OBJECTIVES To study the incidence and mode of onset of early reinitiation of atrial fibrillation (ERAF) following successful internal cardioversion of chronic atrial fibrillation, and to determine the effects of sotalol in the prevention of ERAF.

DESIGN The incidence and modes of onset of ERAF and the acute effects of intravenous sotalol in the prevention of ERAF were studied retrospectively.

SETTING Electrophysiology laboratory at a university teaching hospital.

PATIENTS 64 patients, mean (SD) age 62 (10) years, who underwent internal cardioversion of chronic atrial fibrillation (mean duration of atrial fibrillation 31 (39) months).

MAIN OUTCOME MEASURES ECGs and intracardiac electrograms recorded during the internal cardioversion of atrial fibrillation using 3/3 ms biphasic, R wave synchronised shocks.

RESULTS 52 patients (81%) had successful electrical cardioversion, and 20 (31%) of these had ERAF during the procedure. There was no clinical predictor for the occurrence of ERAF. Fifty eight episodes of ERAF were observed. Five ERAF episodes (9%) had preceding bradycardia and 53 (91%) of these were triggered by atrial premature beats with normal preceding heart rate. Atrial premature beats that reinitiated atrial fibrillation had a shorter coupling interval (333 (43) msv 396 (100), p < 0.001) and a lower prematurity index (0.44 (0.11) v 0.55 (0.14), p < 0.001) than those that did not reinitiate atrial fibrillation. Repeated shock delivery and increasing the defibrillation energy did not prevent ERAF. Intravenous sotalol infusion decreased the numbers of atrial premature beats and prolonged their coupling interval, and prevented ERAF after repeated defibrillation in 83% of patients with ERAF.

CONCLUSIONS ERAF is a significant clinical problem after successful internal cardioversion of chronic atrial fibrillation, and was observed in up to 31% of patients. In most episodes, ERAF was triggered by short coupling atrial premature beats with preceding normal heart rate. Intravenous sotalol was effective in preventing ERAF in most cases.