Cardiovasc Med 2022; 9:887461. [PMID: 35571219 PMCID: PMC9091712 DOI: 10.3389/fcvm.2022.887461] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Accepted: 03/23/2022] [Indexed: 11/25/2022] Open
Affiliation(s)
- Gary Tse
- Cardiac Electrophysiology Unit, Cardiovascular Analytics Group, Hong Kong, China
- Tianjin Key Laboratory of Ionic-Molecular Function of Cardiovascular Disease, Department of Cardiology, Tianjin Institute of Cardiology, Second Hospital of Tianjin Medical University, Tianjin, China
- Kent and Medway Medical School, Canterbury, United Kingdom
| | - Nan Zhang
- Tianjin Key Laboratory of Ionic-Molecular Function of Cardiovascular Disease, Department of Cardiology, Tianjin Institute of Cardiology, Second Hospital of Tianjin Medical University, Tianjin, China
| | - Wenhua Song
- Tianjin Key Laboratory of Ionic-Molecular Function of Cardiovascular Disease, Department of Cardiology, Tianjin Institute of Cardiology, Second Hospital of Tianjin Medical University, Tianjin, China
| | | | - Tachapong Ngarmukos
- Faculty of Medicine Ramathibodi Hospital, Mahidol University, Bangkok, Thailand
| | - Kamalan Jeevaratnam
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom
- *Correspondence: Kamalan Jeevaratnam
| | - Tong Liu
- Tianjin Key Laboratory of Ionic-Molecular Function of Cardiovascular Disease, Department of Cardiology, Tianjin Institute of Cardiology, Second Hospital of Tianjin Medical University, Tianjin, China
- Tong Liu
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Chin SH, Allen E, Brack KE, Ng GA. Effects of sympatho-vagal interaction on ventricular electrophysiology and their modulation during beta-blockade. J Mol Cell Cardiol 2020; 139:201-212. [PMID: 32004506 DOI: 10.1016/j.yjmcc.2020.01.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2019] [Revised: 01/25/2020] [Accepted: 01/27/2020] [Indexed: 11/16/2022]
Abstract
AIMS The effects of sympatho-vagal interaction on heart rate (HR) changes are characterized by vagal dominance resulting in accentuated antagonism. Complex autonomic modulation of ventricular electrophysiology may exert prognostic arrhythmic impact. We examined the effects of concurrent sympathetic (SNS) and vagus (VNS) nerve stimulation on ventricular fibrillation threshold (VFT) and standard restitution (RT) in an isolated rabbit heart preparation with intact dual autonomic innervation, with and without beta-blockade. METHODS AND RESULTS Monophasic action potentials were recorded from left ventricular epicardial surface of dual-innervated isolated heart preparations from New Zealand white rabbits (n = 18). HR, VFT and RT were measured during different stimulation protocols (Protocol 1: VNS-SNS; Protocol 2: SNS-VNS) involving low- and high-frequency stimulations. A sub-study of Protocol 2 was performed in the presence of metoprolol tartrate. In both protocols, HR changes were characterized by vagal-dominant bradycardic component, affirming accentuated antagonism. During concurrent high-frequency VNS (HV), SNS prevails in lowering VFT in a frequency-sensitive manner during low (LS) or high (HS)-frequency stimulations (HV-LS: -2.8 ± 0.8 mA; HV-HS: -4.0 ± 0.9 mA, p < .05 vs. HV), with accompanying steepening of relative RT slope gradients (HV-LS: 223.54 ± 37.41%; HV-HS: 295.20 ± 60.86%, p < .05 vs. HV). In protocol 2, low (LV) and high (HV) vagal stimulations during concurrent HS raised VFT (HS-LV: 1.0 ± 0.4 mA; HS-HV: 3.0 ± 0.6 mA, p < .05 vs HS) with associated flattening of RT slopes (HS-LV: 32.40 ± 4.97%;HS-HV: 38.07 ± 6.37%; p < .05 vs HS). Metoprolol abolished accentuated antagonism in HR changes, reduced VFT and flattened RT globally during SNS-VNS. CONCLUSIONS Accentuated antagonism is absent in ventricular electrophysiological changes during sympatho-vagal interaction with sympathetic effect prevailing, suggesting a different mechanism at the ventricular level from heart rate effects. Metoprolol nullified accentuated antagonism with additional anti-fibrillatory effect beyond adrenergic blockade during sympatho-vagal stimulations.
