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Objective: Clinical success of atrial fibrillation ablation depends on persistent transmurality of the lesions. Although bipolar radiofrequency grants acute pulmonary vein isolation, the fate of such ablations in the clinical setting is unknown. We assessed postoperative pulmonary vein isolation up to 3 weeks after open chest bipolar radiofrequency ablation., Methods: Thirteen consecutive patients with mitral valve disease (mean age, 60 +/- 10 years) and atrial fibrillation undergoing concomitant ablation with the BP2 bipolar device (Medtronic, Inc, Minneapolis, Minn) were enrolled for electrophysiologic assessment. During surgery, pairs of additional temporary wires were positioned on the right pulmonary veins and on the roof of the left atrium before bipolar ablation. Entrance block (abatement or disconnection of electrogram potentials) and exit block (no entrainment during pulmonary vein pacing) of the right pulmonary veins and of the free left atrium were assessed before and after ablation. After right pulmonary vein isolation was obtained, one additional encircling line was added. Electrophysiologic assessment was repeated before discharge and at 3 weeks., Results: Baseline right pulmonary vein pacing threshold was 2.9 +/- 1.6 mA. After 3 +/- 1 encircling ablations, bidirectional block was attained in all pulmonary veins. At pre-discharge electrophysiologic study, complete isolation persisted in all cases. At 3 weeks, conduction block persisted in 11 (85%) of 13 patients. All patients were discharged in sinus rhythm. At follow-up (19 +/- 7 months), 12 (92%) of 13 patients were still free from atrial fibrillation., Conclusions: Irrigated bipolar radiofrequency ablation provides acute transmurality after multiple ablations. However, total recovery of conduction occurred in 15% of the patients after 3 weeks. Repeated multiple ablations, possibly complemented by block validation, are suggested to help achieve durable transmurality with such technology., (2010 The American Association for Thoracic Surgery. Published by Mosby, Inc. All rights reserved.)