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By Jeffrey M. Wahl, M.D., Cardiologist
The Chester County Hospital
Published: June 23, 2008
Heart disease is the leading cause of death in both men and women in the United States. The specific problem is called coronary artery disease (CAD). CAD occurs when the blood vessels of the heart become narrowed due to fatty deposits that build up in the walls of the blood vessels. This reduces blood flow to the heart muscle producing chest pain or angina. If a blood vessel becomes completely blocked, there is no blood flow to a part of the heart muscle resulting in a heart attack.
Nuclear cardiology studies use small amounts of radioactive material to evaluate blood flow to the heart muscle and to evaluate the heart's pumping function. Studies that measure the blood flow to the heart can evaluate the extent and severity of problems and determine the significance of narrowing in the blood vessels of the heart. Common radioactive agents that are used are Cardiolite and Thallium.
Blood flow to the heart is usually evaluated at rest and after the heart is put under stress, either with treadmill exercise or with a pharmacologic agent such as dipyridamole (Persantine). In a standard study, the imaging agent is injected at rest and images are obtained of the resting blood flow. Then stress is performed on a treadmill (stress Cardiolite or stress Thallium) or with a drug (Persantine Cardiolite or Persantine Thallium). The imaging agent is again injected during the stress and images are obtained shortly after. By comparing the rest and stress blood flow, we can evaluate the presence and significance of any narrowing that may be present.
Nuclear cardiology studies are safe, non-invasive, and are done in the outpatient setting. These studies are commonly used for screening to detect CAD, for following patients with known CAD, for evaluating patients before non-cardiac surgery, and for determining prognosis. The value and significance of this information has been confirmed in almost 30 years of clinical trials.
Early detection of CAD is particularly valuable now that we have the tools to aggressively manage risk factors such as elevated cholesterol and hypertension. Nuclear imaging can be used to select patients who will benefit most from aggressive risk factor intervention with drugs or lifestyle changes. In addition, nuclear imaging studies are the standard for determining which patients are candidates for cardiac catheterization, coronary intervention (stenting), and coronary bypass surgery.
In addition, nuclear cardiology studies are very helpful in evaluating women and patients with diabetes. Women have a higher incidence of atypical chest symptoms and abnormal stress EKG's. However, nuclear imaging "gets around" these issues and can accurately evaluate CAD in women. Diabetics are at the highest risk of developing CAD; as many as 80% may die from this. Risk factor interventions are most valuable in this latter group.
Nuclear cardiology studies are safe non-invasive tools to detect CAD and to select patients for aggressive risk factor management or revascularization. Appropriate use of these technologies is contributing to the decreasing incidence of death from CAD in the United States.
This article was published as part of the Daily Local News Medical Column series which appears every Monday. It has been reprinted by permission of the Daily Local News.
Last Updated: 7/27/2009