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Inoue K, Sonoda S, Naka Y, Okabe H, Setoyama K, Miura T, Anai R, Araki M, Kataoka M. Clinical Efficacy of Intracoronary Papaverine After Nicorandil Administration for Safe and Optimal Fractional Flow Reserve Measurement. Int Heart J 2021; 62:962-969. [PMID: 34544970 DOI: 10.1536/ihj.21-010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Fractional flow reserve (FFR) is considered the standard for assessment of the physiological significance of coronary artery stenosis. Intracoronary papaverine (PAP) is the most potent vasodilator used for the achievement of maximal hyperemia. However, its use can provoke ventricular tachycardia (VT) due to excessive QT prolongation. We evaluated the clinical efficacy and safety of the administration of PAP after nicorandil (NIC), a potassium channel opener that prevents VT, for optimal FFR measurement.A total of 127 patients with 178 stenoses were enrolled. The FFR values were measured using NIC (NIC-FFR) and PAP (PAP-FFR). We administered PAP following NIC (NIC-PAP). Changes in the FFR and electrogram parameters (baseline versus NIC versus PAP) were assessed and the incidence of arrhythmias after PAP was evaluated. In addition, we analyzed another 41 patients with 51 stenoses by assessing the FFR using PAP before NIC (PAP-NIC). After propensity score matching, the electrogram parameters between 2 groups were compared.The mean PAP-FFR was significantly lower than the mean NIC-FFR (0.82 ± 0.11 versus 0.81 ± 0.11, P < 0.05). The mean baseline-QTc, NIC-QTc, and PAP-QTc values were 425 ± 37 ms1/2, 424 ± 41 ms1/2, and 483 ± 54 ms1/2, respectively. VT occurred in only 1 patient (0.6%). Although PAP induced QTc prolongation (P < 0.05), the PAP-QTc duration was significantly shorter in NIC-PAP compared to PAP-NIC (P < 0.05).The administration of PAP with NIC may induce sufficient hyperemia and prevent fatal arrhythmia through reductions in the PAP-induced QTc prolongation during FFR measurement.
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Affiliation(s)
- Konosuke Inoue
- Second Department of Internal Medicine, University of Occupational and Environmental Health
| | - Shinjo Sonoda
- Second Department of Internal Medicine, University of Occupational and Environmental Health
| | - Yutaro Naka
- Second Department of Internal Medicine, University of Occupational and Environmental Health
| | - Hiroki Okabe
- Second Department of Internal Medicine, University of Occupational and Environmental Health
| | - Koshi Setoyama
- Second Department of Internal Medicine, University of Occupational and Environmental Health
| | - Toshiya Miura
- Second Department of Internal Medicine, University of Occupational and Environmental Health
| | - Reo Anai
- Second Department of Internal Medicine, University of Occupational and Environmental Health
| | - Masaru Araki
- Second Department of Internal Medicine, University of Occupational and Environmental Health
| | - Masaharu Kataoka
- Second Department of Internal Medicine, University of Occupational and Environmental Health
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Hancox JC, Whittaker DG, Zhang H, Stuart AG. Learning from studying very rare cardiac conditions: the example of short QT syndrome. JOURNAL OF CONGENITAL CARDIOLOGY 2019. [DOI: 10.1186/s40949-019-0024-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
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Jeevaratnam K, Chadda KR, Salvage SC, Valli H, Ahmad S, Grace AA, Huang CLH. Ion channels, long QT syndrome and arrhythmogenesis in ageing. Clin Exp Pharmacol Physiol 2017; 44 Suppl 1:38-45. [PMID: 28024120 PMCID: PMC5763326 DOI: 10.1111/1440-1681.12721] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Revised: 12/18/2016] [Accepted: 12/19/2016] [Indexed: 01/08/2023]
Abstract
Ageing is associated with increased prevalences of both atrial and ventricular arrhythmias, reflecting disruption of the normal sequence of ion channel activation and inactivation generating the propagated cardiac action potential. Experimental models with specific ion channel genetic modifications have helped clarify the interacting functional roles of ion channels and how their dysregulation contributes to arrhythmogenic processes at the cellular and systems level. They have also investigated interactions between these ion channel abnormalities and age-related processes in producing arrhythmic tendency. Previous reviews have explored the relationships between age and loss-of-function Nav 1.5 mutations in producing arrhythmogenicity. The present review now explores complementary relationships arising from gain-of-function Nav 1.5 mutations associated with long QT3 (LQTS3). LQTS3 patients show increased risks of life-threatening ventricular arrhythmias, particularly after 40 years of age, consistent with such interactions between the ion channel abnormailities and ageing. In turn clinical evidence suggests that ageing is accompanied by structural, particularly fibrotic, as well as electrophysiological change. These abnormalities may result from biochemical changes producing low-grade inflammation resulting from increased production of reactive oxygen species and superoxide. Experimental studies offer further insights into the underlying mechanisms underlying these phenotypes. Thus, studies in genetically modified murine models for LQTS implicated action potential recovery processes in arrhythmogenesis resulting from functional ion channel abnormalities. In addition, ageing wild type (WT) murine models demonstrated both ion channel alterations and fibrotic changes with ageing. Murine models then suggested evidence for interactions between ageing and ion channel mutations and provided insights into potential arrhythmic mechanisms inviting future exploration.
