Coronary artery fistula from the left circumflex to the coronary sinus

A 27-year-old woman, who had received mitral valve repair for mitral regurgitation resulting from infective endocarditis, was admitted for a close examination of abnormal echocardiographic findings in the left atrium. Transthoracic echocardiography showed trivial mitral regurgitation with normal left ventricular contraction and dilatation of the coronary sinus. Auscultation revealed a grade 2 continuous murmur along the left sternal border. Transesophageal echocardiography demonstrated a marked dilatation of the coronary sinus just behind the posterior wall of the left atrium and turbulent blood flow in the dilated coronary sinus. Cardiac catheterization showed no significant step-up of oxygen saturation in the right heart and normal pulmonary artery pressure. Coronary angiography revealed a markedly dilated and tortuous circumflex coronary artery connected to the coronary sinus through a fistula. A left circumflex artery with a fistulous connection to the coronary sinus is extremely rare.