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Affiliation(s)
- Shui Hao Chin
- Cardiology group, Department of Cardiovascular Sciences, University of Leicester, UK; University Hospitals of Leicester NHS Trust, Leicester, UK
| | - Emily Allen
- Cardiology group, Department of Cardiovascular Sciences, University of Leicester, UK
| | - Kieran E Brack
- Cardiology group, Department of Cardiovascular Sciences, University of Leicester, UK
| | - G André Ng
- Cardiology group, Department of Cardiovascular Sciences, University of Leicester, UK; University Hospitals of Leicester NHS Trust, Leicester, UK; NIHR Leicester Biomedical Research Centre, Leicester, UK.
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Proarrhythmic proclivity of left-stellate ganglion stimulation in a canine model of drug-induced long-QT syndrome type 1. Int J Cardiol 2019; 286:66-72. [PMID: 30777408 DOI: 10.1016/j.ijcard.2019.01.098] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2018] [Revised: 01/24/2019] [Accepted: 01/29/2019] [Indexed: 11/23/2022]
Abstract
BACKGROUND Left-stellate ganglion stimulation (LSGS) can modify regional dispersion of ventricular refractoriness, promote triggered activity, and reduce the threshold for ventricular fibrillation (VF). Sympathetic hyperactivity precipitates torsades de pointes (TdP) and VF in susceptible patients with long-QT syndrome type 1 (LQT1). We investigated the electromechanical effects of LSGS in a canine model of drug-induced LQT1, gaining novel arrhythmogenic insights. METHODS In nine mongrel dogs, the left and right stellate ganglia were exposed for electrical stimulation. ECG, left- and right-ventricular endocardial monophasic action potentials (MAPs) and pressures (LVP, RVP) were recorded. The electromechanical window (EMW; Q to LVP at 90% relaxation minus QT interval) was calculated. LQT1 was mimicked by infusion of the KCNQ1/IKs blocker HMR1556. RESULTS At baseline, LSGS and right-stellate ganglion stimulation (RSGS) caused similar heart-rate acceleration and QT shortening. Positive inotropic and lusitropic effects were more pronounced under LSGS than RSGS. IKs blockade prolonged QTc, triggered MAP-early afterdepolarizations (EADs) and rendered the EMW negative, but no ventricular tachyarrhythmias occurred. Superimposed LSGS exaggerated EMW negativity and evoked TdP in 5/9 dogs within 30 s. Preceding extrasystoles originated mostly from the outflow-tracts region. TdP deteriorated into therapy-refractory VF in 4/5 animals. RSGS did not provoke TdP/VF. CONCLUSIONS In this model of drug-induced LQT1, LSGS readily induced TdP and VF during repolarization prolongation and MAP-EAD generation, but only if EMW turned from positive to very negative. We postulate that altered mechano-electric coupling can exaggerate regional dispersion of refractoriness and facilitates ventricular ectopy.