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Affiliation(s)
- Kamalan Jeevaratnam
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, UK.,School of Medicine, Perdana University-Royal College of Surgeons Ireland, Serdang, Selangor Darul Ehsan, Malaysia
| | - Karan R Chadda
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, UK.,Physiological Laboratory, University of Cambridge, Cambridge, UK
| | | | - Haseeb Valli
- Physiological Laboratory, University of Cambridge, Cambridge, UK
| | - Shiraz Ahmad
- Physiological Laboratory, University of Cambridge, Cambridge, UK
| | - Andrew A Grace
- Division of Cardiovascular Biology, Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Christopher L-H Huang
- Physiological Laboratory, University of Cambridge, Cambridge, UK.,Division of Cardiovascular Biology, Department of Biochemistry, University of Cambridge, Cambridge, UK
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Bohnen MS, Peng G, Robey SH, Terrenoire C, Iyer V, Sampson KJ, Kass RS. Molecular Pathophysiology of Congenital Long QT Syndrome. Physiol Rev 2017; 97:89-134. [PMID: 27807201 PMCID: PMC5539372 DOI: 10.1152/physrev.00008.2016] [Citation(s) in RCA: 114] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Ion channels represent the molecular entities that give rise to the cardiac action potential, the fundamental cellular electrical event in the heart. The concerted function of these channels leads to normal cyclical excitation and resultant contraction of cardiac muscle. Research into cardiac ion channel regulation and mutations that underlie disease pathogenesis has greatly enhanced our knowledge of the causes and clinical management of cardiac arrhythmia. Here we review the molecular determinants, pathogenesis, and pharmacology of congenital Long QT Syndrome. We examine mechanisms of dysfunction associated with three critical cardiac currents that comprise the majority of congenital Long QT Syndrome cases: 1) IKs, the slow delayed rectifier current; 2) IKr, the rapid delayed rectifier current; and 3) INa, the voltage-dependent sodium current. Less common subtypes of congenital Long QT Syndrome affect other cardiac ionic currents that contribute to the dynamic nature of cardiac electrophysiology. Through the study of mutations that cause congenital Long QT Syndrome, the scientific community has advanced understanding of ion channel structure-function relationships, physiology, and pharmacological response to clinically employed and experimental pharmacological agents. Our understanding of congenital Long QT Syndrome continues to evolve rapidly and with great benefits: genotype-driven clinical management of the disease has improved patient care as precision medicine becomes even more a reality.
