PO-718-06 MAXIMUM OUTPUT PACING: IMPROVING POSTERIOR LEFT ATRIAL EPICARDIAL ISOLATION

Abstract

Benefits of posterior wall isolation for persistent AF are unclear. Epicardial posterior wall connection may persist despite achieving standardized endocardial isolation ablation goals. To determine how often epicardial posterior wall connection remains when traditionally defined endocardial isolation is present, where and how does epicardial connection persist and should posterior wall isolation be redefined. Ablation was performed in 34 AF patients with THERMOCOOL SMARTTOUCH SF catheters at 50W, ablation index goal of 350 on the posterior wall, 7 second maximum dwell time. To avoid heat stacking, consecutive lesions were separated by >/=1.5cm. Three horizontal lines at roof, carinal and inferior vein levels were created with confirmed lack of pace capture 10ma/2ms on the lines. Pacing was then performed at 10ma/2ms within the posterior wall and exit maps created with ablation at the earliest exit. If posterior wall capture remained after ablation at the earliest exit, the posterior wall was ablated until no capture remained. This was repeated at 20ma/4ms, then 20ma/10ms. 14/34 patients (41%) had residual pace capture within the posterior wall at 10ma/2ms. After ablation achieved lack of 10ma/2ms capture, 27/34 (79.41%) had recurrent capture at 20ma/4ms. After ablation to lack of capture at 20ma/4ms, 28/34 (82.4%) had residual 20ma/10ms capture. Mean number of additional lesions to achieve posterior wall isolation beyond lack of 10ma/2ms capture was 14.5, 33% greater than the number of lesions to achieve traditional isolation. Compared to 10ma/2ms, areas of residual capture were significantly more frequent in all (p<.05) but one quadrant with 20ma/10ms (figure).Despite using exit mapping with ablation at the earliest exit, connection persisted in 1/14 10ma/2ms pace maps (7.14%), 23/27 20ma/4ms pace maps (85.2%) and 24/28 20ma/10ms pace maps (85.7%) (p<0.01). Traditional endocardial ablation techniques fail to identify epicardial posterior wall connection. Higher output pacing reveals residual epicardial connection at multiple locations in a given patient. Higher output pacing (20ma/10ms) can guide endocardial posterior wall ablation to improve transmural posterior wall isolation.