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Meta-analysis finds no outcome differences between free versus in situ right internal mammary artery in CABGStudy finds no major outcome differences between two coronary artery bypass graft techniques

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Key Takeaway
Consider clinical context over outcome differences when choosing between free or in situ RIMA as second conduit in CABG.

This meta-analysis pooled data from 13 studies involving 9899 patients undergoing coronary artery bypass grafting (CABG). It compared using the free right internal mammary artery (fRIMA) versus the in situ right internal mammary artery (isRIMA) as a second conduit, with median follow-up durations ranging widely from 1 to 20 years across the included studies.

The analysis found no statistically significant differences between the two techniques across multiple clinical endpoints. For overall mortality, the hazard ratio was 1.16 (95% CI: 0.79-1.69). Graft occlusion showed a hazard ratio of 1.04 (95% CI: 0.90-1.21). Major adverse cardiac events had a hazard ratio of 0.87 (95% CI: 0.62-1.21), and repeat revascularization showed a hazard ratio of 1.34 (95% CI: 0.68-2.66).

Safety and tolerability data were not reported in the meta-analysis. Key limitations include the inherent constraints of the available evidence, the wide variation in follow-up duration (1-20 years), and the absence of absolute event rates. The analysis notes that 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.

Researchers analyzed data from 13 previous studies involving 9,899 patients who had coronary artery bypass surgery. They compared two different surgical techniques for using the right internal mammary artery as a second blood vessel graft: one where the artery is left attached to its original blood supply (in situ) and one where it's completely detached and reattached (free). The goal was to see if one technique led to better long-term results.

The analysis looked at several important outcomes including overall survival, whether grafts stayed open, major heart-related complications, and whether patients needed additional procedures. After pooling all the data, researchers found no statistically significant differences between the two techniques for any of these outcomes over follow-up periods ranging from 1 to 20 years.

This was a meta-analysis, meaning it combined results from existing studies rather than conducting new research. The studies included had different designs and follow-up times, and the analysis didn't report absolute event rates. No safety concerns were specifically reported in the available data.

For patients, this suggests that both surgical approaches appear similarly effective based on current evidence. The choice between techniques may depend more on individual patient anatomy, surgeon experience, and specific clinical circumstances rather than expecting one method to clearly lead to better outcomes. Patients should discuss with their cardiac surgeon which approach makes the most sense for their particular situation.

What this means for you:
Two coronary bypass techniques show similar outcomes; choice depends on individual factors rather than clear superiority.

Study Details

Study typeMeta analysis
Sample sizen = 9,899
EvidenceLevel 1
Follow-up240.0 mo
PublishedMar 2026
View Original Abstract ↓
OBJECTIVES: 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. METHODS: 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. RESULTS: 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]). CONCLUSIONS: 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.
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