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Related Experiment Videos

Optimization of biphasic waveforms for human nonthoracotomy defibrillation

J F Swartz1, R D Fletcher, P E Karasik

  • 1Department of Medicine, Uniformed Services University, Bethesda, Md.

Circulation
|December 1, 1993
PubMed
Summary
This summary is machine-generated.

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A 42/42 biphasic waveform significantly reduced defibrillation threshold (DFT) energy compared to monophasic shocks. This specific waveform shape is more effective than the 65/65 biphasic waveform for defibrillation.

Area of Science:

  • Cardiology
  • Biomedical Engineering
  • Electrophysiology

Background:

  • Biphasic waveforms are known to reduce defibrillation threshold (DFT) across various models.
  • Optimal biphasic waveform shape for DFT reduction in humans remains unclear despite studies on long-duration, high-tilt waveforms.

Purpose of the Study:

  • To investigate the impact of single capacitor biphasic waveform tilt modification on DFT in patients undergoing defibrillator implantation.
  • To compare the efficacy of different biphasic waveform configurations (65/65 vs. 42/42 tilt) against monophasic shocks.

Main Methods:

  • A paired study design was used with 18 patients receiving non-thoracotomy defibrillator implantation.
  • Defibrillation threshold was assessed using monophasic shocks and two types of biphasic waveforms: 65/65 tilt and 42/42 tilt.

Related Experiment Videos

  • Shocks were delivered via a right ventricular cathode to coronary sinus or superior vena cava lead and a subscapular patch.

    • Main Results:

    • The 65/65 biphasic waveform reduced stored energy DFT by 25% but did not significantly lower delivered energy DFT compared to monophasic shock.
    • The 42/42 biphasic waveform demonstrated a significant reduction in both stored energy (49%) and delivered energy (49%) DFT compared to monophasic shock.
    • The 42/42 biphasic waveform achieved a 39% lower delivered energy DFT than the 65/65 biphasic waveform.

    Conclusions:

    • Defibrillation threshold reduction by biphasic waveforms is an inherent electrophysiological property, independent of delivered energy.
    • Biphasic waveform tilt and phase amplitudes are critical determinants of defibrillation efficacy.
    • A 42/42 biphasic waveform is more efficacious for defibrillation than a 65/65 biphasic waveform, though the optimal configuration is still under investigation.