PET and Heart Disease

Coronary heart disease results from a narrowing or blockage of the vessels that feed the heart muscles. As plaque or calcifications build up on the inside of the arteries, blood flow to the heart muscle is reduced. A PET Myocardial Perfusion Imaging test can show when this is happening. Because reserve vessels will preserve normal flow to the heart as long as possible, an exercise test may be needed to see areas of the heart with reduced blood flow.

Using a radioactive drug that shows the blood flow or perfusion to tissues, a PET scan will show normal or abnormal patterns of blood flow to the left ventricle of the heart. The muscle tissue around the left ventricle pumps blood to the rest of the body and adequate "pumping" power is needed for our bodies to function well. If blood flow to this heart muscle is restricted by a blockage, then the blood flow picture will show a deficit. In less severe cases of coronary heart disease, the deficit in blood flow may only be seen after exercise or stress (which shows the heart when it is working harder). In more severe heart disease, the blood flow abnormality can be seen at rest as well.

The PET Myocardial Perfusion test shows how well blood flows to the heart muscle and is done while the heart is at rest, but may also be done during exercise or other stress (using a drug that increases blood flow to the heart, mimicking exercise). If the blood flow is:

• Normal during both exercise and rest portion of the test, then blood flow through the coronary arteries is normal.
• Normal during rest but is reduced in part of the heart during exercise, then part of the heart is not getting enough blood when it is working harder than normal, which may be due to a blockage.
• Reduced in a part of the heart during both exercise and rest, then the blood flow to that part of the heart is restricted at all times.

Knowing this will help the doctor identify the best treatment.

Screening is an important way to detect coronary heart disease because the symptoms may not be noticeable or may be very mild. People who have high blood pressure, are not physically active, have high blood cholesterol, smoke or have a history of smoking, or are obese are at a greater risk for developing coronary heart disease. Finding coronary heart disease early is important, because it can lead to a heart attack.