PHASE-ANGLE CONVERGENCE OF MULTIPLE MONOPHASIC ACTION-POTENTIAL RECORDINGS PRECEDES SPONTANEOUS TERMINATION OF VENTRICULAR-FIBRILLATION

Aims To elucidate the mechanism of spontaneous termination of ventricu lar fibrillation (VF) and to define an indicator of its occurrence, th e phase angle, a novel measure to assess synchrony of activation, was evaluated. Methods and results In 7 isolated rabbit hearts, 7 monophas ic action potentials were recorded simultaneously. Ventricular fibrill ation was induced by T wave shocks. Cycle lengths (CL) and phase angle s between all 7 recordings were analyzed until spontaneous termination or shock-induced defibrillation. Average phase angle was calculated a s activation time difference to a reference channel and expressed as a fraction of the reference channel's CL with I equaling a complete CL. Initial CLs and phase angles were similar in sustained and terminatin g episodes (CL: 141 +/- 16 ms vs 142 +/- 24 ms, phase angle: 0.244 +/- 0.11 vs 0.263 +/- 0.1, p = NS), During spontaneous termination, CL in creased slightly by 7 %. Average phase angle converged gradually over the last three activations before termination of ventricular fibrillat ion by 22-48 % (p < 0.0005), eventually resulting in phase angles simi lar to paced rhythms directly prior to spontaneous termination of vent ricular fibrillation. Conclusions Gradual synchronization of activatio n is part of the electrophysiological mechanism resulting in spontaneo us ventricular fibrillation termination and can be detected three acti vations before termination. Phase angle convergence may be useful to d etect spontaneous termination of ventricular fibrillation.