Because the normal ECG is risk-free for the resting patient, it is performed as a routine examination when heart disease is suspected. It can detect
- Circulatory disorders (diseases of the coronary vessels, myocardial infarction).
- Cardiac arrhythmias (heartbeat too fast, too slow or irregular, atrial fibrillation/flutter, ventricular fibrillation/flutter).
- Drug overdose
- Mineral deficiency or excess (eg, potassium) and
- Inflammation of the heart muscle or pericardium.
It is also used to monitor the course and therapy of heart disease. Some lung diseases (e.g. embolism [link to “Pulmonary embolism – a life-threatening clot”]) also cause changes in the ECG. Before and during surgery, it is an indispensable part of diagnostics to check the patient’s heart function.
The procedure – how the examination is performed
If the patient is taking any medications, he or she should tell the examiner beforehand. Cardiac medications in particular can alter the ECG and otherwise lead to false diagnoses.
In order to obtain evaluable results, the electrodes are always attached in a specific order to defined locations on the chest (chest wall leads V1-V6) and the wrists and ankles (extremity leads). To increase their conductivity, a gel can be used for suction electrodes and the electrode paper can be moistened; partial shaving may be necessary if there is a lot of chest hair. The electrodes are connected to the ECG machine by means of cables.
- In the resting ECG – the “basic form” – the patient lies still and relaxed during the measurement.
- Some changes such as circulatory or rhythm disturbances only become apparent under physical stress; in such cases, a stress ECG (ergometry) on a bicycle or treadmill is indicated. In this case, the load is increased in a controlled manner in several steps until “exhaustion” (the highest load level, which depends on age and gender, among other things) or until complaints or serious ECG changes occur. In addition to the cardiac current curve, blood pressure and pulse are also measured. Ergometry is also used, among other things, in cases of suspected exercise-induced hypertension, for therapy monitoring and to clarify exercise capacity after a heart attack or after heart surgery. Since complications such as heart pain or even a heart attack can occur, the ergometry always takes place under medical supervision.
- If there is suspicion of cardiac arrhythmia, a long-term ECG may be indicated. In this case, the affected person carries a small recording device with him for 24 hours and notes activities and complaints. Also diseases of the coronary vessels and the control of a pacemaker are areas of application of the long-term ECG.
- Special forms such as intracardiac ECG (during a cardiac catheterization) or esophageal ECG are reserved for certain questions.
