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Background: The high prevalence of obesity makes accurately estimating the impact of body mass index (BMI) on cardiac surgery outcomes critical. There is no consensus on how BMI should be modeled in such evaluations. We assessed the association between BMI and CABG operative mortality, comparing results obtained when applying previous studies’ BMI modeling strategies vs modeling BMI as a continuous variable without assumptions of linearity.
Methods: We identified 25 studies investigating BMI and operative mortality: 22 categorized BMI, 2 treated it as a linear continuous variable, 1 used spline functions. Our cohort of 12,715 consecutive patients underwent isolated CABG from 2008-2012. We modeled BMI using restricted cubic spline functions in a propensity-adjusted model (controlling for STS risk factors) estimating operative mortality, and repeated the analysis using each BMI modeling strategy identified from the literature described above.
Results: BMI (modeled with a restricted cubic spline) was significantly associated with operative mortality (p<0.0001). Risk was lowest for BMI near 30kg/m2, and highest below 20kg/m2 and above 40kg/m2. No categorization, nor the linear continuous model, fully captured this association.
Conclusions: BMI is strongly associated with CABG operative mortality. Categorizing BMI (or assuming a linear relationship) heavily biases estimates of the association. In general, smoothing techniques should be used for all continuous risk factors to avoid bias.
Moderated Poster Contributions
Acute and Stable Ischemic Heart Disease Moderated Poster Theater, Poster Hall, Hall C
Saturday, March 18, 2017, 4:00 p.m.-4:10 p.m.
Session Title: Can CABG Patch CAD?
Abstract Category: 3. Acute and Stable Ischemic Heart Disease: Therapy
Presentation Number: 1266M-05
- 2017 American College of Cardiology Foundation