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.
Before a nuclear stress test
First, 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.
During a nuclear stress test
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 sticky patches (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're 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'll probably walk on a treadmill or ride a stationary bike. You'll 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'll 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:
- 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.
You'll have another injection of radiotracer when your heart rate peaks. About 20 to 40 minutes later, you'll lie still on a table and have a second set of images made of your heart muscle. The dye shows any areas of your heart receiving inadequate blood flow.
Your doctor will use the two sets of images to compare the blood flow through your heart while you're at rest and under stress.
After a nuclear stress test
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.