Pharmacological Stress Test

What are Pharmacological (Chemical) Cardiac Perfusion Imaging Stress Tests?

Usually cardiac perfusion imaging is completed after an exercise (stress) test.  If you are not able to adequately exercise, you may receive a pharmacological "chemical" stress test. A "chemical" stress test involves an injection of a drug that mimics the effect of exercise on the heart.

Adenosine Cardiac Perfusion Imaging Stress Test

The medication most often used for pharmacological stress testing is Adenosine. Adenosine is injected into the vein during the test, causing the coronary arteries to dilate (widen), which increases blood flow to the heart muscle. Arteries that are diseased cannot dilate as much as healthy arteries. Once the dilating medication has been given, a small amount of tracer is injected into a vein. The tracer collects in the areas of the heart muscle with good blood flow.

The tracer gives off a small amount of radiation that is detected with a scanning camera. A computer processes the information and produces pictures that show how the tracer is distributed to the heart. If an area of the heart receives less blood than the rest of the heart (because of a narrowed or blocked artery), it will pick up less radioactivity.  This will show up as a lighter image and is referred to as a defect.

Additional tracer is injected while you are at rest and another set of pictures is taken. The physician is able to identify areas of the heart muscle with reduced blood flow as well as areas that are scarred from a previous heart attack by comparing the stress and resting images.

Dobutamine Cardiac Perfusion Imaging Stress Test

Another medication, Dobutamine, is used for patients who cannot take Adenosine because they have asthma or chronic lung disease. If Dobutamine is the medication of choice, it is injected into a vein during the test. Dobutamine makes the heart beat faster and harder, as if you were exercising. As a result, it increases the flow of the blood to the heart muscle. Once the Dobutamine has been given, a small amount of the radioactive tracer is injected into the vein. The tracer collects in the areas of the heart muscle with good blood flow.

The tracer gives off a small amount of radiation that is detected with a camera. A computer processes the information and produces pictures that show how the tracer is distributed to the heart. If an area of the heart receives less blood than the rest of the heart (because of a narrowed or blocked artery), it will pick up less radioactivity. This will show up as a lighter image and is referred to as a defect.

Additional tracer is injected while you are at rest and another set of pictures is taken. The physician is able to identify areas of the heart muscle with reduced blood flow as well as areas that are scarred from a previous heart attack by comparing the stress and resting images.

Pharmacological (Chemical) Cardiac Perfusion Imaging Stress Test is done to:

  • Identify areas of the heart muscle that have an inadequate blood supply
  • Quantify the extent of the heart muscle with a limited blood flow
  • Provide information about the heart’s pumping function
  • Determine the amount of scarring from a heart attack
  • Evaluate the success of coronary (heart) bypass surgery or angioplasty

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