What Does It Show?

Cardiac perfusion imaging helps doctors diagnose coronary heart disease, which is caused by narrowed or blocked coronary arteries (the vessels that supply blood to the heart muscle).

Figure 1.     Cardiac Perfusion Scan The images show the heart from two different "angles" during stress and at rest. The stress images show a "defect," which disappears at rest. This suggests a narrowing in the artery which supplies blood to that area of the heart muscle.

During a cardiac perfusion test, a small amount of a tracer material is injected into a vein in your arm; once while you exercise, and once at rest.

The tracer then travels through the bloodstream and is picked up by the heart muscle. Areas of the heart muscle that have a good supply of blood pick up the tracer right away. Areas that do not have a good supply pick up the tracer very slowly or not at all.

The tracer gives off a small amount of radiation that is detected with a scanning camera. A computer processes the information and produces images that show how the tracer is distributed in 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 tracer material and will show up as a lighter area, called a "defect."

One set of images is taken after you exercise, another set is taken while you are at rest. The images allow doctors to compare how much blood flows to the heart muscle during stress and at rest. (see Figure 1.)

By comparing the stress and rest images, doctors can identify areas of the heart muscle with reduced blood flow as well as areas that may be scarred from a previous heart attack.

Why Is the Test Done?