Why is the concentration of plasma brain natriuretic peptide in elderly inpatients greater than normal?

BACKGROUND: Higher than normal levels of plasma brain natriuretic peptide (BNP) are often found in elderly patients without overt heart failure.
OBJECTIVE: To investigate the relationships between echocardiographic findings and levels of BNP in inpatients undergoing rehabilitation.
METHODS: Ejection fraction, early-to-atrial peak transmitral velocity ratio (EAR) and left ventricular mass index were calculated. The patients were 34 men and 83 women, aged 83.4 +/- 0.8 years (mean +/- SEM).
RESULTS: The average BNP was 3.5 times higher than the normal range. Age of and BNP level in patients with mild renal dysfunction were significantly greater than age of and BNP level in those with normal renal function. BNP level in patients with left ventricular hypertrophy (LVH) was higher than that in patients without LVH, and there was a positive correlation between left ventricular mass index and BNP level. However, there was no difference between BNP levels of patients with ejection fraction < 50% and > or = 50% (n = 27 versus 90, ejection fractions 40 versus 64%, BNP levels 22.6 +/- 4.0 versus 17.5 +/- 1.6 pmol/l). Moreover, even elderly inpatients without LVH, without cardiovascular diseases, with sinus rhythm, with normal renal function, and with normal left ventricle systolic function had BNP levels that were greater than normal (n = 21, BNP level 11.0 +/- 1.5 pmol/l). We measured EAR of 76 of 90 patients with normal left ventricle systolic function, and 72 of the 76 patients had EAR < 1.
CONCLUSION: These results indicate that renal dysfunction and systolic dysfunction as well as cardiac hypertrophy and lower than normal diastolic function contribute to the elevation of BNP levels in elderly inpatients who do not have overt heart failure.