Clinical implications of normal B-type natriuretic peptide levels in patients with severe chronic heart failure

Abstract

Background: High plasma B-type natriuretic peptide (BNP) levels in patients with severe chronic heart failure (CHF) often indicate poor ventricular function and poor prognosis. However, in some such patients plasma BNP levels are normal. Objective: To investigate the clinical implications of BNP levels in patients with severe CHF. Methods: Fifty-seven patients with severe CHF were divided into group A (13 normal plasma BNP level) and 44 patients (high plasma BNP levels) group B. Diuretics, angiotensin-converting enzyme inhibitors (or angiotensin II receptor antagonist, e.g., metoprolol) and digitalis were used as conventional treatment. The clinical characteristics of all patients in two groups were analyzed and compared. Results: At the first admission, left ventricular end diastolic diameter in group B was significantly lower than group A (p < 0.05), and the plasma BNP level in group B was significantly higher than group A (p < 0.05). When metoprolol was used, 6 and 5 patients in group A and B could not tolerate the initial dose. In other cases using metoprolol at average maximum tolerance dose of metoprolol 12.5 6.25 and 24.20 11.22 mg/day in group A and B, respectively, there was a significant difference between them (p < 0.05). There were no significant differences in plasma BNP levels between two groups during stable period. The plasma BNP level in group B during acute worsening stage was significantly higher than in the remission stage (962.73 165.00 ng/L vs 876.24 167.70 ng/L, p < 0.05). However, there was no significant difference between group A (74.03 11.18 ng/L) and group B (71.38 11.68 ng/L) (p > 0.05). The mobility of group A was higher than group B (11/12 vs 6/44, p < 0.05). Logistic regression analysis showed that, the plasma BNP level was the independent risk factor for predicting cardiac death (regression coefficient, 3.817; OR, 45.488; 95% CI, 5.322"388.791). Conclusion: In patients with severe CHF, normal plasma BNP level suggests depletion of BNP secretion and further deterioration of cardiac function, indicating a poor prognosis.