Relationship between left ventricular preload and N-terminal pro-brain natriuretic peptide in obese patients.

BACKGROUND:The reason for low plasma N-terminal pro-brain natriuretic peptide (NT-proBNP) levels in patients with a high body mass index (BMI) is unknown. Although left ventricular end-diastolic pressure (LVEDP) is the gold standard of preload, the estimated trans left ventricular end-diastolic transmural pressure (eLVTMP) may be true preload especially in obese patients. MATERIALS AND METHODS:We measured hemodynamic parameters and the plasma NT-proBNP level in the aortic root (AO) and coronary sinus (CS) in 602 left-sided heart disease patients. We defined normal as BMI < 25 kg/m2 (n = 436), overweight as 25 ≤ BMI<30 kg/m2 (n = 117), and obese as BMI ≥ 30 kg/m2 (n = 49). RESULTS:There were no significant differences in left ventricular ejection fraction (LVEF) or LVEDP among the three groups, and log (CSAO) NT-proBNP was significantly lower in overweight or obese patients than in normal patients. From stepwise multivariate analyses, eLVTMP (eLVTMP = LVEDPright atrial pressure), LVEF, and BMI were independent predictors of log (CSAO) NT-proBNP, but LVEDP was not. The eLVTMP was significantly lower in obese patients than in overweight patients (7.5 ± 5.1 vs. 9.6 ± 5.3 mmHg, p < 0.05) or normal patients (7.5 ± 5.1 vs. 9.6 ± 4.7 mmHg, p < 0.01). CONCLUSION:Lower eLVTMP, as a marker of left ventricular preload, may contribute to the lower NT-proBNP secretion from the heart in obese patients.