How to decipher ECG signs of irregular heartbeat rhythm


Violation of the rhythm of cardiac contractions is a sign of pathological processes in the myocardium or blockade of nerve impulses emanating from the drivers of rhythm. To identify the cause and establish the correct form of pathology, doctors conduct electrocardiography. How to correctly recognize this or that form of arrhythmia or blockade, read in this article.

On the electrocardiogram it is possible to recognize the root causes of the disturbed heart rhythm


  • Heart rhythm disturbance: causes
  • How to detect the disturbed automatism of the heart on the ECG?
    • Sinus arrhythmia
    • Ectopic rhythms
    • Nodal rhythms of AV connections
    • Migrating the pacemaker
    • Extrasystolia
  • Fibrillation of the heart on an electrocardiogram
    • Atrial fibrillation
    • Atrial flutter
    • Ventricular flutter
    • Ventricular fibrillation
  • Blockade of the heart on the ECG
    • Blockade of the sinus node
    • Atrial atrial block
    • Atrioventricular block
    • Blockade of the bundle branch legs

Heart rhythm disturbance: causes

The causes lie in the violation of one of the functions of the heart, and often this is a violation of automatism or conduction

Arrhythmia refers to disorders of the heart rhythm that can be characterized by an uneven distribution or an abnormal sequence of contractions in the myocardium. Arrythmia arises due to dysfunction that conducts nerve impulses in the pathways.


Attention!Pulses that originate in the atrium are transmitted along the AV node to the ventricle, which is contracted by signals and emits blood into the vessels.


The heart muscle has several functions:

  1. Automatism.
  2. Excitability.
  3. Conductivity.
  4. Contractility.
  5. Refractoriness.

If any function is violated, an arrhythmia occurs.

If we consider the type of impaired function, we note that the pathologies of the sinus node can develop (malfunctions of automatism, development of impulses for contraction), conduction of impulses (there is a so-called blockade in different parts of the myocardium, which blocks the signal for contraction), combined disorders and fibrillation.

It is worthwhile to consider separately the possible manifestations of ECG disturbances of the heart rhythm.

How to detect the disturbed automatism of the heart on the ECG?

The first reason for the impaired production of nerve impulses is the poor functioning of the sinus node

Sinus arrhythmia

Because of deviations in the automatism of the heart, there is a so-called sinus arrhythmia. The development of impulses by the sinus node is most important for the functioning of the heart, therefore it is called the rythm driver of the 1st order. The sinus node generates signals with a frequency of 60-80 times per minute.

The following types of sinus arrhythmia of the heart are distinguished:

  1. Tachycardia. Occurs when the sympathetic nervous system predominates. By ECG, you can observe during arrhythmias a rapid contraction, more than 80 beats per minute. It is noted after eating, exercising or in stressful situations. These are the physiological causes. Tachycardia can develop when exposed to medications, alcohol, or because of heart failure (CH).
  2. Bradycardia. The decrease in the excitability of the sinus node is due to the predominance of parasympathetic processes. Physiological bradycardia can appear even in the absence of physical exertion or stressful situations. If it is caused by sclerotic changes in the myocardium, then they say about a pathological bradycardia. Regardless of the cause, the ECG has a heart rate of less than 59, which can be traced in the change in the interval of the R-R teeth.

In this case, sinus arrhythmia can occur with unequal intervals of time. Irregular cuts are caused due to uneven automatic failures. If the ECG diagnosis of sinus arrhythmia showed a difference of more than 10% between the largest and small R-R interval, then a diagnosis of sinus arrhythmia is made.

Distinguishes respiratory and non-respiratory arrhythmia.

Ectopic rhythms

Examples of ectopic rhythms and their display on the ECG

The violation of automatism can be associated with the appearance of an electric pulse in groups of cells outside the sinus node. Then an ectopic rhythm arises. Distinguish:

  1. Right atrial. Occur when the right atrium prevails in the automata.
  2. Left atrial. Prevail in the formation of pulses of the left atrial cell.
  3. Rhythm of the coronary sinus. It arises with the active participation of cells in the formation of impulses that are found in the coronary sinus vein. Arrhythmia on the ECG is detected by a flattened in aVL and I lead to the tooth P and negative in the aVF, II, III lead.

Nodal rhythms of AV connections

There are only 3 options in relation to the arousal:

  1. Preceded to him. On the ECG there is a negative P-wave to the QRS complex in leads I, II, aVF and in V1-V. Segment PQ does not exceed, 2 sec, and the heart rate is 50-60.
  2. Simultaneously. Pit P is not observed, because the QRS complex overlaps it. Heart rate is 40-50.
  3. It precedes the excitation of the ventricles. It is caused by delayed passage of signals to contraction, which causes excitation after the ventricles. Pit P is negative, going for QRS. The distance between the teeth Q and P does not exceed, sec. The heart rate is in the range of 30-40.

Migrating the pacemaker

The transition to the atrium of the pulse source can be seen by reversing the polarity P

This means that the source of pulses from the CA of the compound goes over the atria. On an electrocardiogram, this is seen from the changing tooth P, the long intervals PQ and RR. Deformations of the QRS complex are possible.


Extraordinary impulses for reduction can be caused by a violation of automatism. In such situations, the impulse for shortening is compared with the leading impact. Extrasystoles also appear in the presence of an ectopic source. The picture of the study may be different depending on the location of the ectopic source.

There are the following types of extrasystoles for localization:

  1. Sinus. On the electrocardiogram before the extrasystoles, there will be a reduced R-R interval, and after the normal.
  2. AV connections.
  3. Ventricular. The QRST complex is strongly deformed, and the QRS complex is extended, exceeding, 1 second. And the form can vary depending on the ectopic focus. Pins P must not be unambiguous, and the segment ST must be shortened or completely absent.
  4. Coronary sinus.
  5. Atrial. As a rule, the interval PQ is shortened, and changes in the tooth P.

