Apart from trials of aspirin and dipyridamole in post-CABG patients that demonstrated a significant reduction in graft closure within the first year after surgery, there were no large systematic studies of interventions in these patients. Graft occlusion has been shown to correlate with high LDL-cholesterol and low HDL-cholesterol, and the severity of atherosclerosis has been additionally shown to be related to cigarette smoking and increased levels of coagulation factor. Therefore, lowering the LDL cholesterol (by diet and drugs), and anti-thrombotic therapy with warfarin were logical choices for intervention.