(RNA, MUGA, Gated Blood Pool Scan [Resting and Exercise], Gated Cardiac Scan, Exercise Gated Blood Pool Scan, Cardiac Blood Pool Imaging)
What is a resting and exercise radionuclide angiogram (RNA)?
RNA is a type of nuclear medicine procedure. This means that a tiny amount of a radioactive substance, called a radionuclide (radiopharmaceutical or radioactive tracer), is used during the procedure to assist in the examination of the tissue under study. Specifically, resting RNA evaluates the heart's chambers in motion.
A radionuclide (usually technetium) will be injected into an arm vein to "tag" the blood cells so their progress through the heart can be traced with a scanner. A special camera (gamma camera) will make recordings of the heart wall at work, like a motion picture. These recordings will be synchronized with the heartbeat by using the electrocardiogram (ECG, or recording of the heart's electrical activity).
A doctor specially trained in nuclear cardiology will study the films to evaluate the heart's pumping function and ejection fraction (the volume of blood pumped out with each heartbeat).
An RNA procedure with rest and exercise is performed to assist the doctor in assessing the heart's function during exercise after comparing it to the heart's function at rest. If the heart muscle does not move in a normal manner, and/or a less-than-normal amount of blood is pumped out by the heart, this may indicate one or more of the following:
Injury to the heart muscle, possibly as a result of decreased blood flow to heart muscle due to clogged coronary arteries
An enlargement of one or more of the heart's chambers
Aneurysm (a weak area in the heart muscle)
Toxic effects of certain medications
Other related procedures that may be used to assess the heart include resting or exercise electrocardiogram (ECG or EKG), Holter monitor, signal-averaged ECG, cardiac catheterization, chest X-ray, computed tomography (CT scan) of the chest, echocardiography, electrophysiological studies, magnetic resonance imaging (MRI) of the heart, myocardial perfusion scans, and cardiac CT scan.
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Coronary artery disease
Coronary artery disease is the narrowing of the coronary arteries (the blood vessels that supply oxygen and nutrients to the heart muscle), caused by a buildup of fatty material within the walls of the arteries. This process leads the inside of the arteries to become rough and narrowed, limiting the supply of oxygen-rich blood to the heart muscle.
To better understand how coronary artery disease affects the heart, a review of basic heart anatomy and function follows.
The heart is basically a pump. The heart is made up of specialized muscle tissue, called the myocardium. The heart's primary function is to pump blood throughout the body, so that the body's tissues can receive oxygen and nutrients and have waste substances taken away.
Like any pump, the heart requires fuel in order to work. The myocardium requires oxygen and nutrients, just like any other tissue in the body. However, the blood that passes through the heart's chambers is only passing through on its trip to the rest of the body. This blood does not give oxygen and nutrients to the myocardium. The myocardium receives its oxygen and nutrients from the coronary arteries, which lie on the outside of the heart.
When the heart tissue does not receive an adequate blood supply, it cannot function as well as it should. If the myocardium's blood supply is decreased for a length of time, a condition called ischemia may develop. Ischemia can decrease the heart's pumping ability because the heart muscle becomes weakened due to a lack of oxygen.
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If the blood supply to the heart muscle continues to decrease as a result of increasing obstruction of a coronary artery, a myocardial infarction, or heart attack, may occur. If the blood flow cannot be restored to the particular area of the heart muscle affected, the tissue dies.
Fortunately, the technology is available to restore blood flow to heart tissue when coronary artery blockages are diagnosed. One of several procedures used to diagnose and evaluate coronary artery disease is the RNA.
What are the reasons for a MUGA procedure?
Reasons for your doctor to request a radionuclide angiography include, but are not limited to, the following:
Shortness of breath
If a screening examination (such as an ECG) suggests a possibility of some type of heart disease process that needs to be explored further, a resting and exercise RNA may be performed.
There may be other reasons for your doctor to recommend resting and exercise RNA.
Make a Health Promise
Heart disease remains the number one killer nationwide. To help prevent heart disease or catch symptoms early, adults over 50 should have a full cardiovascular assessment. A coronary calcium scan can show just how at risk you are for a heart attack or other heart issues before other signs and symptoms occur. This is particularly useful for those with a family history of heart disease or other significant risk factors.
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What are the risks of a MUGA exam?
