Electrophysiological determinants of hypokalaemia-induced arrhythmogenicity in the guinea-pig heart

Hypokalaemia is an independent risk factor contributing to arrhythmic death in cardiac patients. In the present study, we explored the mechanisms of hypokalaemia-induced tachyarrhythmias by measuring ventricular refractoriness, spatial repolarization gradients, and ventricular conduction time in iso...

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Bibliographic Details
Published in:	Acta Physiologica Vol. 197; no. 4; pp. 273 - 287
Main Authors:	Osadchii, O.E, Olesen, S.P
Format:	Journal Article
Language:	English
Published:	Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01-12-2009 Blackwell Publishing Ltd Wiley-Blackwell
Subjects:	Action Potentials - physiology Animals arrhythmia Arrhythmias, Cardiac - etiology Arrhythmias, Cardiac - physiopathology Biological and medical sciences cardiac arrhythmia dispersion of repolarization Electric Stimulation Electrocardiography Female Fundamental and applied biological sciences. Psychology Guinea Pigs Heart - physiopathology Heart Conduction System - physiology Heart Conduction System - physiopathology Heart Ventricles - physiopathology Humans hypokalaemia Hypokalemia - complications Myocardial Contraction - physiology ventricular conduction ventricular refractoriness Vertebrates: anatomy and physiology, studies on body, several organs or systems Heart Repolarization Hydroelectrolytic balance disorder Arrhythmia cardiac arrhythmia hypokalaemia Rodentia Electrophysiology dispersion of repolarization Cardiovascular disease ventricular refractoriness Inorganic element ventricular conduction Metabolic disorder Vertebrata Mammalia Guinea pig Heart disease Hypokaliemia Circulatory system Potassium
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Summary:	Hypokalaemia is an independent risk factor contributing to arrhythmic death in cardiac patients. In the present study, we explored the mechanisms of hypokalaemia-induced tachyarrhythmias by measuring ventricular refractoriness, spatial repolarization gradients, and ventricular conduction time in isolated, perfused guinea-pig heart preparations. Epicardial and endocardial monophasic action potentials from distinct left ventricular (LV) and right ventricular (RV) recording sites were monitored simultaneously with volume-conducted electrocardiogram (ECG) during steady-state pacing and following a premature extrastimulus application at progressively reducing coupling stimulation intervals in normokalaemic and hypokalaemic conditions. Hypokalaemic perfusion (2.5 m m K⁺ for 30 min) markedly increased the inducibility of tachyarrhythmias by programmed ventricular stimulation and rapid pacing, prolonged ventricular repolarization and shortened LV epicardial and endocardial effective refractory periods, thereby increasing the critical interval for LV re-excitation. Hypokalaemia increased the RV-to-LV transepicardial repolarization gradients but had no effect on transmural dispersion of APD₉₀ and refractoriness across the LV wall. As determined by local activation time recordings, the LV-to-RV transepicardial conduction and the LV transmural (epicardial-to-endocardial) conduction were slowed in hypokalaemic heart preparations. This change was attributed to depressed diastolic excitability as evidenced by increased ventricular pacing thresholds. These findings suggest that hypokalaemia-induced arrhythmogenicity is attributed to shortened LV refractoriness, increased critical intervals for LV re-excitation, amplified RV-to-LV transepicardial repolarization gradients and slowed ventricular conduction in the guinea-pig heart.
Bibliography:	http://dx.doi.org/10.1111/j.1748-1716.2009.02028.x istex:946B29DF2E513C74F62D1A9066874C51669E9C80 ark:/67375/WNG-5X007R45-S ArticleID:APHA2028 ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	1748-1708 1748-1716
DOI:	10.1111/j.1748-1716.2009.02028.x