Post-shock spatial gradients of transmembrane potential as a source for post-shock activations during failed defibrillation

Recent studies suggest that defibrillation success is influenced by the production of new activations at (or after) the end of a post-shock refractory period. The authors examined if post-shock spatial gradients of transmembrane potential (GTMP) could serve as a possible source for electrotonically evoking post-shock activations. Previously measured action potential prolongations were used to mathematically model the post-shock recovery of tissue along a simple one-dimensional strip and to find GTMP. Following both monophasic and biphasic shocks, GTMP first increased and then decreased with time (peak at 65 to 90 ms). Peak GTMP decreased for stronger shocks and occurred earlier (/spl ap/15 ms) after biphasic shocks. These results are consistent with the effect of shock intensity and waveform on defibrillation and with the hypothesis that GTMP can cause defibrillation failure by evoking post-shock activations.