The ECG (= electrocardiogram) records the sum of the electrical voltages of all myocardial fibers and thus serves to evaluate myocardial function. In addition to the heart rhythm and heart rate, malfunctions of individual sections of the heart muscle can be detected. Every heart action is preceded by an electrical excitation, which usually begins in the sinus node.
From here, the excitation propagates according to a known pattern over all cells of the heart muscle. This results in a recurring image of the heart action, and by changing this image it is possible to draw conclusions about possible malfunctions. The ECG is increasingly evaluated by computer programs. Nevertheless, manual evaluation by the physician is still not dispensable to this day.
The ECG is a non-invasive method for evaluating heart function that can be repeated at any time. In addition to rhythm, heart rate and position type, the function of the atria and ventricles can also be read. It is possible to detect a myocardial infarction, AV block, rhythm disturbances or even hypertrophy of the myocardium (thickening of the heart muscle) by means of the ECG.
Furthermore, inflammations of the pericardium (pericarditis), the heart muscle (myocarditis) and electrolyte disorders can be detected by an altered ECG image. In principle, the electrocardiogram is a routine examination; almost every general practitioner or cardiologist in private practice, as well as every hospital, is able to perform an ECG. Furthermore, the examination is completely painless and usually causes no problems.
At first, the patient lies down on a couch with the upper body completely undressed and without shoes and stockings, relaxed. It is important to find a position that is as comfortable and relaxed as possible, since muscle tension can lead to a distorted ECG. It is also important to avoid muscle tremor, for example due to excitement or cold.
In the next step, the medical assistant attaches about ten electrodes to the upper body, as well as to the arms and ankles. Under certain circumstances, the chest hair of very hairy men may have to be shaved, as otherwise conductivity may be reduced. In contrast to the adhesive electrodes of the upper body, so-called clamp electrodes are used on the arms and legs.
Afterwards the appropriate cables are attached to the individual electrodes and connected to the ECG device. Now the patient should lie as still as possible; movements, coughing, hiccups, but also particularly deep inhalation can falsify the result. Diseases that cause involuntary tremor, such as Parkinson’s disease, should therefore be taken into account when interpreting the ECG.
At the push of a button, the devices write an electrocardiogram within a few minutes. In some cases, a repeat performance must be initiated, for example if electrodes are not optimally positioned or skin contact is insufficient. After a meaningful ECG has been written, the medical staff removes the electrodes and cables. As a rule, the adhesive electrodes can be easily removed and cause hardly any skin irritation.