Relationship between obesity and B-type natriuretic peptide levels.

BACKGROUND: The relationships among B-type natriuretic peptide (BNP) levels, body mass index (BMI), and congestive heart failure (CHF) as an emergency diagnosis are unknown.

METHODS: Of 1586 participants in the Breathing Not Properly Multinational Study who had acute dyspnea, 1369 (86.3%) had BNP values and self-reported height and weight. Two independent cardiologists masked to the BNP results adjudicated the final diagnosis.

RESULTS: Congestive heart failure was found in 46% of participants. Individuals with higher BMIs were younger and had more frequent edema on examination but were equally as likely to have CHF vs noncardiac sources of dyspnea. A nearly 3-fold difference was seen in mean +/- SD BNP values at the low and high extremes of the BMI groupings (516.7 +/- 505.9 vs 176.3 +/- 270.5 pg/mL, respectively; P< .001). The correlations between BMI and log BNP among those with and without CHF were r = -0.34 and r = -0.21, respectively (P< .001 for both). Multivariate analysis for the outcome of log BNP among a small subset with CHF (n = 62) found that Framingham score (P = .002), estimated glomerular filtration rate (P = .007), female sex (P = .03), New York Heart Association functional class (P = .09), and third heart sound (P = .08) were independent predictors. However, BMI was not found to be independently related to log BNP (P = .59).

CONCLUSIONS: In patients with and without CHF, BNP levels are inversely related to BMI. When considering demographics, severity of disease, and renal function, BMI is not independently related to BNP levels in a small subgroup when detailed information about CHF severity is known.