Impact of atrial fibrillation duration on postcardioversion recurrence

"Begetting," a mechanistic tenet of atrial fibrillation (AF), stipulates that the rate of recurrence of AF after cardioversion is proportional to the preceding arrhythmia duration. However, recent reports suggest that, for brief durations, the incidence of early recurrence of AF (ERAF) is inversely proportional to duration. These reports were based on potentially biased data.

We performed a prospective study to examine the impact of AF duration on postcardioversion recurrence.

Forty-four patients underwent placement of an implantable cardioverter-defibrillator (ICD) capable of delivering patient-elicited AF cardioversion shocks. Subsequently, in the ambulatory setting, the timing of shocks in relationship to perceived AF onset was randomly assigned within individuals to early (as soon as possible) or delayed (1 day later).

During a follow-up averaging 199 days per patient, a total of 61 AF episodes among 17 patients occurred for which a patient-elicited cardioversion shock was delivered. Twenty-three shocks were delivered using early protocol (mean 6.8 hours after AF onset), and 38 shocks were delivered using delayed protocol (mean 34.7 hours after AF onset). The incidence of ERAF was significantly lower using the delayed protocol.

A strategy of approximately 24-hour delay in cardioversion shock timing decreased the incidence of ERAF, relative to a shock delivered within a few hours of AF onset. This observation has important mechanistic and therapeutic implications.