Hospital Volume and Outcome after Bilateral Internal Mammary Artery Grafting

Bilateral internal mammary artery (BIMA) grafting largely is underutilized in patients undergoing coronary artery bypass grafting (CABG), partly because of the perceived increased complexity of the procedure. In this study, we evaluated whether BIMA grafting can safely be performed also in centers, where this revascularization strategy infrequently is adopted. Out of 6,783 patients from the prospective multicenter E-CABG study, who underwent isolated non- emergent CABG from January 2015 to December 2016, 2,457 underwent BIMA grafting and their outcome was evaluated in this analysis. The mean number of BIMA grafting per center was 82 cases/year and hospitals were defined as high or low volume, according to this cutoff value. Six hospitals were considered as centers with a high volume of BIMA grafting (no. of procedures ranging from 120 to 267/year; overall: 2,156; prevalence: 62.2%) and nine hospitals as centers with a low volume of BIMA grafting (no. of procedures ranging from 2 to 39/year; overall: 301; prevalence: 9.1%). Multilevel mixed-effects regression analysis showed that the low- and high-volume cohorts had similar outcomes. Propensity score one-to-one matching analysis of 292 pairs showed that the low-volume cohort had a significantly shorter intensive care unit stay (2.2 ± 2.3 versus 2.9 ± 4.8 days, P = .020). The rates of in-hospital death (1.0% versus 0.3%, P = .625), deep sternal wound infection/mediastinitis (3.8% versus 3.1%, P = .824), and 1-year survival (98.1% versus 99.7%, P = .180) as well as other outcomes were similar between the high- and low-volume cohorts. BIMA grafting can be safely performed also in centers in which this revascularization strategy is infrequently performed.