A 39-year-old male ex-smoker gave a history of exertional chest pain ever since he suffered a respiratory tract infection. Clinical examination, electrocardiogram and echocardiography were normal and he was referred for a cardiac CT scan to assess coronary artery calcification and patency. The scan demonstrated incidental fistulae between the right internal mammary artery and the right coronary artery, and the left internal mammary artery and the left anterior descending artery.