Free Versus In situ Right Internal Mammary Artery as a Conduit in Coronary Artery Bypass Surgery: A Meta-Analysis

There is debate regarding the optimal choice for a second conduit in coronary artery bypass grafting. The right internal mammary artery (RIMA) is commonly employed as a second conduit; however, it is unclear whether the free (fRIMA) or in situ (isRIMA) configuration yields superior outcomes. We performed a systematic review and meta-analysis to compare clinical outcomes between fRIMA and isRIMA as the second conduit.

A comprehensive search of PubMed (MEDLINE), EMBASE, and CENTRAL was performed through May 2025 to identify studies comparing outcomes in patients undergoing coronary artery bypass grafting with either fRIMA or isRIMA as a second conduit. The outcomes of interest were overall mortality, graft occlusion, major adverse cardiac events (MACE), and repeat revascularization. Data with 95% confidence intervals (CIs) were extracted. Pooled analysis was performed using a random-effects model.

A total of 13 studies with 9899 patients were included (fRIMA, n = 3095; isRIMA, n = 6804). The median study follow-up duration ranged from 1 to 20 years across the studies. No statistically significant differences were observed in overall mortality (hazard ratio [95% CI] = 1.16 [0.79-1.69]), graft occlusion (1.04 [0.90-1.21]), MACE (0.87 [0.62-1.21]), and repeat revascularization (1.34 [0.68-2.66]).

In this meta-analysis, no statistically significant differences were observed between fRIMA and isRIMA configurations across the evaluated clinical outcomes. These findings suggest that, within the limitations of available evidence, the choice between fRIMA and isRIMA may be guided by clinical context, surgeon preference, patient anatomy, and target vessel characteristics rather than expected differences in major clinical outcomes.