A nuclear cardiology stress test, sometimes called a nuclear or myocardial perfusion imaging study, measures the function of your heart.

For a nuclear cardiology stress test, you will be injected with a radioactive substance called an isotope. Injection of this isotope will be done when you are relaxed and again after your heart is stressed, which is done through exercise on a treadmill or by medication. After each injection of the radioactive isotope, pictures of your heart will be taken. This process may be repeated.

What does it tell the doctor?
This test tells your doctor if you have a blockage in any of your coronary arteries or if you have ever had a heart attack. It can also evaluate the pumping ability of your heart.

What happens before the test?
There are several instructions you should follow before having this test.

• Get a good night's rest.
• Take medicines as instructed by your doctor with small sips of water.
• If you are a diabetic, talk to your doctor before the procedure because your medication may need to be adjusted.
• Wear comfortable, loose-fitting clothes and comfortable shoes.
• Do not wear pantyhose or overalls.
• Do not eat or drink eight hours before the test.
• Do not have caffeine 24 hours before your test, such as coffee, tea, chocolate, soft drinks and Excedrin.
• Do not smoke for at least three hours before the test.
• Do not exercise before the test.
• Do not take a beta-blocker for 24 hours before the test unless your doctor has instructed you otherwise.
• If you have any questions, talk with your doctor.

What will I experience?
You will be given a small amount of a radioactive isotope through an intravenous line (IV) placed in your arm. You will lie flat with your left arm above your head for about 15-20 minutes. A scanner (camera) will rotate around your chest to take pictures. Next, you will walk on a treadmill. Walking on the treadmill will be easy at first, but your speed and the incline will increase every few minutes.

During the test, you will be connected to a heart monitor by electrodes and wires. Your blood pressure and heart rhythm will be checked frequently. If at any time during the testing you develop pain or tightness in your chest, dizziness or difficulty breathing, tell a staff member immediately. You will exercise until you are unable to continue or until you are asked to stop.

At the end of your treadmill test, you will receive a second injection of radioactive isotope. A second set of pictures will be taken after your heart rate has returned to normal. The staff will let you know if you are allowed eat or drink between sets of pictures. The test will take three-four hours.

Your doctor may decide that you do not have to take a treadmill test. In that case, your heart will be stressed with a medication. One of the following two medications will be used:

• Adenosine is given to you through an intravenous line (IV) over four minutes. It causes blood vessels to get wider for a short time just as they would if you were actually exercising. Adenosine may make your chest feel full, or it may make your face feel flushed.
   
• Dobutamine is given through your IV for up to 15 minutes. It increases your heart rate slowly as if you were actually exercising.