A nuclear stress test is an imaging test used to check blood flow to the heart muscle at rest and during physical or medication-induced stress. It can help show whether certain areas of the heart are receiving enough blood.
The test may be recommended to evaluate coronary artery disease or a previous heart attack, especially in people with chest pain or a higher risk of heart disease. It may also be used in people with heart failure, after a heart transplant, or with certain heart valve conditions.
To prepare for a nuclear stress test, also called myocardial perfusion imaging or myocardial perfusion scintigraphy, you may need to avoid certain foods and drinks and temporarily stop some medications. Any medication changes should only be made according to your healthcare provider's instructions.
What is a nuclear stress test?
A nuclear stress test is used to evaluate how blood flows through the myocardium, or heart muscle, both at rest and during physical or medication-induced stress. This makes the test useful for identifying certain heart conditions or abnormalities.
The test can help identify areas of ischemia, which occurs when part of the heart muscle does not receive enough blood. Detecting cardiac ischemia can help guide treatment and reduce the risk of complications such as heart failure or a heart attack.
When it is recommended
According to guidance from leading US heart organizations, including the American College of Cardiology, American Heart Association, and American Society of Nuclear Cardiology, a nuclear stress test may be recommended when:
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There is chest pain, shortness of breath, or other symptoms that may be caused by reduced blood flow to the heart
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An electrocardiogram (ECG or EKG) or another heart test is abnormal or does not provide a clear answer
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Coronary artery disease is suspected or already known and more information is needed about blood flow to the heart
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New or worsening symptoms develop after a heart procedure such as angioplasty, stent placement, or coronary artery bypass surgery
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A person has reduced heart function and the doctor needs to assess how much heart muscle is still healthy
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A person is being evaluated before major noncardiac surgery, has a higher risk of heart complications, and has limited or unknown exercise capacity
Whether a nuclear stress test is appropriate depends on a person's symptoms, medical history, previous test results, and overall risk of heart disease.
How to prepare
Preparing for a nuclear stress test may involve changes to medications, food, and drinks.
1. Medications to avoid
Talk to your healthcare provider about all medications you take before the test. Depending on the type of nuclear stress test, you may be instructed to temporarily stop certain medications because they can affect your heart rate or interfere with the test results.
These medications may include calcium channel blockers such as verapamil and diltiazem, beta-blockers such as atenolol, propranolol, metoprolol, and bisoprolol, and methylxanthines such as aminophylline or theophylline.
Nitrate medications, such as isosorbide mononitrate, may also need to be temporarily stopped before the test if your healthcare provider determines that it is safe and appropriate.
Do not stop taking any prescription medication unless your healthcare provider specifically tells you to do so.
2. Eating and drinking before the test
According to the American Heart Association, patients may be asked to avoid caffeine for 24 hours before a nuclear stress test. This includes coffee, tea, caffeinated and decaffeinated beverages, energy drinks, certain sodas, chocolate, and other foods or drinks that contain caffeine.
Follow the testing center's instructions about eating before the test. You may be asked not to eat or drink for several hours beforehand, although small amounts of water may sometimes be allowed for taking medications.
You may also be advised to avoid alcohol before the test.
How the test is performed
During a nuclear stress test, a small amount of a radioactive tracer is injected into the bloodstream so that blood flow to the heart muscle can be evaluated. After the tracer is given, you may be instructed to drink water, eat a light snack, or walk briefly, depending on the testing center's protocol, to help improve the quality of the images.
The test generally has two stages:
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Resting phase: Images of the heart are taken while you are resting, usually while lying down.
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Stress phase: Images are taken after the heart has been stressed. This may be done through physical exercise, most commonly on a treadmill, or with medication that simulates the effects of exercise on the heart.
In some cases, medication-induced stress and physical exercise may be combined. The healthcare professional performing the test will determine the most appropriate approach after evaluating you.
Heart imaging begins after the radioactive tracer has had enough time to circulate and reach the heart muscle. Images are taken using a special camera that rotates around the chest or upper body.
Because both resting and stress images are usually needed, the test may be completed over one or two days, depending on the testing center's protocol. If both parts are performed on the same day, the order may vary.
Possible risks
Side effects are more likely during the medication-induced stress portion of the nuclear stress test because of the medication used to stress the heart. Possible symptoms include:
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A warm or flushed feeling
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Chest pain or discomfort
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Dizziness
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A drop in blood pressure
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Shortness of breath
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Nausea
Serious complications are uncommon, and patients are monitored throughout the test so that any adverse effects can be treated promptly. Hospital admission is generally not necessary after an uncomplicated nuclear stress test.
Contraindications for use
A nuclear stress test is generally avoided during pregnancy unless the potential medical benefit outweighs the risks associated with radiation exposure.
People who are breastfeeding should tell the healthcare team before the test. Depending on the radioactive tracer used, temporary interruption of breastfeeding or other precautions may be recommended.
