Prognostic utility of serum albumin in underweight patients who underwent isolated surgical aortic valve replacement

OBJECTIVE: The clinical impact of underweight on outcomes in patients undergoing surgical aortic valve replacement (SAVR) remains unclear. This study aimed to investigate the prognostic significance of underweight status in patients undergoing SAVR and to identify key determinants of adverse outcomes within this population. METHODS: 805 patients underwent SAVR between January 2016 and December 2021 at eight Japanese centers. After excluding 31 patients with missing laboratory data, a total of 774 patients were included. Patients were categorized into underweight group (Body mass index [BMI] < 18.5 kg/m², 79 patients), normal-weight group (BMI 18.5-25 kg/m², 464 patients), and overweight group (BMI ≥25 kg/m², 231 patients). The primary endpoint was all-cause mortality. RESULTS: The median age was 76 years (interquartile range [IQR]: 71-79), and the median BMI was 23.3 kg/m² (IQR: 20.9-25.8). Underweight patients had the highest 5-year mortality, followed by normal-weight and overweight patients (23.5%, 11.9%, and 7.4%; p = 0.001). In multivariable analysis, BMI was an independent predictor of mortality (1.0 kg/m² increase, adjusted hazard ratio: 0.92; 95% confidence interval: 0.86 to 0.99; p = 0.020). Among underweight patients, serum albumin was independently associated with all-cause mortality (p = 0.002). Underweight patients were stratified by median albumin into low (< 4.0 g/dL, n = 43) and normal (≥ 4.0 g/dL, n = 36) groups, and 5-year mortality was higher in the low albumin group (34.1% vs. 12.6%, p = 0.015). CONCLUSIONS: Low BMI was associated with higher mortality after SAVR, and serum albumin provided additional risk stratification within underweight group.