Second Arterial Graft: Right Internal Mammary Artery and Radial Artery. Systematic Review and Meta-Analysis of Randomized Controlled Trials

Background: Conventional approach for coronary artery bypass grafting (CABG) with left internal mammary artery (LIMA) and saphenous vein grafts (SVG) for the last decades seemed reasonable option in patients with multi-vessel coronary artery disease (CAD). However, unfavorable long-term patency of SVG gives the clue to use more arterial grafts. The aim of this study is to assess Randomized Controlled trials (RCT) data in the field of second arterial graft: Right internal mammary artery (RIMA) and Radial artery (RA). Methods: A systematic review and meta-analysis was made according with the Cochrane Handbook for Systematic Reviews of Interventions and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. The primary outcomes were the following: 1) Angiographic patency for RA vs SVG 2) Any cause of death for bilateral internal mammary arteries BIMA-LIMA groups. Medline, Cochrane library and Embase were screened and analyzed by first and second investigator. Also, additional sources of data were used to lower publication bias. Last search was performed on March 3, 2019. Meta-analyses was calculated for only RCT with as long as possible follow-up, but not less than 2 years. Authors assess Risk Ratio as intuitive, simple-to-interpret measure. Random-effect model is used in case of heterogeneity, otherwise fixed effect model used. Binary events have been combined with Inverse Variance method by Review Manager 5. Results: For 5 RCT with total population of 5274 patients, Systematic review and Meta-analysis was performed. RA vs SVG: 3 RCT with 5, 7.7 and 10 year follow-up, 1322 patients. Angiographic patency was significant higher in RA arm compared to SVG (Risk ratio 0.55; 95% CI 0.35 0.86; I2 = 8%). BIMA(Multi-Arterial) vs LIMA(Single-Arterial): 2 RCT with 2 and 10 year follow-up, 3952 patients. In not-adjusted data (only BIMA vs LIMA) All causes death did not achieved statistically significant difference between two groups (Risk ratio 0.93; 95% CI 0.75 1.15; I2 = 10%). Adjusted data for our research question comparing Multi-Arterial vs Single arterial strategy showed next: All causes of death statistically significant favor Multi-Arterial arm (Risk ratio 0.80; 95% CI 0.70 0.92; I2 = 0%). More on our adjustment in correspondent section. Conclusions: In present meta-analysis we assessed 5 RCT studies and population of 5274 patients. We looked on this RCT from the multi-arterial point of view, be aware of this. Shown statistically significant angiographic superiority of using a RA over SVG. Surveillance data from all causes of death in BIMA (LIMA+RIMA) compared to LIMA+SVG/RA group didn’t show superiority. In contrast, adjusted from multi-arterial point of view statistical results (Multi-Arterial vs Single-Arterial) favour Multi-arterial arm. Although these findings may differ from some official conclusion of included studies, in discussion section we had been figured out reasons for that. On the other hand, these results coincided with numerous meta-analysis of huge observational studies. Emphasize on the need to utilize the second arterial graft (RA or BIMA or other) according to indications for arterial grafting. We emphasize on benefits for patients in terms of long -term patency as well as all causes surveillance. To assess our hypotheses ROMA trial results are awaited. Additional RCT data are of crucial importance.