The effects of second and third phase duration on defibrillation efficacy of triphasic rectangle waveforms

Area of Science:

• Cardiovascular Research
• Biomedical Engineering
• Electrophysiology

Background:

• Biphasic waveforms are more effective than monophasic waveforms for terminating ventricular fibrillation (VF).
• The superiority of triphasic waveforms over biphasic waveforms for VF termination remains debated.
• This study investigates triphasic rectangle waveform efficacy by analyzing second and third phase durations in a rabbit VF model.

Purpose of the Study:

• To evaluate the impact of second and third phase durations of triphasic rectangle waveforms on defibrillation efficacy.
• To compare the defibrillation threshold (DFT) of optimized triphasic waveforms against standard biphasic waveforms.
• To determine optimal parameters for triphasic waveform design in ventricular defibrillation.

Main Methods:

• Ventricular fibrillation (VF) was induced in 20 New Zealand rabbits and untreated for 30 seconds.
• Defibrillation was attempted using one of seven waveforms: six triphasic rectangle waveforms and one biphasic rectangle waveform.
• A 5-step up-and-down protocol determined the defibrillation threshold (DFT), with procedures repeated after a 5-minute interval.

Main Results:

• Two triphasic waveforms with identical first and second phase durations but shorter third phase durations showed significantly lower DFT energy compared to biphasic waveforms (0.57±0.18J and 0.60±0.18J vs. 0.80±0.28J).
• No significant difference in DFT energy was found between triphasic waveforms with identical phase durations but varying voltages.
• The results indicate that phase duration, particularly the third phase, is critical for triphasic waveform performance.

Conclusions:

• Phase durations are the primary determinant of defibrillation success for triphasic rectangle waveforms.
• Optimal triphasic rectangle waveforms, characterized by identical first and second phase durations and a shorter third phase, outperform biphasic waveforms in ventricular defibrillation.
• These findings suggest that tailored triphasic waveforms offer enhanced efficacy for treating ventricular fibrillation.