Optimal Anticoagulation for Massive Left Atrial Appendage Thrombus in Atrial Fibrillation With a History of Gastrointestinal Bleeding.

Systemic embolism is a serious complication of atrial fibrillation (AF), most commonly originating from thrombi in the left atrial appendage (LAA). Thrombi that are large (≥15 mm) or exhibit mobility carry particularly high embolic risk, yet management can be challenging in patients with elevated bleeding risk. Advanced echocardiographic techniques now allow quantification of thrombus mobility, and dense spontaneous echo contrast (SEC) on transesophageal echocardiography has been identified as an independent predictor of thromboembolic events. We report the case of an 80-year-old woman with paroxysmal AF, non-Hodgkin lymphoma in remission, hypothyroidism, and a history of perforated gastric ulcer, in whom a large, mobile LAA thrombus (8 × 15 mm) was incidentally detected and confirmed by transesophageal echocardiography. Anticoagulation with warfarin, titrated to an INR of 2.5-3.0, led to complete thrombus resolution within six weeks. This case illustrates the substantial embolic risk associated with mobile LAA thrombi and demonstrates that individualized anticoagulation with careful monitoring can achieve safe and effective thrombus resolution in patients at high risk of bleeding. The novelty lies in highlighting individualized management as a viable strategy in this complex clinical setting, providing an important teaching point for practice.