Is the Risk of Wound Infection Related to Bilateral Internal Thoracic Artery Graft Potentiated by Age?

Background Older age and the use of bilateral internal thoracic artery (ITA) grafting are both considered risk factors for surgical wound infection (SWI) after coronary artery bypass grafting (CABG). The 2014 European Guidelines recommend that bilateral ITA grafting should be considered in patients aged younger than 70 years. Our aim was to investigate interaction between age and the number of ITA grafts. Methods All patients aged 18 years and older who had undergone CABG with at least 1 ITA at Rouen University Hospital between 2001 and 2012 were selected. Data regarding surgical procedure (single/bilateral ITA grafting) were extracted from the medical information system. SWI was identified from prospective surveillance of patients according to Centers for Disease Control and Prevention criteria. Independent factors associated with SWI were assessed by logistic regression, and an interaction test between age (≤69 or ≥70 years) and the number of ITA grafts was performed. Results SWI occurred in 71 of 2,726 patients (2.6%). Bilateral ITA grafting was associated with SWI (adjusted odds ratio [aOR], 2.55; 95% confidence interval, 1.51 to 4.30). After fitting an interaction term between age and number of ITA grafts, the aORs for SWI after bilateral ITA grafting substantially differed between patients aged 69 years and younger (aOR, 1.88; 95% confidence interval, 0.94 to 3.75) and 70 years and older (aOR, 3.52; 95% confidence interval, 1.69 to 7.33). However, this interaction failed to reach statistical significance ( p = 0.2213), possibly because of insufficient statistical power (23.5%) despite the large sample size. Conclusions Age 70 years and older compared with age 69 years and younger was associated with higher occurrence of SWI after bilateral ITA grafting, but this interaction was not statistically significant. Larger studies are needed to test this interaction.