A 74-year-old woman underwent elective double valve replacement (aortic and mitral) for rheumatic valvular disease. She failed to wean from cardiopulmonary bypass due to marked left ventricular dysfunction. At autopsy, severe giant cell arteritis confined to the intramural coronary arteries was seen. Furthermore, there were multiple areas of recent microscopic myocardial infarction around the intramural coronary arteries. This report describes a rare case of giant cell arteritis confined to intramural coronary arteries which lead to inadequate myocardial protection at the time of surgery.