For patients with known coronary artery disease and those at risk for developing heart disease, a physician may recommend a nuclear stress test to evaluate the adequacy of blood flow to the heart muscle. Low perfusion, or blood flow, to a certain wall of the heart could indicate that there is a blockage of the artery that feeds that specific wall. In this case, intervention by medication, cardiac catheterization, stenting, or even open heart surgery may be advised.
A nuclear stress test typically involves taking two sets of images of your heart -- one set while you are at rest and the other during a stress test while you're exercising on a treadmill or stationary bike, or with medication called a vasodilator that stresses your heart. In other words, there are before-stress and after-stress pictures. Sometimes, for maximum diagnostic quality, the physician will elect to combine both the exercise and vasodilator aspects of the stress test, thus prescribing a VEX treadmill test.
How the Test Works
The vasodilator plus exercise, or VEX, stress test is prescribed only after the primary physician or cardiologist performs a thorough history and physical examination. This will ensure that the study is completely appropriate, based on your condition and symptoms.
After you have an intravenous line inserted, the nuclear technologist will administer an imaging isotope to visualize the heart under a gamma camera. An initial set of heart images at rest will be taken. Then a medical professional will hook you up to a heart monitor, which displays a continuous electrocardiogram, or ECG. You will then be instructed to walk on a treadmill, during which time the technician will give a standard dose of vasodilator through the IV line. Your blood pressure will be taken periodically, and you will be evaluated for symptoms like chest discomfort or shortness of breath. Once your heart rate reaches the target zone, or you are unable to continue, you will receive a second dose of imaging isotope and the exercise will be concluded. You will then have a final set of images under the camera.
The Benefits of a VEX Test
Because the study merges two valuable diagnostic tests, the results offer a clear and concise idea of heart muscle status. A study published in June 1995 in the "Journal of Nuclear Medicine" suggests that, when compared to dynamic exercise alone and vasodilator alone, the combination test shows a higher incidence of physiologic indicators, like chest pain, and positive electrocardiogram changes. Both of these indicators are important considerations in diagnosing heart disease or suggesting more advanced testing.
Possible Adverse Reactions
With any diagnostic test, there are potential risks or side effects that may occur. Commonly, the administration of the vasodilator will cause some unpleasant, but not life-threatening, side effects. Among them are chest discomfort, dizziness, nausea, palpitations, or headache. The Cardiac Society of Australia and New Zealand reports that major reactions like myocardial infarction, or a heart attack, are extremely rare.
Typically, common side effects resolve just minutes after the completion of the stress test. If you experience lingering symptoms, the medical professional may administer a reversal agent to quicken resolution.
Considerations
The VEX stress test is part of a group of minimally-invasive cardiac diagnostic tests. Often, this test is prescribed for patients with known heart disease or those demonstrating moderate to high suspicion for cardiac related illness. For those who carry low suspicion for heart disease, the physician is likely to prescribe a noninvasive type of stress test.
References
- MayoClinic.com: Nuclear Ttress Test
- "Journal of Nuclear Medicine"; The VEX-Test for Myocardial Scintigraphy with Thallium-201 and Sestamibi: Effect on Abdominal Background Activity; Gilbert A. Hurwitz, et al.; June 1995
- The Cardiac Society of Australia and New Zealand; Safety and Performance Guidelines for Pharmacologic Stress Testing in Conjunction with Clinical Cardiac Imaging Procedures