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Shattock MJ, Park KC, Yang HY, Lee AWC, Niederer S, MacLeod KT, Winter J. Restitution slope is principally determined by steady-state action potential duration. Cardiovasc Res 2018; 113:817-828. [PMID: 28371805 PMCID: PMC5437364 DOI: 10.1093/cvr/cvx063] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/28/2016] [Accepted: 03/22/2017] [Indexed: 12/02/2022] Open
Abstract
Aims The steepness of the action potential duration (APD) restitution curve and local tissue refractoriness are both thought to play important roles in arrhythmogenesis. Despite this, there has been little recognition of the apparent association between steady-state APD and the slope of the restitution curve. The objective of this study was to test the hypothesis that restitution slope is determined by APD and to examine the relationship between restitution slope, refractoriness and susceptibility to VF. Methods and results Experiments were conducted in isolated hearts and ventricular myocytes from adult guinea pigs and rabbits. Restitution curves were measured under control conditions and following intervention to prolong (clofilium, veratridine, bretylium, low [Ca]e, chronic transverse aortic constriction) or shorten (catecholamines, rapid pacing) ventricular APD. Despite markedly differing mechanisms of action, all interventions that prolonged the action potential led to a steepening of the restitution curve (and vice versa). Normalizing the restitution curve as a % of steady-state APD abolished the difference in restitution curves with all interventions. Effects on restitution were preserved when APD was modulated by current injection in myocytes pre-treated with the calcium chelator BAPTA-AM – to abolish the intracellular calcium transient. The non-linear relation between APD and the rate of repolarization of the action potential is shown to underpin the common influence of APD on the slope of the restitution curve. Susceptibility to VF was found to parallel changes in APD/refractoriness, rather than restitution slope. Conclusion(s) Steady-state APD is the principal determinant of the slope of the ventricular electrical restitution curve. In the absence of post-repolarization refractoriness, factors that prolong the action potential would be expected to steepen the restitution curve. However, concomitant changes in tissue refractoriness act to reduce susceptibility to sustained VF. Dependence on steady-state APD may contribute to the failure of restitution slope to predict sudden cardiac death.
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Affiliation(s)
- Michael J Shattock
- Cardiovascular Division, King's College London, St Thomas' Hospital, Westminster Bridge Road, London SE1 7EH, UK
| | - Kyung Chan Park
- Cardiovascular Division, King's College London, St Thomas' Hospital, Westminster Bridge Road, London SE1 7EH, UK
| | - Hsiang-Yu Yang
- NHLI, ICTEM Building, Hammersmith Campus, Du Cane Road, London W12 0NN, UK.,Department of Surgery, Division of Cardiovascular Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei 114, Taiwan
| | - Angela W C Lee
- Biomedical Engineering, King's College London, St Thomas' Hospital, Westminster Bridge Road, London SE1 7EH, UK
| | - Steven Niederer
- Biomedical Engineering, King's College London, St Thomas' Hospital, Westminster Bridge Road, London SE1 7EH, UK
| | - Kenneth T MacLeod
- NHLI, ICTEM Building, Hammersmith Campus, Du Cane Road, London W12 0NN, UK
| | - James Winter
- Cardiovascular Division, King's College London, St Thomas' Hospital, Westminster Bridge Road, London SE1 7EH, UK
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Autonomic conflict exacerbates long QT associated ventricular arrhythmias. J Mol Cell Cardiol 2018; 116:145-154. [PMID: 29408217 PMCID: PMC5855091 DOI: 10.1016/j.yjmcc.2018.02.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Revised: 01/19/2018] [Accepted: 02/01/2018] [Indexed: 11/27/2022]
Abstract
