Evaluation/interpretation

After recording the electrocardiogram, the doctor interprets the ECG, sometimes using a ruler standardized for this purpose. He analyzes the height of the individual deflections, the time intervals between them, as well as their duration and steepness.Thus, a correct evaluation of the ECG can make pathological processes and changes, such as infarcts or rhythm disturbances in the heart, visible. Nowadays, in many places modern computer programs analyze the written ECG in a few seconds.

Nevertheless, it is essential that a physician additionally carries out the interpretation personally, as the devices can overlook or misinterpret pathological changes. The ECG is recorded on graph paper or electronically. As a rule, the writing speed is 50mm/s and the deflection 10 mm/mV.

Thus, 1mm in writing direction corresponds to 0.02s and upwards to 0.1mV. Since the ECG records the excitation of the individual heart muscle cells, the standard ECG contains various waves and spikes as well as their distances, which represent signs of a certain excitation or its regression: In addition to the waves and spikes, certain functions can also be assigned to the distances between them:

The P-wave represents the anterior yard excitation through the sinus node, usually represented by the first small, positive wave starting from the zero line; it should last a maximum of 0.12 seconds.
The QRS complex represents the physiological propagation of the excitation through the chamber, which should take a maximum of 0.10 seconds. It shows itself in the form of the: Q-wave as the first negative rash, theR-wave as the following positive rash and theS-wave as the second negative rash.
Q-point as the first negative deflection, the
R- tine as the subsequent positive rash and the
S- tine in the shape of the second negative deflection.
The QRS complex is followed by the relatively broad T-wave: this characterizes the regression of excitation in the heart chambers.
In some cases, a U-wave may occur after the T-wave.
The U-wave corresponds to post-fluctuation fluctuations during excitation regression, although its origin has not yet been conclusively clarified. On the one hand, it is assumed that it reflects the repolarization in the excitation conduction system (Purkinje fibers), other sources assume that it can occur, for example, in the case of electrolyte disorders such as a potassium deficiency.
Q-point as the first negative deflection, the
R- tine as the subsequent positive rash and the
S- tine in the shape of the second negative deflection.
The PQ interval represents the distance between the beginning of the P-wave and the beginning of the Q-wave and should not be longer than 0.2 seconds and should be isoelectric, i.e. on the zero line. This interval is an expression of the transition time between Vorhof excitation and chamber excitation.
The QT interval (also known as QT time) is the distance between the beginning of the Q-wave and the beginning of the T-wave and represents the duration of the entire chamber excitation.
Depending on the current heart rate, this time can vary, so there is no standard value.
The ST section comprises the end of the S-wave to the beginning of the T-wave and marks the repolarization. Normally it lies on the isoelectric line and should not be raised above 0.2 mV. However, its duration varies considerably and depends, among other things, on the heart rate.

Depending on the problem, different methods for ECG recording can be used.

The most common method is the resting ECG. Usually, the patient lies still, but it can also be done in a sitting position. Since it only takes a few seconds, it can also be used in an emergency.

In addition, it is very informative and is therefore the most frequently used. However, it is only a snapshot, so that rarely occurring rhythm disturbances may not be recorded. To detect these, the long-term ECG is used.

This is recorded over 24 hours using a portable ECG device. The patient should move normally and usually follow a normal daily routine in order to be able to recognize possible situation-dependent changes. In most cases, the long-term ECG is used for rhythm diagnostics.

The stress ECG (ergometry) is used to record possible stress-related rhythm disturbances. The patient is loaded in a defined manner by means of a treadmill or ergometry, whereby heart rate and blood pressure can be observed under stress. In addition, excitation-reduction disorders can be provoked and recorded.