This type of stress test uses "Cardiolyte", a radioactive substance, to produce images of the heart muscle. For patients who cannot exercise or are unable to exercise adequately, "Persantine" is given. Persantine is a medication that dilates (makes larger) the arteries around the heart similar to exercise. Arteries that are blocked or narrowed cannot dilate as much as normal arteries.
Before the Persantine is given, resting images are taken of the heart. A small amount of radioactive tracer is injected via an IV, and then pictures are taken with a scanning camera while the patient is at rest.
The arteries are then dilated with the Persantine, and a small amount of the radioactive tracer is injected again via the IV. The tracer is carried in the blood to the arteries surrounding the heart, and is picked up by the heart muscle. Areas in the muscle that have an adequate blood supply (by 'unblocked' arteries) pick up the trace substance quickly and completely. Areas that do not have adequate blood supply (due to blocked or narrowed arteries) pick up the tracer slowly or, at times, not at all. Due to the nature of the tracer, a small amount of radiation is given off and can be detected by a 'scanning camera', a computer than processes the information and makes images of the heart. If an area receives less blood than the rest of the heart, because of a blocked or narrowed artery, the scan will show it as a lighter area. This called a 'defect.'
The test generally takes about 3 hours, including preparation, the exercise or 'stress' portion, and imaging.
The radiation exposure is minimal, however, women that are pregnant or suspect they may be pregnant should let the physician and the staff know. Infrequently, the Persantine administration can cause shortness of breath, abnormal heart rhythms, or heart attacks. The staff has been trained to handle any type of emergencies, and a physician is always available.
The results of the tests are not known until the resting images are compared with the stress images. If there is an abnormality, the physician will contact the patient to discuss it.