Obstetric applications studied for heart failure test.(Obstetrics)

NEW ORLEANS -- Measurement of B-type natriuretic peptide levels in pregnancy shows promise for the management of preeclamptic patients, Vikas Bhalla, M.D., said during the annual scientific sessions of the American Heart Association.

The plasma B-type natriuretic peptide (BNP) test is a rapid, relatively inexpensive point-of-care test approved for diagnosis of heart failure in patients presenting with shortness of breath to the emergency department and other acute care settings. In this setting, BNP level correlates with wedge pressure, severity of heart failure, and prognosis.

Potential obstetric applications under study include use of the BNP test to identify women with preeclampsia before they become hypertensive and protein-uric, as well as to guide physicians in the particularly thorny problem of when to deliver affected patients, according to Dr. Bhalla of the University of California, San Diego.

BNP is synthesized in cardiac ventricular tissue, primarily in response to volume expansion and pressure overload. Preeclampsia, which complicates 5% of pregnancies and causes considerable maternal and neonatal morbidity, is characterized by markedly increased peripheral vascular resistance, which leads to increasing blood pressure, in turn causing pressure overload in the already volume-overloaded hemodynamic state of pregnancy.

Dr. Bhalla reported on 119 women who underwent serial BNP testing in each trimester of normal pregnancy, 9 mildly preeclamptic patients, 25 women with severe preeclampsia, and 25 normal controls at term.

Plasma BNP stayed in the range of 16-18 pg/mL throughout normal pregnancy, remaining in all cases below 20 pg/mL. Levels in mild preeclampsia were significantly higher, with a median value of 21.1 pg/mL. BNP levels were even higher in severe eclampsia, at a median 88.1 pg/mL.

Statistical analysis showed the best cutoff point for the diagnosis of preeclampsia was a BNP of 40 pg/mL. It yielded a sensitivity of 73%, a specificity of 85%, a positive predictive value of 57%, an accuracy rate of 82%, ...