Congenital fistula between the left internal mammary artery (LIMA) and the pulmonary artery: cause of LIMA bypass occlusion?

Congenital fistulas from the left internal mammary artery to the pulmonary artery are rare. We describe a 49-year-old patient with severe aortic valve regurgitation and coronary artery disease. Percutaneous transluminal coronary angioplasty and left anterior descending artery (LAD) stenting had been performed because of a significant proximal LAD lesion. Repeated coronary angiogram 3 months later revealed a patent stent but severe sclerosis up to a 40% stenosis of the LAD after the area of stenting. An aortic valve replacement and a left internal mammary artery (LIMA) bypass to LAD were performed during standard cardiopulmonary bypass (CPB). Because of patient chest pain, a control angiogram was carried out 2 years after surgery and revealed a LIMA-bypass occlusion and a large fistula deriving from the proximal part of the LIMA to the pulmonary artery. The fistula was occluded by coils during an interventional cardiological procedure. Diminished flow in the LIMA bypass due to the fistula in combination with a nonsignificant proximal LAD stenosis are possible reasons for IMA-bypass occlusion. From this case we conclude that angiography of the IMA to detect malformations preoperatively should be mandatory in all cases of arterial coronary revascularization using IMA bypasses.