Objective: To investigate the initial energy level required for electrical cardioversion of atrial fibrillation (AF).
Methods: We studied patients undergoing electrical cardioversion in the 1st Multicenter Trial of SOCESP. Patients were divided into 2 groups according to the initial energy level of electrical cardioversion: 100J and >/=150J. We compared the efficacy of the initial and final shock of the procedure, the number of shocks administered, and the cumulative energy levels.
Results: Eight-six patients underwent electrical cardioversion. In 53 patients (62%), cardioversion was started with 100J, and in 33 patients (38%), cardioversion was started with >/=150J. Groups did not differ regarding clinical features and therapeutical interventions. A tendency existed towards greater efficacy of the initial shock in patients who received >/=150J (61% vs. 42% in the 100J group, p=0.08). The number of shocks was smaller in the >/=150J group (1.5+/-0.7 vs. 2.1+/-1.3, p=0.04). No difference existed regarding the final efficacy of electrical cardioversion and total cumulative energy levels in both groups. In the subgroup of patients with recent-onset AF (</=48h), the cumulative energy level was lower in the 100J group (240+/-227J vs. 324+/-225J, p=0.03).
Conclusion: Patients who were given initial energy of >/=150J received fewer counter shocks with a tendency toward greater success than those patients who were given 100J; however, in patients with recent-onset AF, the average cumulative energy level was lower in the 100J group. These data suggest that electrical cardioversion should be initiated with energy levels >/=150J in patients with chronic AF.