A nuclear stress test lets doctors see pictures of your heart while you are resting and after you have exercised. The test can show the size of the heart’s chambers, how well the heart is pumping blood, and whether the heart has any damaged or dead muscle.

What is a Nuclear Stress Test?

A nuclear stress test measures blood flow to your heart at rest and while your heart is working harder as a result of exertion or medication. The test provides images that can show areas of low blood flow through the heart and damaged heart muscle.

The test usually involves taking two sets of images of your heart — one while you’re at rest and another after you heart is stressed, either by exercise or medication.

You may be given a nuclear stress test, which involves injecting a radioactive dye into your bloodstream, if your doctor suspects you have coronary artery disease or if a routine stress test didn’t pinpoint the cause of symptoms such as chest pain or shortness of breath. A nuclear stress test may also be used to guide your treatment if you’ve been diagnosed with a heart condition.

What should I expect?

A nuclear stress test can take two to five hours. When you arrive, you’ll be asked about your medical history and how often and strenuously you exercise.

During a nuclear stress test

Before you start the test, a technician inserts an intravenous line (IV) into your arm or hand and places sticky patches (electrodes) on your chest, legs and arms, which connect by wires to an electrocardiogram machine. The electrocardiogram records the electrical signals that trigger your heartbeats. A cuff on your arm checks your blood pressure during the test.

If you’re unable to exercise adequately, you may be given a medication through your IV that increases blood flow to your heart muscle — simulating what exercise does — for the test. Depending on which medication is used, possible side effects may be similar to those caused by exercise, such as a flushing or shortness of breath.

If you’re exercising, you’ll likely begin walking on the treadmill slowly. As the test progresses, the speed and incline of the treadmill increases. You can use the railing on the treadmill for balance, but don’t hang on tightly, as this may skew the results of the test. On a stationary bike, the resistance increases as the test progresses, making it harder to pedal.

You continue exercising until 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
  • Dizziness

You can stop the test any time you’re too uncomfortable to continue.

Injection of dye

A radioactive dye is injected into your bloodstream through the IV. First, images will be taken of your heart at rest. Then, after you’ve exercised or been given medication to stimulate your heart, you’ll receive more radioactive dye through the IV. You’ll again lie on a table while a scanner similar to an X-ray machine creates images of your heart muscle. The dye shows inadequate blood flow to part of your heart as a light spot on the images.

The two sets of images allow your doctor to compare the blood flow through your heart while you’re at rest and while your heart is pumping harder as a result of exercise or medication.

After a nuclear stress test

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, but drinking plenty of water will help flush the dye out of your system.