Electrophysiological Findings in Patients Undergoing Surgical Cryo-ablation for Treatment of Atrial Fibrillation

Objectives Current recommendations support surgical treatment of atrial fibrillation (AF) in patients indicated for cardiac surgery. These procedures are referred to as concomitant and may be carried out using radiofrequency energy or cryo-ablation. This study aimed to assess the electrophysiological findings in patients undergoing concomitant cryo-ablation. Methods Patients with non-paroxysmal AF undergoing coronary artery bypass grafting and/or valve repair/replacement were included in the trial if concomitant cryo-ablation was part of the treatment plan according to current guidelines. The patients were assigned to undergo radiofrequency catheter ablation (RFCA), i.e., hybrid treatment, as a part of the multicenter trial. Results We analyzed 103 patients who underwent RFCA 105±35 days after surgery. Left and right pulmonary veins (PVs) were found isolated in 65 (63.1%) and 63 (61.2%) patients, respectively. The LA posterior wall isolation and mitral isthmus conduction block were found in 38 (36.9%) and 18 (20.0%) patients, respectively. Electrical reconnections (gaps) in the left PVs were more often localized superiorly than inferiorly (57.9% vs. 26.3%, P=0.005) and anteriorly than posteriorly (65.8% vs. 31.6%, P=0.003). Gaps in the right PVs were more equally distributed anteroposteriorly but dominated in superior segments (72.5% vs. 40.0%, P=0.003). There was a higher number of gaps on the roof line compared to the inferior line (131 (67.2%) vs. 67 (42.2%), P <0.001). Compared to epicardial cryo-ablation, endocardial was more effective in creating PVs and LA posterior wall isolation (P <0.05). Cryo-ablation using nitrous oxide (N 2 0) or argon (Ar) gas as cooling agents was similarly effective (P=NS). Conclusions The effectiveness of surgical cryo-ablation in achieving transmural and durable lesions in the left atrium is surprisingly low. Gaps are located predominantly in the superior and anterior portions of the PVs and on the roof line. Endocardial cryo-ablation is more effective than epicardial ablation, irrespective of the cooling agent used.