Document Detail


Mechanisms of hypokalemia-induced ventricular arrhythmogenicity.
MedLine Citation:
PMID:  20584206     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Hypokalemia is a common biochemical finding in cardiac patients and may represent a side effect of diuretic therapy or result from endogenous activation of renin-angiotensin system and high adrenergic tone. Hypokalemia is independent risk factor contributing to reduced survival of cardiac patients and increased incidence of arrhythmic death. Animal studies demonstrate that hypokalemia-induced arrhythmogenicity is attributed to prolonged ventricular repolarization, slowed conduction, and abnormal pacemaker activity. The prolongation of ventricular repolarization in hypokalemic setting is caused by inhibition of outward potassium currents and often associated with increased propensity for early afterdepolarizations. Slowed conduction is attributed to membrane hyperpolarization and increased excitation threshold. Abnormal pacemaker activity is attributed to increased slope of diastolic depolarization in Purkinje fibers, as well as delayed afterdepolarizations caused by Ca2+ overload secondary to inhibition of Na+--K+ pump and stimulation of the reverse mode of the Na+--Ca2+ exchange. Hypokalemia effect on repolarization is not uniform at distinct ventricular sites thereby contributing to amplified spatial repolarization gradients which promote unidirectional conduction block. In hypokalemic heart preparations, the prolongation of action potential may be associated with shortening of effective refractory period, thus increasing the propensity for ventricular re-excitation over late phase of repolarization. Shortened refractoriness and slowed conduction contribute to reduced excitation wavelength thereby facilitating re-entry. The interplay of triggering factors (early and delayed afterdepolarizations, oscillatory prepotentials in Purkinje fibers) and a favorable electrophysiological substrate (unidirectional conduction block, reduced excitation wavelength, increased critical interval for ventricular re-excitation) may account for the mechanism of life-threatening tachyarrhythmias in hypokalemic patients.
Authors:
Oleg E Osadchii
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Publication Detail:
Type:  Journal Article; Review    
Journal Detail:
Title:  Fundamental & clinical pharmacology     Volume:  24     ISSN:  1472-8206     ISO Abbreviation:  Fundam Clin Pharmacol     Publication Date:  2010 Oct 
Date Detail:
Created Date:  2010-09-21     Completed Date:  2011-01-05     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8710411     Medline TA:  Fundam Clin Pharmacol     Country:  England    
Other Details:
Languages:  eng     Pagination:  547-59     Citation Subset:  IM    
Copyright Information:
© 2010 The Author Fundamental and Clinical Pharmacology © 2010 Société Française de Pharmacologie et de Thérapeutique.
Affiliation:
Department of Biomedical Sciences, The Danish National Research Foundation Centre for Cardiac Arrhythmia, The Panum Institute, University of Copenhagen, Blegdamsvej 3, 2200 Copenhagen N, Denmark. osadchii@mail.ru
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MeSH Terms
Descriptor/Qualifier:
Action Potentials
Animals
Arrhythmias, Cardiac / etiology,  physiopathology*
Electrophysiological Phenomena
Heart Conduction System / physiopathology
Humans
Hypokalemia / complications*
Risk Factors
Tachycardia, Ventricular / etiology,  physiopathology*
Ventricular Fibrillation / etiology,  physiopathology

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