Effect of Device Size on Outcomes Following Left Atrial Appendage Closure in Borderline-Sized Anatomy

BACKGROUND: Selecting the optimal WATCHMAN FLX (a second-generation left atrial appendage [LAA] closure device) size for a borderline-sized LAA, for which 2 device sizes are acceptable, remains challenging. OBJECTIVES: The aim of this study was to evaluate how device size affects procedural and clinical outcomes in borderline-sized LAAs undergoing LAA closure. METHODS: From the Japanese multicenter TERMINATOR (Transcatheter Modification of Left Atrial Appendage by Obliteration with Device in Patients With NVAF) registry, 1,190 patients who underwent LAA closure with the second-generation device between May 2021 and September 2023 were reviewed. Of these, 757 with borderline-sized LAAs were included and categorized into large (n = 390) and small (n = 367) device groups. The median follow-up duration was 274 days (Q1-Q3: 100-368 days). Outcomes included peridevice leak (PDL), all-cause mortality, ischemic cerebrovascular accident or systemic embolism, major bleeding, and device-related thrombus. RESULTS: PDL occurred less frequently in the large device group compared with the small device group (1.54% [6 of 390] vs 4.90% [18/367]; P = 0.015). Ischemic cerebrovascular accident or systemic embolism was lower in the large device group (8.4% [95% CI: 1.8%-34.1%] vs 10.5% [95% CI: 3.6%-28.4%]; P = 0.036). No significant difference was observed in all-cause mortality (15.2% [95% CI: 6.0%-35.7%] vs 12.3% [95% CI: 4.6%-30.6%]; P = 0.288), major bleeding (4.5% [95% CI: 2.6%-7.7%] vs 15.7% [95% CI: 4.3%-48.7%]; P = 0.570), or device-related thrombus (8.6% [95% CI: 3.2%-22.2%] vs 3.2% [95% CI: 1.6%-6.4%]; P = 0.603). CONCLUSIONS: In borderline-sized LAAs, the larger device was associated with fewer PDLs and ischemic events without increased procedural risk.