To prepare for the test, you should not eat after midnight on the night before the test. You should also wear comfortable clothing and shoes for exercising. Avoid caffeine products like coffee, tea, and chocolates before the test as these will interfere with the test. Some over-the-counter medications and pain relievers also contain caffeine; make sure to check the labels before you take them. Even decaffeinated coffee contains small amounts of caffeine. Some medications may interfere with the results of your test. These include some drugs for asthma and erectile dysfunction medications. Consult your doctor about these. Take your other regular medications unless told not to.
During this test, you will have an IV line started and a radioactive substance called thallium will be injected. You will lie down and wait for about 15-45 minutes. Then a camera will scan your heart and create pictures that show how well the substance has entered your bloodstream and traveled through your heart. Most people will then exercise on a treadmill or stationary bicycle. The exercise portion will begin slowly but pick up speed as time passes. If you can't exercise, you will either be given a vasodilator that dilates your arteries or a drug that makes your heart beat faster and harder. This mimics the effects of exercise. Your blood pressure and heart rhythm will be monitored throughout the test. When your heart is working at its peak capacity, you will lie down and more thallium is injected into your veins. The camera will scan your heart again to create images. The two sets of images will be compared.
Usually, people do not have adverse effects from the stress test. If you are given a drug to mimic exercise, you may feel a pinch as the medication is injected, and then a warm feeling. Some people also experience headaches, nausea, and a racing heart. The injected medication will leave via your urine. Drink a lot of water for the next few days to help get the medication out of your system. Complications from the radioactive material are very rare. These can include arrhythmia, heart palpitations, chest pain or discomfort, shortness of breath, large blood pressure swings, or skin rash. It is important to let the lab personnel know if you are experiencing any of these symptoms during your test.