Nuclear Stress Testing and Imaging

Why are you being sent for a nuclear stress test?

As coronary artery disease (CAD) progresses, the heart muscle may not receive enough blood supply when under stress.  This often results in chest pain (angina pectoris) or shortness of breath. On the other hand, there may be no outward physical signs of significant disease. If CAD is limiting blood flow to part of your heart, the nuclear stress test may be useful in detecting the presence and significance of CAD.

What is a nuclear stress test and what does it show?

A nuclear stress test is a diagnostic nuclear imaging study that uses radioactive tracers, called technetium and thallium, to produce images of the heart muscle. When combined with the stress component, either through exercise or use of an intravenous pharmacological agent, the nuclear stress images can help determine if the heart muscle is getting sufficient blood supply. After the radioactive tracers are injected through an IV, they travel in the bloodstream through the coronary arteries until they are picked up by the heart muscle. The areas of the heart that have an adequate blood supply pick up the tracer right away and more completely while areas that do not have adequate blood supply pick up the tracer very slowly or not at all.  The radioactive isotopes give off a small amount of radiation that is detected with a nuclear scanning camera.  If an area receives less blood than the rest of the heart (because of a blocked or narrowed artery), it will pick up a lower level of radioactivity and will show up as a lighter area, called a "defect." This is how we can tell whether or not there might be a blocked artery in the heart.

		Normal nuclear stress test demonstrating equal uptake of the radioisotope throughout the entire heart muscle.
		Abnormal nuclear stress test demonstrating significantly decreased uptake of radioisotope in the anterior wall consistent with a tight narrowing of the coronary artery (LAD) that supplies blood to the front of the heart.

What if you can’t exercise?

If you are unable to exercise, the stress test can still be completed by either using Lexiscan (regadenoson) or dobutamine (intravenous medications), to simulate exercise and obtain similar information as an exercise stress test.

What is the safety of this test?

You won't feel any different after you are injected with the radioactive isotopes. Most patients experience no side effects. Occasionally patients have a metallic taste in their mouth.

How do I prepare for the test?

• Do not eat or drink for after 12:00 midnight prior to the test, except water only with prescribed medications. 
• Take ALL prescribed medications unless otherwise told. The exceptions are Aggrenox and Dipyridamole, which should not be taken for 24 hrs prior to the test.
• Diabetic patients: If on insulin: Take ½ dose of your prescribed dose the night before and morning of the test.
  If taking oral (by mouth) diabetic medications: Take NO oral diabetic medications on the day of the stress test.  After completion of the test, please return to your normal doses of medications.
• NO CAFFEINE 24 hours prior to study.  For example, no coffee, tea, soda, chocolate, etc., including decaf/caffeine free drinks.
• Bring busy material. You will have periods of waiting throughout the test so bring a book, newspaper, knitting or something to keep you busy.
• No smoking for at least 12 hours prior to the test as smoking may interfere with the test results.
• Bring or wear comfortable clothing and shoes.  Slacks or shorts are preferred if you are exercising. You should wear comfortable footwear appropriate for brisk exercise if you are doing an exercise test.
• Do not wear oils or lotions before your test. Small sticky patches (electrodes) will need to stick to your chest.
• Please bring with you: insurance card(s), list of medications, and completed referral form (if required by your insurance company).

What happens during the test?

You will be greeted by a certified technician that will have you sign a consent form and will make sure you understand the test. A small IV will be started in a vein in your arm. Twelve electrode patches will be placed on your chest and torso. If you have hair on your chest, small areas may need to be shaved for the electrodes to adhere properly. Thallium will be injected through the IV and then you will be asked to relax for at least 20 minutes to let the thallium circulate to your heart. Once your waiting period is over, the nuclear medicine technician will have you lie under the camera for about 15-20 minutes. You will lay on your back on a comfortable table with your left hand behind your head. It is important that you remain still while the images are being taken. The camera will move around you (but don’t worry, your head is always exposed and therefore, even patients with “claustrophobia” usually have no difficulty with this test).

Following the completion of the first scan, you will be escorted to a stress testing room. A resting EKG and blood pressure will be recorded. Please be informed that your cardiologist may not be present during the stress test.  However, our physician assistant (PA), nurse practitioner, one of the other cardiologists in the group will be present and will forward the results to your cardiologist. 

