Hospital volume and outcome after bilateral internal mammary artery grafting

Background: 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. Aims: In this study, we evaluated whether BIMA grafting can safely be performed also in centers, where this revascularization strategy infrequently is adopted. Methods: 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. Results: 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. Conclusions: BIMA grafting can be safely performed also in centers in which this revascularization strategy is infrequently performed.