Myocardial Perfusion PET Stress Test Indications
A myocardial perfusion scan is a nuclear medicine procedure. A tiny amount of a radioactive substance is used to examine the tissue under study and evaluate the heart’s function and blood flow. The radioactive tracer is absorbed by the healthy heart muscle tissue. On the scan, the areas that absorb the radionuclide will show up differently than the area that does not absorb the radionuclide, demarcating the healthy tissue from the damaged tissue.
A stress myocardial perfusion scan assessed blood flow to the heart muscle when it is stressed by exercise or medication and determines what areas of the heart have reduced blood flow during exercise. There are two types of myocardial perfusion scans, one that is used in conjunction with exercise and one that is used in conjunction with a pharmacological stressor. The exercise myocardial perfusion scan is done on a treadmill. The intensity of the exercise is gradually increased. When the patient reaches the maximum exercise point, determined by the heart rate and age, the radionuclide is injected into the IV line.
A pharmacological scan may be used for patients who cannot exercise on the treadmill for various reasons. Adenosine induces direct coronary artery dilation by activating the A2A receptor. This results in a 3.5-4 fold increase in myocardial blood flow.
This procedure evaluates the perfusion through the coronary arteries to the heart muscle using a radioactive tracer. It can show areas of the heart that are not getting sufficient blood flow. It is useful in patients with chest discomfort as it can determine if the discomfort comes from lack of blood flow to the heart muscle caused by narrowed or blocked arteries.
Major indications for a myocardial perfusion test are:
- Diagnosis of CAD and various cardiac abnormalities
- Identifying the location and degree of CAD in patients
- Prognosis of patients who are at a risk of having a myocardial infarction, coronary aneurysm or wall motion abnormalities
- Assessment of viable myocardium following heart attacks to justify revascularization
- Post intervention reevaluation of the heart