A stress test is designed to see whether you may have an issue with the blood supply to your heart, called ischaemia. They are different types of stress test – a stress echocardiogram involves performing an ultrasound of your heart (an echo), then putting your heart under a form of stress and repeating the ultrasound, then comparing the images to see if the heart muscle pumps differently at rest and when it is working hard.
The heart muscle is supplied by the coronary arteries, tubes that taken blood immediately pumped out and supply the heart muscle itself. These tubes can narrow down if patients have coronary artery disease.
The gold standard method to look for coronary artery disease is invasive angiography. This involves a tube being passed up to the heart from the wrist or groin, and dye injected into the heart arteries and an X-ray takes an image.
One of the tests that can help determine whether a narrowing is present is called a stress echocardiogram. This is a non-invasive test, and takes about 45 minutes. The basic idea is to do an ultrasound of the heart at test (an echo), then repeat it when the heart is ‘stressed’, or working hard. If there is a narrowing in the blood supply in one area, the heart won’t pump quite as well in that spot and this can be seen with the ultrasound.
The test is non-invasive and doesn’t require any radiation, but it can be difficult in people who don’t have good quality images or people with certain electrical abnormalities.
There are a few ways to challenge the heart, but the most common and most accurate is to exercise. After the resting ultrasound is complete, you will either ride a bicycle or walk on a treadmill. Every few minutes, the resistance on the bike increases or the treadmill gets a little faster with a higher incline. During this time the cardiologist will ask you about your symptoms, and you will be continually monitored with an ECG. Once you reach your limit, you will quickly be ushered back to the bed to take another ultrasound while the heart is pumping hard, to compare to the resting pictures.
It’s important to get your heart under a good amount of challenge, either by provoking your symptom or by getting your heart rate up to a good level.
Various medications can also be used instead of exercise to challenge your heart, such as dobutamine. This method is only used for people who aren’t able to exercise enough, and it isn’t quite as accurate as the exercise version of the test.