Evaluation of B-type natriuretic peptide (BNP) levels in normal and preeclamptic women

Abstract

B-type natriuretic peptide (BNP) is synthesized in cardiac ventricular tissue in response to volume expansion and pressure overload. It is an approved marker for the diagnosis of congestive heart failure (CHF) in patients with dyspnea in an acute care setting. BNP levels correlate to wedge pressure, severity of CHF, and medical prognosis. BNP has also been used to screen for ventricular dysfunction in high-risk patients such as diabetics and hypertensives. The objectives of this study were to determine whether BNP levels fluctuated during pregnancy and if BNP could be a useful diagnostic tool in preeclamptic women. We studied 195 BNP levels in 78 women longitudinally from the first trimester to term. An additional 33 patients admitted with preeclampsia (9 mild, 24 severe) were studied and compared to 21 normal controls with term pregnancies. Plasma BNP values were determined using a standard point of care assay. BNP levels did not change significantly across gestation in normal pregnant women. In early pregnancy, BNP values are 25 pg/mL±2.4, and at term, values are 22 pg/mL±3.6. BNP remains stable at this level throughout the midtrimester. Patients with mild preeclampsia had higher BNP levels than controls; however, this difference was not statistically significant (44.4 vs 22.1 pg/mL, P = 1.0). Women with severe preeclampsia, in the absence of evidence of clinical cardiac disease, had mean BNP levels of 124.6 vs 22.1 pg/mL in controls (P = 0.17). In normal pregnancies, BNP values are stable throughout gestation. Patients with severe preeclampsia have elevated BNP values. This may reflect ventricular stress and/or subclinical cardiac dysfunction associated with the disease process.