Bilateral Internal Thoracic Artery Grafting Increases Mediastinitis: Myth or Fact?

Abstract

There is controversy about the risk of mediastinitis associated with the use of both internal thoracic arteries (ITA). We performed a case-control study of patients operated on at a single institution from January 2003 to December 2014. A total of 3,118 consecutive patients undergoing isolated coronary artery bypass graft surgery were included; 81.3% (n= 2,533) underwent bilateral ITA (BITA) grafts exclusively and constitute the BITA group, and 18.7% (n= 585) constitute the single ITA (SITA) group. Mediastinitis was defined as deep tissue mediastinal infection, with clinical or microbiologic evidence. Continuous variables were expressed as mean ± SD, and categoric variables as percentage (range). Student's t test and Fisher's exact test were used, as appropriate. Propensity score matching analysis was performed according to the nearest neighbor estimation method (n= 1,040). The incidence of diabetes mellitus was similar in both groups (29%, p= 0.9). The BITA patients were more like to be younger (p < 0.001), men (p < 0.001), had a higher prevalence of hypertension (p < 0.01), higher body mass index (p < 0.001), lower prevalence of left ventricular dysfunction (p < 0.001) and of previous myocardial infarction (p < 0.01), and greater use of off-pump coronary artery bypass graft surgery (p < 0.01). The BITA patients had lower unadjusted hospital mortality (1.6%, versus 5.3% for SITA, p < 0.0001). The total incidence of mediastinitis was 1.8% (BITA 1.9% versus SITA 1.5%, p= 0.6). Diabetes (p < 0.01) and nonelective surgery (p= 0.004) were the only predictors of mediastinitis in the entire population. Propensity score matching showed no differences in mediastinitis: BITA 2.5% versus SITA 1.3% (p= 0.17). In this series of patients, BITA did not increase the risk of mediastinitis in the total population or in the propensity score matched subgroups.