Document Detail

Effects of pacing rate and timing of defibrillation shock on the relation between the defibrillation threshold and the upper limit of vulnerability in open chest dogs.
MedLine Citation:
PMID:  1939961     Owner:  NLM     Status:  MEDLINE    
To test the relation between the defibrillation threshold and the upper limit of vulnerability, the shock strength associated with 50% probability of successful defibrillation (DFT50) and that associated with 50% probability of reaching the upper limit of vulnerability (ULV50) were determined in 20 open chest dogs with use of the delayed up-down method, with pacing drive cycle lengths of 150 to 500 ms and either single 6-ms shocks (10 dogs) or 12-ms biphasic shocks (10 dogs) given at the mid-upslope, peak and mid-downslope of the T wave of electrocardiographic lead II. The shocks were given by means of a patch-patch configuration on the anterior and posterior surfaces of the heart, which was paced from a stimulating electrode attached to the left ventricular apex. Analysis of variance showed no statistically significant differences in ULV50 as determined with different pacing cycle lengths. For monophasic shocks, DFT50 (331 +/- 66 V or 5.8 +/- 2.7 J) was not significantly different from ULV50 determined at the mid-upslope of the T wave (318 +/- 64 V or 5 +/- 2 J). The correlation coefficients between the two values were 0.74 (p = 0.014) for voltage and 0.67 (p = 0.034) for energy. In contrast, DFT50 was significantly higher than ULV50 as determined at the peak of the T wave (219 +/- 43 V or 2.3 +/- 1 J) and mid-downslope of the T wave (200 +/- 38 V or 1.9 +/- 0.9 J). In three dogs, ventricular fibrillation could not be induced at the mid-downslope of the T wave with any baseline pacing (Si) cycle length.(ABSTRACT TRUNCATED AT 250 WORDS)
P S Chen; G K Feld; M M Mower; B B Peters
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Journal of the American College of Cardiology     Volume:  18     ISSN:  0735-1097     ISO Abbreviation:  J. Am. Coll. Cardiol.     Publication Date:  1991 Nov 
Date Detail:
Created Date:  1991-12-13     Completed Date:  1991-12-13     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  8301365     Medline TA:  J Am Coll Cardiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1555-63     Citation Subset:  AIM; IM    
Department of Medicine, University of California, San Diego 92103-8411.
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MeSH Terms
Analysis of Variance
Cardiac Pacing, Artificial* / methods
Electric Countershock* / methods
Heart Ventricles / physiopathology*
Time Factors
Ventricular Fibrillation / physiopathology

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

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