Both longer length of stay and early complications were tied to severe obesity in patients undergoing coronary artery bypass grafting (CABG) surgery, according to research published in the Journal of the American Heart Association.

Researchers sought to clarify the association between obesity and perioperative adverse outcomes in patients undergoing CABG. They analyzed data from 7560 patients who were part the Alberta Provincial Project for Outcome Assessment in Coronary Heart Disease (APPROACH) registry.

Patients were divided into 5 body mass index (BMI) classes: normal BMI (18.5-24.9), overweight (25.0-29.9), obese class I (30.0-34.9), obese class II (35.0-39.9), and obese class III (≥40.0). A total of 1509 patients (20%) were identified as normal, 3080 patients (40.7%) as overweight, 1942 patients (25.7%) as obese class I, 696 patients (9.2%) as obese class II, and 333 patients (4.4%) as obese class III.

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Compared with those patients who had normal BMIs, those classified as class III obese tended to have higher rates of hyperlipidemia (86.2 % vs 79.3%; P=.004), pulmonary disease (15.3% vs 10.8%; P=.02), diabetes(62.5% vs 25.4%; P<.001), hypertension (85.6% vs 69.5%; P<.001), and previous percutaneous coronary intervention (17.15 vs 12.0%; P=.012).  Patients with class III obesity also tended to be younger (62.0 ± 9.3 vs 68.8 ± 10.6; P<.001) than those with normal BMIs, but with a lower prevalence of peripheral vascular disease (8.7% vs 14.7%; P=.011).

After adjusting for covariates, they observed no differences in postoperative mortality between the BMI groups. However, patients categorized as class II and III obesity had  higher risks of overall early postoperative complications than patients with normal BMIs (class II: adjusted odds ratio [aOR]: 1.35; 95% confidence interval [CI]: 1.11-1.63; class III: aOR: 1.56: 95% CI: 1.21-2.01; P=.001 for both).

Risks for early postoperative complications in the class II and III groups remained after propensity analysis (aOR: 1.33; 95% CI: 1.10-1.60; and aOR: 1.53; 95% CI: 1.20-1.96, respectively). Furthermore, classes I, II, and III were identified as independent risk factors for postoperative infection by propensity analysis (aOR: 1.59; 95% CI: 1.24-2.03; aOR: 2.24; 95% CI: 1.66-3.01; and aOR: 3.13; 95% CI: 2.20-4.46, respectively). 

Only the patients with obesity class III were found to have a 1.14 times longer total length of stay than those with normal BMI (7 days vs 6 days).

Post hoc analysis of patients with class III obesity identified several factors that were positively associated with length of stay: female sex (r=8.9; P=.004), infection (r=11.2; P=.029), renal complication (r=14.1; P=.002), dialysis (r=28.1; P<.001), ejection fraction <20% (r=47.3; P<.001). However, diabetes alone was not associated with prolonged length of stay.

When diabetes and infection were analyzed together, they found that the length of stay was 3.2 times longer (95% CI: 2.6-4.1) in the obese class III group that had both infection and diabetes (median 19 days vs 6 days), and 1.9 times longer (95% CI: 1.4-2.6) in infection alone (10 days).

The authors highlighted that diabetes is more prevalent in obese class III patients and may help explain the higher rate of infections. Therefore, appropriate perioperative glucose control and more aggressive antibiotic prophylaxis may be important in reducing both postsurgical infection, length of stay, and costs.

In addition, use of BMI may not accurately capture the severity of obesity, actual healthcare costs were not included, and the study only included a small number of patients with obesity class III.

As cardiac surgery needs increase among patients with severe obesity, understanding the risks for perioperative complications and lengthened hospital stays may aid in risk stratification.


Terada T, Johnson JA, Norris C, et al. Severe obesity is associated with increased risk of early complications and extended length of stay following coronary artery bypass grafting surgery. J Am Heart Assoc. 2016. doi: 10.1161/JAHA.116.003282.