The ABC of sealing following left atrial appendage closure

BACKGROUND: Peri-device leak (PDL) following left atrial appendage closure (LAAC) can be diagnosed by both transesophageal echocardiography (TEE) and cardiac computed tomography (CCT). Yet, there is a substantial discrepancy in leak quantification. AIMS: We propose a novel ABC classification of LAA sealing for TEE and CCT based on the pattern of intra-device thrombosis (IDT). METHODS: A single-center observational study including patients undergoing LAAC with Watchman FLX or FLX-Pro between 2022 and 2024. Patients underwent CCT and TEE at 14 days, 45 and 90 days after LAAC. Images were analyzed by three blinded investigators. LAA sealing was classified by four distinct morphological patterns of IDT: Type A: Complete IDT (> 95% of the device). Type B: Incomplete IDT (50-95% of the device). Type B1: Incomplete thrombosis of the distal parts of the device. Type B2: Incomplete thrombosis in the proximal part near the atrial device surface. Type C: Partial IDT (< 50% of the device). RESULTS: Overall, 68 patients (mean age 76.1 years, 37% female) with complete CCT follow-up were included. At 90-day IDT classifications by CCT were Type A (53.8%), Type B1 (29.2%), Type B2 (0%), and Type C (16.9%). Type B2 was present on 14 days (1.5%) and 45 days (3.1%). PDL was observed in only 2.9% (95% CI, 0.7%-14.5%) of Type A, 73.7% (95% CI, 52.4%-93.6%) of Type B1, and 100% of Type C. Inter- and intra-reader agreements were very high for CCT and substantial for TEE imaging. CONCLUSION: Type A was associated with sealing irrespective of imaging modality, while Type C was always an indicator of PDL. This unifying classification was highly reproducible across imaging modalities and among readers of differing levels of experience.