What Is A Pharmacological Stress Test?
The pharmacological stress test is a diagnostic test used to evaluate blood flow to the heart. During the pharmacological stress test, a small amount of a radioactive tracer is injected into a vein. A special camera, called a gamma camera, detects the radiation from the tracer to produce computer images of the heart.
In combination with medication, the pharmacological stress test can help determine if there is adequate blood flow to the heart during activity versus rest. The drug does not increase the heart rate. The drug widens the blood vessels leading to the heart, which increases blood flow, thereby simulating exercises for patients unable to exercise on a treadmill.
Why may I need a pharmacological stress test?
You may need a pharmacological stress test if you have heart-related symptoms but cannot exercise. Caregivers may also use a pharmacological stress test to do any of the following:
- Find the cause of symptoms such as chest pain, shortness of breath, and weakness
- Monitor or diagnose a heart condition, such as heart disease or an irregular heartbeat (abnormal heart rhythm)
- Check your risk of heart attack
- Decide if you can have surgery for another health condition
- An intravenous (IV) line will be started to allow the technician to inject Cardiolite (the radioactive substance). Cardiolite is a radiological tracer used in computer imaging of your heart that will be taken later. Cardiolite is not a drug or dye and it causes no known side effects or symptoms. After about 45-60 minutes, you will be set up under the camera and asked to lie on your back with your arms over your head for 15-20 minutes.
- The second part of your test is the “stress” part. The exercise technician will place electrodes (small patches) on your chest, wrists, and ankles. The lead wires will then be connected to the electrodes.
- You will lie on your back for about 20-45 minutes, as you are not required to take this pharmacological stress test. An electrocardiogram (EKG) and blood pressure will be obtained to ensure that there are no major abnormalities preventing the test.
- The pharmacological agent (usually Persantine or Lexisan) will be administered for four minutes through the IV line. This medication allows your blood vessels to dilate (increase in size).
- There are possible side effects of this drug, such as feeling warm, redness, headache, nausea, or chest pain. If you experience any of these symptoms, a drug called aminophylline may be given intravenously to reverse the symptoms.
- After Persantine or Lexiscan has been injected, the second injection of Cardiolite will be given through an IV.
- It is your responsibility to inform the testing technician of any symptoms that develop (headache, chest pain, dizziness, lightheadedness, shortness of breath). If any abnormal responses are present, the test may be stopped and/or aminophylline administered.
- Then a short recovery period is performed with continuous heart rate, EKG, and blood pressure monitored periodically. Once these measurements get close to the initial or comfort values, you will be disconnected from the screen.
- About one hour after the brassantine or Lexiscan injection and the cardio lite injection, you will be taken to the nuclear medicine department to have a second series of images of your heart. You will lie on your back with your arms above your head for 15-20 minutes. You may likewise be approached to lie on your stomach for an extra 15-20 minutes for the second arrangement of pictures.
- The cardiologist and nuclear medicine doctor will review and interpret the pharmacological stress test for a follow-up visit or for re-direction to your referring doctor.
- Leave approximately 3-4 hours for your procedure as long wait times are required between each step of pharmacological stress testing. Waiting time is necessary to ensure good under-camera images.
What may keep me from having a stress test?
- You are having an asthma attack
- You have used a medication containing dipyridamole in the past 24 hours. Dipyridamole is a blood thinner
- Ask your care provider for more information about medicines that may contain dipyridamole
- You have consumed foods or drinks containing caffeine in the past 12 hours
- Your heart rate is 40 beats per minute or less
- You have a low blood pressure reading
- You suffer from uncontrolled high blood pressure
Risks and Complications
Like many tests, this pharmacological stress test has some risks. They may include:
- Shortness of breath or wheezing
- Fainting, dizziness, or fatigue
- Rise or fall in blood pressure
- Nausea or headache
- Heart attack or stroke (rare)
- Abnormal heartbeat or heart rate
Diagnosing heart disease with a pharmacologic stress test
A pharmacological stress test helps your primary care physician analyze and oversee coronary illness by:
- Evaluate symptoms such as chest pain or shortness of breath in patients at risk for coronary artery disease (CAD)
- Find out how well stents or bypass grafts work in patients diagnosed with CAD
- Help diagnose heart failure
If the pharmacological stress test results are abnormal, this indicates that the patient has a blockage in a coronary artery. After being reviewed by a cardiologist, this may require more work [examination]. A drug stress test is as good as a stress test at identifying coronary artery disease – a study of 117 heart patients who underwent both types of tests found that when the tests are performed properly, the results are strikingly similar.