Test Overview

A cardiac blood pool scan shows how well your heart is pumping blood to the rest of your body. During this test, a small amount of a radioactive substance called a tracer is injected into a vein. A gamma camera detects the radioactive material as it flows through the heart and lungs.

The percentage of blood pumped out of the heart with each heartbeat is called the ejection fraction. It provides an estimate of how well the heart is working.

This test has other names, including cardiac flow study, cardiac nuclear scan, first-pass scan, and MUGA scan. This test can be done in slightly different ways to check how well the heart is working.

Why It Is Done

A cardiac blood pool scan is done to:

• Check the size of the heart chambers (ventricles).
• Check the pumping action of the lower ventricles.
• Look for an abnormality in the wall of the ventricles, such as an aneurysm.
• Look for abnormal movement of blood between the heart chambers.

How To Prepare

Before having a cardiac blood pool scan, tell your health professional if you:

• Are allergic to any medicines.
• Are or might be pregnant.
• Have recently had any test that uses a radioactive tracer, such as a bone scan or thyroid scan.
• Have a pacemaker or other metal device implanted in your chest. These devices may make it hard to obtain clear pictures of the blood flow through the heart.

You may be asked not to eat or drink for a few hours before the test. You may be asked to not have any caffeine or smoke for a few hours before the test.

If testing will include exercise, you should wear comfortable shoes and clothing.

Many medicines may affect the results of this test. Be sure to tell your health professional about all the non-prescription and prescription medicines you take.

Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean.

How It Is Done

A cardiac blood pool scan usually is done in a hospital by a radiology or nuclear medicine technician. Most people do not have to stay overnight in the hospital.

How the test is done is based on the type of scan you are having and the way your hospital does this test.

There are different types of scans. Two of these types are:

• First-pass scan. This scan makes pictures of the blood as it goes through the heart and lungs the first time.
• MUGA scan (multigated acquisition scan). This scan uses the electrical signals of the heart to trigger the camera to take a series of pictures that can be viewed later like a video. The pictures record the heart's motion and check how well it is pumping blood. A MUGA scan may be done before and after your heart is stressed with exercise.

Before the test

You will need to remove any jewellery that might interfere with the scan. You may need to take off all or most of your clothes. You will be given a cloth or paper gown to use during the test.

During the test

You will lie on an examination table beneath the gamma camera. Electrocardiogram (EKG, ECG) electrodes are attached to your chest so that the electrical signal of your heart can also be detected. Then the camera will be positioned close to your body. If you are cold or uncomfortable lying on the table, ask the technician for a pillow or blanket. The camera may be positioned in different places across your chest to record different views of your heart.

The technician cleans the site where the radioactive tracer will be injected. The injection site is typically in the arm, but it may be in the neck. If the arm is used, an elastic band, or tourniquet, is then wrapped around your upper arm to temporarily stop the flow of blood through the veins in your arm. This makes it easier to put the needle into a vein properly. A small amount of the radioactive tracer is then injected, usually into a vein on the inside of your elbow. The radioactive tracer is designed to attach to your blood cells for a short time.

If you are having a multigated acquisition (MUGA) scan, a blood sample may be taken and the tracer added to it, and then it will be reinjected into your vein.

The gamma camera will take pictures as the radioactive tracer moves through your bloodstream and into your heart. It is important not to move while the scan is under way.

The camera does not produce any radiation, so you are not exposed to any additional radiation while the scan is being done. You will need to hold still during each view. You may be asked to:

• Change position for each different view.
• Do some exercise between scans to see how well your heart functions after the stress of exercise.
• Take nitroglycerin to see how well your heart responds to the medicine.

After the test

Once your scan is complete, you usually will be able to leave the testing room right away. You may have to wait at the test centre until all of your scan images have been reviewed. If you moved during the scan and the images turned out blurry, the scan may have to be repeated.

Drink lots of water and urinate frequently after your scan to make sure that the tracer flushes completely out of your body. It takes a day or two for the tracer to be completely eliminated.

How long the test takes

How long the test takes depends on the type of scan you are having. Ask your doctor how long your test will take. It could be about 1 hour, or it could take a few hours.

How It Feels

You may feel nothing at all from the needle puncture when the tracer is injected, or you may feel a brief sting or pinch as the needle goes through the skin. Otherwise, a cardiac blood pool scan is usually painless. You will not feel anything from the operation of the gamma camera. You may find it hard to remain still during the scan. The examination table may feel cool. Ask for a pillow or blanket to make yourself as comfortable as possible before the scan begins.

Risks

Allergic reactions to the radioactive tracer are rare.

Occasionally, some soreness or swelling may develop at the injection site. These symptoms can usually be relieved by applying moist, warm compresses to your arm.

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.

Most of the tracer will leave your body through your urine or stool within a day. So be sure to flush the toilet right after you use it, and wash your hands well with soap and water. The amount of radiation in the tracer is very small. This means it isn't a risk for people to be around you after the test.

Results

A cardiac blood pool scan shows how well your heart is pumping blood to the rest of your body.

The most commonly reported value is the ejection fraction. This is the average amount of blood pumped out of the heart's left ventricle during each contraction.

Normal results include the following:

• The ejection fraction is more than 55%.
• The walls of the ventricles are contracting normally.

Many conditions can affect cardiac blood pool scan results. Your doctor will discuss any significant abnormal results with you in relation to your symptoms and past health.