Why it's done

During a nuclear stress test

Before you start the test, a nurse or technician inserts an IV line into your arm and injects the radiotracer (also called a radiopharmaceutical).

The radiotracer may feel cold when it's first injected into your arm. It takes a few minutes for your heart cells to absorb the radiotracer. Once it does, you'll lie still on a table and have your first set of images taken while your heart is at rest.

Then, 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 (ECG or EKG) 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 a medication into your IV line that increases 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.

If your nuclear test is combined with a traditional exercise stress test, you'll be asked to walk on a treadmill or ride a stationary bike. You'll start slowly. The exercise gets more difficult as the test continues. You can use the railing on the treadmill for balance. Don't hang on tightly, as this may alter the results.

You'll continue exercising until your heart rate has reached a set target or you develop symptoms that don't allow you to continue, which may include:

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

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 after exercising. Then, you'll lie still on a table and have the second set of images taken. The radiotracer shows up on the images and highlights any areas of your heart that don't get enough blood flow.

Your doctor will compare the two sets of images taken to see how blood flows through your heart while you're at rest and under physical stress.