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Affiliation(s)
- M S Bohnen
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
| | - G Peng
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
| | - S H Robey
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
| | - C Terrenoire
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
| | - V Iyer
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
| | - K J Sampson
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
| | - R S Kass
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
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Abstract
Cardiac arrhythmias can follow disruption of the normal cellular electrophysiological processes underlying excitable activity and their tissue propagation as coherent wavefronts from the primary sinoatrial node pacemaker, through the atria, conducting structures and ventricular myocardium. These physiological events are driven by interacting, voltage-dependent, processes of activation, inactivation, and recovery in the ion channels present in cardiomyocyte membranes. Generation and conduction of these events are further modulated by intracellular Ca2+ homeostasis, and metabolic and structural change. This review describes experimental studies on murine models for known clinical arrhythmic conditions in which these mechanisms were modified by genetic, physiological, or pharmacological manipulation. These exemplars yielded molecular, physiological, and structural phenotypes often directly translatable to their corresponding clinical conditions, which could be investigated at the molecular, cellular, tissue, organ, and whole animal levels. Arrhythmogenesis could be explored during normal pacing activity, regular stimulation, following imposed extra-stimuli, or during progressively incremented steady pacing frequencies. Arrhythmic substrate was identified with temporal and spatial functional heterogeneities predisposing to reentrant excitation phenomena. These could arise from abnormalities in cardiac pacing function, tissue electrical connectivity, and cellular excitation and recovery. Triggering events during or following recovery from action potential excitation could thereby lead to sustained arrhythmia. These surface membrane processes were modified by alterations in cellular Ca2+ homeostasis and energetics, as well as cellular and tissue structural change. Study of murine systems thus offers major insights into both our understanding of normal cardiac activity and its propagation, and their relationship to mechanisms generating clinical arrhythmias.
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Affiliation(s)
- Christopher L-H Huang
- Physiological Laboratory and the Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
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Abstract
For individuals and the society as a whole, the increased risk of sudden cardiac death in obese patients is becoming a major challenge, especially since obesity prevalence has been increasing steadily around the globe. Traditional risk factors and obesity often coexist. Hypertension, diabetes, obstructive sleep apnea and metabolic syndrome are well-known risk factors for CV disease and are often present in the obese patient. Although the bulk of evidence is circumstantial, sudden cardiac death and obesity share common traditional CV risk factors. Structural, functional and metabolic factors modulate and influence the risk of sudden cardiac death in the obese population. Other risk factors such as left ventricular hypertrophy, increased number of premature ventricular complexes, altered QT interval and reduced heart rate variability are all documented in both obese and sudden cardiac death populations. The present review focuses on out-of-hospital sudden cardiac death and potential mechanisms leading to sudden cardiac death in this population.
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Affiliation(s)
- Benoit Plourde
- Department of Medicine, Faculty of Medicine, Quebec City, QC, Canada
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Watanabe I, Okumura Y, Ohkubo K, Nagashima K, Mano H, Sonoda K, Kofune M, Kunimoto S, Kasamaki Y, Hirayama A. Effect of the ATP-sensitive K⁺ channel opener nicorandil in a canine model of proarrhythmia. Int Heart J 2011; 52:318-22. [PMID: 22008444 DOI: 10.1536/ihj.52.318] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Increased action potential duration (APD) induces early afterdepolarization (EAD) in vitro and torsade de pointes in vivo, and ATP-sensitive K(+) channel openers decrease APD in cardiac tissue. We tested whether the ATP-sensitive K(+) channel opener nicorandil has antiarrhythmic effects on class III antiarrhythmic drug-induced ventricular arrhythmia. In 10 anesthetized dogs with chronic atrioventricular block, we recorded monophasic action potentials (MAPs) from the left and right ventricular (LV and RV) endocardium. The class III antiarrhythmic drug nifekalant (1 mg/kg, IV) was administered at 5 minute intervals (total doses; 2-6 mg/kg) until the appearance of EADs, premature ventricular contractions (PVCs), or polymorphic ventricular tachycardias (PVTs). Five minutes after the end of nifekalant administration, nicorandil (1.0 mg/kg) was administered over 5 minutes. Nifekalant decreased the ventricular escape rate from 75 ± 5 beats/minute to 45 ± 10 beats/minute and increased RV-MAP duration (MAPD) from 217 ± 32 msec to 308 ± 2 msec (P < 0.01) and LV-MAPD from 232 ± 32 msec to 353 ± 82 msec (P < 0.01). EADs were recorded in 9 dogs, frequent premature ventricular contractions (PVCs) developed in 10 dogs, incessant PVTs developed in 3 dogs, and monomorphic ventricular tachycardia developed in 3 dogs after nifekalant administration. Nicorandil decreased RV-MAPD to 267 ± 57 msec and LV-MAPD to 279 ± 44 msec. It suppressed EADs, decreased the incidence of PVCs, and abolished PVT. Nicorandil may be clinically useful for treatment of PVCs and PVTs accompanying acquired long QT syndrome.
