Left internal thoracic artery (LITA) has been acknowledged as the first graft of choice for coronary artery bypass grafting (CABG). However, it is still not conclusive which one is the best second graft of choice among right internal thoracic artery, radial artery, right gastroepiploic artery, saphenous vein, and etc., as well as its configuration for CABG. In our institution, saphenous vein has been primarily used for the second graft and we have harvested it with 'No touch technique'. We have been demonstrated the excellent long-term patency of this 'No touch saphenous vein' in many studies. However, it is still unknown which configuration is the better strategy for the saphenous vein as a Y-composite graft based on the left internal thoracic artery versus an aortocoronary conduit. Thus, we aimed to evaluate morphologic change of saphenous vein graft by 1-year intravascular ultrasound (IVUS) study and angiographic patency results between Y-composite graft and aortocoronary conduit.