Improved defibrillation efficacy with an ascending ramp waveform in humans

Area of Science:

• Cardiovascular medicine
• Biomedical engineering
• Electrophysiology

Background:

• Animal studies indicated ascending ramp (RAMP) waveforms may have lower defibrillation thresholds (DFT) than biphasic truncated exponential (BTE) waveforms.
• Previous research suggests potential advantages of RAMP waveforms in defibrillation efficacy.

Purpose of the Study:

• To compare the efficacy of an ascending ramp waveform (RAMP) against a standard biphasic truncated exponential (BTE) waveform for human defibrillation.
• To evaluate defibrillation threshold (DFT) and upper limit of vulnerability (ULV) for both RAMP and BTE waveforms.

Main Methods:

• 63 patients undergoing implantable cardioverter-defibrillator placement were studied.
• Two RAMP waveform variations (7-ms and 12-ms ascending first phase) were tested against BTE.
• Defibrillation threshold (DFT) and upper limit of vulnerability (ULV) were measured using a binary search protocol.

Main Results:

• The 7-ms RAMP waveform demonstrated a significantly lower delivered energy at DFT compared to BTE (P < .01).
• Both RAMP waveforms resulted in significantly lower maximal voltage at DFT compared to BTE (P < .01).
• A strong correlation between ULV and DFT was observed for both RAMP and BTE waveforms (P < .01).

Conclusions:

• The 7-ms ascending ramp waveform significantly reduced delivered energy (18%) and voltage (24%) at DFT, outperforming BTE.
• This study presents the first human data suggesting a waveform superior to BTE for defibrillation.
• ULV correlates with DFT for RAMP, supporting its use in device implantation protocols.