Nuclear Stress Test

What is a nuclear stress test (NST)? A nuclear stress test uses an imaging machine and mildly radioactive material to create detailed pictures showing the blood flow into and out of your heart both while at rest and during exertion.

A nuclear stress test is done if your doctor wants to guide treatment of a heart disorder or check for a heart disorder. A nuclear stress can also help you and your doctor to understand how well your heart is pumping, if your heart is too large, and your risk for heart disease or complications.


A nuclear stress test is usually safe, complications are rare. A few possible complications are allergic reaction to the radioactive material, arrhythmias brought on by stress, dizziness, chest pain, low blood pressure, and heart attack. Heart attacks because of a nuclear stress test are extremely rare, but possible. Low blood pressure usually resolves at the end of the test.

Preparing for the test

You may be asked not to eat, drink or smoke before the nuclear stress test. For an NST, you may also be asked not to have any caffeine before the test. You may want to avoid tea, coffee, soda (including those labeled caffeine-free), chocolate, and certain pain relievers in order to avoid caffeine. If you have an inhaler, please bring it to the test and inform your doctor or technician that you use an inhaler. Inform your doctor about all medications you are taking, you may be asked to discontinue a certain medication before the test. Do not discontinue any medication without consulting your doctor first. Be sure to wear comfortable shoes and clothes for the test.

During the test

An IV line is started, a radioactive substance is injected into one of your veins. After that, you'll lie down for between 15 and 45 minutes. Then you'll have pictures of your heart taken while at rest.

In order to understand how blood flows through your heart during exercise, the doctor or technician will next have you walk on a treadmill, or in some cases, pedal a stationary bicycle. While you are walking on the treadmill, your blood pressure and heart rhythm will be monitored. Your heart rhythm is monitored through an ECG, which requires multiple sticky electrodes to be attached to your chest, to watch for any cardiac arrhythmias. Once you have finished with the treadmill, you'll have another injection of the radioactive substance. You'll wait for 15 to 45 minutes again, and then another set of pictures of your heart will be taken.

Your Results

If you have normal results for your blood flow at rest and during exercise, you may not need further tests.

If you have abnormal results, this could mean that a part of your heart has a blockage or narrowing. Reduced blood flow could also be because of scarring of your heart muscle due to a previous heart attack (myocardial infarction). Your doctor may start a treatment plan or send you for more testing.


An exercise stress test is generally safe, though there is a risk of complications, such as low blood pressure, abnormal heart rhythms, and heart attack. A heart attack is rare, but possible as a result of an exercise stress test. Both low blood pressure and abnormal heart rhythms brought on by exercise usually go away after you stop exercising.