Incremental Value of Increasing Number of Arterial Grafts: The Effect of Diabetes Mellitus

Background. Multiarterial coronary grafting with two arterial grafts leads to improved survival compared with conventional single artery based on left internal thoracic artery to left anterior descending artery and saphenous vein grafts. We investigated whether extending arterial grafting to three or more arterial grafts further improves survival, and whether such a benefit is modified by diabetes mellitus. Methods. We analyzed 15-year coronary artery bypass graft surgery mortality data in 11,931 patients (age 64.3 +/- 10.5 years; 3,484 women [29.2%]; 4,377 [36.7%] with diabetes mellitus) derived from three US institutions (1994 to 2011). All underwent primary isolated left internal thoracic artery to left anterior descending artery grafting with at least two grafts: one artery (n = 6,782; 56.9%); two arteries (n = 3,678; 30.8%); or three or more arteries (n = 1,471; 12.3%). Long-term survival was estimated by Kaplan-Meier methods. Propensity score matching and comprehensive covariate adjustment (Cox regression) were used to derive long-term risk-adjusted hazard ratio (HR) with 95% confidence interval (CI) for increasing number of arterial grafts in the overall cohort and for diabetes and no-diabetes cohorts. Results. Radial artery (94%) and right internal thoracic artery (6%) were used as additional arterial grafts. Multivariate analysis in all patients showed that diabetes was associated with decreased survival (HR 1.43, 95% CI: 1.34 to 53), whereas increasing number of arterial grafts was associated with decreased mortality (one artery HR 1.0 [reference]; two arteries HR 0.87, 95% CI: 0.80 to 0.95; and three arteries HR 0.83, 95% CI: 0.72 to 0.95). Pairwise comparisons also showed an incremental benefit of additional arterial grafts: two arteries versus one artery, HR 0.89 (95% CI: 0.80 to 0.98); and three arteries versus one artery, HR 0.80 (95% CI: 0.68 to 0.94). A three-artery versus two-artery survival advantage trend was also noted, but was not significant in either the overall study cohort (HR 0.90, 95% CI: 0.75 to 1.07), the diabetes cohort (HR 0.79, 95% CI: 0.60 to 1.03), or the no-diabetes cohort (HR 01.00, 95% CI: 0.79 to 1.26). Among diabetes patients, the survival advantage of two arteries versus one artery was modest (HR 0.96, 95% CI: 0.72 to 1.11), whereas it was significant for three arteries versus one artery (HR 0.74, 95% CI: 0.58 to 0.96). Analyses of propensity matched subcohorts were also consistent. Conclusions. Increasing number of arterial grafts improves long-term survival and supports extended use of arterial grafts in coronary artery bypass graft surgery, irrespective of diabetes status. (C) 2018 by The Society of Thoracic Surgeons