An 80-year-old woman was admitted to our hospital with a complaint of progressive dyspnea for the last month. She had a history of rhemautical mitral stenosis, type 2 diabetes mellitus, hypertension, and stroke. She had also chronic atrial fibrillation; however, she was not taking warfarin. On admission, the blood pressure was 120/70 mmHg, with an irregular pulse of 110 beats/min and a grade 3/6-degree diastolic murmur was heard over the mitral valve area. Laboratory findings were as follows: leukocyte count was 12,600/mm 3 ; hemoglobin, 13.6 g/dl; hematocrit, 42.2%; urea, 30 mg/dl; creatinine, 1.2 mg/dl; and international normalized ratio (INR), 1.2. Electrocardiography showed atrial fibrillation with a rate of 115 beats/min. On transthoracic and transesophageal echocardiography, the mitral valve was thickened and calcified. Doppler examinations demonstrated severe mitral stenosis (peak/mean gradient: 20/11 mmHg) with a valve area of 1.0 cm 2 , moderate tricupid regurgitation, and a pulmonary artery systolic pressure of 50 mmHg. Left atrium was dilated with a diameter of 50 mm, and a large freely mobile thrombus measuring 56×41 mm was observed in the left atrium ( Fig. 1 ). Coronary angiography ruled out coronary artery disease and demonstrated atypical dual vascularization of the left atrial thrombus originating from the right and circumflex coronary artery ( Fig. 2 ). We advised mitral valve replacement and the removal of the thrombus to the patient, but she refused them. As a result, anticoagulation with full-dose intravenous heparin followed by warfarin was administered. After hospital discharge, long-term oral anticoagulation was planned with a target INR of 2.5–3.5 at the follow-up visits. One month after the discharge, the patient was asymptomatic and recurrrent transthoracic echocardiographic studies revealed a mild resolution of the thrombus.
