Poster No. 128 Association of platelet markers with occurrence of thromboembolic and bleeding events following left atrial appendage occlusion

Background Patients undergoing left atrial appendage occlusion (LAAO) often are at increased risk for bleeding or thromboembolic events. In most implanting centers, baseline blood is drawn as a pre-procedural check-up. However, it is unknown what laboratory parameters have added value in this specific population. Platelet count (PLC) and mean platelet volume (MPV) may identify which patients are at risk for thromboembolic events or bleeding. Materials and methods Five implanting centers retrospectively gathered data on pre-procedural platelet markers. Composite endpoints on thromboembolic events (stroke, transient ischemic attack, device-related thrombus and systemic embolism) and bleeding (minor, major, and intracranial hemorrhage) were collected. Results and conclusions A total of 1138 patients were included (73 ± 8 years, 63% male, CHA2DS2-VASc: 4.4 ± 1.5; HAS-BLED: 3.2 ± 1.1). Implanted devices consisted of Watchman 2.5/FLX (n = 778), Amplatzer Cardiac Plug/AMULET (n = 315), or another device (n = 45). Baseline PLC was present in 91% and MPV in 41%. PLC was significantly lower in the 97 patients developing a thromboembolic event (206 ± 73 vs. 225 ± 72*10*9/L, P = 0.028), but no difference in MPV was observed (9.7 ± 1.4 vs. 9.5 ± 1.5 fL, P = 0.40). In another 97 patients, significant bleeding was observed during follow-up. No difference in baseline PLC was found (216 ± 79 vs. 207 ± 72*10^9/L, P = 0.30) and a trend towards lower MPV could be observed (9.5 ± 1.3 vs. 9.8 ± 1.5 fL, P = 0.07). Patients developing bleeding more often were discharged with antiplatelet therapy, while patients developing a thromboembolic event more often received anticoagulation therapy. In conclusion, occurrence of a thromboembolic event was associated with lower baseline PLC, which may be explained by PLC being lower in more frail patients.