In the case of an exercise ECG, an ECG device is used to capture and record the electrical signals of the heart while the person being treated is physically active, thus putting strain on the heart and circulation. The exercise ECG is an important diagnostic tool for diagnosing certain diseases of the heart. In particular, diseases that are associated with a lack of oxygen to the heart are usually diagnosed or excluded with a stress ECG.
In principle, the devices used are those for a normal ECG, which are attached to the body with cables of sufficient length. The person who is to be examined must be on a piece of sports equipment, usually a bicycle ergometer, during the examination and must produce a certain output (measured in watts). If there is a lack of oxygen to the heart, the electrical activity changes visibly during physical activity and a suspected diagnosis can be made. If there is no disease of this kind, the ECG changes due to the faster heartbeat, but typical changes of an oxygen deficiency cannot be found.
Who needs it?
Typically, exercise ECGs are performed when the attending physician suspects that there may be a lack of oxygen supply to the heart. Symptoms that may indicate the presence of such a disease are therefore a reason to perform a stress ECG. These include chest pain in particular.
Even if there are no symptoms, the examination can be useful. If one or more risk factors for the development of coronary heart disease (CHD) are present, it is advisable to check the heart regularly. Carrying out a stress ECG can thus help long-term smokers, people who are overweight, have high blood lipids or high blood pressure to prevent serious consequences of heart disease.
The exercise ECG is also used as a control examination for many heart diseases after treatment. With the help of the exercise ECG, the long-term success of the therapy can be monitored and, if necessary, follow-up treatment can be initiated in good time. The exercise ECG is also recommended as part of a regular health check for men (45 and older) and women (55 and older) of a certain age to monitor the development of heart disease away from risk factors and previous illnesses.
Procedure of the exercise ECG
A stress ECG is usually carried out as part of a routine examination by your family doctor or cardiologist, or if there is a concrete suspicion of heart disease. The examination itself is usually always similar. First, the person to be examined is asked to go to the treatment room where the ECG device and either a bicycle ergometer or a treadmill are located.
In order to be able to connect the electrodes of the ECG, the upper part of the body must be cleared. Now the electrodes are connected and a blood pressure cuff is attached to the upper arm or leg and a first measurement is taken at rest. Now the patient is asked to sit on the ergometer or to stand on the treadmill.
As soon as the patient is ready, the physical activity is started and the ECG records the heart activity and blood pressure at regular intervals. The power which has to be applied can usually be displayed directly on the ergometer in the form of watts. The power is increased during the recording as much as possible to provoke possible changes in heart activity.
Strict attention is paid to how the person being examined feels throughout the entire examination, so that the examination can be aborted if the person feels unwell. We also keep an eye on the blood pressure and the electrical activity of the heart in order to be able to abort the examination in case of critical changes. A stress ECG takes about 10-15 minutes in total.
With preparation and introduction to the examination by the attending physician, the entire examination can take up to 30 minutes. After the examination, the power to be provided is reduced to gently reduce the stress. The patient can usually go home again after discussing the results.
If the exercise ECG led to the suspicion of a heart disease, further diagnostic examinations may follow and possibly a hospital visit may be necessary. The power achieved during the exercise ECG is expressed in watts. At the beginning of the examination, 25 to 50 watts are set on the ergometer, which corresponds approximately to the performance for normal or somewhat faster walking.
Afterwards the exercise level is increased by 25 watts every two minutes. A performance of 75 to 100 watts can be compared with slow cycling or swimming, 125 to 150 watts correspond to fast cycling or jogging. If 150 watts or more is reached, this is an extreme sporting performance.
How far the performance is increased depends on the individual values. It is increased until the maximum heart rate is reached, which can be calculated using the formula 220 heart beats/minute – age (in years) +/- 12 heart beats/minute. For a 40-year-old person, the maximum heart rate would be 186-192 beats per minute, for example. At how many watts, i.e. at what power, this frequency is reached varies from person to person.