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Affiliation(s)
- Ichiro Watanabe
- Division of Cardiology, Department of Medicine, Nihon University School of Medicine, Tokyo, Japan
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Nicorandil normalizes prolonged repolarisation in the first transgenic rabbit model with Long-QT syndrome 1 both in vitro and in vivo. Eur J Pharmacol 2010; 650:309-16. [PMID: 20959120 DOI: 10.1016/j.ejphar.2010.10.016] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2010] [Revised: 10/05/2010] [Accepted: 10/06/2010] [Indexed: 01/08/2023]
Abstract
Transgenic rabbits expressing loss-of-function pore mutants of the human gene KCNQ1 (K(v)LQT1-Y315S) have a Long QT-Syndrome 1 (LQT1) phenotype. We evaluated for the first time the effect of nicorandil, an opener of ATP-sensitive potassium channels, and of isoproterenol on cardiac action potential duration and heart rate dependent dispersion of repolarisation in transgenic LQT1 rabbits. In vivo LQT1 and littermate control were subjected to transvenous electrophysiological studies; in vitro monophasic action potentials were recorded from explanted Langendorff-perfused hearts. In vivo ventricular effective refractory periods (VERP) at the right ventricular base were significantly prolonged in LQT1 as compared to littermate control, resulting in a more pronounced VERP dispersion in LQT1. This difference in VERP dispersion between LQT1 and littermate control disappeared after infusion of nicorandil. In vitro, mean action potential durations (APD(75) and APD(90)) of LQT1 were significantly prolonged compared to littermate control at baseline. Nicorandil decreased APD(75) and APD(90) in LQT1 and littermate control at all stimulated heart rates. After adding nicorandil, the APD(90) at all hearts rates and the APD(75) at high heart rates were no longer different. Dispersion of repolarisation (∆APD(75) and ∆APD(90)) was heart rate dependently decreased after nicorandil at all tested stimulation cycle lengths only in LQT1. We demonstrated phenotypic differences of LQT1 and littermate control in vivo and in vitro. Nicorandil 20μmol/l improved repolarisation abnormalities and heterogeneities in transgenic LQT1 rabbits.
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Testai L, Cecchetti V, Sabatini S, Martelli A, Breschi MC, Calderone V. Effects of KATPopeners on the QT prolongation induced by HERG-blocking drugs in guinea-pigs. J Pharm Pharmacol 2010. [DOI: 10.1211/jpp.62.07.0014] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
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Grunnet M. Repolarization of the cardiac action potential. Does an increase in repolarization capacity constitute a new anti-arrhythmic principle? Acta Physiol (Oxf) 2010; 198 Suppl 676:1-48. [PMID: 20132149 DOI: 10.1111/j.1748-1716.2009.02072.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The cardiac action potential can be divided into five distinct phases designated phases 0-4. The exact shape of the action potential comes about primarily as an orchestrated function of ion channels. The present review will give an overview of ion channels involved in generating the cardiac action potential with special emphasis on potassium channels involved in phase 3 repolarization. In humans, these channels are primarily K(v)11.1 (hERG1), K(v)7.1 (KCNQ1) and K(ir)2.1 (KCNJ2) being the responsible alpha-subunits for conducting I(Kr), I(Ks) and I(K1). An account will be given about molecular components, biophysical properties, regulation, interaction with other proteins and involvement in diseases. Both loss and gain of function of these currents are associated with different arrhythmogenic diseases. The second part of this review will therefore elucidate arrhythmias and subsequently focus on newly developed chemical entities having the ability to increase the activity of I(Kr), I(Ks) and I(K1). An evaluation will be given addressing the possibility that this novel class of compounds have the ability to constitute a new anti-arrhythmic principle. Experimental evidence from in vitro, ex vivo and in vivo settings will be included. Furthermore, conceptual differences between the short QT syndrome and I(Kr) activation will be accounted for.
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Affiliation(s)
- M Grunnet
- NeuroSearch A/S, Ballerup, and Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Denmark.