This study tested the hypothesis that concomitant sympathetic and parasympathetic stimulation (“autonomic conflict”) may act as a trigger for arrhythmias in long QT syndrome (LQTS). Studies were performed in isolated innervated rabbit hearts treated with clofilium (100 nmol/L); a potassium channel blocker. The influence of vagus nerve stimulation (VNS) on spontaneous ventricular arrhythmias was assessed in the absence/presence of sustained noradrenaline perfusion (100 nmol/L) and with sudden adrenergic stress (injections of noradrenaline into the perfusion line). Hearts were instrumented for a pseudo-electrocardiogram and monophasic action potential recordings. VNS, which slows heart rate, was associated with a stimulation frequency-dependent incidence of spontaneous early after-depolarisations (EADs) and ventricular tachycardia (VT), best predicted by the duration of the electrocardiographic T-wave and by triangulation of the ventricular action potential. In the presence of sustained (steady-state) noradrenaline perfusion, the incidence of EADs and VT with VNS was decreased from 73/55% to 45/27%, respectively. However, sudden adrenergic stress, imposed during periods of sustained VNS, was associated with a transient increase in the incidence of severity of observed arrhythmias, as indicated by an increase in the average arrhythmias score (1.6 ± 0.4 vs. 2.1 ± 0.7, p = .01). Analysis of electrophysiological parameters suggests that sudden adrenergic stress is associated with a transient prolongation, and increased triangulation, of the ventricular action potential, which may predispose to triggered activity. This study demonstrates that autonomic conflict is a pro-arrhythmic stimulus in LQTS. However, combined adrenergic and parasympathetic stimulation has a complex relationship with arrhythmogenicity, with differences in the effects of steady-state adrenergic activation vs. sudden adrenergic stress. Long QT syndrome associated arrhythmias were studied with dual autonomic stimulation. EADs and TdP were triggered by increased vagal tone. Sudden adrenergic stress increased the severity of observed arrhythmias. Arrhythmias were prevented by sustained adrenergic stimulation. The sequence of autonomic stimulation influences the severity of long QT arrhythmias.
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Arteyeva NV, Azarov JE. Effect of action potential duration on T peak-T end interval, T-wave area and T-wave amplitude as indices of dispersion of repolarization: Theoretical and simulation study in the rabbit heart. J Electrocardiol 2017; 50:919-924. [PMID: 28784265 DOI: 10.1016/j.jelectrocard.2017.07.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2017] [Indexed: 10/19/2022]
Abstract
BACKGROUND The aim of the study was to differentiate the effect of dispersion of repolarization (DOR) and action potential duration (APD) on T-wave parameters being considered as indices of DOR, namely, Tpeak-Tend interval, T-wave amplitude and T-wave area. METHODS T-wave was simulated in a wide physiological range of DOR and APD using a realistic rabbit model based on experimental data. A simplified mathematical formulation of T-wave formation was conducted. RESULTS Both the simulations and the mathematical formulation showed that Tpeak-Tend interval and T-wave area are linearly proportional to DOR irrespectively of APD range, while T-wave amplitude is non-linearly proportional to DOR and inversely proportional to the minimal repolarization time, or minimal APD value. CONCLUSION Tpeak-Tend interval and T-wave area are the most accurate DOR indices independent of APD. T-wave amplitude can be considered as an index of DOR when the level of APD is taken into account.
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Affiliation(s)
- Natalia V Arteyeva
- Laboratory of Cardiac Physiology, Institute of Physiology, Komi Science Center, Ural Branch, Russian Academy of Sciences, 50, Pervomayskaya st., Syktyvkar 167982, Russia.
