Document Detail

Reduced arrhythmogenicity of biphasic versus monophasic T-wave shocks. Implications for defibrillation efficacy.
MedLine Citation:
PMID:  8873676     Owner:  NLM     Status:  MEDLINE    
BACKGROUND: Biphasic waveforms defibrillate more effectively than monophasic waveforms; however, the mechanism remains unknown. The "upper-limit-of-vulnerability" hypothesis of defibrillation suggests that unsuccessful defibrillation is due to reinduction of ventricular fibrillation (VF). Thus, VF induction mechanisms may be important for the understanding of defibrillation mechanisms. We therefore compared myocardial VF vulnerability for monophasic versus biphasic shocks. METHODS AND RESULTS: In 10 Langendorff-perfused rabbit hearts, monophasic and biphasic T-wave shocks were randomly administered over a wide range of shock coupling intervals and shock strengths, and the two-dimensional coordinates within which VF was induced were used to calculate the area of vulnerability (AOV) for both shock waveforms. The arrhythmic response to biphasic shocks differed from that to monophasic shocks in three distinct ways: (1) the AOV was smaller (8.9 +/- 4.2 versus 13.9 +/- 6.0 area units, P < .02), (2) the transition zone between VF-inducing and nonarrhythmogenic shocks was narrower (14.7 +/- 4.8 versus 29.9 +/- 6.4 area units, P < .001), and (3) the entire AOV shifted toward longer coupling intervals (by 11.0 +/- 8.8 ms at the left border [P < .005] and 6.0 +/- 5.2 ms at the right border [P = .005] of the AOV). CONCLUSIONS: Biphasic shocks encounter a smaller AOV than monophasic shocks, a narrower transition zone from VF to no arrhythmia induction, and a lesser effectiveness in inducing VF at short coupling intervals. In keeping with the upper-limit-of-vulnerability hypothesis, these waveform-dependent differences in VF inducibility might help explain the lower defibrillation threshold for biphasic shocks.
S Behrens; C Li; P Kirchhof; F L Fabritz; M R Franz
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Publication Detail:
Type:  In Vitro; Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Circulation     Volume:  94     ISSN:  0009-7322     ISO Abbreviation:  Circulation     Publication Date:  1996 Oct 
Date Detail:
Created Date:  1996-12-16     Completed Date:  1996-12-16     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0147763     Medline TA:  Circulation     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1974-80     Citation Subset:  AIM; IM    
Cardiology Division, Veterans Administration Medical Center, Washington, DC 20422, USA.
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MeSH Terms
Differential Threshold
Electric Countershock / methods*
Ventricular Fibrillation / etiology*,  physiopathology
Ventricular Function

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

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