Monthly Archive December 2018

The time of occurrence of ventricular extrasystoles

The time of occurrence of ventricular extrasystoles

Ventricular ectopic complexes, which occur very early in the cardiac cycle, may be superimposed on the T wave of the previous contraction and are referred to as extrasystoles “R on T”. Most episodes of ventricular fibrillation (VF) and many episodes of ventricular tachycardia (VT) are initiated by extrasystoles “R on T”, although this does not mean that extrasystoles “R on T” always cause these forms of arrhythmia.

Ventricular extrasystoles occurring in the cardiac cycle only slightly prematurely, may accidentally occur immediately after the P wave caused by the normal activity of the sinus node: the P wave, thus, unlike the atrial extrasystoles, will not be premature. Such ventricular extrasystoles are called end-dia-table.

Usually, there is a pause after the ventricular extrasystoles. When such a pause is absent and the extrasystole, thus, looks “sandwiched” between two normal complexes, the extrasystole is called interpolated.

Frequency of ventricular extrasystoles

When extrasystoles are followed after each sinus complex, the term “bigeminy” is used. If extrasystoles follow after a couple of normal complexes, this is “trigeminia.” When two ectopic complexes follow in succession, they are referred to by the term “pair beats,” or “couplet.” “Zalpom” refers to more than two consecutive ectopic complexes.

ECG for ventricular extrasystoles

ECG for ventricular extrasystoles

Ventricular ectopic impulse is carried out through the ventricles not through the His-Purkinje system, but through a relatively slowly conducting myocardium. Changing the sequence and slowing down the activation of the ventricles causes the forming ventricular complexes to become deformed and broadened.

The complexes are premature, wide (<0.12 s), deformed and, unlike atrial extrasystoles, they are never preceded by a premature R-wave.

ECG characteristics of ventricular extrasystoles: – QRS complex of ventricular extrasystoles: Premature Wide (> 0.12s) Changed in shape (deformed) It is not preceded by a premature P wave. Several terms are used to describe the location of the source, time of occurrence and number of ventricular extrasystoles.

Characteristic source (focus) of ventricular premature beats

Ectopic complexes of the same form, following with the same intervals of adhesion, occur in the same focus. They are called “monofocal”, “monomorphic”, “monotopic”. Different in shape and adhesion intervals, ventricular complexes suggest the presence of more than one focus. Such extrasystoles are called “multifocal”, “polytopic”, “polymorphic”.

Ventricular extrasystole

Ventricular extrasystole

The clinical significance of ventricular premature beats depends on how often extrasystoles appear and whether they are single, paired or group. Under the group understand several extrasystoles, following each other. Next, you should also consider the configuration of extrasystoles. If extrasystoles have the same configuration, then they come from the same focus and are called monomorphic or monotopic, if extrasystoles are different in configuration, then we are talking about polymorphic or polytopic extrasystole.

In ventricular premature beats, unlike atrial beats, there is always a compensatory pause. This means that the total duration of 2 contractions (before and after extrasystoles) is equal to twice the RR interval of normal contractions. Under the interval RR understand, as mentioned earlier in the chapter on atrial extrasystoles, the distance from one R wave to the adjacent R wave.

The compensatory pause is explained as follows: the excitability of the sinus node and the atria during ventricular extrasystole is not disturbed. Since the excitation from the sinus node reaches the ventricles in the absolute refractory period associated with the extrasystole, the excitation of the ventricles is impossible. Only with the arrival of the next excitation wave from the sinus node is a normal contraction of the ventricles possible.

In ventricular arrhythmia, due to the pathological propagation of the excitation wave, a secondary violation of repolarization also appears in the form of ST segment depression and a negative T wave.

For the treatment of ventricular premature beats, a doctor has various antiarrhythmic drugs, such as beta-adrenergic receptor blockers and propafenone (prescribed only for severe clinical symptoms). Due to the arrhythmogenic effect inherent in all antiarrhythmic drugs (the frequency of heart rhythm disturbances caused by them is on average 10%), the attitude towards them is currently more restrained and they are prescribed with greater caution.

Features ECG with ventricular extrasystoles:

• Premature appearance of the QRS complex
• The broadening of the QRS complex, the configuration of which resembles the blockade of the corresponding PG leg
• Presence of compensatory pause
• Sometimes found in healthy people, but more often in people with heart disease.
• Treatment is indicated only when clinical symptoms appear. Assign beta-adrenergic receptor blockers, propafenone, amiodarone

Signs of ventricular extrasystoles on ECG

Signs of ventricular extrasystoles on ECG

• For ventricular extrasystoles, premature appearance of a wide and deformed QRS complex is characteristic.
• Unlike the atrial extrasystoles, there is always a compensatory pause before the ventricular one.
• Ventricular extrasystole – a frequent disturbance of the heart rhythm. It can be observed both in healthy people, without being accompanied by any other symptoms, or in people with a heart condition.

