Cardiac Blood Pool Scan

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.

There are two types of cardiac blood pool scans.

    First-pass scan. This scan makes pictures of the blood as it goes through the heart and lungs the first time. A first-pass scan can be used in children to look for heart problems that have been present since birth (congenital heart disease).
    Gated scan or multigated acquisition (MUGA) 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 motion picture. The pictures record the heart's motion and determine if it is pumping (contracting) properly. MUGA scanning may take 2 to 3 hours to obtain all the needed views and can be done both before and after you exercise. You may be given nitroglycerin to see how your heart responds to this medicine. MUGA scanning may be done after a first-pass scan. It is usually not done on children.

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 should not have any caffeine or smoke for 4 to 6 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 nonprescription and prescription medicines you take.



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.
Before the test

You will need to remove any jewelry 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, which is a round metal instrument about 3 ft (1 m) wide, 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 on your arm where the radioactive tracer will be injected. 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.

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, which may take up to 5 minutes. 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.

The radioactive tracer is designed to attach to your blood cells, which takes 20 to 30 minutes. You will then have to wait 2 to 4 hours until the tracer is completely absorbed by your red blood cells. During that time, you may have to stay at the test center. Some test centers may allow you to leave and come back when it is time for your scan.

Testing usually takes 10 minutes to an hour, depending on which studies are done. MUGA scanning may require 2 to 3 hours to obtain all the needed views.
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 center 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 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. Most of the tracer will be eliminated from your body (through your urine or stool) within a day, so be sure to promptly flush the toilet and thoroughly wash your hands with soap and water. The amount of radiation is so small that it is not a risk for the people you come in contact with after the test.

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.

There is always a slight risk of damage to cells or tissue from being exposed to any radiation, including the low level of radiation released by the radioactive tracer used for this 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, which is the average amount of blood pumped out of the heart's left ventricle during each contraction.

Normal results include:1

    Ejection fraction is 55% to 65%.
    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.
What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

    Fast or irregular heart rhythms.
    Long-acting nitrate medicines and digoxin.
    Recent nuclear scans, such as thyroid or bone scans.
    Barium, such as from a barium enema, and bismuth, such as Pepto-Bismol.
    Inability to remain still during the test. You may not be able to have the test if you have severe back problems or other physical disabilities that prevent you from lying flat.
    Obesity.

What To Think About

    Cardiac blood pool imaging is not usually done during pregnancy because the radiation could damage a developing fetus.
    The cardiac blood pool scan is a safe and accurate way to determine overall heart function.
    Multigated acquisition (MUGA) scans are routinely used before and after receiving a heart transplant to assess how well the heart is working. MUGA also may be used to monitor the ejection fraction in people receiving chemotherapy.
    Generally, an echocardiogram provides as much information as a MUGA scan and is less invasive. But a MUGA scan provides more accurate information about ejection fraction than an echocardiogram, especially in people who are obese or who have lung disease. For more information, see the topic Echocardiogram.