BMI disparities in coronary artery bypass grafting outcomes: A single center Society of Thoracic Surgeons (STS) database analysis

Disparities in Body Mass Index (BMI) has been a potential risk factor for intraoperative outcomes, postoperative morbidity and mortality after coronary artery bypass graft (CABG). This study aims to quantify the effect of BMI on early clinical outcomes following CABG. The Society of Thoracic Surgeons (STS) Adult Cardiac Surgery Database was queried for adult patients who underwent first-time Coronary Artery Bypass Graft (CABG) patients in our center from 2014 to 2020. BMI and gender were investigated as primary risk factors for intraoperative outcomes, in-hospital postoperative outcomes, and hospital readmission using multiple logistic regression models. Propensity score weighting was used due to imbalances in the observational groups. Locally weighted smoothing (LOESS) plots of BMI were inspected for each outcome with a predicted probability plot of the interaction between BMI and gender. Among 591 patients meeting inclusion criteria, 79% were male (n=468) and 21% were female (n=124). Healthy(H), overweight/obese (O), and morbidly obese (MO) BMI was defined as <25, 25–35 and >35 respectively. There were significantly higher proportions of females in the healthy and obese categories, and males in the overweight BMI category (F vs M: H:33.9 vs 66.1% O: 15 vs 85%, MO:35 vs 65%, p < 0.001). Patient demographics and comorbidities are all well-balanced with no significant differences after propensity weighting. There was no significant difference in intraoperative outcomes including operating room time, cross clamp time, by-pass time and intraoperative blood loss requiring blood transfusion (p >0.05). Approximately half (49.16%) of patients had one or more in-hospital postoperative events, and 62 (10.56%) had hospital readmission follow discharge. After propensity weighting, the incidence of surgical site infection (SSI) was significantly higher in the morbidly obese group (H: 1.5%, O: 0.6%, MO: 4.5%, p  = 0.016) and pneumothorax requiring intervention appears to be significantly higher also for those in the morbidly obese group (H: 0.3%, O: 1%, MO: 2%, p  = 0.028). Death at discharge was found to be significantly higher in the healthy group (H: 2.5%, O: 0.3%, MO: 0.3%, p  = 0.028, p = 0.008). Loess plots for in-hospital postoperative events and hospital readmission by BMI and gender showed a slight downward trend in postoperative events as BMI increases. Healthy and morbidly obese patient appear to have slightly higher values of hospital readmission for both genders. There was no difference in perioperative outcomes among the cohort. Morbidly obese patients undergoing CABG have a higher risk of SSI. Mortality was higher in the underweight patients. In general, BMI disparities did not affect the risk of perioperative death and other adverse outcomes.