First-in-human left atrial appendage closure using the WATCHMAN FLX Pro device – a case report

Abstract Background Device-related thrombosis (DRT) is a known complication to left atrial appendage closure (LAAC). The surface of a LAAC device should ideally have antithrombotic properties. The novel WATCHMAN FLX Pro (WFP) incorporates a fluoropolymer-coated fabric membrane designed to increase thromboresistance and facilitate endothelialization. Such features could potentially allow for a minimal post-procedural antithrombotic regimen. Radiopaque platinum markers at the device shoulders and a large 40 mm device are other novel features of the WFP. Case summary A 75-year-old man with atrial fibrillation was referred for LAAC due to prior subdural haemorrhage during direct-acting anticoagulation treatment. He underwent the first-in-human WFP implantation as part of the WATCHMAN FLX Pro CT study (NCT05567172). Computed tomography (CT) was used for pre-planning, and the procedure was performed under local analgesia guided by intracardiac echocardiography from the left atrium (LA) without any complications. Post-procedural antithrombotic treatment consisted of acetylsalicylic acid 75 mg/day only, and 45-day CT, transoesophageal echocardiography (TEE), and magnetic resonance imaging demonstrated optimal device position with complete LAAC. Hypoattenuated thickening (6 mm) appeared on the device as a smooth surface in continuity with the left atrial wall on CT and TEE. A specific magnetic resonance T1-weighted scan, used for visualization of fresh thrombus, suggested this to represent tissue ingrowth rather than thrombus. Discussion The advanced follow-up imaging protocol suggested a good WFP implantation result with signs of tissue ingrowth at 45 days. The added radiopaque markers facilitated optimal deployment, evaluation of device stability during tug test, and assessment of device protrusion into the LA.