The selection of grafts for myocardial revascularization has been a recurring topic of debate over recent decades. Buxton’s group’s experiences with the radial artery, the adverse outcomes of the ART study due to its design, the recent publications of meta-analyses by Gaudino et al. and the long-term RAPCO study, among others, have sustained uncertainty, leading surgeons to cling to their established practices in the absence of definitive evidence, apart from the widely accepted anastomosis of the left internal mammary artery (LIMA) to the left anterior descending artery.

The study under discussion, though seemingly another contribution to this unending debate, aims to further explore the question of the best choice for a second graft in revascularization strategies. The study stands out, without delving into details, due to its meticulous methodology, including an appropriate literature search, careful selection of studies, and comprehensive bias and sensitivity analyses. For the meta-analysis, the authors selected 39 studies comparing outcomes of revascularization using either a single or multiple arterial grafts from 1995 to 2022, comprising a sample of 180,459 patients (multiple arterial grafts: 56,175 patients; LIMA + saphenous vein: 124,284 patients). They analyzed median overall survival and event-free survival, as well as secondary analyses comparing arterial grafts between mammary and radial arteries, and subgroup considerations, including patients over 70 years old, individuals with diabetes mellitus, and women. The multiple arterial graft group demonstrated superior survival (interquartile range = 0.58; p < 0.0001) and better event-free survival (interquartile range = 0.82; p < 0.0001) compared to isolated LIMA and saphenous vein revascularization. Using the right internal mammary artery as the second arterial conduit was associated with superior survival compared to the radial artery (HR = 0.93; p = 0.009). Multiple arterial revascularization showed consistent survival benefits across subgroup analyses in patients over 70 years old, women, and those with diabetes mellitus.

The authors conclude that this meta-analysis indicates that using multiple arterial grafts is associated with better survival outcomes compared to single arterial grafting in patients undergoing isolated myocardial revascularization surgery.

COMMENTARY:

The ongoing shifts in evidence, the flexibility in recommendations, patient heterogeneity, and surgical preferences rooted in each surgeon’s or institution’s practice contribute to maintaining a spotlight on the diversity of surgical revascularization strategies.

The work of Magouliotis et al. supports the survival benefit of multiple arterial revascularizations, similar to the findings of Gaudino et al. and other review studies. However, this study sheds light on two critical issues:

First, the distinct technical and clinical characteristics of patients undergoing surgical revascularization. Reducing patient heterogeneity to clinical variables and grafts alone is simplistic, but currently, it is the only contribution available from existing evidence. This study is one of the few to conduct independent meta-analyses with subgroups, assessing the benefit of multiple arterial revascularizations in elderly patients, those with diabetes, and women—all of whom showed benefits. Previous experiences aggregate outcomes into common evidence without addressing the unique characteristics of these three patient groups, where the use of multiple arterial grafts might not have shown benefits given the limited natural survival, potential infectious complications, or differential benefit in women, respectively. Nonetheless, new evidence will continue to be needed in the future. Studies underpinning such research often include patients in whom graft availability and quality of target vessels are, so to speak, unrestricted. This sometimes distances such evidence from real-world scenarios. The elevated risk of mediastinitis in some subgroups (obese diabetic women, particularly insulin-dependent or with poor HbA1c control >7%), peripheral venous insufficiency (treated or untreated), reservation of the saphenous vein graft for peripheral ischemia revascularization, radial artery atheromatosis and/or percutaneous manipulation, or contraindications to using this graft (lesions <90%, especially in the right territory, dialysis candidates, carpal tunnel syndrome, or previous surgeries, vasospastic phenomena…). Along with other factors such as ascending aortic calcification, patient age and expected survival, ventricular dysfunction, associated surgical procedures, hemodynamic stability, and potential inotropic and/or vasoconstrictor requirements, etc., make surgical revascularization a truly bespoke strategy for each patient. And, of course, while most surgical practices involve individual grafts with cardiopulmonary bypass (CPB), these studies do not adequately consider other variables, such as off-pump surgery and anastomotic configurations, like sequential or composite grafts.

Second, the advantage of the right internal mammary artery over the radial artery as the second preferred graft. This result may seem to contradict findings from the RAPCO study and Gaudino et al.’s meta-analysis, where the radial artery yielded excellent outcomes. However, it is essential to consider that study design influences results. Gaudino et al.’s work shares apparent similarities with the analyzed study (a meta-analysis comparing single versus multiple arterial grafting and evaluating the radial artery against the right internal mammary artery as a second graft) but has notable differences (it includes 10,256 patients from 4 recent randomized studies, but with propensity score resampling, reducing the sample to only 1,776 patients). The RAPCO study is a multicenter effort from groups skilled in selecting and using the radial graft appropriately, based on the characteristics mentioned above. Magouliotis et al.’s work spans 27 years, a period when double internal mammary artery use was more widely integrated than radial artery use, which was less accurately selected for target territories. Thus, even while consistently showing the survival benefit of multiple arterial revascularizations, the choice of the second best graft varies according to each study’s design characteristics. Perhaps the lesson to be learned is that “one-size-fits-all” revascularization strategies, like systematic double internal mammary use, may be less appropriate than individualized approaches based on patient characteristics. RAPCO’s successful outcomes with the radial artery derive from its appropriate selection and use. The right internal mammary artery may indeed be more versatile than the radial artery, yet it remains an arterial graft, occasionally with limited caliber, potentially susceptible to competitive flow in vessels with intermediate lesions, and despite various proximal and distal anastomotic configurations, may not deliver equivalent outcomes in terms of patency and performance for the coronary territory. Moreover, the risk of mediastinitis is significantly higher in some subgroups where the use of the radial artery could maintain multiple arterial revascularizations with a lower complication rate.

Therefore, we can conclude that, in most patients undergoing myocardial revascularization, the use of multiple arterial grafts will provide a survival benefit regardless of clinical characteristics, such as age, diabetes, or sex. The choice of arterial graft(s) accompanying the left internal mammary artery should be tailored as a custom suit, considering both clinical and coronary anatomy characteristics of each patient, to maximize clinical benefit and minimize the risk of complications (bleeding, mediastinitis, vasospasm…).

REFERENCE:

Magouliotis DE, Fergadi MP, Zotos PA, Rad AA, Xanthopoulos A, Bareka M, et al. Differences in long-term survival outcomes after coronary artery bypass grafting using single vs multiple arterial grafts: a meta-analysis with reconstructed time-to-event data and subgroup analyses. Gen Thorac Cardiovasc Surg. 2022 Nov 17. doi: 10.1007/s11748-022-01891-7.

Buxton BF, Hayward PA, Raman J, Moten SC, Rosalion A, Gordon I, et al.; RAPCO Investigators*. Long-Term Results of the RAPCO Trials. Circulation. 2020 Oct 6;142(14):1330-1338. doi: 10.1161/CIRCULATIONAHA.119.045427.

Gaudino M, Audisio K, Di Franco A, Alexander JH, Kurlansky P, Boening A, et al. Radial artery versus saphenous vein versus right internal thoracic artery for coronary artery bypass grafting. Eur J Cardiothorac Surg. 2022 Jun 15;62(1). doi: 10.1093/ejcts/ezac345.