A 5-week-old child presented with a cardiac arrest secondary to myocardial ischaemia. Echocardiography demonstrated a single coronary artery arising from the right sinus of Valsalva. The coronary artery branched into left and right arteries, with the left artery then coursing anomalously in the tissue plane between the aortic root and the subpulmonary infundibulum. Compression of the left coronary artery caused severe myocardial ischaemia that resolved following construction of a bypass graft using the left internal thoracic artery. Stenosis at the anastomosis between the graft and the coronary artery was successfully treated by coronary angioplasty 2 years later.