Abstract
Electrical defibrillation is a well-established treatment for cardiac dysrhythmias. Studies have suggested that shock-induced spatial sawtooth patterns and virtual electrodes are responsible for defibrillation efficacy. We hypothesize that high-frequency shocks enhance defibrillation efficacy by generating temporal sawtooth patterns and using rapid virtual electrodes synchronized with shock frequency. High-speed optical mapping was performed on isolated rat hearts at 2000 frames/s. Two defibrillation electrodes were placed on opposite sides of the ventricles. An S1-S2 pacing protocol was used to induce ventricular tachyarrhythmia (VTA). High-frequency shocks of equal energy but varying frequencies of 125–1000 Hz were used to evaluate VTA vulnerability and defibrillation success rate. The 1000-Hz shock had the highest VTA induction rate in the shorter S1-S2 intervals (50 and 100 ms) and the highest VTA defibrillation rate (70%) among all frequencies. Temporal sawtooth patterns and synchronous shock-induced virtual electrode responses could be observed with frequencies of up to 1000 Hz. The improved defibrillation outcome with high-frequency shocks suggests a lower energy requirement than that of low-frequency shocks for successful ventricular defibrillation.
Highlights
Ventricular tachyarrhythmia (VTA), which includes ventricular tachycardia and ventricular fibrillation, is a major cause of sudden cardiac death [1]
Tissue response observed using optical mapping revealed that the virtual cathode and anode continued to appear backward and forward on the heart surface during electrical shocks
The main findings of this study are as follows: (1) temporal sawtooth patterns can be observed using optical mapping during high-frequency shocks, (2) repeated virtual electrode responses prolonged postshock action potential and tissue refractoriness, (3) high-frequency defibrillation waveforms coupled with short S1-S2 intervals produced the highest VTA vulnerability and defibrillation success rates, and (4) the action potential rise time and isochronal maps of shock-induced optical potentials are the same irrespective of shock frequency
Summary
Ventricular tachyarrhythmia (VTA), which includes ventricular tachycardia and ventricular fibrillation, is a major cause of sudden cardiac death [1]. High-frequency biphasic shocks enhance ventricular fibrillation vulnerability providing new insights into complicated VTA activation patterns and defibrillation mechanisms [2,3,4,5]. The first theory at the cell level is the sawtooth hypothesis, which posits that a chain of cells interconnected by highresistance gap junctions can generate a sawtooth pattern during the shock [6,7,8,9]. The temporal sawtooth pattern was observed at the tissue level during high-frequency defibrillation. This phenomenon may support the defibrillation propagation mechanism and improve defibrillation efficacy
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