Document Detail

Improved efficacy of anodal biphasic defibrillation shocks following a failed defibrillation attempt.
MedLine Citation:
PMID:  10642128     Owner:  NLM     Status:  MEDLINE    
Although it is generally assumed that defibrillation becomes more difficult when the duration of VF is prolonged, after a failed defibrillation attempt, there is little information on the defibrillation efficacy of multiple shocks delivered at the same energy. The purpose of this study was to systematically examine the efficacy of a second shock delivered at the same or reversed polarity after a failed first shock. Defibrillation was attempted after 10 seconds of VF in 12 pigs (30-56 kg) using biphasic waveforms and a nonthoracotomy lead system. Shock energy was held constant for the first and second shocks at 50%-90% of the DFT. The second shock was delivered 10 seconds after a failed first shock. First and second shock polarity (first phase) was randomized to (+, +), (+, -), (-, -), (-, +). The incidence of successful defibrillation (for all polarities) was 12.3% for first and 49.1% for second shocks (P < 0.0001). Anodal first shocks had a 17.2% incidence of success as opposed to a 7.4% incidence of success with cathodal first shocks (P = 0.001). Anodal second shocks had a 55.5% incidence of success compared to a 42.7% incidence of success with cathodal second shocks (P = 0.008). There was no significant benefit from polarity reversal after a failed first shock (P = 0.29). In conclusion, less energy is required for successful defibrillation by a second shock after a failed first. The optimal configuration for first and second shocks is with the RV as anode. Polarity reversal of a second shock after a failed first does not affect the probability of second shock success.
P R Roberts; S Allen; D C Smith; J F Urban; D E Euler; M J Kallok; J M Morgan
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Pacing and clinical electrophysiology : PACE     Volume:  22     ISSN:  0147-8389     ISO Abbreviation:  Pacing Clin Electrophysiol     Publication Date:  1999 Dec 
Date Detail:
Created Date:  2000-02-03     Completed Date:  2000-02-03     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  7803944     Medline TA:  Pacing Clin Electrophysiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1753-9     Citation Subset:  IM    
Wessex Cardiothoracic Centre, Southampton General Hospital, United Kingdom.
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MeSH Terms
Electric Countershock / instrumentation,  methods*
Electric Impedance
Electric Stimulation
Heart Ventricles / physiopathology
Random Allocation
Time Factors
Treatment Outcome
Ventricular Fibrillation / physiopathology,  therapy*

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