Document Detail

Mechanism of repolarization alternans has restitution of action potential duration dependent and independent components.
MedLine Citation:
PMID:  16426408     Owner:  NLM     Status:  MEDLINE    
INTRODUCTION: Investigation of relationship between diastolic-interval (DI)-dependent restitution of action potential duration (APD) and alternans of APD has produced conflicting results. We used a novel pacing protocol to determine the role of restitution in alternans by minimizing changes in DI preceding each activation. METHODS: Transmembrane potentials were recorded from right ventricular endocardial tissue isolated from five dogs. We used three pacing sequences: (i) The tissue was paced at a constant DI for 100 beats. (ii) The DIs were changed randomly between two sequences of constant DI. (iii) Each constant DI trial was followed by constant cycle length trial where pacing cycle length was equal to average cycle length during previous constant DI trial. RESULTS: Alternans of APD occurred even when DIs preceding each activation were invariant. Slopes of restitution during constant DI pacing were both negative and positive and were much larger than unity. Alternans amplitude during constant cycle length pacing was larger than during constant DI, 32.2 +/- 12.3 versus 7.5 +/- 2.8 msec, P < 0.01. Random perturbation of DI decreased alternans amplitude during constant DI pacing from 14.7 +/- 4.8 to 10.5 +/- 3.4 msec, P < 0.01. CONCLUSION: Our results indicate that mechanism of repolarization alternans has restitution-dependent and restitution-independent components. However, our results also provide direct evidence that shows that DI-dependent restitution of APD is not a necessary mechanism for the alternans to exist. Ability to pace with explicit control of DI provides a novel approach to dissect mechanisms of alternans into restitution-dependent and restitution-independent effects.
Runze Wu; Abhijit Patwardhan
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Publication Detail:
Type:  Comparative Study; In Vitro; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of cardiovascular electrophysiology     Volume:  17     ISSN:  1045-3873     ISO Abbreviation:  J. Cardiovasc. Electrophysiol.     Publication Date:  2006 Jan 
Date Detail:
Created Date:  2006-01-23     Completed Date:  2006-05-04     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  9010756     Medline TA:  J Cardiovasc Electrophysiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  87-93     Citation Subset:  IM    
Center for Biomedical Engineering, University of Kentucky, Lexington, Kentucky 40506-0700, USA.
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MeSH Terms
Action Potentials / physiology
Cardiac Pacing, Artificial
Diastole / physiology
Endocardium / cytology,  physiology*
Heart Ventricles / cytology
Myocardial Contraction / physiology*
Patch-Clamp Techniques / instrumentation
Ventricular Function*
Comment In:
J Cardiovasc Electrophysiol. 2006 Jan;17(1):94-6   [PMID:  16426409 ]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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