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), normal-weight (18.5-23.9 kg/m), overweight (24-27.9 kg/m), and obese (≥ 28 kg/m) 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 (β = - 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.