From defibrillation theory to clinical implications.

Area of Science:

• Cardiovascular Research
• Biomedical Engineering
• Electrophysiology

Background:

• Defibrillation theory posits mean voltage threshold is hyperbolic to pulse duration.
• Voltages below rheobase are counterproductive; truncation at rheobase yields minimal stored energy.
• Animal experiments were conducted to validate this defibrillation theory.

Purpose of the Study:

• To experimentally verify or falsify the theory on defibrillation thresholds.
• To determine the optimal pulse truncation strategy for minimizing stored energy.
• To investigate the relationship between pulse duration, voltage, and stored energy.

Main Methods:

• 212 defibrillation thresholds in 22 swine were determined using biphasic pulses.
• 92 pulses were optimally truncated in phase 1.
• A step-up test procedure defined the threshold as the first successful shock.

Main Results:

• Experimental proof confirms truncation at the rheobase condition yields the lowest stored energy.
• Lower output capacitances significantly reduce energy requirements.
• Deviations from optimal pulse duration (shorter or longer) increase energy demands.

Conclusions:

• Truncation above or below rheobase increases stored energy thresholds.
• Average voltage during pulse duration is a hyperbolic function of pulse duration.
• Clinical implications include abandoning the constant tilt concept for optimal truncation in implantable cardioverter defibrillators (ICDs) and reducing output capacitance.