Abstract
Defibrillation of the heart by timely application of a strong electric shock is now recognized as the only effective means for prevention of sudden cardiac death, however understanding of the defibrillation mechanisms remains incomplete. While recent developments in experimental methodology have provided new characterizations of tissue responses to shocks, mechanistic inquiry into the success and failure of defibrillation is hampered by the inability of current optical mapping techniques to resolve electrical behavior confined to the depth of the ventricles during. We have recently developed a 3D finite-element model of stimulation/defibrillation of the rabbit ventricles. The model includes realistic geometry and fiber orientation, as well as blood in the cavities and a perfusing bath. Further, membrane models representing 1) normal kinetics, 2) kinetics under the conditions of global ischemia phases 1A and 1B, and 3) mechano-electric feedback via stretch-activated channels are also incorporated. In addition, we have developed simulated “optical maps” based on photon scattering in the rabbit ventricles, thus allowing us to reconstruct the averaging process taking place during optical mapping and to conduct meaningful comparisons between model and experimental data. This talk presents examples of electrophysiological studies employing the new modeling strategy. Vulnerability under normal and ischemic conditions as well as successful and failed defibrillation episodes are presented and the mechanisms underlying the observed behavior examined. [Jpn J Physiol 55 Suppl:S39 (2005)]
