Lexiscan Stress Electrocardiography

Your caregiver has ordered a Lexiscan Stress Test with nuclear imaging. The purpose of this test is to evaluate the blood supply to your heart muscle. This procedure is referred to as a "Non-Invasive Stress Test." This is because other than having an IV started in your vein, nothing is inserted or "invades" your body.

Cardiac stress tests are done to find areas of poor blood flow to the heart by determining the extent of coronary artery disease (CAD). Some patients exercise on a treadmill, which naturally increases the blood flow to your heart. However, almost half of the patients undergoing a treadmill stress test each year are unable to exercise adequately. This is due to various medical conditions. For these patients, a pharmacologic/chemical stress agent called Lexiscan is used on patients without a history of asthma. This medicine will mimic walking on a treadmill by temporarily increasing your coronary blood flow. The side effects of this medicine include:

  • Headache.

  • Dizziness.

  • Shortness of breath.

  • Flushing.

  • Chest pain/pressure.

  • Feeling sick to your stomach (nauseous).

  • Increased heart rate.

  • Abdominal discomfort.

  • Low blood pressure.

BEFORE THE PROCEDURE

  • Avoid all forms of caffeine 24 hours before your test. This includes coffee, tea (even decaffeinated brands), caffeinated sodas, chocolate, cocoa and certain pain medications that contain caffeine.

  • Do not eat anything 6 hours before the test. In hospitalized patients, this means nothing by mouth after midnight.

  • Patients with diabetes that are not hospitalized (outpatients) should talk to their caregiver about how much, if any, insulin or oral diabetic medications they should take the day of the test. You should also talk about the type of light snack that you should eat the morning of the test.

  • Patients with diabetes that are hospitalized (inpatients) will follow the cardiologist's written instructions that will be given to you.

  • Outpatients should bring a snack. Use the hospital vending machines so that you may eat right after the stress phase.

  • Wear comfortable shoes. There is at least an hour wait before the stress phase of nuclear scanning is done. The total procedure time is approximately 3 hours.

  • The following medications should be stopped 24 hours before your stress test: Beta-blockers and nitroglycerine (patches or paste should be removed 4 hours before the test).

  • Women, tell your caregiver if there is any possibility that you may be pregnant or if you are currently breastfeeding.

PROCEDURE

There are two separate nuclear images taken using a nuclear camera. These images require a small dose of a radiotracer called an isotope. Most diagnostic nuclear medicine procedures result in low radiation exposure. Allergic reactions to the isotope may include slight redness going up the arm and pain during the injection. However, these reactions are extremely rare and usually mild.

Lexiscan is given very rapidly over 10-15 seconds in the vein (intravenously) followed by a nuclear isotope. The medication causes the arteries in your heart to widen (dilate), and the nuclear isotope lights up those arteries so that the nuclear images are clear. Together, this shows whether the coronary blood flow is normal or abnormal. During this stress phase, you will be connected to an EKG machine. Your blood pressure and oxygen levels will be monitored by the cardiologist and cardiac nurse. This part usually lasts 5-10 minutes. For inpatients, the procedure is done in the patient's room. For outpatients, the procedure is done in the stress lab.

The "Resting Phase" is done before the Lexiscan injection and shows how your heart functions at rest.

The "Stress Phase" is done about 1 hour after the Lexiscan injection and determines how your heart functions under stress.

LEXISCAN STRESS TEST IS USEFUL FOR DETERMINING:

  • The adequacy of blood flow to your heart during increased levels of activity in order to clear you for discharge home.

  • The extent of coronary artery blockage caused by CAD.

  • Your prognosis if you have suffered a heart attack.

  • The effectiveness of cardiac procedures done, such as an angioplasty, which can increase the circulation in your coronary arteries.

  • Cause(s) of chest pain/pressure.

Finding out the results of your test

Ask when your test results will be ready. Make sure you get your test results.