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Hothi SS, Thomas G, Killeen MJ, Grace AA, Huang CLH. Empirical correlation of triggered activity and spatial and temporal re-entrant substrates with arrhythmogenicity in a murine model for Jervell and Lange-Nielsen syndrome. Pflugers Arch 2009; 458:819-35. [PMID: 19430811 PMCID: PMC2719739 DOI: 10.1007/s00424-009-0671-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2009] [Accepted: 04/07/2009] [Indexed: 11/23/2022]
Abstract
KCNE1 encodes the β-subunit of the slow component of the delayed rectifier K+ current. The Jervell and Lange-Nielsen syndrome is characterized by sensorineural deafness, prolonged QT intervals, and ventricular arrhythmogenicity. Loss-of-function mutations in KCNE1 are implicated in the JLN2 subtype. We recorded left ventricular epicardial and endocardial monophasic action potentials (MAPs) in intact, Langendorff-perfused mouse hearts. KCNE1−/− but not wild-type (WT) hearts showed not only triggered activity and spontaneous ventricular tachycardia (VT), but also VT provoked by programmed electrical stimulation. The presence or absence of VT was related to the following set of criteria for re-entrant excitation for the first time in KCNE1−/− hearts: Quantification of APD90, the MAP duration at 90% repolarization, demonstrated alterations in (1) the difference, ∆APD90, between endocardial and epicardial APD90 and (2) critical intervals for local re-excitation, given by differences between APD90 and ventricular effective refractory period, reflecting spatial re-entrant substrate. Temporal re-entrant substrate was reflected in (3) increased APD90 alternans, through a range of pacing rates, and (4) steeper epicardial and endocardial APD90 restitution curves determined with a dynamic pacing protocol. (5) Nicorandil (20 µM) rescued spontaneous and provoked arrhythmogenic phenomena in KCNE1−/− hearts. WTs remained nonarrhythmogenic. Nicorandil correspondingly restored parameters representing re-entrant criteria in KCNE1−/− hearts toward values found in untreated WTs. It shifted such values in WT hearts in similar directions. Together, these findings directly implicate triggered electrical activity and spatial and temporal re-entrant mechanisms in the arrhythmogenesis observed in KCNE1−/− hearts.
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Affiliation(s)
- Sandeep S Hothi
- Physiological Laboratory, Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge, CB2 3EG, UK.
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Markiewicz-Łoskot G, Moric-Janiszewska E, Mazurek U. The risk of cardiac events and genotype-based management of LQTS patients. Ann Noninvasive Electrocardiol 2009; 14:86-92. [PMID: 19149798 DOI: 10.1111/j.1542-474x.2008.00278.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
This review discusses the risk of cardiac events and genotype-based management of LQTS. We describe here the genetic background of long QT syndrome and the eleven different genes for ion-channels and a structural anchoring protein associated with that disorder. Clinical Background section discusses the risk of cardiac events associated with different LQTS types. Management and Prevention section describes in turn gene-specific therapy, which was based on the identification of the gene defect and the dysfunction of the associated transmembrane ion channel. In patients affected by LQTS, genetic analysis is useful for risk stratification and for making therapeutic decisions. A recent study reported a quite novel pathogenic mechanism for LQTS and suggested that treatments aimed at scaffolding proteins rather than specific ion channels may be an alternative to antiarrhythmic strategy in the future.
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hERG1 channel activators: A new anti-arrhythmic principle. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2008; 98:347-62. [DOI: 10.1016/j.pbiomolbio.2009.01.002] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Hothi SS, Booth SW, Sabir IN, Killeen MJ, Simpson F, Zhang Y, Grace AA, Huang CLH. Arrhythmogenic substrate and its modification by nicorandil in a murine model of long QT type 3 syndrome. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2008; 98:267-80. [DOI: 10.1016/j.pbiomolbio.2009.01.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Shivkumar K, Valderrabano M. Use of potassium channel openers for pharmacologic modulation of cardiac excitability. J Cardiovasc Electrophysiol 2004; 15:821-3. [PMID: 15250870 DOI: 10.1046/j.1540-8167.2004.04324.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Bisinov E, Mitchell JH, January CT. Potassium andlong QT syndrome. J Am Coll Cardiol 2003; 42:1783-4. [PMID: 14642688 DOI: 10.1016/j.jacc.2003.08.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Xu X, Salata JJ, Wang J, Wu Y, Yan GX, Liu T, Marinchak RA, Kowey PR. Increasing I(Ks) corrects abnormal repolarization in rabbit models of acquired LQT2 and ventricular hypertrophy. Am J Physiol Heart Circ Physiol 2002; 283:H664-70. [PMID: 12124214 DOI: 10.1152/ajpheart.00076.2002] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Excessive action potential (AP) prolongation and early afterdepolarizations (EAD) are triggers of malignant ventricular arrhythmias. A slowly activating delayed rectifier K+ current (I(Ks)) is important for repolarization of ventricular AP. We examined the effects of I(Ks) activation by a new benzodiazepine (L3) on the AP of control, dofetilide-treated, and hypertrophied rabbit ventricular myocytes. In both control and hypertrophied myocytes, L3 activated I(Ks) via a negative shift in the voltage dependence of activation and a slowing of deactivation. L3 had no effect on L-type Ca(2+) current or other cardiac K+ currents tested. L3 shortened AP of control, dofetilide-treated, and hypertrophied myocytes more at 0.5 than 2 Hz. Selective activation of I(Ks) by L3 attenuates prolonged AP and eliminated EAD induced by rapidly activating delayed rectifier K+ current inhibition in control myocytes at 0.5 Hz and spontaneous EAD in hypertrophied myocytes at 0.2 Hz. Pharmacological activation of I(Ks) is a promising new strategy to suppress arrhythmias resulting from excessive AP prolongation in patients with certain forms of long QT syndrome or cardiac hypertrophy and failure.
