BOSTON, MA — Rarely does a new diagnostic test have an immediate impact on clinical practice, but the new test for BNP (B-type natriuretic peptide) has done just that. It’s a simple, safe blood test that can help doctors evaluate cardiac function, reports the February 2007 issue of Harvard Men’s Health Watch.
BNP belongs to a family of protein hormones called natriuretic peptides, which includes ANP, BNP, CNP, and DNP. Natriuretic peptides are part of the body’s natural defense mechanisms designed to protect the heart from stress and play an important role in regulating circulation. They promote urine excretion, relax blood vessels, lower blood pressure, and reduce the heart’s workload. Most scientific study has focused on ANP and BNP.
Measurement of BNP helps doctors diagnose and treat congestive heart failure. In this condition, the heart is unable to pump blood efficiently, and the heart chambers swell with blood. As the heart cells stretch, they produce extra BNP, which pours into the bloodstream. By measuring blood levels of BNP, doctors can spot signs of congestive heart failure in its early stages, when it may be hard to distinguish from other disorders. A normal BNP level is about 98% accurate in ruling out heart failure. And, in general, the higher the level, the worse the heart failure. Falling BNP levels indicate that treatment is working.
Cardiologists are also exploring the role of BNP in coronary artery disease. Although measuring BNP to help diagnose and treat this form of heart disease is still experimental, scientists have found that BNP levels rise during treadmill stress tests in patients with coronary disease. BNP testing will never replace treadmill tests, heart scans, or coronary angiography, but it may soon help doctors decide which patients need additional tests.