Abstract
BACKGROUND: Left atrial appendage closure (LAAC) effectively lowers stroke risk in atrial-fibrillation (AF) patients who cannot tolerate long-term anticoagulation. Device-related thrombosis (DRT), although infrequent, carries a threefold increase in subsequent embolic events and remains a therapeutic challenge, even with the newer Watchman FLX occluder. CASE SUMMARY: A 72-year-old woman with paroxysmal AF (CHA(2)DS(2)-VASc = 5; HAS-BLED = 2) underwent LAAC with a 30 mm Watchman FLX after bleeding-limited warfarin use. She was prescribed dual antiplatelet therapy (DAPT) post-procedure. Eight weeks later, cardiac CT detected a device-surface thrombus; warfarin (INR 2.5-3.0) achieved complete resolution by 7 months. Despite continued anticoagulation, repeat CT at 22 months revealed a larger thrombus. Transesophageal echocardiography confirmed recurrent DRT. DISCUSSION: This case underscores multifactorial DRT pathogenesis: patient-specific hypercoagulability (age, persistent AF, PAI-1 variant), anatomic factors (large LAA, 30 mm device), and premature INR reduction. Current evidence indicates that early hypoattenuation thickening on cardiac CT, peri-device leak, and suboptimal antithrombotic regimens are associated with DRT. Emerging data support CT-based surveillance, individualized anticoagulation-potentially favoring direct oral anticoagulants (DOACs)-and next-generation, endothelialization-oriented device designs. CONCLUSION: Recurrent, large-burden DRT can occur late after Watchman FLX implantation despite initial thrombus resolution and guideline-directed therapy. Optimal management requires (1) vigilant, multimodality imaging follow-up; (2) stringent, patient-tailored anticoagulation with real-time INR or DOAC level assessment; (3) consideration of genetic or laboratory markers of thrombophilia; and (4) advances in device bioengineering to accelerate endothelial healing. Further studies should refine risk-stratified antithrombotic strategies and validate imaging biomarkers to pre-empt DRT in high-risk LAAC recipients.