Document Detail

Improved internal defibrillation success with shocks timed to the morphology electrogram.
MedLine Citation:
PMID:  9727552     Owner:  NLM     Status:  MEDLINE    
BACKGROUND: A previous retrospective study by our group suggested that shocks timed to the upslope of the shocking lead electrogram improved defibrillation efficacy. The goal of this study was to prospectively determine whether defibrillation threshold could be reduced by use of an algorithm that timed shocks to the upslope of coarse ventricular fibrillation (test treatment) compared with shocks delivered asynchronously after 10 seconds of fibrillation (control treatment). METHODS AND RESULTS: Ten pigs were instrumented with a 3-lead system for internal defibrillation. Initial estimates of the energy required to achieve defibrillation E50 for both treatments were made by an up/down method. Subsequently, additional shocks at V50+/-10% and V50-20% were given for each treatment to obtain data points at higher and lower intensities. Probability-of-success curves were estimated for both treatments by the best-fit method. Energies required were significantly lower for the timed shocks than for the asynchronous shocks (P<0.00 1). E80 was reduced 15.5%, from 27.1+/-2.5 to 22.9+/-1.8 J (P<0.002). The width of the probability-of-success curve (E80-E20) for the test treatment was also significantly narrower than that for the control treatment (7.1+/-0.9 versus 10.8+/-1.7, P<0.01). Normalized curve width (E80-E20)/E50 was decreased from 51+/-5% of E50 for control shocks to 37+/-4% of E50 for synchronous shocks (P<0.02). CONCLUSIONS: In this model, defibrillation threshold is lower and more deterministic when shocks are timed to the upslope of the shocking lead electrogram. If a similar reduction is observed in humans, shock timing may lower defibrillation threshold and simplify programming of shock intensity.
W Hsu; Y Lin; D J Lang; J L Jones
Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Circulation     Volume:  98     ISSN:  0009-7322     ISO Abbreviation:  Circulation     Publication Date:  1998 Aug 
Date Detail:
Created Date:  1998-09-17     Completed Date:  1998-09-17     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0147763     Medline TA:  Circulation     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  808-12     Citation Subset:  AIM; IM    
Department of Tachyarrhythmia Research, CPI/Guidant, St Paul, Minn, USA.
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MeSH Terms
Electric Countershock*
Prospective Studies
Time Factors
Treatment Outcome
Grant Support

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

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