B-type natriuretic peptide and its precursor in cardiac venous blood from failing hearts.

BACKGROUND Plasma concentrations of B-type natriuretic peptide (BNP-32) and its precursor (proBNP) are increased in chronic heart failure. Accordingly, BNP-32 and proBNP are both being implemented as clinical markers. AIM To determine the molar relation of BNP-32 and proBNP in different cardiovascular regions. METHODS AND RESULTS Blood samples were obtained from different cardiovascular regions during right heart catheterization in heart failure patients, and from normal subjects. Plasma BNP-32 and proBNP concentrations were measured using sequence-specific radioimmunoassays. Patients with severe left ventricular dysfunction (n=21) displayed increased peripheral plasma concentrations of both BNP-32 (four-fold, P=0.0008) and proBNP (seven-fold, P=0.0002) compared with normal subjects. Moreover, the peripheral concentrations were highly correlated with the corresponding concentrations in the coronary sinus (BNP-32: r=0.97, P<0.0001; proBNP: r=0.94, P<0.0001). Despite comparable peripheral concentrations of BNP-32 and proBNP, the BNP-32 concentration was higher than the proBNP concentration in the coronary sinus (median 126 pmol/l (21-993) vs. 103 pmol/l (16-691), P=0.035). CONCLUSIONS The BNP-32 and proBNP concentrations are closely related in venous cardiac blood. The findings suggest an overall constitutive secretion of processed proBNP, i.e. an N-terminal precursor fragment and BNP-32, in chronic heart failure.