A myocardial perfusion scan, also known as a nuclear stress test, is an imaging test to determine how well the blood is flowing through the muscles of the heart. The scan also helps doctors understand how effectively the heart muscle is performing the pumping function. This test may be performed during exercise or at rest, depending on the condition the doctor suspects. The test also enables an examination of the damage after a heart attack.

Procedure
The procedure of a myocardial perfusion scan involves inserting a small amount of radioactive material that acts as a tracer into the bloodstream. The substance then gets absorbed into the healthy cardiac muscles. A special kind of camera then detects the radioactive energy. When the images are extracted and compared, the areas that absorbed the tracer will look different from those that do not. The test can cost anywhere between $800 and $3,000.

Results
For a myocardial perfusion scan, images can be taken in two conditions: at rest and during stress (or exercise). The comparison of the pictures taken during the two states helps differentiate the affected areas with viable and reversible perfusion defects from those with non-reversible defects. This information is used to determine whether or not treatment to restore the blood flow (revascularization) should be conducted. The areas the radioactive substance did not reach are called “defects” or “cold spots” and are considered to be damaged or have poor blood flow. The main aspects technicians need to consider for image interpretation are:

• Evaluation of raw images to check the distribution of tracer activity
• Clinical factors that may influence the conclusion
• Correct alignment of rest and post-stress images
• Interpretation of images in terms of size, severity, cardiac chamber sizes, reversibility of perfusion defects, and the absence or presence of increased pulmonary uptake

All these factors contribute to the production of a clinical report.

Side effects
Myocardial perfusion imaging can lead to the following side effects:

• Slight chest pain following the test
• Tightness or pressure
• Pain in the back, arm, neck, jaw, or ears
• Abnormal heart rhythm after the test
• Possible allergic reactions to the tracer
• Soreness in the area where the tracer is inserted
• Weakness
• Dizziness
• Feeling warm and flushed
• Fatigue

One should discuss possible side effects and outcomes with a doctor to make an informed decision.

Who should not undergo the test?
People with certain health conditions should not opt for this procedure. Here is where one may not be asked to undergo a myocardial perfusion test:

• Nursing mothers, as the baby could be affected
• Those who may be pregnant
• Those who have mild chest discomfort and no other reason to suspect heart problems

Further, those with no particular heart issues or a low risk of a heart attack would usually not be recommended to undergo this test. In case of any concerns regarding such diagnostic techniques, one should consult a doctor and understand the outcomes and risks before undergoing the procedure. One can also ask doctors to suggest an alternative when pregnant or nursing.