The amount of the radionuclide injected into your vein for the procedure is small enough that there is no need for precautions against radioactive exposure. The injection of the radionuclide may cause some slight discomfort. Allergic reactions to the radionuclide are rare.
If you are pregnant or suspect that you may be pregnant, you should notify your health care provider due to the risk of injury to the fetus from radionuclide angiography. Radiation exposure during pregnancy may lead to birth defects. If you are lactating, or breastfeeding, you should notify your health care provider due to the risk of contaminating breast milk with the radionuclide.
Patients who are allergic to or sensitive to medications, contrast dyes, iodine, tape, or latex should notify their doctor.
There may be other risks depending on your specific medical condition. Be sure to discuss any concerns with your doctor prior to the procedure.
Nicotine in cigarettes may cause spasm in the coronary arteries, which could affect the test results.
How do I prepare for a MUGA exam?
PLEASE NOTE: Nicotine in cigarettes may cause spasm in the coronary arteries, which could affect the test resuts.
Notify your doctor and when you schedule the exam if you have a pacemaker.
PRECAUTIONS: If you are pregnant or think you may be pregnant, please check with your doctor before scheduling the exam. We will discuss other options with you and your doctor.
BREASTFEEDING: If you are breastfeeding, you should notify your health care provider due to the risk of contaminating breast milk with the tracer.
CLOTHING: You may be asked to change into a patient gown. A gown will be provided for you. Lockers are provided to secure your personal belongings. Please remove all piercings and leave all jewelry and valuables at home.
Please to wear loose, comfortable clothing for the exercise portion of the test, as well as a comfortable pair of shoes.
EAT/DRINK: Fasting may be required before the procedure. You will be given specific instructions as to how long you should withhold food and/or liquids when you schedule your appointment.
ALLERGIES: Notify the radiologist or technologist if you are allergic to or sensitive to medications, contrast dyes or iodine. The injection of the radiotracer may cause some slight discomfort. Allergic reactions to the radiotracer are rare, but may occur.
MEDICATIONS: Please bring a list of all medications (prescription and over-the-counter) and herbal supplements that you are taking.
Based on your medical condition, your doctor may request other specific preparation.
What happens during a MUGA?
A resting and exercise RNA may be performed on an outpatient basis or as part of your stay in a hospital. Procedures may vary depending on your condition and your doctor's practices.
Generally, a resting and exercise RNA follows this process:
You will be asked to remove any jewelry or other objects that may interfere with the procedure.
If you are asked to remove clothing, you will be given a gown to wear.
An intravenous (IV) line will be started in your hand or arm.
You will be connected to an ECG machine with electrodes (leads) and a blood pressure cuff will be attached to your arm.
You will lie flat on a table in the procedure room.
The radionuclide will be injected into the vein to "tag" the red blood cells. Alternatively, a small amount of blood will be withdrawn from your vein so that it may be tagged with the radionuclide. The radionuclide will be added to the blood and will be absorbed into the red blood cells.
During the procedure, it will be very important for you to lie as still as possible, as any movement can adversely affect the quality of the scan.
The gamma camera will be positioned over you as you lie on the table.
The gamma camera will obtain images of the heart as it pumps the blood through your body.
You may be asked to change positions during the test; however, once you have changed position, you will need to lie still without talking.
After the resting scan has been completed, you will be asked to exercise on the treadmill or stationary bicycle. If you notice any discomfort, such as chest pain, dizziness, headache, shortness of breath, or extreme fatigue while exercising, you should let the technologist or doctor know.
Once all the heart images have been obtained, your vital signs (heart rate, blood pressure, and respiration rate) will be monitored for a period of time.
The IV line will be discontinued, and you will most likely be allowed to leave, unless your doctor instructs you differently.
What happens after a MUGA?
You should move slowly when getting up from the scanner table to avoid any dizziness or lightheadedness from lying flat for the length of the procedure.
You will be instructed to drink plenty of fluids and empty your bladder frequently for 24 to 48 hours after the test to help flush the remaining radionuclide from your body.
The IV site will be checked for any signs of redness or swelling. If you notice any pain, redness, and/or swelling at the IV site after you return home following your procedure, you should notify your doctor as this may indicate an infection or other type of reaction.
Your doctor may give you additional or alternate instructions after the procedure, depending on your particular situation.