Nuclear Cardiology Diagnosis and Tests

The most common procedure in this field is the Single Photon Emission Computed Tomography (SPECT) scan. This is what most people mean when they say “nuclear stress test.” The goal is to compare blood flow at rest versus blood flow during stress.

Exercise vs. Chemical Stress

The “stress” part of the test is crucial. To determine if an artery is blocked, the patient must work hard for a minute.

• Exercise Stress: If you can walk, you will walk on a treadmill. The speed and incline increase every few minutes. The goal is to get your heart rate up to a target level. After you reach that goal, the tracer is injected into your IV, and you walk for another minute to circulate it.
• Chemical (Pharmacologic) Stress: If you cannot walk well due to arthritis, lung issues, or poor balance, you will receive a medication (like adenosine, regadenoson, or dipyridamole). This drug dilates your coronary arteries, mimicking the blood flow of exercise without you having to move a muscle. You might feel a flushed sensation or mild shortness of breath, but it passes quickly.

The Imaging Process

The imaging happens in two phases: the “rest” scan and the “stress” scan.

• Rest Phase: You receive an injection of the tracer while sitting quietly. You will wait for about 30 to 60 minutes for the tracer to be absorbed. Then you lie on the camera table for about 15 minutes with your arms above your head while the camera rotates around you.
• Stress Phase: After the treadmill or chemical stress, you wait another short period and then get back on the camera for the second set of pictures. The computer then lines up these two sets of images. If a part of the heart is bright at rest but dark after stress, it proves there is a blockage restricting flow when the heart needs it most.