Abstract 4359066: Free Right Internal Mammary Artery vs In-situ Right Internal Mammary Artery as a Second Conduit for Coronary Artery Bypass Surgery: A Meta-Analysis

Background: In coronary artery bypass grafting (CABG), left internal mammary artery (LIMA) grafting to the left anterior descending coronary artery is the established gold standard. However, the optimal choice and configuration for a second conduit remain a matter of debate. The right internal mammary artery (RIMA) is frequently used in this role; however, whether it provides superior outcomes as a free graft or in situ is unclear. We aimed to evaluate and compare long-term clinical outcomes between free RIMA and in-situ RIMA used as a second conduit in CABG involving LIMA grafting using a meta-analysis. Methods: A comprehensive literature search of PubMed and Embase was conducted through May 2025 to identify studies comparing free RIMA (fRIMA) and in-situ RIMA (isRIMA) in CABG. The primary outcomes assessed were overall mortality, graft occlusion, major adverse cardiac events (MACE), and revascularization. Results: A total of 13 studies were included in this meta-analysis, comparing outcomes between the use of fRIMA and isRIMA as a second conduit in patients undergoing CABG. Pooled analysis showed no statistically significant difference in overall mortality between the two groups (HR [95% confidence interval (CI)] = 0.87 [0.58-1.30]). Similarly, graft occlusion (HR [95% CI] = 1.01 [0.87-1.18]), MACE (HR [95% CI] = 1.08 [0.83-1.39]), and revascularization (HR [95% CI] = 0.81 [0.55-1.19]) were comparable between fRIMA and isRIMA. Conclusion: This meta-analysis demonstrated no significant differences in clinical outcomes between free and in-situ RIMA when used as a second conduit in conjunction with LIMA. These findings support the use of RIMA in either configuration, allowing surgeons procedural flexibility without compromising patient outcomes.