| | - Jan E Azarov
- Laboratory of Cardiac Physiology, Institute of Physiology, Komi Science Center, Ural Branch, Russian Academy of Sciences, 50, Pervomayskaya st., Syktyvkar 167982, Russia; Department of Physiology, Medical Institute of Pitirim Sorokin Syktyvkar State University, 11, Babushkin st., Syktyvkar 167000, Russia
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Winter J, Cook AR, Patient DH, Emmett SR, Tattersall J, Shattock MJ. Reversal of cardiac vagal effects of physostigmine by adjunctive muscarinic blockade. Neurotoxicology 2016; 57:174-182. [PMID: 27693445 DOI: 10.1016/j.neuro.2016.09.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Revised: 08/31/2016] [Accepted: 09/28/2016] [Indexed: 11/18/2022]
Abstract
Pre-treatment with reversible acetylcholinesterase (AChE) inhibitors is an effective strategy for reducing lethality following organophosphate nerve agent exposure. AChE inhibition may have unwanted cardiac side effects, which could be negated by adjunctive anti-cholinergic therapy. The aims of the present study were to examine the concentration-dependent effects of physostigmine on cardiac responses to vagus nerve stimulation (VNS), to test whether adjunctive treatment with hyoscine can reverse these effects and to assess the functional interaction and electrophysiological consequences of a combined pre-treatment. Studies were performed in an isolated innervated rabbit heart preparation. The reduction in heart rate with VNS was augmented by physostigmine (1-1000nmol/L), in a concentration-dependent manner - with an EC50 of 19nmol/L. Hyoscine was shown to be effective at blocking the cardiac responses to VNS with an IC50 of 11nmol/L. With concomitant perfusion of physostigmine, the concentration-response curve for hyoscine was shifted downward and to the right, increasing the concentration of hyoscine required to normalise (to control values) the effects of physostigmine on heart rate. At the lowest concentration of hyoscine examined (1nmol/L) a modest potentiation of heart rate response to VNS (+15±3%) was observed. We found no evidence of cardiac dysfunction or severe electrophysiological abnormalities with either physostigmine or hyoscine alone, or as a combined drug-therapy. The main finding of this study is that hyoscine, at concentrations greater than 10-8M, is effective at reversing the functional effects of physostigmine on the heart. However, low-concentrations of hyoscine may augment cardiac parasympathetic control.
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Affiliation(s)
- James Winter
- Cardiovascular Division, King's College London, UK.
| | - Alexandra R Cook
- Defence Science and Technology Laboratory, Porton Down, Wiltshire, UK
| | - Dawn H Patient
- Defence Science and Technology Laboratory, Porton Down, Wiltshire, UK
| | - Stevan R Emmett
- Defence Science and Technology Laboratory, Porton Down, Wiltshire, UK
| | - John Tattersall
- Defence Science and Technology Laboratory, Porton Down, Wiltshire, UK
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Winter J, Shattock MJ. Geometrical considerations in cardiac electrophysiology and arrhythmogenesis. Europace 2015; 18:320-31. [PMID: 26585597 DOI: 10.1093/europace/euv307] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Accepted: 08/14/2015] [Indexed: 11/14/2022] Open
Abstract
The rate of repolarization (RRepol) and so the duration of the cardiac action potential are determined by the balance of inward and outward currents across the cardiac membrane (net ionic current). Plotting action potential duration (APD) as a function of the RRepol reveals an inverse non-linear relationship, arising from the geometric association between these two factors. From the RRepol-APD relationship, it can be observed that a longer action potential will exhibit a greater propensity to shorten, or prolong, for a given change in the RRepol (i.e. net ionic current), when compared with one that is initially shorter. This observation has recently been used to explain why so many interventions that prolong the action potential exert a greater effect at slow rates (reverse rate-dependence). In this article, we will discuss the broader implications of this simple principle and examine how common experimental observations on the electrical behaviour of the myocardium may be explained in terms of the RRepol-APD relationship. An argument is made, with supporting published evidence, that the non-linear relationship between the RRepol and APD is a fundamental, and largely overlooked, property of the myocardium. The RRepol-APD relationship appears to explain why interventions and disease with seemingly disparate mechanisms of action have similar electrophysiological consequences. Furthermore, the RRepol-APD relationship predicts that prolongation of the action potential, by slowing repolarization, will promote conditions of dynamic electrical instability, exacerbating several electrophysiological phenomena associated with arrhythmogenesis, namely, the rate dependence of dispersion of repolarization, APD restitution, and electrical alternans.
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Affiliation(s)
- James Winter
- Cardiovascular Division, The Rayne Institute, 4th Floor, Lambeth Wing, St Thomas' Hospital, King's College London, London SE1 7EH, UK
| | - Michael J Shattock
- Cardiovascular Division, The Rayne Institute, 4th Floor, Lambeth Wing, St Thomas' Hospital, King's College London, London SE1 7EH, UK
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