Real-time Control during Cardiac Defibrillation

The mechanisms of cardiac defibrillation
are the subject of major interest in the treatment of human heart disorders. Significant progress in the understanding of defibrillatory action has been made recently through advanced high-resolution mapping studies. The research focus has now advanced from the traditional empirical approach to the mechanistic interactions of shocks and wavefront propagation. Recent progress in optical imaging techniques has enabled such studies to produce detailed spatial information of the transmembrane potential (Vm) distribution around the entire heart throughout the defibrillation episode, providing unobstructed panoramic views of the epicardial wavefronts. Similarly, experimental results using optical imaging have promoted the concept of cardiac bidomain from theoretical considerations to a valid representation of myocardium, thus generating new hypotheses in defibrillation mechanism and prompting the necessity to re-evaluate traditional ones.

Our Focus is the study of basic defibrillation mechanisms from the perspective of cardiac bidomain. We are making the first attempt to use dynamic high resolution (Vm) images interactively in defibrillation by including the imaging result as a feedback component in a real-time, intelligent multi-electrode shock delivery system. The interactive shock system allows the test of important hypotheses pertaining to the mechanisms of defibrillation, which historically have been examined empirically without such a capability.

We're investigating (1) the interaction of direct activation sites with the tissue status during the shock; (2) the optimal timing for the shock delivery during different stages of the formation of a reentry pattern; and (3) the optimal timing and sites to deliver the shock during the interaction of multiple spiral reentry patterns. By combining various predictions and hypotheses related to the concept of bidomain continuum for syncytial cardiac tissue, it is expected that the results from this proposal will offer new insights of the defibrillation mechanisms based on spatio-temporal wavefront interactions as predicted by the cardiac bidomain, and could provide practical guidelines for future improvement of arrhythmia intervention.

Marc Lin
marc.lin@vanderbilt.edu