Association of N-terminal pro-B-type natriuretic peptide levels and mortality risk in acute myocardial infarction across body mass index categories: an observational cohort study

Background The prognostic value of N-terminal pro-B-type natriuretic peptide (NT-proBNP) across body mass index (BMI) categories in patients with acute myocardial infarction (AMI) is unclear. We aimed to assess the predictive value of NT-proBNP levels and identify the best cutoff values for mortality risk prediction across BMI categories in AMI.Methods We analyzed 4677 patients with AMI from the Cardiovascular Centre Beijing Friendship Hospital Database Bank. Patients were classified into underweight (< 18.5 kg/m(2)), normal-weight (18.5-23.9 kg/m(2)), overweight (24-27.9 kg/m(2)), and obese (>= 28 kg/m(2)) groups. The association between NT-proBNP (ln-transformed) and mortality was investigated using Cox regression and stratified by BMI.Results During follow-up (13,787 person-years of observation), 718 patients died, averaging 52.1 events per 1000 person-years. NT-proBNP levels were inversely correlated with BMI (beta = - 0.096, P < 0.001). After adjustment, NT-proBNP was independently associated with all-cause mortality (hazard ratio [HR] per 1-SD: 1.82; 95% confidence interval [CI] 1.60-2.07) in patients with AMI. Similar findings were observed in analyses stratified by BMI category, except for the underweight group. Adding NT-proBNP to conventional risk models improved risk discrimination in normal-weight, overweight, and obese patients (C-index changes of 0.036, 0.042, and 0.032, respectively) and classification of patients into predicted mortality risk categories (net reclassification improvement 0.263, 0.204, and 0.197, respectively). The best NT-proBNP cutoff values for 5-year mortality risk prediction across BMI categories were 5710, 4492, 2253, and 1300 pg/ml.Conclusion NT-proBNP level was an independent prognostic factor for mortality in patients with AMI and varied according to BMI. The best NT-proBNP cutoff values for mortality risk prediction reduced as BMI increased.