Peri-device leak and late massive thrombus formation after left atrial appendage occlusion: A case report.

RATIONALE: Stroke prevention in patients with non-valvular atrial fibrillation who cannot tolerate long-term anticoagulation remains a major clinical challenge. Left atrial appendage occlusion (LAAO) offers an alternative strategy to reduce thromboembolic risk, but device-related thrombus (DRT) formation can undermine its protective benefit. Although most DRT occur early, late thrombus formation related to minimal peri-device leak (PDL) is increasingly recognized. Understanding this rare but serious complication is crucial for optimizing long-term post-LAAO management. PATIENT CONCERNS: A 65-year-old male with prior ischemic stroke presented to the emergency department 10 months after LAAO with acute dizziness but no neurological deficits. DIAGNOSES: Transesophageal echocardiography and cardiac computed tomography angiography revealed a large thrombus (3.8 × 2.4 cm) on the Watchman device with minimal PDL, consistent with massive late DRT. INTERVENTIONS: The patient was started on high-intensity warfarin therapy (international normalized ratio: 2.5-3.5) for anticoagulation. Clopidogrel was temporarily discontinued to reduce bleeding risk. OUTCOMES: After 2 months of warfarin therapy, repeat cardiac imaging confirmed complete thrombus resolution. The patient remained neurologically intact without embolic complications. LESSONS: Even minimal PDL can serve as a nidus for significant late thrombus formation, particularly in patients with interrupted anticoagulation. This case highlights the importance of continued long-term imaging surveillance after LAAO and individualized anticoagulation strategies. Clinicians should maintain vigilance for late DRT, especially in high-risk patients, and consider extended follow-up protocols to optimize outcomes.