What you can expect

By Mayo Clinic Staff

When you arrive for your nuclear stress test, your doctor asks you about your medical history and how often you typically exercise. This helps determine the amount of exercise that's appropriate for you during the stress test.

During a nuclear stress test

Before you start the test, a member of your health care team places sticky patches (electrodes) on your chest, legs and arms. The electrodes are connected by wires to an electrocardiogram (ECG or EKG) machine. The electrocardiogram records the electrical signals that trigger your heartbeats. A blood pressure cuff is placed on your arm to check your blood pressure during the test.

If you're unable to exercise adequately, you may be injected with a medication that increases blood flow to your heart muscle — simulating exercise — for the test.

You then begin walking on the treadmill or pedaling the stationary bike slowly. As the test progresses, the speed and incline of the treadmill increases. A railing is provided on the treadmill that you can use for balance, but don't hang on to it tightly, as that may skew the results of the test. On a stationary bike, the resistance increases as the test progresses, making it harder to pedal.

The length of the test depends on your physical fitness and symptoms. The goal is to have your heart work hard for about eight to 12 minutes in order to thoroughly monitor its function. You continue exercising until your heart rate has reached a set target, you develop symptoms that don't allow you to continue or warning signs are detected by those monitoring your test, including:

  • Moderate to severe chest pain
  • Severe shortness of breath
  • Abnormally high or low blood pressure
  • An abnormal heart rhythm
  • Dizziness

You may stop the test at any time if you are too uncomfortable to continue exercising.

Injection of dye

Once you've reached your maximum level of exercise, a radioactive dye called thallium or sestamibi (Cardiolite) is injected into your bloodstream through an intravenous (IV) line, usually in your hand or arm. This substance mixes with your blood and travels to your heart. A special scanner similar to an X-ray machine — which detects the radioactive material in your heart — creates images of your heart muscle. Inadequate blood flow to any part of your heart will show up as a light spot on the images because not as much of the radioactive dye is getting there.

After exercising, you'll be asked to rest for two to four hours. During this time, you shouldn't eat or drink anything or do any strenuous activities. After this time, you'll have a second set of images taken of your heart while you lie on an examination table. Again, a technician will inject radioactive dye through an IV and will take images of your heart. This second set of images will let your doctor compare the blood flow through your heart while you're exercising and at rest.

After a nuclear stress test

When your nuclear stress test is complete, you may return to your normal activities for the remainder of the day.

Dec. 08, 2011