The B-type natriuretic peptide blood test is used to assess heart function, especially for individuals with a high risk for heart failure. B-type natriuretic peptide, or BNP, aids the detection of congestive heart failure while still in its initial stages when it may resemble other disorders. BNP works on blood vessels by expansion or dilation, and on the kidneys by increasing the volume of urine excreted and subsequently reducing blood pressure and relieving heart stress.
BNP Function
B-type natriuretic peptide, a protein hormone, is secreted by the lower chambers of the heart in response to stretching caused by a backup of blood. B-type natriuretic peptide's primary function is essentially a protective process of supporting the heart while under stress. BNP counters the effects of congestive heart failure by enlarging blood vessels, lowering blood pressure, increasing urine production and decreasing the heart's workload. With treatment, the heart recovers, stretching decreases and less BNP is secreted.
Heart Failure
Heart failure occurs most commonly as a result of cardiovascular diseases. The hearts ability to pump is diminished with less oxygen-rich blood delivered to tissues. The heart chambers become distended with blood causing excess blood to back up into the lungs and veins. Symptoms include shortness of breath, heart irregularities, elevated blood pressure, swollen feet, ankles and legs and increased weight referred to as congestive heart failure. Heart failure is a progressive disease once established.
Diagnostic Value
B-type natriuretic peptide levels, classified as hormonal markers of heart failure, can reflect the severity of signs and symptoms by increasing as symptoms worsen, and decreasing with improvement as a result of treatment. BNP levels can help determine whether other tests are necessary, guide treatment methods and indicate further deterioration in heart function. The BNP level may remain moderately elevated in chronic heart failure even with treatment and symptom relief.
Considerations
Other conditions can increase the workload of the heart, such as thyroid disease, diabetes, heart defects and valvular diseases, resulting in an elevation of BNP levels. These conditions require treatment before BNP values can improve. In addition, lung diseases, liver disorders, kidney conditions and the aging process can imitate the symptoms of congestive heart failure and may initially reflect elevated BNP values, which remain increased regardless of treatment and require further evaluation.
Sickle Cell Anemia
The BNP test is of value in detecting individuals at high risk for developing a disorder called pulmonary hypertension, a frequent and severe complication of sickle cell anemia. Pulmonary hypertension, or high blood pressure in the lungs, is caused by blood vessels narrowing and sharply altering the volume of blood flowing through the lungs. The decreased blood flow results in very low blood oxygen levels and an increased workload for the heart and a poor prognosis.
References
- Harvard Health Publications: Harvard Medical School: BNP blood test: Natriuretic peptide levels in a heart failure test
- Cleveland Clinic: Treatments & Procedures: B-type Natriuretic Peptide(BNP) blood test
- National Heart Lung and Blood Institute: Hormone called BNP Detects Pulmonary Hypertension
- Cleveland Clinic: Diagnosis
- MetroHealth: MetroHealth Heart & Vascular Center
- The Harvard Medical School Family Health Guide: BNP: An Important New Cardiac Test
