The acute effect of Metoprolol upon NT-proBNP level in patients with congestive heart failure.

UNLABELLED: Brain natriuretic peptide (BNP) is a sensitive and specific marker of left ventricular (LV) function. The acute effect of beta blockers upon plasma BNP levels in CHF patients has been less studied but it is important because of the initial possible depressing effect upon LV function.

PURPOSE: To investigate the acute effect of oral Metoprolol upon plasma proBNP levels in CHF patients.

METHODS: There were included 56 patients with congestive heart failure, 38 with ischemic heart disease and 18 with idiopathic dilated cardiomyopathy, 40 males and 16 females, aged between 25 and 65 years, who were compared with 19 healthy individuals, 12 males and 7 females, of the same age. All patients were free of beta blockers treatment. Plasma Nt-proBNP was determined in fasting state using ELISA method (NV <250 fmol/mL). After this, every patient received 50 mg Metoprolol succinate and at three hours (considered as peak plasmatic concentration) venous blood samples were again obtained and Nt-proBNP determined.

RESULTS: NT-pro BNP was increased (1400 +/- 130 fmol/mL) in heart failure patients and normal (187 +/- 17.2 fmol/mL) in healthy controls. After Metoprolol the plasmatic level of NT-proBNP was not significantly different in both healthy controls (162 +/- 13.3 fmol/mL) and heart failure patients (1419 +/- 133 fmol/ml) in comparison with baseline values. After Metoprolol NT-proBNP decreased (from 1266 +/- 121 to 1120 +/- 107, p>0.05) in III NYHA class patients and increased (from 1457 +/- 142 to 1530 +/- 150, p<0.05) in IV NYHA class patients. It remained unchanged in patients with LVEF >30% (1384 +/- 140 vs 1389 +/- 129 fmol/mL) and increased (from 1480 +/- 134 to 1690 +/- 161 fmol/mL, p<0.05) in patients with LVEF <30%; it was not significantly modified in patients with atrial fibrillation in comparison with those in sinus rhythm (1348 +/- 132 vs 1516 +/- 168 fmol/mL).

CONCLUSION: Beta blockers do not have a severe depressant effect on left ventricular performance in all patients with systolic heart failure. A LVEF>30% suggests, but the lack of modification of NT-proBNP levels after administration of 50 mg Metoprolol confirm, that the beta blocking treatment can be initiated with higher doses than those recommended until now.