Cardiac Nuclear Imaging (Nuclear Stress Test)

Healthcare providers giving man on treadmill a cardiac stress test.

Cardiac nuclear imaging measures the flow of blood in your heart at rest and then during exercise. The images are compared to determine whether there are any blockages in the arteries, changes in blood flow or oxygen supply from resting to the stressed state, areas of scar tissue, or if there has been a prior heart attack. It also measures how well the heart muscle squeezes and pumps. The test is also sometimes called a “perfusion scan” or a "SPECT MPI" (single photon emission computed tomography myocardial perfusion imaging). For the scan, a small amount of radioactive material called “tracer” is delivered into the bloodstream. A special camera then scans the tracer in the blood as it flows through the heart muscle. Areas of the heart that have good blood flow absorb the tracer. Areas that are not getting enough blood will not absorb the tracer. This can be a sign of a blocked artery, vessel narrowing, or any area of the heart not receiving blood, perhaps as a result of damage from a heart attack. The tracer leaves your body within hours. This test can be done in a hospital or test center.

Before your test

Be prepared for your test by knowing the following: 

  • The entire test will take a few hours. For best results, prepare for your test as directed.

  • When you schedule the test, be sure to tell your healthcare provider about any medicines you take. Ask if you should stop taking any of them the day of the test.

  • Before your test, stop smoking and avoid caffeine for as long as directed. This includes avoiding medicines that have caffeine as an ingredient and all caffeine containing beverages and foods such as coffee, tea, and chocolate.

  • Don’t eat or drink for 4 to 6 hours before the test. Sips of water are OK.

  • On the day of the test, dress for comfort. Wear a 2-piece outfit, top and bottoms. Be sure to wear walking shoes.

During your test

Here is what to expect during your test:

  • You may be asked to change into a hospital gown from the waist up.

  • You will be attached to EKG, which monitors your heart rhythm, and blood pressure monitors. An IV (intravenous) line will be started in your arm.

  • At some point, scanning pictures will be taken while you rest. This may be done before you exercise or you may be asked to return for resting scans later that day or the next.

  • You will exercise on a treadmill or stationary bike for a few minutes. This increases the rate of blood flow to your heart muscle.

  • Speak up when you feel that you cannot exercise for even 1 more minute. At this point, the tracer is given to you through the IV, as this is considered the point of maximum stress. 

  • If you cannot exercise by using a treadmill or bicycle, special medicines can be used to artificially increase heart rate while you are resting. This is done to put your heart under stress. 

  • After you have received the tracer, you will be positioned on the scanning bed.

  • You must lie very still for up to 30 minutes. During this time, a scanning camera will be taking pictures of your heart. The images will show where blood flows through your heart muscle.

After your test

Before going home, ask when you may eat. Also, find out when to resume taking any medicines you were told to skip before the test. If you need to return for resting scans, follow any instructions. Most people can go back to their normal routine as soon as all parts of the test are finished. Drink plenty of water to help flush the tracer from your body.

Let the technologist know

Inform the technologist about the following:

  • What medicines you take

  • If you have diabetes, knee or hip problems, arthritis, asthma, or chronic lung disease

  • Recent chest pain since your last appointment

  • Inability to participate in exercise 

  • If you have had a stroke or have vascular disease of the leg

  • If you are pregnant, think you might be, or are nursing

Report any symptoms

Be sure to tell the healthcare provider if you feel any of the following during the test:

  • Chest, arm, or jaw discomfort

  • Severe shortness of breath

  • Dizziness or lightheadedness

  • Feelings of panic

  • Inability to participate in exercise 

  • Palpitations

  • Leg cramps or pain