B-type natriuretic peptide as a surrogate marker for survival in patients undergoing cardiac surgery

Background B-type natriuretic peptide (BNP) is a biomarker predicting morbidity and mortality in patients with congestive heart failure. However, the usefulness of pre- or postoperative BNP levels in patients undergoing cardiac surgery remains uncertain. We sought to determine the association of pre- or postoperative BNP levels on mortality in patients undergoing cardiac surgery under cardiopulmonary bypass (CPB). Methods This study retrospectively evaluated 1,642 patients undergoing cardiac surgery under CPB over 2 years. The primary outcomes were 30-day and overall mortality after cardiac surgery. Results The 30-day mortality rate was 3.0% (n=49), and the overall mortality occurred in 118 patients during the mean follow-up period of 24.9±8.9 months. In multivariable analyses, preoperative BNP level was not significantly associated with 30-day [odds ratio (OR), 1.03; 95% confidence interval (CI), 0.99-1.06; P=0.06] or overall [hazard ratio (HR), 1.01; 95% CI, 0.98-1.03; P=0.50] mortalities. However, the postoperative BNP level was significantly associated with 30-day (OR, 1.05; 95% CI, 1.02-1.09; P=0.001) and overall (HR, 1.03; 95% CI, 1.01-1.04; P=0.01) mortalities. As a sensitivity analysis, postoperative BNP levels were divided into quartiles. The top quartile (≥484 pg/mL) was identified as a strong predictor of overall mortality (HR, 2.18; 95% CI, 1.14-4.19; P=0.02). Conclusions Preoperative BNP level was not associated with mortality after cardiac surgery. However, postoperative BNP level was associated with mortality after cardiac surgery, especially in patients with high levels (≥484 pg/mL). Further studies in larger cohorts are necessary to validate these results.