N-Terminal Pro-B-Type Natriuretic Peptide as a Diagnostic Test for Ventricular Dysfunction in Patients with Coronary Disease
This study examined whether the peptide NT-proBNP, secreted by myocardial cells in response to increased blood flow and pressure, is useful for detecting ventricular dysfunction in patients with stable coronary heart disease (CHD) and no history of heart failure. Other studies have examined NT-proBNP levels in acute care/emergency settings and found them predictive of future cardiac events and mortality. Data were gathered as part of the Heart and Soul Study, a prospective cohort study designed to examine associations between psychosocial factors and health outcomes. Association of NT-proBNP levels with systolic dysfunction was examined in 815 patients, with diastolic dysfunction in 730 patients, and with one or the other in 740 patients. Questionnaires were used to determine age, sex, ethnicity, activity level, medical history and other information.
- Compared to patients with lower NT-proNB levels, those with higher levels were more likely to be older, white or male, have a history of hypertension, myocardial infarction, or coronary artery grafting. They also were less active and less likely to smoke.
- After adjusting for variables, each 1.3-point increase in NT-proNB level was associated with a 3.8 fold increase in odds of having a systolic dysfunction, a 2.9 fold odds of having a pseudonormal or restrictive filling, and a 5.1 fold odds of having either systolic or diastolic dysfunction.
- At a cut-off point of 100 pg/ml, NT-proNB was 88 percent sensitive for ventricular dysfunction. A negative test reduced likelihood of ventricular dysfunction from a pretest probability of 18 percent to a post-test probability of 6 percent. At 500 pg/ml, NT-proNB levels were 89 percent specific for dysfunction. In between 100–500 pg/ml, NT-proNB levels were not able to rule in or out ventricular dysfunction.
Because the presence of ventricular dysfunction in patients without evidence of heart failure is low (18%) the positive predictive value of the NT-proNB test also was low, only 47 percent. This means that more than half of patients with levels over 500 pg/ml did not have ventricular dysfunction, implying that this test is better at ruling out the presence of dysfunction than in identifying it. Testing for NT-proNB levels may help lower costs by avoiding echocardiography in up to a third of patients, as well as may help identify a subgroup of patients who might benefit from aggressive treatment of risk factors. Further study is necessary to determine whether NT-proNB testing can reduce the burden of heart failure in high-risk patients.