Comparison of Saphenous Vein Graft Harvested From Upper Versus Lower Leg in Coronary Artery Bypass Grafting

Inclusion Criteria: * Patients with multivessel disease who were planned to undergo off-pump coronary artery bypass grafting * Patients whose left internal thoracic arteries can be used, and whose saphenous vein grafts will be Y-anastomosed to left internal thoracic arteries. * Patients whose saphenous vein grafts can be harvested from both upper and lower legs. Exclusion Criteria: * Patients with overt heart failure symptoms * Patients with intractable ventricular arrhythmia * Patients with history of cancer or malignancy * Patients with coagulation or other hematologic disorder * Patients who needs concomitant cardiac procedures