Shock timing on high power spike of the morphology electrogram improves shock outcome: the study in defibrillator patients

Previous studies have demonstrated that pulse delivery timed on the upslope of a morphology electrogram (ME) during the high-voltage phase significantly improved the shock outcome. However, the mechanism is poorly understood. We hypothesised that the ME upslope may indicate the activation in the obtained segment of the myocardium. Recently, we found that reliable identification of local depolarization in the atrial fibrillatory signal can be achieved using adaptive estimation of the instantaneous signal power (P). The spikes of P reflected local activation in the mapped atrial site. The aim of this study was to investigate the relation of high-power ME spikes to the ventricular shock outcome and to the upslope. 575 ventricular fibrillation (VF) episodes recorded and stored during ICD (implantable cardioverter defibrillator) implantation in 77 patients were used for analysis