Cardiovascualr Institute of San Diego


Nuclear Stress Tests

During a traditional stress test, the heart’s electrical activity is measured by electrocardiograms (EKGs) both at rest and under exertion.

A nuclear stress test is a noninvasive test that combines exercise with a form of nuclear imaging, a SPECT.  The test can reveal more detailed information than a conventional exercise EKG test.  The test is divided into three parts: A treadmill or pharmacologic stress test, imaging at rest, and imaging after exercise.

During a treadmill stress test, sticky electrodes are attached to the chest, shoulders and hips and connected to the EKG portion of the Stress test machine. A 12-lead EKG is recorded on paper. Each lead of the EKG represents a different portion of the heart. The treadmill is then started at a relatively slow “warm-up” speed. The speed and inclination are then increased until a preset target heart rate is achieved.

In patients unable to undergo adequate exercise stress due to physical or medical limitations, a pharmacologic stress test is performed.  Lexiscan, a pharmacologic stress agent indicated for nuclear stress tests, is injected intravenously and simulates the effects of exercise on the heart.

During a SPECT exercise test, a patient is injected with an isotope, usually thallium but sometimes a technetium labeled agent such as sestamibi or tetrofosmin, to take pictures of the heart muscle. The isotope is absorbed by the heart muscle (myocardium), allowing physicians to use a special camera to obtain images of the heart. By studying the distribution of the isotope into the heart muscle, physicians can gauge the health of the heart and adequacy of coronary blood supply at rest and under stress. Patients undergoing either exercise or pharmacological stress testing receive the same imaging portion of the nuclear stress test.

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Cardiology is the science and study of the cardiac (heart) system. It pertains to heart disorders, including diagnosis and treatment of congenital heart defects, coronary artery disease, electrophysiology, heart failure and valvular heart disease.

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