A “stress test” or “Stress ECG” is when we need to check the heart under pressure or “stress”. There are different methods to “stress” the heart, yet the simplest and oldest one is increasing the heart rate via walking or running on a treadmill. You will be connected to an ECG machine, which records your heart rate and rhythm when running.
What is an ECG?
ECG or electrocardiogram records the heart’s electrical activity into line tracings on paper. The spikes and dips in the line tracings are called waves. Any change in the pattern of these waves can indicate a specific disease in the heart like Atrial Fibrillation (AF) or heart attack. Many other conditions could be diagnosed on a “resting ECG” (an ECG done when you are lying in bed). The above picture is an example of ECG.
Why do we need to "stress" the heart and how do we do it?
However, some heart diseases come into light only when the heart is under pressure or stress and not at rest. A simple example is a significant blockage in a heart artery (coronary artery) that might not cause any abnormality on “resting ECG” but emerge only after stressing the heart.
To put the heart under pressure and stress, we would ask you to start walking on a treadmill which increases your heart rate. While exercising, you would be connected to an ECG machine that continuously records your ECG. “Stress” comes from walking on the treadmill and “ECG” from the machine, hence the name stress ECG (electrocardiogram), also called “stress test” or an “exercise test.”
Then the “resting ECG” is compared to the ECG during stress, looking for any meaningful changes which could indicate disease. Many other pieces of information are gathered by performing a stress test. These include the fitness level, evaluating complaints like shortness of breath or chest pain that arises with exertion (like walking up the stairs) and overall one’s body’s ability to perform under stress.
What are the most important reasons we do a "stress test"?
- Finding the cause of chest pain, pressure or heaviness,
- Helping to decide on the best treatment for a person with angina,
- Check exercise capacity after heart attack or heart surgery,
- Finding the cause of symptoms that only emerge during physical activity, such as dizziness, fainting, rapid and erratic heartbeat (palpitations), shortness of breath (dyspnea), and chest pain,
- Help you decide about starting an exercise program if you have been physically inactive for several years, increasing the likelihood of heart disease.
How do we stress the heart if I could not walk on a treadmill?
Although exercising and walking on a treadmill is the best way to assess someone’s heart and complaints, if you cannot walk on a treadmill for any reason, there are other ways to “stress” the heart. The most common test is a pharmacologic nuclear test called “Myocardial Perfusion Scan“. We first “stress” the heart with some specific medications given intravenously and then take pictures of the heart with the help of nuclear material and scanners.
What is the difference between stress ECG and Stress Echocardiogram?
Stress ECG and Stress Echocardiogram are both “stress tests”. The “stress” component of the tests are the same. The patient starts exercising on a treadmill, increasing the heart rate and the “pressure” on the heart. They both involve the continuous recording of the ECG when exercising to look for changes compared to the resting state. The only difference is that stress echocardiogram adds an imaging part to the test, i.e. Echocardiogram, which is simply an ultrasound machine taking pictures of the heart. This addition increases the accuracy of the stress test in detecting many abnormalities compared to stress ECG.
There have been many instances when patients were required to repeat a stress test and combine it with an Echocardiogram to confirm or rule out a diagnosis. Nowadays, many cardiology practices only perform “stress echocardiograms” to avoid this problem.