Description of ECG

We describe the standard twelve-lead ECG according to the so-called ECG of ten. We systematically measure the individual parameters of the ECG recording. From the values obtained in this way, a relatively accurate diagnosis can be determined, i.e. whether it is a o pathology of the electrical activity of the heart, or a o physiological finding. It is important to always clarify the units and their ratio in the ECG recording before measuring ! This can be determined from the so-called standard, which is equal to 1 mV, and   speed of the paper advance. Usually 1 mm on the  y- axis is equal to 0,1 mV. At a displacement of 25 mm/s, 1 mm on the  x-axis is equal to 0.04 s, at a displacement of 50 mm/s, 1 mm = 0.02 s.

Summary of ECG ten
By following a uniform and clear procedure confusion and  mistakes can be avoided even during a later inspection. Therefore, we immediately compare the measured values with the physiologigal ones, and we will visibly mark the pathologies found (to faciliate orientation). In the  end, it is necessary to merge the data found and   establish a diagnosis only from them.
 * ECG ten:


 * 1) ,
 * 2) heart rhythm,
 * 3) heart rate,
 * 4) P vlna,
 * 5) PQ interval,
 * 6) QRS complex,
 * 7) ST section,
 * 8) T wave,
 * 9) QT interval,
 * 10) electrial cardiac axis.

Heart action
In the first point, we examine the regularity of heart action. We measure the distances between the selected point of the ventricular complex (most often the R wave) in each cycle in the entire ECG. We calculate the average from the measured values and  measure the same distances again.


 * if the difference between the RR distances and the average is less than 0.16 s, we mark the action as regular = within the norm,
 * if this is not the case, we mark the action as irregular = pathology,
 * if there is only one extrasystole in the record and the other distances are normal, we write  the action is regular with one extrasystole.

Heat rhythm
Rhythm is the determination of the place where an action potential (controlling impulse) arises in the heart, which leads to depolarization of the ventricles. We monitor the presence of the P wave and its relationship to the ventricular QRS complex.

Heart rhythm Rhythm is the determination of the place where an action potential (controlling impulse) arises in the heart, which leads to depolarization of the ventricles. We monitor the presence of the P wave and its relationship to the ventricular QRS complex.

Sinus rhythm

Physiologically the excitation originates in the sino-atrial node  (SA)  and then spreads to the ventricular musculature via the atria,  atrio-ventricular  (AV) and budle of His. This is reflected in the ECG recording by a P wave, which is: a) positive in leads I and II (the impulse spreads through the atria from right down to left), and b) the QRS comples is preceded by a P wave in aconstant PQ interval (the exception is the lenghtening PQ interval in the Wnkebach period - see there). The fulfillment of these condition is evidence that the depolarization of the ventricles is controlled from the sinus node and therefor the ECG recording shows a '''sinus rhythm. '''

If the rhythm originates outside the SA noe (atrial muscle, AV node, transmission system/ventricular muscle), it is always a pathology and we are talking about a  non-sinus rhythm, which can be determined more closely:

Atrial rhythm

An atrial rhythm means that the driving impulse originated in the atrial region, but outside the SA node. The wave of depolarization spreads along the atria in a different direction than from right to left down, and therefore the P wave is negative in lead I. or in lead II. If the P wave on the ECG is negative in lead I and the P wave is positive in lead II, then the impulse originated in the upper part of the left atrium and spread down to the right. If the P wave is negative in lead II and the P wave is positive in lead I, then the impulse originated in the lower part of the right atrium and propagated upward to the left. The wave of depolarization also hits the AV node and the impulse spreads along the conduction system to the ventricles, where it causes depolarization of the ventricles. On the ECG, the QRS complex is preceded by a P wave with a constant PQ interval. Depolarization of the ventricles is controlled from the atria and therefore in this case the rhythm is atrial. The abnormal site of origin of the controlling impulse will not affect the distal conduction of the impulse through the ventricles and therefore the shape and duration of the QRS complex will not change on the ECG. In atrial rhythm, the frequency of atrial impulses can be up to 200/min. In normal AV conduction (1:1 AV conduction), all impulses are transmitted to the ventricles and the ventricular rate (QRS) will be the same as the atrial rate (P waves). From a didactic point of view, these are abnormal P waves indicating abnormal depolarization of the atria. If the frequency of atrial depolarizations is 220-350/min, then the waves on the ECG with this frequency are referred to as  F waves and these are typical of atrial flutter. If the frequency of atrial depolarizations is 375-600/min, then the waves on the ECG with this frequency are referred to as    f waves and these are typical for atrial fibrillation. In atrial fibrillation, the heart's action is markedly irregular. Under normal circumstances, fast atrial impulses (F or f) are transferred to the ventricles in a lower number. The ave conversion of excitations can then be in a ratio of 2:1, 3:1, 4:1. We do not measure PQ interval for atrial rhythms.

Junctional rhythm

The driving impulse originates in the AV node or in the bundle of His (junction) and spreads through the bundles of Tawar to the ventricles and may or may not pass back and cause retrograde depolarization of the atria. If the impulse is transferred to the atria, then on the ECG there is a P wave in leads I. and II. negative (the wave of depolarization spreads through the atria from bottom to top). If the atrial impulse does not propagate, there is no depolarization of the atrial muscle and the P wave is missing in all ECG leads. The abnormal site of origin of the controlling impulse does not affect the distal conduction of the impulse through the ventricles and therefore the shape and duration of the QRS complex on the ECG do not change.

Ventricular rhythm

In ventricular rhythm, the impulses that trigger ventricular depolarization occur in the conduction system below the point where the bundle of His divides into the bundles of Tawar. The depolarization wave usually takes a different route through the ventricles and the depolarization always takes longer than normal. This changes the shape of the QRS on the ECG, but mainly the duration of the QRS complex to 0.12 s and more than 0.12 s. In the ventricular rhythm, the ECG recording either lacks P waves or the P waves that precede the QRS complex have a different frequency than the frequency QRS complexes (time continuity of QRS complexes with P waves is not proven).

Heart rate
One of the important signs of heart performance is the frequency of ventricular contractions. Together with the stroke volume it determines minute cardiac output.

$$SF=\frac{300}{N}$$ [beats/min]
 * Calculation of heart rate from ECG


 * N= number of large squares on the ECG recording

Physiological values of heart rate at rest range from 55 to 90 beats per minute.


 * a slower frequency (< 55 beats/min) is called bradycardia → bradyarrhythmia,
 * faster (> 90 beats/min) is called tachycardia → tachyarrhythmia.

Depending on the ECG rhythm, the bradycardia or tachycardia is called sinus, atrial, junctional or ventricular bradycardia/tachycardia.

P wave
Physiologically the P wave precedes each QRS complex, from which it is separated by the PQ interval. (see below). The frequency of its occurence is therefore the same as the frequency of ventricular contractions.

Description: A single P wave is present that precedes each QRS complex with a rate of (e.g.).../min Next, we evaluate the positivity and negativity, amplitude and duration of the P wave of all bipolar limb leads (I., II. and III.). Physiologically, the P wave is in I. and II. lead positive, in III. lead can be positive, negative or absent. '''Negative P wave in I. or II. lead is pathological (see rhythm)'''.

With a normal finding, the amplitude of the P wave does not exceed 0,25 mV. Higher values indicate possible enlargement of the atria. Slender tall P waves are referred to as P pulmonale, and may be on the ECG in patients with cor pulmonale. High P waves wider than 0.11 s, sometimes double-peaked, are called P-mitral waves  and can be seen on the ECG in patients with left atrial enlargement, e.g. mitral valve stenosis.