Fate of left atrial thrombi in patients with atrial fibrillation determined by transesophageal echocardiography and cerebral magnetic resonance imaging.

Patients with atrial fibrillation (AF) and atrial thrombi have an increased risk for cerebral embolism. However, there is little knowledge about the long-term fate of atrial thrombi and the incidence of cerebral embolism in patients receiving continued oral anticoagulation. Forty-three consecutive patients with AF and atrial thrombi were enrolled in the study. Serial and prospective transesophageal echocardiographic studies, cranial magnetic resonance imaging (MRI), and clinical examinations were performed during a period of 12 months. Oral anticoagulation was continued or initiated in all patients. An international normalized ratio of 2.0 to 3.0 was regarded as effective. During follow-up, 56% of the thrombi disappeared (7 [16%] at 1 month, 18 [42%] at 3 months, 21 [49%] at 6 months, and 24 [56%] at 12 months). Patients with the disappearance of thrombi had significantly smaller thrombi compared with patients with persistent thrombi (1.5 +/- 0.8 cm in length and 0.8 +/- 0.5 cm in width vs 1.9 +/- 0.6 cm in length and 1.3 +/- 0.4 cm in width, p = 0.04), reduced echogenicity of thrombi (46% vs 89%, p <0.01), and smaller left atrial (LA) volume (83 +/- 27 vs 116 +/- 55 cm(3)). Seven patients (16%) had embolic lesions during follow-up MRI. Six of these patients (86%) had clinically apparent embolisms, and 1 died from stroke. The only independent predictors of cerebral embolism were an elevated peak emptying velocity of the LA appendage (p <0.01) and previous thromboembolic events (p = 0.02). Patients with AF and atrial thrombi have a large likelihood of cerebral embolism (16%) and/or death despite oral anticoagulation therapy. Thrombus size may predict thrombus resolution under continued anticoagulation.