What Is A Nuclear Stress Test
A nuclear stress test uses radioactive dye and an imaging machine to create pictures showing the blood flow to your heart. The test measures blood flow while you are at rest and are exerting yourself, showing any areas with damage or low blood flow. First, a radioactive dye is injected, then two sets of images are taken of your heart; one set during rest and the other during exertion. A nuclear stress test can help better determine your risk of a heart attack or other cardiac event if your doctor knows or suspects that you have coronary artery disease. The Nuclear Medicine unit of the Radiology Department will provide Nuclear Cardiac Stress tests for those patients who cannot walk on a treadmill.
Why the Test is Performed
A nuclear stress test may be necessary if a routine stress test did not discover the cause of your chest pain or shortness of breath. A nuclear stress test can help determine if you have coronary artery disease and how severe the condition is. A nuclear stress test may also be used to guide your treatment if you’ve been diagnosed with a heart condition to find out how well your treatment is working. It may also determine how much exercise your heart can handle.
How to Prepare for the Test
- Your doctor may ask you not to eat or drink for a period of time prior to the test.
- Do not smoke prior to the test.
- Do not consume caffeine the day before or day of the test.
- Talk to your doctor about all of the medications you are taking, including over the counter, to determine whether any of them will interfere with the outcome of the test.
- If you use an inhaler for asthma, bring it with you to the test. Make sure the staff monitoring you know you use an inhaler.
- Wear comfortable clothes and walking or running shoes.
- Do not apply creams, lotions, or perfumes the day of the test.
What To Expect During the Test
A nuclear stress test may be performed in combination with an exercise stress test, in which you walk on a treadmill. If you aren’t able to exercise, you’ll receive a drug through an IV that mimics exercise by increasing blood flow to your heart. A nuclear stress test can take two or more hours, depending on the radioactive material and imaging tests used.
- Your doctor will ask you some questions about your medical history and how often and strenuously you exercise. This helps determine the amount of exercise that’s appropriate for you during the test. Your doctor will also listen to your heart and lungs for any abnormalities that might affect your test results.
- Before you start the test, a technician inserts an intravenous (IV) line into your arm and injects a radioactive dye (radiopharmaceutical or radiotracer).
- The radiotracer may feel cold when it’s first injected into your arm. It takes about 20 to 40 minutes for your heart cells to absorb the radiotracer. Then, you’ll lie still on a table and have your first set of images taken while your heart is at rest.
- A nurse or technician will place electrodes on your chest, legs, and arms. Some areas may need to be shaved to help them stick. The electrodes have wires connected to an electrocardiogram machine, which records the electrical signals that trigger your heartbeats. A cuff on your arm checks your blood pressure during the test. You may be asked to breathe into a tube during the test to show how well you are able to breathe during exercise.
- If you can’t exercise, your doctor will inject the drug into your IV line that mimics exercise by increasing blood flow to your heart. Possible side effects may be similar to those caused by exercise, such as flushing or shortness of breath. You might get a headache.
For an exercise stress test, you will be asked to walk on a treadmill or ride a stationary bike. You will start slowly, and the exercise gets more difficult as the test progresses. You can use the railing on the treadmill for balance. Don’t hang on tightly, as this may skew the results.
- You will continue exercising until either your heart rate has reached a set target, you develop symptoms that don’t allow you to continue, or you develop one of the following symptoms:
- Moderate to severe chest pain
- Severe shortness of breath
- Abnormally high or low blood pressure
- An abnormal heart rhythm
- Certain changes in your electrocardiogram
- You and your doctor will discuss your safe limits for exercise. You can stop the test anytime you’re too uncomfortable to continue.
- When your heart rate peaks, you will have another injection of radiotracer. About 20 to 40 minutes later, a second set of images will be made of your heart. The dye shows any areas with inadequate blood flow.
- Your doctor will use the images to compare the blood flow through your heart while you are at rest and under stress.
- After you stop exercising, you might be asked to stand still for several seconds and then lie down for a period of time with the monitors in place. Your doctor can watch for any abnormalities as your heart rate and breathing return to normal.
- When the test is complete, you may return to normal activities unless your doctor tells you otherwise. The radioactive material will naturally leave your body in your urine or stool. Drink plenty of water to help flush the dye out of your system.
What the Test Results Show
Your doctor will discuss your nuclear stress test results with you. Your results could show:
- Normal blood flow during exercise and rest. You may not need further tests.
- Normal blood flow during rest, but not during exercise. Part of your heart isn’t receiving enough blood when you’re exerting yourself.
- This might mean that you have one or more blocked arteries (coronary artery disease).
- Low blood flow during rest and exercise. Part of your heart isn’t getting enough blood at all times, which could be due to severe coronary artery disease or a previous heart attack.
- Lack of radioactive dye in parts of your heart. Areas of your heart that don’t show the radioactive dye have tissue damage from a heart attack.
- If you don’t have enough blood flow through your heart, you may need to undergo coronary angiography. This test looks directly at the blood vessels supplying your heart. If you have severe blockages, you may need a coronary intervention (angioplasty and stent placement) or open-heart surgery (coronary artery bypass).
Potential Risks of the Test
While generally safe, some potential risks of a nuclear stress test include:
- Allergic reaction. Though rare, you could be allergic to the radioactive dye that’s injected during a nuclear stress test.
- Abnormal heart rhythms (arrhythmias). Arrhythmias brought on during a stress test usually go away shortly after you stop exercising or the medication wears off. Life-threatening arrhythmias are rare.
- Heart attack (myocardial infarction). Although extremely rare, it’s possible that a nuclear stress test could cause a heart attack.
- Dizziness or chest pain. These symptoms can occur during a stress test. Other possible signs and symptoms include nausea, shakiness, headache, flushing, shortness of breath and anxiety. These signs and symptoms are usually mild and brief, but tell your doctor if they occur.
- Low blood pressure. Blood pressure may drop during or immediately after exercise, possibly causing you to feel dizzy or faint. The problem should go away after you stop exercising.