Does body mass index affect outcomes for aortic valve replacement surgery for aortic stenosis?

Background: Obesity is a worldwide healthcare concern, and its association with several chronic diseases is well documented. However, the effect obesity may have on the acute care delivery is not well understood, and in cardiac surgery, reports are conflicting. The purpose of this study is to evaluate the effect of obesity in an isolated aortic valve replacement population. The hypothesis is that increasing body mass index (BMI) will portend worse long-term outcomes and greater short-term resource utilization secondary to perioperative complications but will not affect perioperative mortality.

Methods: Data were collected on 1,066 patients undergoing isolated AVR between January 2000 and December 2010. All definitions follow The Society of Thoracic Surgeons guidelines. Body mass indexes were calculated and used both as a continuous independent variable and to categorize patients into three BMI groups. Long-term mortality follow-up was by Social Security Death Index search. Standard bivariate and multivariate comparisons were performed with hierarchical models used for odds ratios.

Results: When controlling for standard covariates that negatively impact outcome (sex, age, renal failure needing dialysis, diabetes mellitus, and current smoker), BMI was not predictive for either operative mortality or a composite morbidity-mortality outcome. When divided into three equal-sized groups, there was again no statistical difference among groups for mortality or for the composite variable. Separate analyses for females and males yielded the same lack of correlation. Long-term follow-up out to 12 years shows that the low BMI group has statistically worse survival than the moderate or high BMI groups.

Conclusions: Increasing BMI has no independent association with worsened outcomes in the short or long term, and overweight patients have a survival benefit after surgery. Patients who are at the lower end of the BMI scale, however, are at increased risk for poor long-term survival.