What Is a Cardiac BNP Test? Uses, Side Effects, Procedure, Results (2024)

A B-type natriuretic peptide or brain natriuretic peptide (BNP), is a commonly performed blood test that is used to diagnose or rule out heart failure. Specifically, the test measures levels of the protein BNP that is made in the heart and blood vessels.

Usually, low levels of the BNP protein are found in the blood, but during heart failure levels are significantly higher. Blood is obtained via a venous or arterial puncture and send to the lab for analysis.

Purpose of the Test

A BNP is clinically recommended for the following reasons:

• Detect or rule out heart failure, including heart failure with preserved ejection fraction
• Predictor of death and cardiovascular events in persons without a previous cardiac dysfunction diagnosis
• Useful tool in predicting prognoses in patients with heart failure and appears to be a stronger predictor than some traditional indicators (e.g., left ventricular ejection fraction, ischemic etiology, serum levels, New York Heart Association classification)

If heart failure is suspected, a BNP level can help determine the severity of the disease and help the medical team develop a plan of care including a medication regimen and surgical options if applicable. Patients will often experience some symptoms of heart failure that would prompt a BNP level. These symptoms may include:

• Difficulty breathing
• Coughingor wheezing
• Fatigue
• Swellingin abdomen, legs, and/or feet
• Loss of appetite ornausea
• Weight gain
• Dyspnea on exertion
• Palpitations

Healthcare providers will often obtain an N-terminal pro b-type natriuretic peptide (NT-proBNP) level as well as a BNP for diagnostic purposes. NT-proBNP is a non-active prohormone that is released in the same way BNP is.

The NT-proBNP level will also be increased if there are indications of new-onset or worsening heart failure. Medical professionals still use a BNP as the gold standard bloodwork for heart failure diagnosis.

Some providers may also obtain anatrial natriuretic peptide (ANP) level. ANP is a natriuretic peptide hormone, similar to BNP, but is secreted in a different area of the heart. This test may not be as indicative of heart failure unless it has progressed to severe.

Healthcare providers may also order the following tests in addition to a BNP and/or NT-proBNP:

• Stress test
• Echocardiogram
• Electrocardiogram (ECG or EKG)
• Chest X-ray
• Complete blood count
• Complete metabolic panel
• Magnetic resonance imaging (MRI)
• Computed tomography (CT)

What Is Congestive Heart Failure (CHF)?

Congestive heart failure (CHF) is a dangerous condition in which the heart fails to adequately pump blood throughout the body. As a result, the body’s tissues and organs do not get enough nutrients and oxygen.

CHF is failure of the heart muscle and inability to perform properly. Heart failure can be either acute, happens quickly, or chronic, develops slowly over a long period of time.

Heart failure does not mean that the heart has stopped beating, it simply means the heart is not functioning properly. It can affect one or both sides of the heart. Specifically, congestive heart failure is a type of heart failure; however, the terms are often used interchangeably.

Congestive heart failure is specifically when blood returning to the heart backs up and causes congestion in the body resulting in edema. The fluid can also back up into the lungs causing pulmonary edema. CHF affects the body's inability to function properly including the kidneys' ability to dispose of sodium and water.

According to the Centers for Disease Control and Prevention, approximately 6.2 millionadults in the United States have heart failure.

Medical conditions that can increase risk associated with CHF include but are not limited to:

• Coronary artery disease (CAD)
• Diabetes
• High blood pressure
• Obesity
• Valvular heart disease

CHF can be deadly if left untreated by a healthcare provider. A BNP level is used to determine cardiac function and while there is no agreed-upon first line test, a BNP is often a good cardiac marker for heart failure.

How Does the Test Work?

BNP, first discovered in 1988, belongs to the natriuretic peptide family that also contains atrial natriuretic peptide (ANP), C‐type natriuretic peptide (CNP), and urodilatin.

Naturally the heart secretes natriuretic peptides to maintain a normostatic blood pressure and blood plasma volume and to prevent excess salt and water retention. The major source of BNP synthesis and secretion is the ventricular myocardium specifically in response to the left ventricular stretching or wall tension.

Other actions of natriuretic peptides, including BNP include:

• Down-regulating the sympathetic nervous system and the renin-angiotensin-aldosterone system
• Facilitating natriuresis and diuresis through the afferent and efferent hemodynamic mechanisms of the kidney and distal tubules
• Decreasing peripheral vascular resistance
• Increasing smooth muscle relaxation

In CHF, these natriuretic peptides are unable to function properly. This causes a rise in your BNP which is used as an indicator for new onset heart failure or worsening heart failure.

Limitations

One notable limitation of a BNP test is the differentiation of heart failure versus other causes of dyspnea in patients with an atypical heart failure presentation. For example, BNP does not reliably differentiate between heart failure with preserved ejection fraction and heart failure with reduced ejection fraction.