Exercise dual isotope stress test

If you are having an exercise stress test, you get onto the treadmill and will be initially started at a slow speed. The treadmill’s speed and incline will be increased every three minutes until one of the following occurs:

• You exceed a "target" heart rate and become fatigued.
• Significantly abnormal changes on your EKG.
• You experience significant symptoms, such as shortness of breath, chest discomfort, dizziness, etc. that do not permit you to exercise any longer.
• Your blood pressure goes up too high.

If you are tiring, it is important that you warn the physician and technician because the test should not be terminated abruptly. One minute prior to the end of the test, the technician will need to inject the second isotope, technetium, followed by your completing one more minute of exercise. You will be given some time to rest before having your second scan under the nuclear camera. Please do not leave the area until you have been instructed that your test has been completed.

Lexiscan Dual Isotope Stress Test

For patients who are unable to exercise adequately on the treadmill, the drug Lexiscan may be given to produce an effect on the heart similar to exercise. During the test, you will be lying on a padded table and the drug Lexiscan will be injected through your IV. Lexiscan is a vasodilator, so you may feel warm or flushed, or experience chest pressure, headache, dizziness, nausea, or shortness of breath though most patients feel no symptoms. If you experience these symptoms it is perfectly normal, and they will shortly disappear. The Lexiscan is injected into your IV in less than one minute and directly followed by the second dose of nuclear isotope. You will be given some time to rest before having your second scan.  Please do not leave the area until you have been instructed that your test has been completed.

What is Lexiscan?

Lexiscan, a substance engineered based on a naturally occurring substance in your body, when injected acts as a vasodilator. It increases the blood vessel circumference of the coronary arteries (arteries that feed the heart) in order to increase blood flow to the heart. We have selected Lexiscan to replace the previously used Adenosine because of the fewer associated side effects and its ease of use. Any side effects you may experience will be generally predictable, short-lived, and easily tolerated. Side effects can include: chest pressure, dizziness, shortness of breath, flushing, headache, lightheadedness, nausea, or numbness. Lexiscan should not be used in patients who have a hypersensitivity to this drug and in patients who have known severe bronchospastic or bronchoconstrictive lung disease (e.g., asthma or COPD and are using regular inhalers or wheezing is heard on examination of your lungs prior to the procedure).  Each patient will be evaluated on the day of the procedure prior to the start of the stress test.

Dobutamine Dual Isotope Stress Test

For patients who are unable to exercise adequately on the treadmill and can’t take adenosine, the drug dobutamine can be used. Dobutamine works by increasing one’s heart rate and strength of heart contraction producing an effect on the heart similar to exercise. During the test, you will be lying on the padded table and the drug dobutamine will be infused through your IV. The dobutamine dose is increased every three minutes until you reach the target heart rate. If your heart rate has not reached the predicted "target" heart rate, a drug called atropine can be added to reach that goal.  Once your heart rate is at or has exceeded your "target" heart rate, you will receive the second radioactive isotope, technetium through your IV. The dobutamine will then be shut off and the test terminated.   You will be given some time to rest before having your second scan under the nuclear camera. Please do not leave the area until you have been instructed that your test has been completed, but certainly you can have something to drink while you wait.

MUGA

A multigated acquisition (MUGA) scan is used to accurately determine how well your heart is pumping.  During the test, a radiotracer is injected into a vein, and 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 and provides an estimate of how well the heart is working.  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. These scans are routinely used before and after receiving a heart transplant to assess how well the heart is working, prior to being considered for a automatic internal cardiac defibrillator (AICD), and also may be used to monitor the ejection fraction in people receiving chemotherapy, especially those receiving doxorubicin (Adriamycin).

What are the qualifications of the nuclear cardiology facility as well as the training of the physicians interpreting the studies?

The nuclear facility meets the highest level of standards.  It is a certified laboratory by The Intersocietal Commission For The Accreditation of Nuclear Medicine Laboratories (ICANL).  In addition, not only have all of the nuclear cardiologists met the American College of Cardiology training requirements but they are also all individually certified by the Certification Board of Nuclear Cardiology after having passed the certification test.