A stress test is also called an exercise stress test and sometimes a treadmill test. The test is performed to assess the function of the heart during physical activity. It is based on the concept exercise causes the heart to pump harder and faster; hence, the test can indicate the heart (cardiovascular) status of the patient and the ability of the heart to pump blood and reveal problems with blood flow within the heart.
A stress test usually involves walking on a treadmill or riding a stationary bike, under supervision, during which the heart rhythm and rate, blood pressure, and breathing are continuously monitored. During the test, the patient is on a treadmill or a stationary bike till he achieves at least 80% of the target heart rate. The target heart rate may be achieved faster in old people; young people and athletes take up to 20 minutes or even longer to attain the target heart rate. The patient who may not be able to perform a treadmill test due to other problems such as physical disabilities or trauma may receive medication intravenously called dobutamine that mimics the effects of exercise on the body.
Why is a stress test done?
The doctor may recommend a stress test for the following:
- Diagnosis of coronary artery disease: Coronary arteries are the major blood vessels that supply blood to the heart, hence delivering oxygen and nutrients to the heart. Coronary artery disease occurs when the coronary arteries get damaged or diseased, especially due to the accumulation of cholesterol and other substances (plaques) in the artery.
- Diagnosis of cardiac arrhythmia: Arrhythmia is a problem with the heart rhythm. The heartbeat may be too fast, too slow, or irregular. Arrhythmias occur due to improper coordination of the electrical impulses that help the heart function normally.
- Guide treatment of heart disorders: If a patient has already been diagnosed with a heart condition, an exercise stress test can help the doctor assess the progression of the heart condition and the effects of treatment, which can help establish the treatment plan accordingly. A stress test can also help plan cardiac surgery if necessary. Similarly, it may be done after six weeks of heart revascularization procedure to see how much stamina the heart has recovered.
- Diagnose cardiovascular health: A stress test is sometimes done in patients with diabetes and those who suffer from erectile dysfunction. The microscopic damage to small blood vessels in both these conditions may be an indicator of poor heart reserve as well.
How is a stress test performed?
Before a stress test: The doctor obtains a detailed history and performs a physical examination. The doctor would advise certain pre-procedure instructions. You may have to skip certain medicines on the day of the test.
During a stress test: Your entire stress test, including the prep time, would take about 45 minutes to an hour. The actual test takes only around 15-20 minutes. The patient would have to walk on a treadmill or pedal a stationary bicycle. As time passes, both the treadmill slope and speed increase at a fixed time interval.
Any patient who is unable to exercise would receive drugs through veins that would mimic the effects of exercise by increasing blood flow to the heart.
The nurse or technician will place electrodes on the chest, legs, and arms. Some areas of the body may need to be shaved to help the electrodes stick. The electrodes are connected to an electrocardiogram (ECG) machine, which records the electrical signals from the heart. A cuff is placed on the upper arm to monitor blood pressure during the test. Throughout the test, your blood pressure, ECG, and heart rate are recorded.
The patient continues exercising till the heart rate reaches the target set or till any of the following signs and symptoms occur (Your target heart rate is calculated by the system based on your age and weight.):
- Chest discomfort or pain
- Difficulty in breathing
- Abnormally high or low blood pressure
- Cardiac arrhythmia
- Abnormal changes in the ECG
The test is safe and performed under supervision. The patient may stop anytime they feel uncomfortable.
After a stress test: After the patient finishes exercise, they may be asked to stand still for several seconds and then lie down for some time while still being monitored. The doctor would observe for any abnormalities in heart rate and breathing while returning to normal. Once a stress test is complete, the patient can return to their normal activities unless they are advised otherwise. Studying the results of the stress test would help the doctor make a diagnosis and advise an appropriate treatment plan.
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