Effect of Obesity and Underweight Status on Perioperative Outcomes of Congenital Heart Operations in Children, Adolescents, and Young Adults: An Analysis of Data From the Society of Thoracic Surgeons Database

Abstract

Background: Extreme body mass index (BMI; either very high or very low) has been associated with increased risk of adverse perioperative outcome in adults undergoing cardiac surgery. The effect of BMI on perioperative outcomes in congenital heart disease patients has not been evaluated.

Methods: A multicenter retrospective cohort study was performed studying patients 10 to 35 years of age undergoing a congenital heart disease operation in the Society of Thoracic Surgeons Congenital Heart Surgery Database between January 1, 2010, and December 31, 2015. The primary outcomes were operative mortality and a composite outcome (1 or more of operative mortality, major adverse event, prolonged hospital length of stay, and wound infection/dehiscence). The associations between age- and sex-adjusted BMI percentiles and these outcomes were assessed, with adjustment for patient-level risk factors, with multivariate logistic regression.

Results: Of 18 337 patients (118 centers), 16% were obese, 15% were overweight, 53% were normal weight, 7% were underweight, and 9% were severely underweight. Observed risks of operative mortality (P=0.04) and composite outcome (P<0.0001) were higher in severely underweight and obese subjects. Severely underweight BMI was associated with increased unplanned cardiac operation and reoperation for bleeding. Obesity was associated with increased risk of wound infection. In multivariable analysis, the association between BMI and operative mortality was no longer significant. Obese (odds ratio, 1.28; P=0.008), severely underweight (odds ratio, 1.29; P<0.0001), and underweight (odds ratio, 1.39; P=0.002) subjects were associated with increased risk of composite outcome.

Conclusions: Obesity and underweight BMI were associated with increased risk of composite adverse outcome independently of other risk factors. Further research is necessary to determine whether BMI represents a modifiable risk factor for perioperative outcome.

Keywords: cardiac surgical procedures; cardiology; mortality; obesity; outcome assessment (health care); pediatrics.

Figure 1

Study population

Figure 2. Distribution of subject BMI category and STAT mortality category

This histogram depicts the distribution (percent) of subject BMI category (x-axis) within each STAT Mortality Class (y-axis).

Figure 3. Linear spline model for operative mortality by BMI percentile

The results of a multivariate model utilizing restricted cubic splines for risk of operative mortality are depicted. The line of best fit (red line), knots (red circles), and 95% confidence intervals (black hashed line) are shown. For operative mortality the nonlinear association depicted is not statistically significant.

Figure 4. Linear spline model for composite outcome by BMI percentile

The results of a multivariate model utilizing restricted cubic splines to measure the risk for a composite outcome are depicted. The line of best fit (red line), knots (red circles), and 95% confidence intervals (black hashed line) are shown. For composite outcome the nonlinear association depicted is statistically significant. The odds of a composite outcome are increased at either extreme of BMI. Above the inflection point (a BMI percentile of 57%), increasing BMI increases risk of composite outcome. Below that same inflection point decreasing BMI is also associated with increased risk of composite outcome. Compared to a patient with normal weight (BMI percentile of 64%), the odds of composite outcome are 1.53:1 for a severely underweight patient (BMI percentile of 5%) and 1.21:1 for an obese patient (BMI percentile of 95^%).