[Congenital Left Internal Mammary Artery to Pulmonary Artery Fistula with Aneurysmal Change Diagnosed Incidentally:Report of a Case].

An internal mammary artery to pulmonary artery (IMA-PA) fistula is a very rare vascular abnormality. Patients with this disease are often asymptomatic, but they may develop symptoms such as heart failure and hemoptysis. A 60-year-old woman was incidentally diagnosed with left IMA-PA fistula by chest computed tomography (CT) during an examination for colon cancer. She was asymptomatic, but we determined that surgery was indicated because of the presence of an aneurysmal change. We performed complete surgical resection of the IMA-PA fistula and aneurysm under cardiopulmonary bypass. Her postoperative course was uneventful. Although a specific management strategy for IMA-PA fistula has not yet been established, surgical treatment should be performed to prevent rupture in cases with aneurysmal change.