Document Detail

Defibrillation efficacy using high-frequency switching to proportion current among simultaneous shock pathways.
MedLine Citation:
PMID:  9083877     Owner:  NLM     Status:  MEDLINE    
INTRODUCTION: Multiple-pathway electrode configurations generally allow improved current distribution over the heart and lower defibrillation thresholds than single-pathway systems. However, current distributions using multiple pathways are largely determined by electrode type and location. We hypothesized that switching the current among multiple pathways at high frequency (HF) could allow the switching duty cycle to control the proportion of time-averaged current flowing in each pathway, thus permitting altered (possibly improved) defibrillation efficacy using the same electrodes and shock waveform. METHODS AND RESULTS: In dogs, we measured the current (I50) for 50% defibrillation success using catheter electrodes in the right ventricular apex (cathode) and superior vena cava (A-pathway anode) and a subcutaneous patch on the left chest wall (B-pathway anode). In group 1 (N = 7), we measured I50s for shocks that used HF to proportion 10% to 90% of the current to the A-pathway. Shocks with 10% to 30% of the current in the A-pathway had significantly lowr I50s than nonproportioned shocks using all three electrodes. However, the resistance differed among single and simultaneous pathways so energy did not necessarily parallel these changes. In group 2 (N = 6), we measured I50s for shocks to the B-pathway alone, for nonproportioned shocks to A and B, and for shocks that proportioned 80% of the current to the B-pathway using either HF, sequential, or amplitude proportioning methods. All proportioning methods had similar I50s that were significantly lower than the I50 for nonproportioned shocks to A and B and that were comparable to shocks to the B-pathway alone. CONCLUSIONS: Shocks with most current proportioned to the B-pathway had lower defibrillation currents than nonproportioned shocks using both pathways. Thus, defibrillation efficacy was changed by HF proportioning without changing the electrodes or shock waveform. These findings suggest that HF proportioning may be a method to improve defibrillation.
R J Sweeney; R M Gill; P R Reid
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of cardiovascular electrophysiology     Volume:  8     ISSN:  1045-3873     ISO Abbreviation:  J. Cardiovasc. Electrophysiol.     Publication Date:  1997 Mar 
Date Detail:
Created Date:  1997-05-22     Completed Date:  1997-05-22     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  9010756     Medline TA:  J Cardiovasc Electrophysiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  271-80     Citation Subset:  IM    
Department of Electrophysiology Research, Lilly Research Laboratories Division, Eli Lilly and Co., Indianapolis, Indiana, USA.
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MeSH Terms
Electric Countershock / methods*

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