Atrial thrombi resolution after prolonged anticoagulation in patients with atrial fibrillation - A transesophageal echocardiographic study

Background: Cardioversion of atrial fibrillation in nonanticoagulated patients may be associated with clinical thromhoembolism. Prolonged anticoagulation with warfarin before cardioversion of atrial fibrillation produces st marked reduction of cardioversion-related thromboembolism. The benefit of anticoagulant therapy is generally believed to be due to atrial thrombi organization. Patients a,ld methods: Transesophageal echocardiography (TEE) is highly accurate for diagnosis of atrial thrombi and gives the possibility to serially evaluate the effects of anticoagulant therapy. One hundred twenty-three patients with atrial fibrillation lasting longer than 2 days underwent TEE before cardioversion. An atrial thrombus was identified in II patients (9%), and was always confined to the left atrial appendage, TEE was repeated after a median of 4 weeks of oral warfarin. Atrial thrombus had completely resolved in 9 of 11 patients (81.8% 95% CI, 48.2 to 97.7%); in two patients, clot was still present. No patient had clinical thromhoembolism between the two TEE studies. Conclusions: In the population of our study a prolonged course of warfarin therapy was associated with resolution of atrial thrombi in the majority of patients. According to these data, the mechanism of thromboembolism reduction with 4 weeks of anticoagulation before cardioversion in patients with atrial fibrillation seems to be related mainly to thrombus lysis rather than organization. Due to the possibility of thrombus persistence even after prolonged anticoagulation, follow-up with TEE before cardioversion is necessary to document thrombus resolution.