191: Acute rate of transmural lesions induced by the Epicor system® during peri-operative left atrial ablation for atrial fibrillation

Introduction The Epicor system ® is based on high intensity focused ultrasound (HIFU) energy used for creating a wide circumferential linear left atrial lesion encircling both left atrial posterior wall and pulmonary veins (box lesion) and provides long-term cure in patients with atrial fibrillation undergoing heart surgery. Whether if acute complete disconnection of the box lesion is achieved by application of HIFU is unknown. Methods bipolar pacing and detection into the box lesion was studied in 9 pts (5 men, 77 ± 18 yo) undergoing heart surgery (5 aortic valve replacement, 3 mitral valve repair or replacement and one coronary by-pass) using bipolar electrophysiological catheter and a real time telemetry (Medtronic CareLink ® programmer), just after completion of the ablation process on the beating heart prior to initiation of extracorporeal circulation. Sinus rhythm was present or obtained using internal cardioversion in each before the ablation process. Results Entrance block was absent in 7 (1 to 1 conduction from sinus rhythm inside the box lesion), undetermined in one and present in one (dissociated slow local rhythm). Exit block was lacking in 6 (capture of the cardiac rate by pacing inside the box lesion) and present in 3 (dissociated sinus rhythm from the paced area). Conclusion Acute complete block of the Epicor ® HIFU induced box lesion is lacking in the vast majority of pts despite completion of the energy deliverance according to the automated ablation process. Whether block later happens, or whether supplementary applications would increase the electrophysiological and clinical success rate is unknown.