This test measures the level of PRO BNP ( B-type natriuretic peptide (BNP) and N-terminal-pro-BNP (NT-pro-BNP))in the blood. BNP is a substance secreted from the ventricles or lower chambers of the heart in response to changes in pressure that occur when heart failure develops and worsens. The level of BNP in the blood increases when heart failure symptoms worsen, and decreases when the heart failure condition is stable. The BNP level in a person with heart failure – even someone whose condition is stable – is higher than in a person with normal heart function. Testing may be performed if a person has symptoms such as swelling in the legs (edema), difficulty breathing, shortness of breath, and fatigue. It can be used, along with other cardiac biomarker tests, to detect heart stress and damage and/or along with lung function tests to distinguish between causes of shortness of breath. Chest X-rays and Echocardiography may also be performed.