Effect of obesity on B-type natriuretic peptide levels in patients with pulmonary arterial hypertension.

Brain natriuretic peptide (BNP) levels are lower in obese patients with left ventricular failure than in their comparably ill, leaner counterparts. The effect of obesity on BNP in patients with pulmonary arterial hypertension (PAH) is unknown. We reviewed our prospective PAH registry data collected from November 2001 to December 2007 for patients undergoing right heart catheterization who met the criteria for PAH and had the BNP level and body mass index determined at baseline. The median BNP level for the lean, overweight, and obese patients was 285 pg/ml (interquartile range 131 to 548), 315 pg/ml (interquartile range 88 to 531), and 117 pg/ml (interquartile range 58 to 270), respectively (p = 0.029). A greater body mass index was associated with a lower BNP level, adjusted for age, gender, New York Heart Association functional class, hypertension, coronary artery disease, and mean right atrial and pulmonary arterial pressures (p <0.001). No statistically significant differences were found among the groups in age, race, medical co-morbidities, underlying etiology of PAH, use of vasoactive medications, New York Heart Association functional class, echocardiographic parameters, or pulmonary function. Obese patients had greater right atrial and pulmonary artery pressures. Increased BNP was associated with worse survival in the lean and overweight patients only. In conclusion, the BNP levels are attenuated in obese patients with PAH despite similar or worse hemodynamics or functional class compared to lean or overweight patients and should therefore be interpreted with caution.