What is a Nuclear Cardiology Stress Test?

What is a Nuclear Cardiology Stress Test?

Nuclear cardiology stress testing is performed to determine the presence and severity of coronary artery disease (CAD). This test is an effective method of viewing the circulation to the muscles of your heart under both rest and stress conditions. Motion images will also be taken to show the wall motion and efficiency of the left ventricle of your heart. If you are having a treadmill test, your physician can also obtain information regarding your blood pressure/heart rate response to exercise, any EKG abnormalities, and your conditioning.

A nuclear cardiology stress test consists of three parts:

  1. A chemically induced test or treadmill test.
  2. Imaging of the heart at rest
  3. Imaging of the heart after the stress part

The appropriate type of stress test will be decided by your physician or his/her assistant.

The reason this is referred to as a “nuclear” test is because a small amount of a radiopharmaceutical tracer is injected into your vein; this will tag to the muscles of your heart and be viewed by a gamma camera. Your test may be done in one day using 99mTc Tetrofosmin (radiopharmaceutical tracer) or in two days for patients with a weight in excess of 290lbs.

What does a Nuclear Treadmill Stress Test Involve?

When you first come in, a brief medical history will be taken by a technologist, nurse, or exercise physiologist. An intravenous line (IV) will be started. A radioactive dose will be injected and rest images will be done. You will wait approximately one-half hour, to allow the nuclear tracer time to be absorbed into the heart muscle, before taking images of your heart. The images take approximately 12-18 minutes using a specialized gamma camera. An exercise physiologist/nurse will put EKG leads onto your chest in order to monitor your heart. You will then walk on the treadmill using a standard exercise protocol. Your blood pressure, EKG rhythm and any symptoms you may have will be monitored by the exercise physiologist/nurse. When you reach a certain target heart rate, with or without symptoms, the radioactive agent 99mTc Tetrofosmin will be injected through the IV line and flushed with saline. You will need to continue to walk on the treadmill for another minute to circulate the radioactive material. Three EKG patches will be left on your chest. You will be wired up to acquire “gated” images to analyze the wall motion and left ventricular ejection fraction of the heart during the stress imaging portion of your test. There will be a half hour rest before taking your second set of images, in which you will then receive a light snack and fluids to ensure optimal images. The stress images will be done with the gamma camera, once again taking 12-18 minutes. There is a possibility of a third set of images, called prone imaging, where you will be asked to lay on your stomach and a gamma camera will rotate underneath of you. The purpose of this set of images is to distinguish breast or diaphragm artifact versus a true blockage in the coronary arteries. This set of images is dependent on the patient’s ability to lie in the necessary position.

The stress images will be compared to rest images in order to look at the blood flow to the heart. If a significant blockage is present in your coronary arteries a perfusion defect will show. If there is a defect in the stress but the rest images look normal, this is called ischemia. If there are matching defects in both stress and rest, an infarction (heart attack) has occurred. If there are no defects then the study is normal.

What is a “Chemical” Nuclear Stress Test?

When you first come in, a brief medical history will be taken by an exercise physiologist/nurse. An intravenous line (IV) will be started and a radioactive dose of 99mTc Tetrofosmin will be injected. After a half hour delay, resting images will be done of your heart. These images take approximately 12-18 minutes using a specialized gamma camera. An exercise physiologist/nurse will then put EKG leads onto your chest to monitor your heart.

If a patient cannot walk on the treadmill uphill and at an increasing speed due to a physical reason, or has certain EKG abnormalities such as a left bundle branch block, the physician may order a Lexiscan (Regadenosen) stress test. If a patient has severe asthma or other significant lung disease, the physician may order a Dobutamine stress test.

Regadenoson is a pharmacological agent that will cause dilation of all the blood vessels in the body. You may experience a flushed feeling, chest pressure and/or shortness of breath, similar to exercising. This part only takes 5 minutes and any of the side effects resolve quickly after the infusion is done. Your blood pressure and EKG will be monitored by an exercise physiologist/nurse. The radioactive material, 99mTc Tetrofosmin will be injected into the IV by the Nuclear Medicine Technologist immediately following the Regadenosen infusion. After the stress test is over, you will receive a light snack and fluids. You will have a half hour break before the stress images are acquired.

