Document Detail

Shock timing lowers transvenous defibrillation energy requirement.
MedLine Citation:
PMID:  9988003     Owner:  NLM     Status:  MEDLINE    
Previous studies suggested that time periods exist during ventricular fibrillation when defibrillation shocks are more effective. However, there is no agreement on the amount of energy that can be saved or whether an implantable defibrillator can time shocks to these time periods. We conducted a study having two parts to investigate if there was any advantage to synchronizing internal defibrillation shocks to morphological patterns in ventricular fibrillation (VF). VF electrograms were recorded from the same three-electrode lead system used for internal defibrillation. In Part 1, we found no difference in the probability of successful defibrillation between shocks that were delivered into coarse and fine VF (48% vs 46%). However, shocks that were delivered to the upslope of coarse VF electrograms were more efficacious than those to the downslope of the waveform (67% vs 39%, P < .001). In the second study, we developed a real time computer system to prospectively deliver shocks on the upslope feature we identified in the first study. We found that the energy requirements at E50 and E80 were significantly lower for shocks delivered on the upslope of coarse VF than those delivered randomly at the end of 10 sec. We estimated a probability of success (POS) defibrillation curve using a maximum likelihood method for the timed and random shocks. The POS curve width was significantly narrower for shocks that were delivered to the upslope feature than the control treatment (7.1 +/- 0.9 vs. 10.8 +/- 1.7 J, P < 0.01). If these findings extend to clinical defibrillation, they may allow programming of internal defibrillators at lower energies. This could reduce potential postshock cardiac dysfunction, allow production of smaller devices, and improve battery life.
W Hsu; Y Lin; D J Lang; J L Jones
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Journal of electrocardiology     Volume:  31 Suppl     ISSN:  0022-0736     ISO Abbreviation:  J Electrocardiol     Publication Date:  1998  
Date Detail:
Created Date:  1999-04-13     Completed Date:  1999-04-13     Revised Date:  2009-11-11    
Medline Journal Info:
Nlm Unique ID:  0153605     Medline TA:  J Electrocardiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  35-40     Citation Subset:  IM    
Department of Tachyarrhythmia Research, CPI/Guidant, St. Paul, Minnesota, USA.
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MeSH Terms
Defibrillators, Implantable
Disease Models, Animal
Electric Countershock / methods*
Follow-Up Studies
Heart Rate
Prospective Studies
Random Allocation
Retrospective Studies
Treatment Outcome
Vena Cava, Superior
Ventricular Fibrillation / physiopathology,  therapy*
Grant Support

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

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