ObjectiveTo explore the outcomes achieved by using left internal mammary artery (LIMA) to radial artery (RA) or saphenous vein (SV) Y-composite grafts in minimally invasive direct coronary artery bypass grafting (MIDCAB) for patients with multiple vessel disease. MethodsFrom January 2009 through May 2015, 56 patients (36 males and 20 females) with multiple vessel disease underwent MIDCAB with LIMA-RA or LIMA-SV Y-composite grafts without cardiopulmonary bypass in our hospital. MIDCAB was performed through a left anterior minithoracotomy. Thirty four patients used LIMA-RA grafts, and twenty two patients used LIMA-SV grafts. ResultsAll patients success-fully underwent MIDCAB with LIMA-SV or LIMA-RA Y-composite grafts. No patient required to convert to sternotomy during the surgery. Revascularization was performed for 2 target vessels in 12 patients, 3 target vessels in 41 patients and 4 target vessels in 3 patients. Mean postoperative ventilation time was 27.14±31.35 h. Mean ICU time was 3.16±2.53 d, and mean postoperative inhosptial time was 11.89±3.91 d. Thirty-day mortality was 1.79% (1/56). At a follow-up of 1 to 77 months, no patients received revascularization. The overall survival at 2 years postoperatively was 94.4%±5.4% in the LIMA-RA group and 86.8%±9.2% in the LIMA-SV group (P=0.299). The patency rate of LIMA was 100.0%. The overall patency rate of RA or SV grafts at 2 years postoperatively was 90.3%±5.3% or 86.7%±6.3% with no statistical difference (P=0.265). ConclusionMIDCAB with LIMA-RA or LIMA-SV Y-composite grafts is a safe and an effective procedure with favorable early and mid-term outcomes for patients with multiple vessel disease. LIMA-SV composite graft can be used as an alternative graft for patient whose RA is not possible or advisable.