No randomized trial has confirmed significantly better long-term survival for either radial artery or saphenous vein graft recipients in coronary artery bypass grafting surgery

I read with great interest the expert systematic review on the choice of conduits for coronary artery bypass grafting (CABG) surgery [1]. Among other details, authors [1] presented differences in long-term outcomes/survival between radial artery (RA) or saphenous vein graft (SVG) recipients in CABG surgery. It was emphasized that in a meta-analysis of 14 studies [20 931 patients, 7 randomized control trials (RCTs)—1852 patients, plus 7 adjusted observational studies—19 079 patients], the use of the RA rather than the SVG as the second conduit was associated with a 26% relative risk reduction in mortality at 6.6-year follow-up [2]. The authors [2] emphasized that inclusion of observational studies raises the possibility of bias from unmatched confounders due to treatment allocation by the operating surgeons, and they acknowledge that even the best matching techniques can be inadequate to minimize the effect of treatment allocation bias in studies of this type. Goldman et al. [3] underlined that outcomes from observational studies are likely influenced by surgeon expertise and imperfect risk adjustment. Although unmeasured variables (target vessel and conduit size and quality, target vessel stenosis and run-off territory) are not included, there is a risk of bias introduced by patients with better coronary targets receiving RA grafts. Although 91.15% (19 079 patients) of the sample [2] is from observational studies, maybe results can be misleading.