The following extrasystoles are distinguished by time:

  1. Supernumerary.
  2. Early.
  3. Late.

Attention!If the extrasystole appears after each contraction, this is called bigemia, after two - trigeminy.


Fibrillation of the heart on an electrocardiogram

Signs of extraordinary contractions of the heart muscle

There are four types of violations:

  1. Atrial fibrillation.
  2. Atrial flutter.
  3. Ventricular fibrillation.
  4. Ventricular flutter.

Atrial fibrillation

The most frequent variant of a fibrillation - a fibrillation of auricles. The reasons are associated with the fact that in the atria are formed small circular waves, which become multiple foci of signals and cause a chaotic contraction of muscle fibers. In some cases, fibrillation is created by ectopic sources of different sizes.

With atrial fibrillation, the number of cuts per minute can reach 650-750, but not all reach the ventricle. Only the strongest impulses pass through the AV-node and force the ventricles to contract. It is significant that the atria are in the diastole phase, which causes a worsening of hemodynamics.

If the impulses reach the ventricles, and their reduction persists, the correct flutter is diagnosed, if not, it is wrong, while the ventricles contract chaotically.

Let's note. that atrial fibrillation can occur in three forms:

  • Bradisystole. The heart rate does not exceed 60.
  • Normosystole. It is within the normal range of 60-90 strokes.
  • Tahisistolia. The heart rate is higher than normal.

Atrial fibrillation has the following symptoms on the data taken from the electrocardiogram:

  1. Pit P absent.
  2. Small irregular waves F arise. They reflect the activity of the atrium, and the waves differ in height and length. It is easier to consider waves in V1-V2 and III leads, since they are rarely large.
  3. Irregular length of R-R. As a rule, accompanying pathologies cause changes in the QRS complex.

Atrial flutter

Not so chaotic as a flickering arrhythmia. In the electrocardiogram, PQ intervals can not be seen with it, because the tooth P disappears. But f-waves with a frequency of 200-350 per minute are manifested.

Ventricular flutter

It is characterized by the disappearance of diastole, which is due to the fusion of the ends of the QRST complex. There is a violation of the ST segment.

Ventricular fibrillation

In ventricular fibrillation, there is a non-synchronous impulse activity of individual groups of muscle fibers that occur with the cessation of ventricular systole. On the data taken from the electrocardiogram, one can observe the monophasic waves that vary in frequency and in height, passing into straight lines.

Blockade of the heart on the ECG

Blockade of the sinus node

Complete loss from the general rhythm of the ventricular complex

This case is very rare, but if it does occur, it can be seen from the fall of a complete contraction. In this case, the blockade of the CA-connection is not complete, since this will cause a stop of cardiac activity.

Atrial atrial block

It also appears rarely. It is characterized by a delayed carrying out of the atrial impulses. On an electrocardiogram, this is seen over a wide (more, sec.) Tooth P, which splits and deforms.


Attention!A similar sign arises on an electrocardiogram with hypertrophy of LP.


Atrioventricular block

The syndrome of Frederic presents the greatest threat to the life of the patient

The blocked rhythm from the AV connection is the most common variant of what is happening, which can have 3 degrees of severity.

The first degree of cardiogram records over an extended interval of PQ and exceeding, seconds.

The second degree of the AV blockade has two subtypes:

  1. Mobitz 1. The progressive interval PQ, which is accompanied by the precipitation of QRS, is characteristic. During a pause, only the prong P is fixed.
  2. Mobitz 2. The QRS complex falls regularly for every second or fourth tooth P.

The third degree of AV blockade is called complete, since the transmission of impulses ceases completely. The ECG displays independent rhythms. Atria are contracted more often, because the sinus node does not cease to excite them, but to reduce ventricles are answered by drivers of a rhythm of 3 order which generate impulses with frequency no more than 30-40 in minute.

Here, too, there are 2 types of pathology:

  1. With a wide complex of QRS - idioventricular blockade, in which ventricular contraction is excited by ectopic foci in the ventricles themselves.
  2. With the normal QRS complex, an idio block block, in which the excitation centers are located on the lower part of the AV node.

Blockade of the bundle branch legs

With this type of blockade, the pulse reaches only one ventricle completely. And the second ventricle involves common work in an unusual way. You can distinguish the following electrocardiographic signs of this blockade:

  1. The ventricular QRST rhythm on the ECG expands.
  2. It is split.
  3. There is an opposite direction of the ends of the ventricular complex.

If the right leg is blocked, then:

ECG signs of blockade of right leg
  1. The QRS complex lasts for 1, and more, 2 for incomplete and complete blockade, respectively.
  2. The QRS complex is serrated in V1-V2 and has a flattened S-wave in V5-V.
  3. The segment ST decreases, and an inverted tooth T appears in V1-V2, III with the dominant tooth R.
  4. In V1-V2 there is an increase in the time of excitation of the ventricles.
  5. EOS deviates to the right (does not always appear).

Blockade of the left leg has characteristic features:

  1. The same duration of the QRS complex as in the blockade of the right leg.
  2. The tooth R is serrated or flattened, wide, or the QRS complex of the M-shaped form in V5-V is manifested.
  3. The segment ST decreases in I, aVL, V5-V6 and is raised in III, V1-V.
  4. Time of excitation of ventricles exceeds, 5 seconds.

All the above signs of abnormal rhythm on the ECG should be identified and deciphered only by a qualified specialist.

On the video, you can see a lesson on how to recognize the symptoms and signs of arrhythmia on the ECG:

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