Researchers have found that a NT-proBNP is the strongest independent predictor of a final diagnosis of acute heart failure.

There are factors that can naturally increase and decrease BNP levels without the presence of heart failure.

BNP levels are elevated in:

• Older adults
• Women
• Renal dysfunction
• Sepsis
• Lung disease
• Hypertension
• Hyperthyroidism
• Excessive cortisol levels
• Advanced liver disease
• Brain hemorrhages

BNP levels are lower in patients with:

• Obesity
• Hypothyroidism
• Advanced end-stage heart failure
• ACE inhibitors
• Diuretics, e.g. Spironolactone
• Beta blockers

It is important to note that some tests can result in false negatives, which might indicate normal values of BNP when a person does have heart failure. For this reason, healthcare providers will assess all symptoms and run other diagnostic tests when warranted.

Risks and Contraindications

There are very few risks or contraindications for a BNP blood test. The main risk from having blood drawn is the initial prick from the needle, slight discomfort, and possible slight bruising at the needle insertion site. These are very minor and often go away almost immediately. The benefits of the BNP far outweigh any risks.

Before the Test

Once a healthcare provider recommends this test, the patient can expect to immediately have the bloodwork drawn. Often this test is done urgently for concern of new onset or worsening heart failure; however, in patients with chronic heart failure this might be an ongoing routine lab.

Timing

The process of obtaining a BNP is rather quick. If the lab is done in an inpatient setting, a phlebotomist will come directly to the patient's room to draw the bloodwork. The results will then be send electronically to the electronic medical record (EMR) and the ordering healthcare provider. Outpatient BNP levels will report to the ordering healthcare provider within several days of the lab being drawn.

Location

A BNP can be drawn in a hospital setting during an inpatient visit, emergency room visit, or office visit. It can also be drawn at an outpatient lab such as Quest Diagnostics or LapCorp.

Food and Drink

Patients can eat and drink prior to the bloodwork. However, it's important that the ordering healthcare provider knows all medications, herbs, vitamins, and supplements you are taking as the results might be altered.

Cost and Health Insurance

A BNP level is generally covered by private and government insurance. It is important to speak to your healthcare provider and insurance specialist regarding healthcare coverage. If the BNP is to be drawn in an outpatient setting, insurance might only cover specific laboratory locations.

Other Considerations

If the bloodwork is drawn at an outpatient lab, patients should expect to bring their insurance information and the lab prescription to the location. Some healthcare providers will be able to electronically send the lab request form; however, it is always recommended to have a hard copy as well.

During the Test

The blood draw will be performed by either your healthcare provider, a nurse, or a phlebotomist. A needle will be inserted into your arm, and blood will be drawn from it. The blood drawn will be transferred into the appropriate test tube or vial.

You may feel a little stinging while the needle is inserted and while it’s being used to pull blood, but that’s normal. If your veins are hard to see, a tourniquet may be tied around your arm for a few seconds prior to and during the blood draw. This will allow your veins to become more prominent and easier to see. Some will also gently slap the vein in order for it to become more prominent.

This entire process is very quick lasting a minute or two. If you feel any serious pain during the process, you should immediately tell the healthcare provider, nurse, or whoever is drawing the blood.

After the Test

Once your blood has been taken, you’re free to leave if the lab was done in the outpatient setting. If you feel a bit dizzy or faint, you should sit for a few minutes and let it pass before you attempt to drive.Labs drawn while admitted as an inpatient require the patient to stay.

Keep the bandage on the site for at least an hour. If it starts to bleed again, apply pressure and raise the site above your head until it stops.Some people may experience bruising, especially if more than one attempt is needed to obtain blood. People who have bleeding disorders or are taking blood thinners are also more likely to experience bruising.

Interpreting Results

BNPs that are drawn at the hospital will often result within 30 minutes; however, labs that are drawn at an outpatient laboratory may take several days to result. Either way, the labs will be sent to the ordering provider and interpreted prior to your notification of the results.

As previously mentioned, BNP levels can be affected by numerous factors. For this reason, interpretation of the findings is left to the provider as these factors are taken into consideration. If previous BNP levels were drawn, healthcare providers will trend the results to determine the severity of the heart failure.

Follow-Up

Follow-up will depend on many factors including the reason why the test was performed in the first place. If your levels are abnormal, it's important to talk to your healthcare provider about the reasons why, any further testing that is indicated, and when you should have a repeat BNP test. It's helpful to write down any specific instructions or follow-up appointments.

A Word From Verywell

Undergoing and receiving test results can cause anxiety for some individuals especially regarding possible or worsening heart failure. It's important to speak to your healthcare provider regarding all results and next steps. Heart failure is manageable but only with the proper course of action including lifestyle changes such as diet and exercise.