Percutaneous left atrial appendage closure (LAAC) has emerged as an alternative option for stroke prevention in patients with atrial fibrillation. Several device related complications, such as device thrombus, may be due to incomplete endothelialization. In this in vitro study, by using human endothelial progenitors cells (EPCs), we compared 2 LAAC devices (Amulet (A) and Watchmann (W)) for endothelialization process and haemocompatibility, with and without antiplatelet agents (AAP).

EPCs from umbilical cord blood were extracted, cultured and characterized. Samples of A and W devices were seeded with 100,000cells/cm². EPCs proliferation on devices was monitored on longitudinal follow-up (Days 1 to 16) under 2conditions: with (AAP+) and without (AAP−) acetylsalicylic acid (500ng/mL). Devices haemocompatibility (platelet activation and partial thromboplastin time (PTT)) was assessed on devices with and without EPC seeding (EPC+/EPC−) and antiplatelets angents (AAP+/AAP−).

Regarding EPCs proliferation, we observed for each device a significant time-dependent EPCs proliferation. No statistically significant difference was found between the 2devices for proliferation at Day 16 or platelet activation, regardless with AAP or EPC presence. Regarding coagulation activation, we observed for Amulet devices a significant increase of PTT in EPC+ devices compared to EPC− [162.5±63.8s vs. 95.6±46s (P=0.001)]. No significant difference was observed for Watchmann devices (Fig. 1).

In this in vitro study, we showed for the first time that haemocompatibility of LAAC devices may be influenced by endothelialization process. The most effective antithrombotic treatement during the time of complete endothelialization should be confirmed by further studies.