Cardiac Perfusion Scan

Test Overview

A cardiac perfusion scan measures the amount of blood in your heart muscle at rest and after it has been stressed. It is often done to find out what may be causing symptoms like angina (such as chest pain or pressure). It may be done after a heart attack to see if areas of the heart are not getting enough blood or to find out how much heart muscle has been damaged from the heart attack.

During the scan, a camera takes pictures of the heart after a special test medicine (radioactive tracer) is given through an I.V. The tracer travels through the blood and into the heart muscle. As the tracer moves through the heart muscle, areas that have good blood flow absorb the tracer. Areas that do not absorb tracer may not be getting enough blood or may have been damaged by a heart attack.

A set of pictures will be made when you are at rest and after your heart has been stressed, either by exercise or after you have been given a medicine. The resting pictures are then compared with the stress images.

This test is also known by other names including myocardial perfusion scan, myocardial perfusion imaging, thallium scan, sestamibi cardiac scan, and nuclear stress test.

Why It Is Done

A cardiac perfusion scan is done to:

• Find the cause of unexplained chest pain or pressure.
• Find the cause of chest pain or pressure brought on by exercise.
• Check for the location and amount of damage caused by a heart attack.
• Identify coronary artery disease (CAD).
• Help make treatment decisions for a person with CAD.
• Check to see that the heart is getting enough blood after heart surgery or angioplasty.
• Identify a congenital heart defect and determine how serious it is. These scans may also be done following surgery to correct a congenital heart defect.

How To Prepare

Tell your doctor ALL the medicines, vitamins, supplements, and herbal remedies you take. Some may increase the risk of problems during your test. Your doctor will tell you if you should stop taking any of them before the test and how soon to do it.

If you take a medicine that prevents blood clots, your doctor may tell you to stop taking it before your test. Or your doctor may tell you to keep taking it. (These medicines include aspirin and other blood thinners.) Make sure that you understand exactly what your doctor wants you to do.

You may be told not to eat or drink for several hours before the scan. You may be told to avoid alcohol, tobacco, and drinks that have caffeine for at least 24 hours before the test.

Wear comfortable shoes, such as running shoes, and loose shorts or pants. Don't wear jewelry to the test.

If you are breastfeeding, you may want to pump enough breast milk before the test to get through 1 to 2 days of feeding. The radioactive tracer used in this test can get into your breast milk and is not good for the baby.

How It Is Done

A cardiac perfusion scan is usually done in a hospital radiology or nuclear medicine department, in a doctor's office, or at an outpatient clinic.

Resting scan

For resting scans, in which you do not exercise, you will be asked to remove your clothing above the waist. You will be given a hospital gown to wear. Electrodes might be attached to your chest to keep track of your heartbeats.

You will have a very thin tube, called an I.V., going into your arm or hand. A small amount of the radioactive tracer will be put in the I.V.

You will lie on your back on a table with a large camera above your chest. The camera records the tracer that has moved from your blood into your heart muscle.

You will be asked to remain very still during each scan. The camera will move to take more pictures at different angles. Several scans will be taken.

Stress scan using medicine

The stress scan is done in two parts. In many hospitals, the first images are taken while the person is at rest. Then a second set of images is taken after the person is given a medicine such as adenosine. It makes the heart respond like it would to exercise. Exercise and the medicine increase the amount of blood that your heart needs. Sometimes the stress scan is done first and the resting scan might be done the next day. Sometimes only a stress scan is done.

A stress test with medicine is often combined with a low-level exercise stress test. Medicine is also used when a person can't exercise for some reason.

For this test, you will be asked to sit or lie on the examining table. You will be given a routine electrocardiogram (EKG or ECG).

Then you will be given the medicine through your I.V. More EKGs and blood pressure measurements are often taken. After the medicine takes effect, a small amount of radioactive tracer is given through your I.V.

You will wait about 30 to 60 minutes. You might be asked to eat or drink something. Then you will lie down on a table for a set of scans. The camera records the tracer that has moved from your blood into your heart muscle.

Sometimes more pictures are taken after you rest for 2 to 4 hours, or even the next day.

Stress scan using exercise

For stress scans using exercise, your heart rate will be checked with an EKG. Because EKG electrodes need to be attached to the chest, men are usually bare-chested and women usually wear a bra, gown, or loose shirt.

The exercise stress scan is done in two parts. First a set of resting images is taken. Then a set of stress images is taken right after exercise. Sometimes the stress scan is done first and the resting scan might be done the next day.

In many hospitals, first resting pictures are taken using one type of tracer. More pictures are taken using a different tracer after your heart has been stressed by exercise.

In this stress test, you exercise on a treadmill or stationary bike. Your heart rate and blood pressure will be checked during the test and for 5 to 10 minutes after the test.

You will start by walking or pedaling slowly and easily. Every few minutes, the speed or incline of the treadmill or resistance of the bike may be increased. You will exercise until you need to stop or until you reach a suitable heart rate. At that point, you will be given a tracer medicine through your I.V.

You will then lie down on a table for scanning.

Sometimes more pictures are taken after you rest for 30 minutes to 4 hours.

How long the test takes

• Each scan may take about 30 to 60 minutes.
• How long the test takes will depend on how many scans you have and how long you wait between scans.

How It Feels

The cardiac scanning test itself is painless.

• You may feel a brief stinging or burning sensation when the I.V. is inserted into your vein.
• You may be uncomfortable lying still for a long time on the table during the scans.
• If medicine to stress your heart is used, you may have symptoms of mild nausea, headache, dizziness, flushing, or chest pain. These symptoms last just a few minutes.
• If you are asked to exercise, you may have chest pain, breathlessness, lightheadedness, aching in your leg muscles, and fatigue. Report these to the technician. If the symptoms are severe, the exercise part of the test may be stopped.

Risks

Cardiac perfusion scans are usually safe.

Anytime you're exposed to radiation, there's a small chance of damage to cells or tissue. That's the case even with the low-level radioactive tracer used for this test. But the chance of damage is very low compared with the benefits of the test.

There will be some risks when the test uses exercise or medicine to stress your heart. The amount of risk depends on the condition of your heart and your general level of health. The risks include:

• Fainting.
• Chest pain.
• An irregular heartbeat.
• Heart attack. There is a slight risk that death may result if a heart attack occurs during the test.

Results

Test results are usually available within 1 to 3 days.

Results are:

• Normal if radioactive tracer is evenly distributed throughout your heart muscle.
• Abnormal if areas of abnormal tracer absorption are present. This means some areas of heart muscle are not getting enough blood (ischemia). This may mean that the heart has been damaged or that coronary artery disease is present.