What is a Nuclear Stress Test (Myocardial Perfusion Imaging)?
A nuclear stress test allows doctors to see images of your heart while at rest and after exercise. A nuclear stress test can show your heart’s chamber size, how well it’s pumping blood, and whether your heart has any damaged or dead muscle. This test can also give inform your doctor about your arteries and if they might be narrowed or blocked due to coronary artery disease. The test is administered at both rest and exercise and is measured by the dye that’s been injected into your body to trace the blood flow to and from your heart.
Why am I Being Told to Have a Nuclear Stress Test Done?
Based on your symptoms, your doctor may require you to do nuclear stress testing to get a better understanding of your heart’s function. If a routine stress test wasn’t able to identify the cause of your symptoms such as chest pain or shortness of breath, you may be under orders to have a nuclear stress test done. This test can also help to diagnose and serve as a guide for:
Coronary artery disease: These major blood vessels supply your heart with blood, oxygen, and nutrients. When these arteries become damaged or diseased, usually due to a buildup of deposits containing cholesterol and other substances such as plaques, coronary artery disease develops.
Treatment of heart disorders: A nuclear stress test can help your doctor find out how well treatment is working for your coronary heart disease. Establishing the right treatment plan for you is critical and one way is to determine how much exercise your heart is able to handle.
How Long Does a Nuclear Stress Test Take?
Depending on if you’re having a one-day test or a two-day test, you’re looking at anywhere between 2 ½ to 3 hours to complete the test. A one-day test should be over in about 2 ½ hours, and a two-day test should take approximately 3 hours in total.
What are the Risks Associated with a Nuclear Stress Test?
With most medical procedures, risks are always present. In terms of this type of stress test, the risks are minimal as complications are rare. Some complications include:
- An allergic reaction: Rare. It’s possible you could be allergic to the radioactive dye that’s injected during a nuclear stress test.
- Arrhythmias: Rare. Abnormal heart rhythms brought on during a stress test usually go away shortly after you stop exercising or the medication wears off. They are seldom life-threatening.
- Heart attack: Extremely rare. It’s still possible though that a nuclear stress test could cause a heart attack.
- Dizziness or chest pain: Possible. Some patients may experience dizziness or chest pain during a stress test of this kind. Others may experience nausea, shakiness, headache, flushing, shortness of breath and anxiety. Tell your doctor if they occur. Patients exhibiting these symptoms recover quickly as they are generally short-lived and mild in nature.
- Low blood pressure: Possible. You may feel dizzy or faint, but any symptoms should go away after the exercising has stopped.
What to Expect
Prior to your test
The doctor will ask some questions about your medical history and understand how often and strenuously you exercise. This will determine the amount of exercise appropriate for you while testing. The doctor will also listen to your heart and lungs for any abnormalities that could potentially affect the results of your test. Before the test starts, a technician inserts an intravenous (IV) line into your arm. In addition to placing an IV, a nurse or technician will place sticky patches (electrodes) on your chest and a blood pressure cuff on your arm. For male patients, some areas of your chest may need to be shaved to help the electrodes stick throughout the exercise portion of the testing. The electrodes will have wires connected to an electrocardiogram machine which records the electrical signals that trigger the heartbeats. The blood pressure cuff that is placed on your arm checks blood pressure throughout the test. 30 minutes prior to your initial resting images radiopharmaceutical tracers will be injected. The radiotracer may feel cold when it’s first injected which is normal. In about 30 minutes your heart cells will have absorbed the radiotracer and you will be ready for the first round of “resting images”.
During the Test
A technician will insert an IV line into your arm and inject a radioactive tracer dye into your body. It may feel cold when it’s first injected, and it takes about 20-40 minutes for your heart cells to absorb the radiotracer. Once that’s taken effect, you’ll lie still on a table while the first set of images is taken of your heart while at rest. Next, electrodes will be placed on your chest, legs, and arms to measure the electrical signals that trigger your heartbeats, the same as an EKG. Your blood pressure will also be monitored for the duration of the test.
If you’re able to exercise:
If you’re physically able to exercise, you will be required to exercise by either walking on a treadmill or riding a stationary bike. The intensity of the exercise will gradually increase by increasing the speed and incline of the treadmill or speed and resistance on the stationary bike. Once you have reached your set target heart rate (determined by your heart rate and age) a second radionuclide will be injected through your intravenous catheter (IV). After the radionuclide has been injected, you will continue exercising for one to two minutes to allow the radionuclide to circulate through your heart. The treadmill is then slowed down to a gradual stop, at which point you will move back to the camera for “stress images”.
If you’re unable to exercise:
Since you’re unable to physically exercise, the doctor will inject the drug into your IV line that mimics exercise. This is achieved by increasing blood flow to your heart. It’s possible that you may get a headache, or feel short of breath during the test, which does occur with some patients. You’ll have another injection of dye when your heart rate peaks and the second set of images will be taken about 20-40 minutes later. The tracer dye will show any areas of your heart receiving inadequate blood flow. Your doctor will use the two sets of images to compare the blood flow through your heart while you’re at rest and under stress.
After the Test
After the test is over, you’ll be able to return to normal activities unless your doctor tells you otherwise. The tracer dye will naturally leave your body in your urine or stool. Drink plenty of water to help flush the dye out of your system.
What to Expect During the Imaging Procedure
If you’ve talked to anyone prior to this test some will tell you they laid down in a machine during the imaging part of the test. Our camera allows you to sit upright while the images of your heart are obtained. If possible, your arms will be elevated slightly above your shoulders and placed on a cushioned arm rest. It is critical for you to sit very still while the images are being recorded, as movement can adversely affect the quality of the images. After both the rest and stress scans have been completed and processed, your test will be complete.