Document Detail

Ventricular refractory period extension caused by defibrillation shocks.
MedLine Citation:
PMID:  2394014     Owner:  NLM     Status:  MEDLINE    
In pentobarbital-anesthetized dogs, transcardiac shocks of up to 30 J or pacing stimuli were delivered to myocardial tissue at different times in the electrical cycle. When delivered midway or later into electrical systole, shocks, but not pacing stimuli, greatly extended the refractory period as determined by left ventricular pacing. There was a positive correlation between both the shock energy and timing and the amount of delay. A 30-J shock given 10 msec before the end of the refractory period extended the refractory period by 63 +/- 15 msec (p less than 0.001), whereas the same shock given 40 msec earlier produced only 25 +/- 10 msec (p less than 0.001) of extension. By comparison, a 5-J shock given at those times produced 36 +/- 18 (p less than 0.005) and 10 +/- 8 msec (p less than 0.001) of extension, respectively. When delivered early into electrical systole, both a pacing stimulus and a shock had no substantial effect on the tissue refractory period. Because the tissue that is late in electrical systole would otherwise be the first to repolarize if no shock were given, the selective refractory period extension may create a period after the shock during which no tissue is repolarized to a level sufficient for wavefront propagation. Thus, the energy- and time-dependent refractory period extension may help explain the mechanism by which ventricular defibrillation occurs during transcardiac shocks.
R J Sweeney; R M Gill; M I Steinberg; P R Reid
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Circulation     Volume:  82     ISSN:  0009-7322     ISO Abbreviation:  Circulation     Publication Date:  1990 Sep 
Date Detail:
Created Date:  1990-10-09     Completed Date:  1990-10-09     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0147763     Medline TA:  Circulation     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  965-72     Citation Subset:  AIM; IM    
Department of Electrophysiology Research, Eli Lilly and Company, Indianapolis, Ind. 46285.
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MeSH Terms
Cardiac Pacing, Artificial
Electric Countershock* / methods
Heart / physiology*
Heart Ventricles
Time Factors
Comment In:
Circulation. 1990 Sep;82(3):1064-6   [PMID:  2393994 ]

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