Comparative impact of low body mass index on patients undergoing transcatheter or surgical aortic valve replacement
Tang, Diane Choun Houy
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OBJECTIVE: This study aims to corroborate recent research demonstrating that patients with low body mass indexes tend to have worse postoperative survival outcomes compared to normal BMI patients. It also intends to compare survival outcomes and postoperative complications in transcatheter and surgical aortic valve replacement patients to determine which procedure, TAVR or SAVR respectively, is better for this challenging low BMI patient population. METHODS: This is a retrospective, single-center study comparing patient data collected from 2000-2013 at New York Presbyterian Hospital/Columbia University Medical Center. Patients were dividing into three groups on the basis of BMI and aortic valve procedure: low BMI SAVR (BMI < 22 kg/m2; n = 148; 20.36%), normal BMI SAVR (22-25 kg/m2; n = 458; 63.00%), and low BMI TAVR (< 22 kg/m2; n = 121; 16.64%). There is a total of 606 SAVR patients and 121 TAVR patients. To corroborate recent research that low BMI patients tend to fare worse than normal BMI patients, an unadjusted comparison were used to compare baseline demographics and postoperative outcomes of 148 low BMI patients who underwent SAVR with 458 normal BMI patients who underwent isolated SAVR. These cohorts were then compared via a Kaplan-Meier survival analysis and the log-rank test for 30 days, 6 months, 1 year and 3 years survival outcomes. The 148 low BMI SAVR patients were then compared to 121 low BMI patients who underwent TAVR on baseline demographics and preoperative risk factors. The two cohorts were compared using the Kaplan-Meier analysis and postoperative complications were compared utilizing a multivariable logistic regression after adjustment for age, gender, BMI and STS Scores. RESULTS: The unadjusted analysis of the low BMI and normal BMI SAVR cohorts displayed similar patient demographics and preoperative risk factors. The normal BMI group demonstrated higher EF (55% vs. 51.5%; p = 0.002) and incidence of HLD (47.68% vs. 37.76%; p = 0.038). Conversely, the low BMI cohort had more females (61.49% vs.42.79%; p < 0.001) and individuals with a history of Afib (27.78% vs.16.96%; p = 0.004). As shown in the Kaplan Meier curve, the normal BMI SAVR patients exhibited superior 6 months, 1 year and 3 years survival rates and low BMI was shown to be a significant independent predictor of mortality (HR 2.56; 95% CI: 1.47 – 4.47; p = 0.0009 at 1 year). The two groups had similar postoperative outcomes, however, the low BMI cohort had longer overall hospital stays (8 vs. 6.5 days; p = 0.0003). The low BMI SAVR and TAVR patient cohorts varied significantly on most patient demographics and preoperative risk factors. The low BMI TAVR patients tend to be older (95.04% vs. 55.41% of patients > 75 years old) and had higher STS Scores (10.41 vs. 3.88; p < 0.0001). They also demonstrated significant increases in all the preoperative risk factors excluding DM and prior CVA. The SAVR patients had significantly longer overall hospital stays (8 vs. 6 days; p < 0.0001), more re-exploration for bleeding (5.41% vs. 0.85%; p = 0.0411) and more patients discharged to home (68.24% vs. 50.85%; p = 0.0039) while the TAVR patients demonstrated higher rates of GI bleed (3.39% vs. 0.00%; p = 0.0240) and new PPM (10.17% vs. 0.68%; p = 0.0004). The low BMI SAVR cohort demonstrated better survival rates at 1 year and 3 years and low BMI TAVR was determined to be a significant independent predictor of mortality (HR 0.51; 95% CI: 0.30 – 0.88; p = 0.0146 at 1 year). After controlling for specific covariates in the multivariate logistic regression analysis, the low BMI SAVR had 1.73 times longer ICU stays, 1.90 times longer hospital stays and the odds of being discharged home was 17% less than the TAVR group (p = 0.0005, <0.0001, 0.5665). CONCLUSION: Although the rates of postoperative complications are fairly similar, patients with low BMIs demonstrated worse survival outcomes when compared to the normal BMI SAVR patients. With the current analysis, low BMI TAVR patients had a significantly worse preoperative profile compared to the corresponding SAVR cohort which explains the worse survival and postoperative outcomes. Despite this, the multivariable analysis showed that the low BMI SAVR patients had longer ICU and hospital stays as well as fewer discharges to home. As this is an ongoing study, steps should be made to balance the preoperative profile such that the low BMI SAVR and TAVR groups are comparable prior to survival and postoperative assessment. However, at the current status, TAVR has proven itself to be the preferred treatment for low BMI patients.