Dobutamine is a pharmacological agent that causes the heart rate to rise and the blood pressure to increase. This test is done with the patient lying down. Your blood pressure and EKG will be monitored by an exercise physiologist/nurse. The Dobutamine will be slowly infused into your IV, increasing in amount every three minutes. When your heart rate has reached a certain target determined by your age, the Nuclear Medicine Technologist will inject the 99mTc Tetrafosmin into the IV. The infusion will continue for another minute. This part usually takes a total of 6-12 minutes.

After the stress test is over, you will receive a light snack and fluids; you will have a half hour break before the stress images are acquired. The stress images will be done with a gamma camera, once again taking 12-18 minutes. Three EKG patches will be left on your chest, they will be wired up to acquire “gated” images to analyze the wall motion and left ventricular ejection fraction of the heart. There is a possibility of a third set of images, called prone imaging, where you will be asked to lay on your stomach and a gamma camera will rotate underneath of you. The purpose of this set of images is to distinguish breast or diaphragm artifact versus a true blockage in the coronary arteries. This set of image is dependent on the patient’s ability to lie in the necessary position.

The stress images will be compared with the rest images to look at the blood flow to the heart. If a significant blockage is present in your coronary arteries a perfusion defect will show. If there is a defect in the stress but the rest images look normal, this is called ischemia. If there are matching defects in both stress and rest images, an infarction (heart attack) has occurred. If there are no defects then the study is normal.

Preparations for Test

  • Do not have any caffeine products 12 hours before your test
        o This includes, but is not limited to, NO coffee, tea, decaffeinated coffee or tea (they have traces of caffeine). NO beverages that may contain caffeine such as pop. NO chocolate.
  • Do not have any food or drink 3 hours before the test.
        o You many drink water
  • Wear comfortable clothes and sneakers.
        o If doing a treadmill stress test NO sandals, slip on shoes, flip flops, high heels or open toed shoes. 
  • Consult with your physician or medical assistant on what medications you should or should not take the morning of the test, especially if you have diabetes. You may use nitroglycerin as needed for pain. 
  • Women under the age of 50, who are not surgically sterile, will need to have a blood test to check for pregnancy.

What information does a Nuclear Cardiology Stress Test Provide?

The treadmill part of the test will give information concerning your physical conditioning, any EKG irregularities, and blood pressure/heart rate response. A pharmacological test will also show any EKG abnormalities under stress conditions.

The stress images show the perfusion of the coronary arteries to the heart muscle. If a coronary artery is significantly blocked, blood flow is reduced and the radioactive tracer will not show or be noticeably diminished in the corresponding heart muscle. Analysis of the gamma camera images can identify the location, severity and extent of the defect of reduced blood flow to the heart.

The stress images will be compared to the rest images to look at the blood flow to the heart. If there is a defect in the stress but the rest images look normal, this is called ischemia. If there are matching defects in both stress and rest images, an infarction (heart attack) has occurred. If there are no defects then the study is normal.

How long does the test take?

A one day Nuclear Stress Test will take approximately 3 hours to complete. A two day Nuclear Stress Test will take approximately 2 - 2.5 hours on the stress day and 1.5 - 2 hours on the rest day.

There will be some wait time in between imaging; you may want to bring some reading material to pass the time.

How safe is a Nuclear Stress Test?

There is some risk involved in having a stress test, especially if you have severe heart disease. Our staff is very experienced at performing cardiac stress tests. Your vital signs will be monitored very carefully during the entirety of test. The test will be stopped if our staff believes that your safety may be compromised. We are prepared to handle any emergencies, should they occur.

The radioactive agents are used to show the blood flow to your heart. These tracers have been used for over thirty years and are considered very safe. The amount of radioactivity that you receive is about the same amount you would normally be exposed to over a period of 1-2 years just from background radiation. The only restriction to this test would be if there is any possibility you may be pregnant, currently trying to become pregnant, or nursing.

What is the Reliability of a Nuclear Cardiology Stress Test?

If good quality images are acquired and the target heart rate is met through a treadmill test, a Nuclear Stress Test is capable of detecting significant coronary artery disease approximately 85% of the time. Nearly 10% of patients may have a “false-positive” test, i.e. when the results show a defect where none actually exists. Technical quality problems with the images may occur if a patient is extremely obese, has large breasts, has a prominent diaphragm, or has an EKG with a left bundle branch block.