Atrial defibrillation threshold in humans minutes after atrial fibrillation induction - 'A stitch in time saves nine'

Alms To assess the effects of atrial fibrillation duration on the defibrill ation threshold in atrial fibrillation patients seconds or minutes after in itiation of the arrhythmia. Methods and Results Nineteen patients with recurrent symptomatic atrial fib rillation 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 10 min. After the specified period, interna l cardioversion was attempted using a balloon-guided catheter that allows t he delivery of biphasic shocks between one electrode array placed in the le ft pulmonary artery and a proximal electrode array on the lateral right atr ial wall. The defibrillation threshold was assessed with energy steps of 0. 5 J with a starting level of 0.5 J. Mean time from induction to successful defibrillation was 92 +/- 30 s after the 'ultrashort' period of atrial fibr illation and 910 +/- 86 s after the short period. The defibrillation thresh old was significantly greater after 10 min of atrial fibrillation than afte r 30 s of arrhythmia (2.32 +/- 0.61 J vs 1.31 +/- 0.66 J. P < 0.001). Clini cal data were not found to affect the defibrillation threshold. Conclusions Prolongation of atrial fibrillation over minutes in patients wi th paroxysmal arrhythmia increases the energy requirements for Successful d efibrillation. (Eur Heart J 2001; 22: 1613-1617, doi:10.1053/euhj.2000. 255 2) (C) 2001 The European Society of Cardiology.