Exercise, especially walking, running, bike riding and the like, are a great way to increase the heart rate and blood flow, and improve health in general. When heart specialists use this same idea to evaluate heart function during strenuous activity, it’s called a cardiac stress test.
People may not have any signs or symptoms of heart disease when their hearts are at rest. But when the heart works harder during exercise, it needs more blood and oxygen. A cardiac stress test uses exercise to help diagnose heart disorders that are easier to find when the heart is under stress, or working harder. A cardiac stress test is a simple, noninvasive way to determine if a patient needs further diagnostic procedures or immediate therapeutic procedures.
Since heart doctors can’t follow people around outside while they exercise, they bring patients into dedicated stress test labs where they can replicate the experience. Stress tests include an EKG (electrocardiogram) that measures and records the heart rate and the strength and timing of electrical signals that pass through the heart as it beats. Your blood pressure and breathing will also be measured and monitored during the test.
If a stress test has been recommended for you, learn more about what to expect so you can feel prepared and relaxed throughout the process.
Reasons for a Stress Test
People may not have any signs or symptoms of heart disease when their hearts are at rest. But when the heart works harder during exercise, it needs more blood and oxygen. Coronary heart disease develops when plaque, a fatty substance made of cholesterol and other material in the blood, builds up in coronary arteries. Plaque narrows the arteries and reduces blood flow to the heart. This also increases the risk of blood clots forming in the arteries.
Narrow arteries can't carry enough blood to keep the heart working well. That’s why some symptoms of heart disease become obvious during exercise. Stress tests are used to:
- Determine a patient’s risk for heart attack or other heart conditions
- Determine the safe level of exercise for an individual
- Diagnose arrhythmia (irregular heartbeat) and coronary artery disease
- Evaluate treatment effectiveness in heart patients
Who Needs a Stress Test?
A stress test can benefit anyone with symptoms of reduced heart blood flow, including:
- Angina, chest pain or discomfort caused by poor heart blood flow
- Irregular heartbeat (arrhythmia)
- Rapid heartbeat (tachycardia)
- Shortness of breath
Others who can benefit from a stress test include those who:
- Had a heart attack
- Have increased risk for heart disease
- Had recent heart surgery
- Want to start an exercise program
There are three types of stress tests: exercise stress tests, nuclear stress tests, and stress echocardiograms. Depending on their condition, patients may have one or a combination of stress tests.
Before a Stress Test
You will receive instructions about diet and medications before the test. They may need to avoid eating or drinking anything except water. This may include not drinking coffee or any caffeinated drinks. Also, some over-the-counter or prescription medications can interfere with test results. If you have diabetes, for example, you will receive instructions about adjusting your medications prior to having a stress test. And patients who use an asthma inhaler should bring it to the stress test and tell the doctor about it.
What to Expect During a Stress Test
Doctors can do a stress test in the office, outpatient clinic or hospital. There are several different types of stress tests, but they all include exercising on a treadmill or stationary bicycle — starting slowly and then gradually increasing speed. These tests include exercise stress tests, nuclear imaging stress test and stress electrocardiograms.
It’s important to stop the test early if you have any symptoms including:
- Abnormal heart rhythm
- Abnormally low or high blood pressure
- Extreme shortness of breath
- Moderate to severe chest pain
If you have any of these symptoms, tell the doctor immediately. You can stop the test at any time the exercise becomes too difficult.
If you have conditions such as arthritis that make it difficult to walk on a treadmill or use an exercise bike will receive medication that produces the effects of exercise instead.
Exercise Stress Test
Exercise stress tests show how fast a person’s heart is beating and whether the heart rhythm is steady or not. With electrodes placed at specific locations on your body and attached by wires to an EKG (electrocardiogram) machine, doctors can measure and record things like heart rate and the strength and timing of electrical signals that pass through the heart as it beats.
As you walk or pedal, the speed, incline and resistance gradually increase until reaching the target heart rate set by the doctor, but you may always stop sooner if you develop symptoms such as chest pain, shortness of breath, dizziness or fatigue. Doctors may also stop the test if the EKG shows a problem with your heart.
Nuclear Imaging Stress Test
A cardiac nuclear imaging test measures blood flow in a person’s heart at rest and then during exercise. It uses radioactive dye and SPECT (single photon emission computed tomography) or PET (positron emission tomography) scans to make images of the blood flow to the heart.
Measuring blood flow while you are at rest and during exercise on a treadmill or exercise bike can show areas of poor blood flow or heart damage. People with conditions such as arthritis that make it difficult to walk on a treadmill or use an exercise bike will take a medication that produces the effects of exercise.
During a nuclear imaging stress test, a doctor inserts an IV into your arm to inject the dye. It takes 15 to 40 minutes for the heart to absorb the dye. First, the doctor will make SPECT or PET scan images of your heart at rest. Then, you are wired to an EKG machine and asked to walk on a treadmill or ride a stationary bike. When the heart is working at its hardest, there’s another injection of radioactive dye. Once the heart has absorbed the dye, in about 15 to 40 minutes, the patient resumes exercise and the SPECT or PET scanner makes more images of the heart. This allows doctors to compare the images of the heart at rest to the images of the heart under stress.
The radioactive dye will leave the body naturally during urination. Drinking lots of water will help remove it faster.
Stress echocardiography uses ultrasound imaging to evaluate how well a person’s heart muscle is working to pump blood throughout the body (typically to find a decrease in blood flow to the heart that results from narrowing in the coronary arteries). The test makes an ultrasound of the heart before and after either strenuous exercise on a treadmill or exercise bike, or after you are given medication that elevates the heart to simulate exercise.
During a stress echocardiogram, a doctor or ultrasound technician rubs a special gel on the ultrasound transducer, a wand-like device. With the transducer held against the patient’s chest, the ultrasound device uses sound waves to make moving images of the heart.
After these images are taken, you then exercise on a treadmill or exercise bike. When the heart rate is increasing or working at its hardest, the doctor or technician will make more images.
The doctor will compare images of the heart at rest with images of the heart working under stress.
After a Stress Test
After a short rest — usually about 10 to 15 minutes or until the heart rate returns to normal — you will be ready to return home the same day and can resume normal activities. Depending on the results of the test, you may not need further treatment or tests, or the doctor may recommend more tests or cardiac catheterization.
Comprehensive Heart Care
When it comes to your heart, you want experts by your side with the most advanced diagnostic technology and medical experts to coordinate your comprehensive heart care. Lean on our our leading-edge cardiology team for more information and to help keep your heart healthy and strong.