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Affiliation(s)
- Xiaoping Xu
- Main Line Health Heart Center, Suite 558, Medical Office Building East, 100 Lancaster Avenue, Wynnewood, PA 19096, USA.
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Ashikaga T, Nishizaki M, Arita M, Yamawake N, Fujii H, Kishi Y, Isobe M, Hiraoka M. Opening of K(ATP) channel attenuates the increase in QT dispersion produced by the first balloon inflation during coronary angioplasty. Circ J 2002; 66:469-72. [PMID: 12030342 DOI: 10.1253/circj.66.469] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Increased QT dispersion predicts the occurrence of lethal ventricular arrhythmias complicating percutaneous transluminal coronary angioplasty (PTCA). Moreover, these arrhythmias occur more frequently at the first balloon inflation. Activation of the K(ATP) channel may influence QT dispersion and ventricular arrhythmias during coronary angioplasty, so 40 consecutive patients with stable angina were randomized to receive 3 mg/h of nicorandil infusion or placebo and QT dispersion and the incidence of ventricular ectopy were investigated before and throughout PTCA. There were no significant differences in QT dispersion at baseline between the nicorandil group (42+/-8 ms) and placebo (42+/-12ms). At the first balloon inflation, the QT dispersion in the nicorandil group (51+/-13 ms) was significantly less than that observed with placebo (76+/-16ms, p<0.001). However, the QT dispersion at the second inflation was similar in both groups (nicorandil: 45+/-12ms; placebo: 52+/-14ms). Ventricular ectopy was observed in 1 patient receiving nicorandil and 5 patients in the placebo group during the first inflation, and none in the nicorandil and 1 patient in the placebo group during the second balloon inflation. Activation of the K(ATP) channel may inhibit the development of ventricular arrhythmias during PTCA, particularly at the first balloon inflation.
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Affiliation(s)
- Takashi Ashikaga
- Department of Cardiology, Yokohama Minami Kyosai Hospital, Kanagawa, Japan.
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Kobayashi Y, Yazawa T, Adachi T, Kawamura M, Ryu S, Asano T, Obara C, Katagiri T. Ventricular arrhythmias with left bundle branch block pattern and inferior axis: assessment of their mechanisms on the basis of response to ATP, nicorandil and verapamil. JAPANESE CIRCULATION JOURNAL 2000; 64:835-41. [PMID: 11110427 DOI: 10.1253/jcj.64.835] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The present study investigated the mechanism of ventricular arrhythmias showing left bundle branch block (LBBB) pattern with an inferior axis. The effects of 3 drugs, adenosine triphosphate (ATP), nicorandil and verapamil, were evaluated in 17 patients. ATP suppressed the arrhythmias in 14 patients and nicorandil suppressed them in 8 of those 14. Verapamil suppressed 5 of the 6 ATP-nicorandil-sensitive arrhythmias. Four patients with ATP- or nicorandil-sensitive arrhythmias were not sensitive to verapamil. On the other hand, 3 of the ATP-insensitive arrhythmias were sensitive to neither nicorandil nor verapamil. The QT intervals and QTc were shortened by nicorandil in 5 of the 6 patients who were sensitive to all 3 drugs. One mechanism of suppression by nicorandil could be related to less Ca++ entering the myocardium, which would decrease the duration of the action potential as indicated by the shortened QT intervals. The results suggest that the mechanism of some ventricular arrhythmias is related to triggered activity. Arrhythmias that are sensitive to ATP or nicorandil, but not to verapamil, may be caused by abnormal automaticity. On the other hand, arrhythmias that are insensitive to all 3 drugs might be related to reentry. The features of ventricular arrhythmias with LBBB pattern and inferior axis differ and therefore the causative mechanisms are not the same.
