Nuclear Stress Test

A nuclear stress test, sometimes called a myocardial perfusion study, shows how well blood is reaching your heart muscle. A small amount of a radioactive tracer is given through an IV, and a camera records where that tracer travels in the heart — once while you are resting and again after your heart has been stressed, either by exercise or by a medication that mimics it. Comparing the two sets of images shows whether any area of the heart muscle is not receiving enough blood.

Because it images the heart muscle itself rather than only its electrical activity, a nuclear stress test can find reduced blood flow that a standard treadmill test or an EKG may miss.

• Chest pain, pressure or shortness of breath that may be coming from the heart
• An abnormal EKG or an inconclusive treadmill stress test
• Known coronary artery disease that needs to be re-checked
• Follow-up after a stent, bypass surgery or a heart attack
• Assessing cardiac risk before a major non-cardiac surgery

Your care team will confirm the specifics for your appointment, and instructions vary by medication and by whether you are scheduled for the exercise or the medication version of the test. Common preparation includes:

• Nothing to eat or drink for several hours beforehand, apart from water
• No caffeine for 24 hours — coffee, tea, soda, chocolate and decaf all interfere with the medication used to stress the heart
• Bring a list of your medications, and ask which ones to hold; beta blockers and some other heart medications are often paused
• If you have diabetes, ask specifically about your insulin or oral medication that morning
• Wear comfortable clothes and walking shoes, and skip lotions, creams or powders on your chest

Plan for two to four hours in total, as there is a waiting period while the tracer circulates. An IV is placed and the tracer is given, and a set of resting images is taken with a camera that moves slowly around your chest while you lie still with your arms above your head.

Your heart is then stressed. If you are able to exercise, you walk on a treadmill while the speed and incline increase and your EKG, blood pressure and symptoms are monitored. If you cannot exercise comfortably, a medication is given through the IV that widens the heart's arteries to produce a similar effect — it may briefly cause flushing, a headache or a sense of breathlessness, which passes quickly. A second dose of tracer is given at peak stress, and a second set of images is taken.

The tracer dose is small, and the radiation exposure is comparable to other common cardiac imaging tests. It leaves your body naturally over the following day or two, and drinking water helps. Serious complications are uncommon, and the test is supervised throughout by staff trained to respond to chest pain, rhythm changes or a drop in blood pressure. Tell the team if you are pregnant or breastfeeding, as the test is usually deferred.

A cardiologist reads the resting and stress images side by side and looks for areas of reduced blood flow, whether they appear only under stress or are present at rest as well. Your cardiologist will go over what the images show and what should happen next — which may be no change at all, a medication adjustment, or further testing such as a cardiac catheterization.