Circumferential Ultrasound Ablation for Pulmonary Vein Isolation: Analysis of Acute and Chronic Failures

INTRODUCTION: In patients undergoing circumferential isolation of the pulmonary veins with an ultrasound ablation system, we analyzed the temperatures achieved while delivering circumferential ostial lesions in the pulmonary veins. We also reviewed the angiograms obtained during the procedure and identified anatomic variants that could be responsible for ineffective lesion formation. METHODS AND RESULTS: During the early clinical use in 33 patients, a total of 85 veins were ablated. A mean of 16.9 +/- 12.3 ablations were delivered per patient, and a mean of 6.7 ablations per vein were applied. Entry block was assessed by placing a deflectable octapolar or a circular catheter in the vein. The following anatomic characteristics and technical limitations were identified as possible reasons for ineffective energy delivery: (1) funnel-shaped ostium; (2) ostial diameter larger than the balloon diameter; (3) inability to deliver the catheter to the right inferior or other vein ostia; (4) ostial instability; (5) early branching of the vein; and (6) eccentric position of the ultrasound transducer in the vein. In patients with recurrence of atrial fibrillation, 40% of the ostial lesions reached a temperature >60 degrees C. However, in patients cured by the ablation, 64% of the ostial lesions reached a temperature >60 degrees C (P < 0.06). At least 12 of the 20 chronic recurrences could have been related to technical limitations of the first system. Duration of atrial fibrillation and eccentric deployment of the ultrasound transducer were more frequent in patients with recurrence of arrhythmias at follow-up. CONCLUSION: Ostial anatomy of the veins may affect delivery of ultrasound energy to achieve circumferential lesions. Energy delivery at the ostium with a temperature > 60 degrees C may be important to maximize success. Reconfiguration of the system to overcome the shortcomings identified in the initial experience could increase its performance.