The effects of phase duration on defibrillation success of dual time constant biphasic waveforms

Yi Shan, Giuseppe Ristagno, Marc Fuller, Shijie Sun, Yongqin Li, Max Harry Weil, James Russell, Wanchun Tang

Research output: Contribution to journalArticlepeer-review


Aim of Study: The effects of first and second phase duration of biphasic waveforms on defibrillation success were evaluated in a guinea pig model of ventricular fibrillation (VF). We hypothesized that waveform duration, and especially the first phase duration, played a main role on defibrillation efficacy in comparison to energy, current and voltage, when a dual time constant biphasic shock was employed. Methods: VF was induced and untreated for 5 s in 30 male guinea pigs, prior to attempting a single defibrillatory shock with one of 5 defibrillation waveforms which had different durations of the first and second phase. A five step up-down protocol was utilized for determining the defibrillation efficacy. After a 3-min interval, the procedure was repeated. A total of 25 cardiac arrest events and defibrillations were investigated for each animal. Results: The defibrillation waveforms with an intermediate first phase of 5 ms, yielded the highest defibrillation success (p <0.05). These waveforms also presented significantly lower energy, current and voltage in comparison to waveforms with shorter or longer first phase durations (p <0.001). However, no differences on defibrillation success were observed among waveforms with different second phase durations varying from 1.5 ms to 3.5 ms. Conclusions: For dual time constant biphasic waveforms, the first phase duration played a main role on defibrillation success. The intermediate first phase duration of 5 ms, yielded the best defibrillation efficacy compared with shorter or longer first phase durations. While the second phase duration did not affect defibrillation outcomes.

Original languageEnglish
Pages (from-to)236-241
Number of pages6
Issue number2
Publication statusPublished - Feb 2010


  • Defibrillation efficacy
  • Dual time constant defibrillation waveform
  • Ventricular fibrillation
  • Waveform duration

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine
  • Emergency
  • Emergency Medicine


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