Ventricular extrasystole is a frequent disturbance of the heart rhythm, which can be observed in healthy people, without being accompanied by any other symptoms, but more often in people with various heart diseases, in particular, coronary heart disease, heart defects, cardiomyopathies, myocarditis. The cause of ventricular premature beats is an ectopic focus of excitation in the pancreas or LV.

Under the ventricular extrasystole understand the premature contraction of the ventricles, caused by a focus of excitation, which is located in the ventricles themselves. Using electrocardiography, it is easier to recognize ventricular premature beats than supraventricular (atrial premature beats). For ventricular extrasystoles, premature broad (more than 0.11 s) and deformed QRS complexes are characteristic, which by their configuration resemble the blockade of PG feet.

So, when extrasystoles occur in the right ventricle (RV), it is excited earlier than the left ventricle (LV), therefore a wide QRS complex is recorded on the ECG, resembling the blockade of LNPH in configuration, as LV excitement occurs late. If the center of extrasystole is in the LV, then the configuration of the QRS complex resembles the blockade of PNPG.

ECG with extrasystole from AV connection

ECG with extrasystole from AV connection

The extrasystoles arising in AV connection were called “nodal” earlier. It is now recognized that at least part of the AV node does not have automatic (pacemaker) activity and is not able to generate pulses, and that extrasystoles arising in the AV node cannot be distinguished from those whose source is in the His bundle.

In this connection, the more general term “extrasystoles from an AV connection” is used. Extrasystoles from the AV connection are less common atrial and ventricular. The need for treatment is rare.

Electrocardiographic manifestations. About an ekstrasistoliya from an AV-connection speak, if on the electrocardiogram the premature QRS complex having the same configuration, as sinus complexes is found.

The focus located in the AV junction can activate both the atria and the ventricles, which leads to the appearance of a retrograde P wave (ie, a negative P wave in leads II, III, aVF).

At the same time, the retrograde P wave can either precede the QRS complex, or be recorded after it or merge with it, depending on the ratio of the speeds of the premature pulse from the AV connection to the ventricles and the atria.

ECG for atrial extrasystole

ECG for atrial extrasystole

Atrial ectopic impulse leads to the appearance of a premature R wave. The place of its occurrence and, consequently, the direction of propagation of the atrial activation wave will differ from those during sinus rhythm, so that the premature R wave will differ in shape from the P wave of sinus origin.

Because atrial ectopic teeth P are premature, they can overlap the T wave of the anterior ventricular complex and thus deform it. Careful analysis of the ECG plays a key role in identifying ectopic P waves; Often the most appropriate for such an analysis is lead V1.

Atrioventricular and intraventricular conduction. Usually, a premature atrial impulse is conducted through the AV connection and along the legs of the His bundle in the same way as if the atria were activated by the sinus node. Therefore, the PR interval and the QRS complex atrial extrasystoles are similar to those of sinus rhythm.

If the QRS complex of sinus origin is deformed due to the blockade of the legs, then the QRS complex of the atrial beats will be the same.

However, sometimes atrial extrasystoles, especially those that occur very early in the cardiac cycle, can reach the AV connection or the bundle of the His bundle at a time when their conductivity has not yet recovered after the previous atrial impulse and which thus remain partially or completely refractory to arousal.

Partial or complete refractoriness of an AV connection will lead to a prolongation of the PR interval or blockage of the atrial extrasystole, respectively. The ECG pattern observed in cases where the atrial extrasystoles are not carried out on the ventricles can be mistakenly interpreted as an indication for an EKS!

Partial or complete refractoriness of one or another of the bundle of His (usually the right leg) may be accompanied by the appearance of signs of a partial or complete blockade of the leg, respectively. This phenomenon of functional blockade of the bundle of the His bundle is called “phase aberrant intraventricular conduction”.

As a result, QRS complexes of atrial extrasystoles become wide and, thus, if the premature P wave preceding the ventricular complex cannot be detected, atrial extrasystoles can be mistaken for ventricular ones.

Value. Atrial extrasystoles occur in many heart diseases, but are also common in people with a healthy heart, especially in the elderly. Usually they are benign, however, frequent atrial premature beats can be a precursor of atrial fibrillation (AF) or atrial tachycardia.