Defibrillation using a high-frequency series of monophasic rectangular pulses: observations and model predictions

Area of Science:

• Biomedical Engineering
• Cardiovascular Research
• Electrical Engineering

Background:

• Capacitor-discharge waveforms are standard for defibrillation but may not be optimal.
• High-frequency (HF) pulse modulation offers potential for waveform shaping and improved defibrillation.
• Limited understanding exists regarding defibrillation efficacy with HF pulses.

Purpose of the Study:

• To investigate defibrillation thresholds using HF pulse series.
• To compare HF pulse defibrillation with continuous waveforms.
• To evaluate a filtered effective waveform model for HF defibrillation.

Main Methods:

• Tested defibrillation thresholds in dogs using continuous and HF pulse waveforms (5-20 ms durations, 100 Hz to 20 kHz).
• HF pulses utilized a 50% 'on-time' duty cycle.
• Measured time-averaged current, peak current, and energy requirements.

Main Results:

• Defibrillation with HF pulses (≥1 kHz) required similar time-averaged current but double the peak current and energy compared to continuous waveforms of the same duration.
• Lower frequencies showed defibrillation requirements approaching those of continuous waveforms.
• The heart's response to HF pulses mimicked a low-pass filter, accurately predicted by a model with a 3.7-ms time constant.

Conclusions:

• Defibrillation is feasible with HF pulses up to 20 kHz, exhibiting a low-pass filter-like frequency response.
• A filtered effective waveform model can predict HF defibrillation results and explain waveform influence on efficacy.
• Modulating HF pulses could lead to more efficacious defibrillation waveforms and reduced thresholds.