Just like an ordinary pump, the heart is more likely to break down when it is called on to work too hard. Consequently, if you are suffering from chest pain and an electrocardiogram (ECG) recorded in the doctor’s surgery is normal, you may be asked to undergo an exercise ECG or stress ECG test. It involves having an ECG done while you are exercising in a carefully controlled manner and also having your blood pressure measured.
A cardiac stress test explores the activity of the heart, not the amount of mental tension to which you are being subjected. It is generally carried out if heart disease is suspected.
First, a calculation is made of your maximum safe heart rate based on variables such as your age and weight. You are then connected to the ECG machine and start off walking slowly on a treadmill machine or riding an exercise bicycle. The pace is gradually increased by speeding up the machine until your heart is beating steadily at the calculated rate. An ECG is taken before, during and after the exercise, so that adverse results of the increased activity on the heart quickly become apparent.
If a person is unable to exercise (e.g. arthritis), a medication called dobutamine can be given to briefly stimulate the heart and mimic the heart stress experienced during moderate exercise.
People whose arteries have narrowed so that the heart is not getting enough blood often have a characteristic ECG pattern. A stress test is also used for someone who is recovering from a heart attack to determine how much blood is getting through to the heart.
The test is painless but it is possible that the patient may feel dizzy or weak, become conscious of their heartbeat becoming irregular or even experience some chest pain. However, it is obviously vital for the doctor supervising the test to ensure that the exercise does not bring on a heart attack and the ECG readings will constantly be monitored so that the test can be stopped if there is any hint of heart distress.
In the same way as an ordinary ECG, an exercise ECG can only show what is happening at the time it is taken. It is not unknown for a person to have a stress test which seems normal and then have a heart attack shortly afterwards.