PO-696-07 LEFT ATRIAL APPENDAGE ANATOMICAL CHANGES FOLLOWING RADIOFREQUENCY-BASED OSTIAL ISOLATION

Background: Left atrial appendage (LAA) electrical isolation (ei) may be achieved via radiofrequency (RF) energy applications at the level of the appendage ostium targeting the sites of earliest activation recorded by a mapping catheter. Notably, RF has long been used in vascular, orthopedic, and aesthetic surgery to promote thermal-induced collagen matrix contraction, fibrosis, and tissue retraction. LAA anatomical changes associated to RF-induced tissue retraction have never been reported. Objective: To quantify the anatomical changes of the LAA ostium following RF-based LAAei. Methods: Thirty-four consecutive patients requiring AF ablation with LAAei underwent transesophageal echocardiography (TEE) within 7 days before (baseline TEE) and >6 months after (follow-up TEE) ablation. The diameter of LAA orifice and landing zone were measured at 4 different views (0°, 45°, 90°, 135°). Measurements were performed by two independent reviewers blinded to the patient’s identity. Results: Among 34 AF patients (68±7yrs, 73.5% males), the LAA morphology was classified as chicken wing in 15 (44%) patients, windsock in 10 (29%), cactus in 6 (18%), and cauliflower in 3 (9%). At baseline TEE, the mean maximum and mean minimum ostial diameters were 25±4mm and 22±4mm, respectively. The mean maximum and mean minimum diameters of the landing zone were 26±4mm and 23±3mm, respectively. On average, LAAei was achieved after 16±7 minutes of RF at a power of 45-47W. Follow-up TEE was performed 257±148 days after LAAei. The median LAA contraction velocity was 0.1 m/s (IQR: 0.04-0.18) and was significantly impaired in all patients. At follow-up TEE, the mean maximum and mean minimum ostial diameters were 19±4mm and 17±3mm, respectively. The mean maximum and mean minimum diameters of the landing zone were 20±4mm and 18±4mm, respectively. The mean relative reduction of the ostium and the landing zone was -24.4% and -22.5%, respectively. Box-Whisker plots of the maximum and minimum ostial diameters before and after LAAei are reported in Fig.1. Conclusion: RF led to a >20% reduction of the diameters of the ostium and the landing zone. These changes may have important implications for a successful percutaneous occlusion procedure and justify a staged approach of isolation and occlusion. [Formula presented]