Electrocardiography (ECG) graphically displays the electrical processes in the heart muscle. This enables the physician to draw a variety of conclusions about the patient's heart function and fitness. The ECG has long been an integral part of everyday medical life. It provides information on a wide variety of heart diseases, ranging from cardiac arrhythmia and myocarditis to myocardial infarction. There are three different types of ECG: resting ECG, long-term ECG and exercise ECG, which are used for certain questions.
For the heart to carry blood continuously through the vascular system, both the ventricles and the atria must contract and relax at the right moment. The "pump" has a system for the formation and conduction of excitation in order to achieve this time-coordinated activity of the heart muscle cells. The sine node occupies a key position. This is where the electrical excitation occurs, which causes the muscle cells to contract. Because it rhythmically drives the heart and determines the frequency of the heartbeat, the sinus node is also called the body's own "pacemaker". The electrical impulses emanating from the sinus node propagate via the excitation line system. They excite first the atria, then the myocardial cells of both chambers, which expel the blood into the pulmonary aorta and the aorta. In the course of each cycle the excitation decreases, again first in the atria and then in the chambers. During all these phases, changes in electrical voltage occur at the heart, which - albeit greatly attenuated - are transmitted to the surface of the body. These voltage fluctuations are continuously picked up by the ECG electrodes applied to the skin. The ECG device records the signals, amplifies them and then displays them as a curve. What the doctor sees on this electrocardiogram is a recurring image of the electrical heart action, with formation, transmission and regression of excitation. Today, computer programs evaluate the ECG. They can support the physician in the assessment, but they cannot replace him.
The physician uses these two variants of electrocardiography for questions that cannot be adequately answered with a resting ECG. With a long-term ECG, the patient receives a small, portable ECG device that continuously records his cardiac output curve, usually over 24 hours, sometimes even over 48 or more hours. The measured data are then read out and evaluated on the computer. The main purpose of the long-term ECG is to detect cardiac arrhythmias that occur only temporarily and therefore may not occur during the period covered by the normal ECG. During the examination period, the patient logs his activities and any complaints that occur. In this way, abnormalities in the ECG can be associated with corresponding events - such as sporting activity.
The exercise ECG is technically written in exactly the same way as a resting ECG. The difference is that the patient exerts physical exertion during the measurement on an ergometer. The examiner individually adjusts the load, depending on the age and fitness of the patient, and gradually increases it according to a defined scheme. During the exercise and subsequent recovery, the doctor observes both the heart flow curve as well as blood pressure and pulse. The purpose of exercise ECG is to identify cardiovascular diseases that only become apparent during physical exertion. For example, circulatory disorders in the coronary arteries (coronary heart disease) or cardiac insufficiency. In addition, this form of electrocardiography can be used to determine the current physical performance of both healthy and sick people.
In the electrocardiogram, the doctor can detect disturbances of the heart rhythm and the propagation of excitation in the heart. They can then draw conclusions about diseases and circumstances that either directly affect the heart or impair its function. These include: In all these diseases, electrocardiography also helps to control the course and check how well a treatment works.