Left atrial appendage anatomical changes following radiofrequency-based ostial isolation

Funding Acknowledgements Type of funding sources: None. 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. Purpose 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 apx 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 43 AF patients (67±6yrs, 72.1% males), the LAA morphology was classified as chicken wing in 19 (44.2%) patients, windsock in 12 (27.9%), cactus in 8 (18.6%), and cauliflower in 4 (9.3%). 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 17±6 minutes of RF at a power of 45W. Follow-up TEE was performed 294±136 days after LAAei. The median LAA contraction velocity was 0.1 m/s (IQR: 0.02-0.18) 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.