The heart plays an essential role in your everyday health by pumping oxygenated blood to all of your organs to help them function properly. The heart uses vessels to transport this blood throughout the body, but these can sometimes narrow due to plaque buildup in the arteries. This doesn’t always produce symptoms when your body is at rest, but when the heart undergoes stress—like during exercise—signs may appear. Discover how cardiologists use stress tests to check for these symptoms.
What’s the purpose of a cardiac stress test?
A cardiac stress test is a tool cardiologists use to determine if someone is likely to have coronary artery disease (CAD). However, they can’t use this test to diagnose the condition. You might wonder, if it won’t provide a yes-or-no answer, what’s the point of doing it? The actual diagnostic tests for CAD, like a coronary catheterization, are invasive, so the stress test provides a non-invasive approach to determine who may need a catheterization and who would not benefit from it.
What are the types of stress tests?
There are two types of stress tests: physical and chemical. They both begin in the same way: A health care professional records your vitals at rest, including your blood oxygen levels and heart rate and rhythm. This will involve placing small electrocardiogram (ECG) sensors around the chest and body, as well as a pulse oximeter (likely on the finger) and a blood pressure cuff (likely on the upper arm). The next steps depend on what type of test you’re receiving.
- Physical stress test. This involves using either a treadmill, a stationary bike, or a system of pedals you operate with your hands if you can’t use your legs. You’ll start at a gentle pace and slowly increase intensity. The test will typically last for 10-15 minutes, but you can end it early if you feel unwell.
- Chemical stress test. During this kind of test, you will receive a dose of dobutamine, a fast-acting drug that mimics the same effects that exercise has on the cardiovascular system. This medication is only active in your system for a few minutes.
Regardless of the type of test you receive, the ECG, pulse oximeter, and blood pressure cuff will record your vitals, which a doctor will later review to see how they change throughout the test.
Either of these tests can also become a nuclear stress test. This means that after you exercise or receive the dobutamine, you will get an injection of a harmless radioactive substance. A health care professional will then take images of your heart. After this happens, you leave for about four hours but then you must return to receive one more injection and take more images while your heart is at rest. Your cardiologist will use these images to see where blood flow might be impeded.
How does a stress test detect signs of coronary artery disease?
CAD occurs when plaque builds up in the coronary artery, reducing blood flow to the heart. However, you may not notice symptoms while at rest if the plaques aren’t large. When the heart needs greater amounts of oxygen-rich blood, like when you’re exercising, the symptoms of CAD can become more pronounced. Therefore, your doctor will look for signs of this during your test, including chest pain, shortness of breath, reduced blood oxygen levels, and more. Stress tests can also give doctors an idea of how extensive the blockages in the artery are. If signs of distress occur at a relatively low intensity of exercise, this might indicate larger blockages.
Dr. Warren Moore, a nuclear cardiologist at Baylor St. Luke’s Medical Center and Texas Heart® Institute, explains how the different aspects of these tests help doctors get a better look at a patient’s cardiovascular health.
“A ‘nuclear medicine stress test’ is really two separate tests; one is the ‘nuclear’ (or imaging [picture]) part of the test, and the other is the ‘stress’ (or ECG) part of the test … Each of these parts yields its own answer to one aspect of the patient’s problem, and each of those parts of the answer may be effectively ‘yes,’ ‘no,’ or ‘maybe.’ Often, both parts come to the same conclusion, or one part is so strong in its answer that it makes the overall answer clear.”
However, the results are not definitive. If you do have symptoms, your cardiologist will likely prescribe a coronary catheterization or another diagnostic test to determine the extent and location of the plaques.
Who needs a stress test?
People with a high risk of CAD or symptoms of it should talk with their cardiologist to see if stress testing may be right for them. Symptoms include:
A stress test is not recommended for people with certain conditions that can make it dangerous, including unstable angina, uncontrolled congestive heart failure, and more. Your cardiologist will review your health history to determine whether a stress test is right for you.
How to prepare for a stress test
If you’ve already scheduled a stress test, you may be a little anxious or, dare we say, stressed, but it’s nothing to worry about. Here’s a breakdown of what you should expect:
- At the scheduling appointment. When your cardiologist recommends scheduling a stress test, they’ll ask about any medications you’re taking. Be sure to include all of them, from prescriptions to over-the-counter medicines to supplements. They may recommend you avoid taking some of them in the day leading up to your test.
- 24 hours before. Stop consuming caffeine, so avoid food and drinks like coffee, tea, and chocolate.
- Four hours before. Stop consuming anything other than water.
- Right before. Dress in a shirt and shorts or pants that you don’t mind sweating in, such as workout clothes, and put on a pair of sneakers. Pack a water bottle and, if you’re heading out to work or another engagement after this appointment, pack a change of clothes and anything you need to freshen up. If you have asthma or another respiratory condition, be sure to pack your inhaler as well.
If you’ve been experiencing symptoms such as chest pain, lightheadedness, dizziness, or any other sign of a heart condition, schedule an appointment with a St. Luke’s Health cardiologist. They can determine which diagnostic tests may be right for you and help you start on the journey to improving your heart health.