Nuclear medicine imaging is one of the more helpful diagnostic tests that can be performed especially on a patient with known coronary artery problems to pinpoint the location or locations of inadequate blood flow in the heart muscle, as well indicating improper blood flow, heart size and other matters relevant to heart health. Often the test is performed as a stress test when another stress test has not shown the expected or needed details.
Why nuclear medicine stress testing is used
The heart functions best when blood vessels in it flow freely, bringing nutrients and flushing out metabolic waste. When vessels become constricted due to plaque or cholesterol buildup on the interior walls, blood flow and heart efficiency are reduced, or where parts of the heart muscle die.
A person with constricted heart blood vessels may feel normal during rest or little physical activity, but under physical stress such as exercise, when the body calls on the heart to pump much more rapidly, constricted blood vessels in the heart will often be clearly felt by the patient, often in terms of lightheadedness, shortness of breath, chest pain, and generally a lack of capacity to exercise strenuously.
At Medical Imaging Center, we may use Lexiscan with a myoview treadmill stress test procedure. Thyroid scans may be performed when prescribed.
A nuclear stress test will not be prescribed if you are at high risk for the test, such as having a known pulmonary embolism or acute pericarditis. Possible, but infrequent risks involved in the test itself include allergic reaction to the injection material, slight risk of cancer from the radioactive material with repeated testing, and whatever risks may be involved in exercising.
During the test
In a nuclear stress test, the patient receives an injection including low dosage radioactive isotopes. The isotopes emit radiation which is “seen” by a special gamma radation camera which takes pictures of the heart while the patient is at rest and during exercise to determine where blood flow is restricted.
For the stress portion of the test, patients are hooked up via electrodes to an EKG monitor and a blood pressure cuff as they walk on a treadmill or peddle on a stationary bike. Patients who are unable to exercise may remain at rest, but are injected with a material which makes the heart race for a short period to mimic heart rate during exercise. The “stress” portion of the test for those who are able to walk rapidly on a treadmill is usually limited to 10 to 15 minutes, but the whole procedure can last about an hour.
All during the procedure, patients are carefully monitored by a board certified radiologist. Patients are periodically asked to tell the attending radiologist of any ill feelings such as nausea, lightheadedness, dizziness, chest pain, heart palpitations, headache, or notable weakness. After the “stress” portion of the test, patients are asked not to stop all exercise at once, but rather to go through a “cool down” period of lighter exercise before rest.
Preparing for the test
Physicians generally ask patients to avoid food, drink (except water), and smoking for 4 hours prior to the test, with special instructions for diabetic patients. Caffeine should be avoided for 12 hours prior to the test, as it may artificially elevate heart rate and blood pressure. Caffeine may be found in certain soft drinks and unexpected places, so be aware of what you eat and drink the day before the test. Wear comfortable clothes for the test, ones appropriate for exercise. A locker will be provided during the test for your personal effects.
Your doctor may instruct you to discontinue certain medications for some period of hours prior to the test, but otherwise do not discontinue taking medication without express instructions from your doctor. Ask your doctor for specific instructions.
Test results are carefully interpreted by a board certified radiologist and delivered by fax to your attending physician within a 24 hour period of the test. This information is later used for heart surgery or other treatment. The nuclear stress test can also help determine the proper boundaries of an exercise regimen which is optimal for the patient.
Disclaimer: This page and website are intended for informational purposes only and should not be taken as medical advice.
–John Loebel, RT(N) and Dr Gregory Goldstein, MD