Document Detail

Improved safety factor for triphasic defibrillator waveforms.
MedLine Citation:
PMID:  2720918     Owner:  NLM     Status:  MEDLINE    
Newly developed biphasic waveforms improve defibrillation efficacy both by reduction of defibrillation threshold and by amelioration of shock-induced dysfunction depending on the relative shape of the first and second pulses. Each of these independent effects improves the waveform's safety factor, the ratio between the shock intensity that produces a specific degree of postshock dysfunction and the shock intensity that produces defibrillation (or cellular excitation). Symmetrical waveforms reduce defibrillation threshold to about 60% that of the corresponding monophasic waveform, probably by reduction of excitation threshold for ischemic cells, but increase postshock arrhythmias. Biphasic waveforms with 10% "tails" reduce postshock arrhythmias. This study tests the hypothesis that these independent mechanisms for improvement of defibrillation efficacy can be combined into a single triphasic waveform that will have a higher safety factor than either of the two biphasic waveforms of which it is composed. Cultured myocardial cells were subjected to high-intensity electric-field stimulation with a control monophasic rectangular waveform, a symmetrical biphasic waveform, and a triphasic waveform consisting of the biphasic waveform with an added 10% "tail." Each waveform portion was 5 msec in duration. Photocell mechanograms monitored contractile activity. We found that the duration of postshock arrest of spontaneous contractile activity increased with stimulus intensity for all waveforms. The voltage gradient producing a 4-second arrest after the biphasic waveform shock was 80.6 +/- 1.3% that of the control waveform (100%), while the voltage gradient for the triphasic waveforms was 87.1 +/- 0.73% of control. The difference between biphasic and triphasic waveforms was significant (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)
J L Jones; R E Jones
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Circulation research     Volume:  64     ISSN:  0009-7330     ISO Abbreviation:  Circ. Res.     Publication Date:  1989 Jun 
Date Detail:
Created Date:  1989-07-06     Completed Date:  1989-07-06     Revised Date:  2007-11-15    
Medline Journal Info:
Nlm Unique ID:  0047103     Medline TA:  Circ Res     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1172-7     Citation Subset:  IM    
Department of Physiology and Biophysics, School of Medicine, Georgetown University, Washington, DC 20037.
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MeSH Terms
Arrhythmias, Cardiac / physiopathology,  therapy
Cells, Cultured
Chick Embryo
Electric Countershock / instrumentation*,  methods
Myocardium / cytology
Grant Support

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