Atrial defibrillation threshold in humans minutes after atrial fibrillation induction. 'a stitch in time saves nine'

Abstract

Aims To assess the effects of atrial fibrillation duration on the defibrillation threshold in atrial fibrillation patients seconds or minutes after initiation of the arrhythmia. Methods and Results Nineteen patients with recurrent symptomatic atrial fibrillation were evaluated. After programmed induction of atrial fibrillation, the defibrillation threshold was assessed after two sequential periods of arrhythmia in the same patient: an ‘ultrashort’ period of 30s duration and a ‘short’ period, which lasted 10min. After the specified period, internal cardioversion was attempted using a balloon-guided catheter that allows the delivery of biphasic shocks between one electrode array placed in the left pulmonary artery and a proximal electrode array on the lateral right atrial wall. The defibrillation threshold was assessed with energy steps of 0·5J with a starting level of 0·5J. Mean time from induction to successful defibrillation was 92±30s after the ‘ultrashort’ period of atrial fibrillation and 910±86s after the short period. The defibrillation threshold was significantly greater after 10min of atrial fibrillation than after 30s of arrhythmia (2·32±0·61J vs 1·31±0·66J, PConclusions Prolongation of atrial fibrillation over minutes in patients with paroxysmal arrhythmia increases the energy requirements for successful defibrillation.