Study of epicardial activation in low voltage gradient regions during a defibrillation shock with panoramic optical mapping

The authors have developed a new optical imaging system from which they can obtain time sequences of images representing the transmembrane potentials across the entire epicardial surface of the isolated rabbit heart. The authors processed these images to obtain quantitative timing and spatial information about the activation wavefronts immediately prior to (PrSA), during, and immediately after (PoSA) a defibrillation (DF) shock. The authors hypothesize that the spatiotemporal dynamics of the wavefronts at the time of a DF shock directly influence it's outcome. The authors delivered threshold level shocks with voltages that were not significantly different for successes (S) and failures (F). But a significantly higher percentage area of the low voltage gradient region (LVGR) was activated by PrSA in S compared to F episodes, while there was no significant difference in the extent of PrSA in the epicardium as a whole. It is concluded that the LVGR is a critical region where the extent of tissue activation is significant in determining the outcome of DF.