Minimal energy requirement for external cardioversion and catheter ablation for long-standing persistent atrial fibrillation.

Background: The minimal energy requirement (E _min ) for electrical cardioversion (ECV) reflects the atrial substrate in patients with long-standing persistent atrial fibrillation (L-PeAF), but the relationship between E _min ECV and radiofrequency catheter ablation (RFCA) has not yet been studied. We hypothesize that E _min ECV before ablation (E _min ECVpre) predicts clinical outcome of RFCA, and that catheter ablation reduces E _min ECVpost.
Methods: We included 172 patients with L-PeAF who underwent RFCA (79.7% males, 57.5±10.0 years) due to AF recurrence after ECV with an anti-arrhythmic drug (AAD). ECV began with 70J (patch electrode on anterior-posterior position) and was serially increased to 100, 150, 200, and 250J until sinus rhythm was achieved, at an average 5.0±5.6 months before RFCA. After RFCA, ECV was repeated (ECVpost) in 42 patients with recurrent AF that was not controlled by AAD.
Results: (1) During 34.8±20.0 months of follow-up after RFCA, 103 patients (59.9%) showed clinical recurrence of AF after RFCA. E _min ECVpre was significantly higher in patients with recurrent AF (129.0±58.6J) than those who remained in sinus rhythm (94.2±39.4J, p<0.001). (2) E _min ECVpre ≥150J (HR=3.31, 95% CI 2.18-5.03, p<0.001) and left atrial volume index (HR=1.02, 95% CI 1.00-1.04, p=0.021) were significantly associated with post-RFCA recurrence. (3) Shorter post-RFCA recurrence timing was also independently related to E _min ECVpre (β=-0.147, 95% CI -0.20 to -0.09, p<0.001). (4) Among 103 patients with recurrent AF after RFCA, 42 AAD-resistant AF patients underwent ECVpost. E _min ECVpost (100.9±50.8J) was significantly lower than E _min ECVpre (130.0±66.1J, p=0.006).
Conclusions: Higher E _min ECVpre was independently associated with clinical recurrence and earlier recurrence timing of AF after catheter ablation among patients with AAD-resistant L-PeAF. Catheter ablation for L-PeAF significantly reduces E _min ECV.
(Copyright © 2016 Japanese College of Cardiology. Published by Elsevier Ltd. All rights reserved.)