The study will compare angiographic patency of the radial artery or saphenous vein graft anastomosed to the native left circumflex coronary territory at 3 months and 5 years after surgery. A substudy will compare 5-year post-surgery diameter and blood flow of in-vivo radial artery and saphenous vein grafts in response to endothelium-dependent and non-endothelium-dependent stimuli when patients attend for their scheduled follow-up angiogram.