Document Detail


Effects of monophasic and biphasic shocks on action potentials during ventricular fibrillation in dogs.
MedLine Citation:
PMID:  8330375     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
This study determined the response of action potentials during ventricular fibrillation (VF) to timed monophasic and biphasic shocks. A floating glass microelectrode was used to record intracellularly from the anterior right ventricle in 10 open-chest dogs. After 10 seconds of electrically induced VF, 5-millisecond monophasic and 2.5/2.5-millisecond biphasic shocks or 16-millisecond monophasic and 8/8-millisecond biphasic shocks were given via mesh electrodes on either side of the microelectrode. Monophasic and biphasic truncated exponential shocks of 5 V/cm were given with coupling intervals timed from the beginning of a VF action potential to the shock ranging from 50 to 70 milliseconds in 5-millisecond increments. Each coupling interval for each waveform was tested during a different VF episode. The interval between successive activations during VF was 86 +/- 15 milliseconds (mean +/- SD). The refractory period during VF was 61 +/- 5 milliseconds for 5-millisecond monophasic shocks and 66 +/- 6 milliseconds for 2.5/2.5-millisecond biphasic shocks (P < .05). At each coupling interval, action potential duration at 50% repolarization (APD50) was significantly prolonged by the shocks compared with the mean preshock APD50 (P < .05). ADP50 duration increased significantly with increases in the coupling interval (P < .05) for both monophasic and biphasic waveforms. For all coupling intervals together, APD50 prolongation as a percent of the mean preshock APD50 was 170 +/- 55%, 192 +/- 45%, 151 +/- 44%, and 175 +/- 45% for 5- and 16-millisecond monophasic and 2.5/2.5- and 8/8-millisecond biphasic waveforms, respectively. This APD50 prolongation was greater for monophasic than biphasic shocks and was greater for longer than shorter waveforms (P < .05). Thus, during VF, (1) the refractory period for 5-V/cm truncated exponential waveforms lasting 5 milliseconds is approximately 75% of the VF activation interval; (2) the refractory period is shorter for monophasic than for comparable biphasic waveforms; (3) both monophasic and biphasic 5-V/cm shock fields cause prolongation of action potential duration; (4) prolongation of action potential duration increases as the coupling interval increases; and (5) prolongation of action potential duration is greater for monophasic shocks and for longer shock waveforms.
Authors:
X Zhou; P D Wolf; D L Rollins; Y Afework; W M Smith; R E Ideker
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Circulation research     Volume:  73     ISSN:  0009-7330     ISO Abbreviation:  Circ. Res.     Publication Date:  1993 Aug 
Date Detail:
Created Date:  1993-08-16     Completed Date:  1993-08-16     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0047103     Medline TA:  Circ Res     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  325-34     Citation Subset:  IM    
Affiliation:
Department of Medicine, Duke University Medical Center, Durham, N.C.
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MeSH Terms
Descriptor/Qualifier:
Action Potentials
Animals
Dogs
Electric Countershock / methods*
Microelectrodes
Myocardium / pathology
Reaction Time
Refractory Period, Electrophysiological
Ventricular Fibrillation / pathology,  physiopathology*
Grant Support
ID/Acronym/Agency:
HL-28429/HL/NHLBI NIH HHS; HL-33637/HL/NHLBI NIH HHS; HL-42760/HL/NHLBI NIH HHS

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


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