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Affiliation(s)
- Y Kobayashi
- The Third Department of Internal Medicine, Showa University School of Medicine, Tokyo, Japan.
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Tokuno T, Muraki K, Watanabe M, Imaizumi Y. Effects of K+ channel modulators on the relationship between action potential duration and Ca2+ transients in single ventricular myocytes of the guinea pig. JAPANESE JOURNAL OF PHARMACOLOGY 1999; 80:243-53. [PMID: 10461770 DOI: 10.1254/jjp.80.243] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Effects of K+ channel modulators, cromakalim and E4031 [1-[2-(6-methyl-2-pyridyl)-ethyl]-4-(4-methylsulfonylaminobenzoyl) piperidine], on the relationship between the action potential duration (APD) and Ca2+ transients were examined in single myocytes isolated from guinea pig cardiac left ventricle. Application of cromakalim decreased APD at 90% repolarization (APD90) and Ca2+ transient elicited at 0.5 Hz (IC50s=0.6 and 3 microM, respectively). Application of 0.3 microM E4031 increased these parameters by 110% and 45%, respectively. Under voltage-clamp, the relation between the duration of depolarization to 0 mV and Ca2+ transients could be described by the sum of two exponential components; the time constants were approximately 5 and 280 msec, respectively. The first component was abolished by 10 microM ryanodine, suggesting the involvement of Ca2+-induced Ca2+ release (CICR). Neither cromakalim nor E4031 directly affected Ca2+ current and Ca2+ transients under voltage clamp. When APD was changed by K+ channel modulators, the relation between APD90 and Ca2+-transients was almost similar to that obtained by changing the depolarization duration under voltage-clamp. CICR was changed significantly only when APD90 was markedly shortened by cromakalim. The extensively prolonged AP and Ca2+ transient in the presence of E4031 were reduced by an addition of cromakalim. It is concluded that these two K+ channel modulators can significantly alter the AP-induced Ca2+ transient mainly by changing APD, which regulates both Ca2+ influx and extrusion.
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Affiliation(s)
- T Tokuno
- Department of Pharmacology & Therapeutics, Faculty of Pharmaceutical Sciences, Nagoya City University, Nagoya, Japan
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Nuss HB, Marbán E, Johns DC. Overexpression of a human potassium channel suppresses cardiac hyperexcitability in rabbit ventricular myocytes. J Clin Invest 1999; 103:889-96. [PMID: 10079110 PMCID: PMC408140 DOI: 10.1172/jci5073] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/1998] [Accepted: 02/09/1999] [Indexed: 11/17/2022] Open
Abstract
The high incidence of sudden death in heart failure may reflect abnormalities of repolarization and heightened susceptibility to arrhythmogenic early afterdepolarizations (EADs). We hypothesized that overexpression of the human K+ channel HERG (human ether-a-go-go-related gene) could enhance repolarization and suppress EADs. Adult rabbit ventricular myocytes were maintained in primary culture, which suffices to prolong action potentials and predisposes to EADs. To achieve efficient gene transfer, we created AdHERG, a recombinant adenovirus containing the HERG gene driven by a Rous sarcoma virus (RSV) promoter. The virally expressed HERG current exhibited pharmacologic and kinetic properties like those of native IKr. Transient outward currents in AdHERG-infected myocytes were similar in magnitude to those in control cells, while stimulated action potentials (0.2 Hz, 37 degrees C) were abbreviated compared with controls. The occurrence of EADs during a train of action potentials was reduced by more than fourfold, and the relative refractory period was increased in AdHERG-infected myocytes compared with control cells. Gene transfer of delayed rectifier potassium channels represents a novel and effective strategy to suppress arrhythmias caused by unstable repolarization.
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Affiliation(s)
- H B Nuss
- Section of Molecular and Cellular Cardiology, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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