Right internal mammary artery versus radial artery as second arterial conduit in coronary artery bypass grafting: A case-control study of 1526 patients

• Arterial grafts improve long-term outcomes in coronary artery bypass grafting (CABG).
• Radial artery (RA) is preferred over right internal mammary artery (RIMA) for CABG.
• RIMA is underutilised due to perceived operative risk and sternal wound issues.
• This largest clinical study to date validates short-term safety of RIMA.
• This study also confirms superiority of RIMA over RA in the long-term.

Objective: Additional arterial grafts such as the right internal mammary artery (RIMA) or the radial artery (RA) have been proposed to improve long term outcomes in coronary artery bypass grafting (CABG). RA is largely preferred over RIMA as it is less technically demanding and there is a perception that bilateral IMA usage increases the risk of sternal wound complications. However, there is a paucity of direct comparison of the two conduits to guide surgeons to choose the best second arterial conduit for CABG. Methods: A propensity score adjusted analysis of patients undergoing multiple arterial grafting with RIMA (n = 747) and RA (n = 779) during the study period (2001–2013) was conducted to investigate the impact of the two strategies on early and late outcomes. Results: RIMA did not increase the incidence of postoperative complications including deep sternal wound infection (P = 0.8). Compared to the RIMA, the RA was associated with an increased risk for late mortality (Hazard Ratio [HR] 1.9; 95% confidence interval (CI) 1.2–3.1; P = 0.008) and repeat revascularization (HR 1.5; 95% CI 1.0–2.2; P = 0.044). A trend towards an extra risk for late mortality from RA over RIMA was observed among diabetic (HR 3.3; 95% CI 1.1–9.7) and obese patients (HR 2.1; 95% CI 0.8–5.46). Conclusions: RIMA as a second conduit did not increase the operative risk including sternal wound complications and improved long term outcomes including overall survival when compared to RA. This advantage was stronger among diabetic and obese patients. These findings strongly support RIMA as the first choice second arterial conduit in CABG. Further randomized studies with angiographic control and long-term follow-up are needed to address this issue.