title: Bilateral mammary artery grafting increases postoperative mediastinitis without survival benefit in obese patients.
abstract: OBJECTIVE
  The prevalence of obesity has risen in the last decade, increasing the percentage of obese patients who undergo cardiac surgery. Deep sternal wound infection (DSWI) is a rare but devastating postoperative complication, more often encountered in the obese population. DSWI is also associated with the use of bilateral internal mammary artery (BIMA), particularly in this high-risk population. The aim of this study is to determine the short-term and long-term outcomes following BIMA revascularization in obese patients.
  
  
  METHODS
  This is a single-centre retrospective cohort study using prospectively collected data including all obese patients who underwent coronary artery bypass grafting (CABG) surgery between April 1991 and April 2014. Preoperative demographic characteristics, operative and postoperative variables were taken from the computerized database of the hospital. A propensity score matching was conducted for the short- and long-term outcomes in the entire study population.
  
  
  RESULTS
  Results showed that 5608 patients with a body mass index of ≥30 kg/m2underwent CABG during the studied period. After propensity scoring, 494 patients receiving BIMA were matched to 5089 patients receiving single internal mammary artery (SIMA). All preoperative characteristics were comparable except for a higher prevalence of left ventricular dysfunction and left main disease as well as higher mean EuroSCORE in the SIMA group. In the postoperative period, short-term mortality was comparable in the two groups (P = 0.68). In-hospital DSWI was also comparable (P = 0.10). However, when considering DSWI occurring after hospitalization (median time; 19 days), the latter was significantly lower in the SIMA than in the BIMA group (1.1 vs 3.2%; P < 0.0001). For long-term survival, no difference was observed between the BIMA and SIMA groups after appropriate matching (P = 0.22).
  
  
  CONCLUSIONS
  In obese patients, CABG surgery using BIMA instead of SIMA increased the risk of postoperative DSWI, without improving survival. According to our results, short-term postoperative risks of infection associated with BIMA are not offset by longer-term benefits in that patient population. Special care should be exerted when selecting conduits for myocardial revascularization in obese patients.
authors.affiliation: Quebec Heart and Lung Institute, Quebec, Canada.|Faculty of Medicine, University of Sherbrooke, Quebec, Canada.
authors.forename: Emmeline
authors.initials: E
authors.lastname: Ruka
authors.affiliation: Quebec Heart and Lung Institute, Quebec, Canada.|Faculty of Medicine, Laval University, Quebec, Canada.
authors.forename: François
authors.initials: F
authors.lastname: Dagenais
authors.affiliation: Quebec Heart and Lung Institute, Quebec, Canada.|Faculty of Medicine, Laval University, Quebec, Canada.
authors.forename: Siamak
authors.initials: S
authors.lastname: Mohammadi
authors.affiliation: Quebec Heart and Lung Institute, Quebec, Canada.|Faculty of Medicine, Laval University, Quebec, Canada.
authors.forename: Vincent
authors.initials: V
authors.lastname: Chauvette
authors.affiliation: Quebec Heart and Lung Institute, Quebec, Canada.|Faculty of Pharmacy, Laval University, Quebec, Canada.
authors.forename: Paul
authors.initials: P
authors.lastname: Poirier
authors.affiliation: Quebec Heart and Lung Institute, Quebec, Canada pierre.voisine@chg.ulaval.ca.|Faculty of Medicine, Laval University, Quebec, Canada.
authors.forename: Pierre
authors.initials: P
authors.lastname: Voisine
mesh_terms: D000368:Aged; D001026:Coronary Artery Bypass / Q000009:adverse effects / Q000379:methods* / Q000401:mortality; D003324:Coronary Artery Disease / Q000150:complications / Q000601:surgery*; D005260:Female; D006801:Humans; D008297:Male; D008323:Mammary Arteries / Q000601:surgery*; D008480:Mediastinitis / Q000209:etiology*; D008875:Middle Aged; D009765:Obesity / Q000150:complications*; D011183:Postoperative Complications / Q000209:etiology*; D057216:Propensity Score; D012189:Retrospective Studies; D012307:Risk Factors
keywords: Bilateral internal mammary artery; Coronary artery bypass grafting; Obesity; Survival