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Violation of the function of automatism



Nomotopic rhythm disturbances. Sinus arrhythmia is manifested in periodically occurring increased and decreased heart rate. Patients do not make complaints. Sinus arrhythmia is often associated with respiratory phases, and can occur in healthy children. Respiratory arrhythmia manifests itself when, when you inhale, the heart rate increases, and when you exhale, the heart rate decreases. It is due to inhalation by a reflex decrease in the tonus of the vagus nerve, while exhalation is due to an increase in the tone of the vagus. On the ECG, a change in heart rhythms (R-R or P-P intervals of various durations due to an increase in diastolic T-P intervals).

Sinus bradycardia - a decrease in the number of heart contractions. It is caused by an increase in the effect on the sinus node of the parasympathetic nervous system or a decrease in the influence of the sympathetic nervous system. It occurs in healthy children-athletes, with vegetovascular dystonia of the vagotonic type, with rheumatism, hypothyroidism, traumatic brain injury, brain tumors, and some infectious diseases. Patients do not make complaints. On the ECG, the atrial and ventricular complexes are not changed, the interactions RR (cardiac cycle), T-P (diastole of the heart) are extended, the duration of the P-Q interval is slightly increased.

Sinus tachycardia is an increase in the number of heart contractions. It is associated with the action on the sinus node of biologically active substances that increase its excitability, or an increase in the tone of the sympathetic nervous system, or a decrease in the tone of the vagal nerve. Sinus tachycardia appears with physical and emotional stress, fever, organic heart diseases, various infections and intoxications, thyrotoxicosis. On the ECG, the atrial and ventricular complexes are unchanged, the interactions R — R (cardiac cycle), T — P (heart diastole) are shortened.

Heterotopic rhythm disturbances. Nodal rhythm - increasing the automatic function of the atrioventricular node and lowering the automatic ability of the sinus node due to functional or organic changes. No complaints are made, sometimes complaints of a pulsation in the neck, which is noted with a simultaneous reduction of the atria and ventricles. With auscultation of the heart, an increase in 1 tone is determined. On the ECG, the negative P wave precedes the QRS complex, the R – R interval is shortened.

There is a periodic rhythm change from the sinus to the atrioventricular node. In this case, the heart is excited under the influence of pulses emanating alternately from the sinus node, then from the conduction system of the atria, then from the atrioventricular connection, and the pacemaker again migrates in the same sequence. No complaints, no objective changes. The clinical picture is reduced to the underlying disease (rheumatism, intoxication). On the ECG, the shape, amplitude, position of the P wave, as well as the duration of the P – Q interval, which becomes shorter when moving to the atrioventricular node, changes.

Extrasystole is a premature contraction of the whole heart or its individual part, arising under the influence of an additional focus of excitation emanating from the sinus node. Causes: inflammatory, dystrophic, degenerative, toxic, mechanical damage and neurogenic disorders. Depending on the place of occurrence, there are ventricular, atrial, atrioventricular. Extrasystoles can be single, multiple, can occur after each contraction in a certain sequence (bigemia) or after two contractions (trigemia). Extrasystoles that occur in various ectopic centers are called polytopic. Complaints are often not presented, sometimes unpleasant sensations in the heart area (fading, stopping, strong push) are noted. With auscultation of the heart, additional pulse beats, additional heart sounds are noted. With atrial extrasystole, excitation from the ectopic focus occurs earlier than monotopic excitation and after a premature contraction of the heart, a prolonged incomplete compensatory pause occurs. On the ECG, the deformed P wave is premature or superimposed on the previous P wave, the R – P interval is shortened, the QRS complex is not changed, the T – P interval is moderately increased.

With atrioventricular extrasystoles, the impulse comes from the Aschoff-Tavara node, spreads to the atria retrograde, from the bottom up, and ventricular excitation usually occurs. On the ECG, there is a negative P wave in a different location in relation to the QRS complex, either in front of the complex, or merges with it, or goes after it, the shape of the QRS complex is not changed, the T-P interval is equal to two normal heart contractions (full compensatory pause).
With ventricular extrasystoles, the sequence of excitation of the heart changes, the impulse arising in the ventricles does not propagate retrograde, and the atria are not excited. Excitation of the ventricles occurs alternately, and at the same time, as normal, which depends on the localization of the ectopic focus.

On an ECG, ventricular extrasystoles are manifested:

1) premature occurrence of the QRS complex without a previous P wave;

2) QRS complex with high voltage, broadened, split, serrated, passing tooth T without S-T interval;

3) the discoordinate direction of the T wave with respect to the maximum tooth of the QRS complex is extrasystic;

4) lengthening of the compensatory pause after extrasystole, the distance between two R – R intervals, including extrasystole, is equal to two normal cycles. Allocate right and left ventricular extrasystoles: with

the right ventricular extrasystole in 1 lead is the largest R wave of the QRS complex, the extrasystoles are directed upwards, and in the 3 lead the largest is the S wave, directed downward.

In the left ventricular type, in 1 lead, the largest tooth S of the QRS complex extrasystoles are directed downward, in 3 leads, the largest tooth is the R wave, directed upwards. The origin of functional extrasystoles due to a violation of extracardiac, often vegetative, regulation.

The main signs of a functional extrasystole (most common in prepubertal and puberty):

1) labile during the day, changes with a change in body position, with physical exertion;

2) in children, signs of vegetovascular dystonia, foci of chronic infection, endocrine disorders are detected;

3) when using special research methods, violations of the myocardial contractility are not detected; clino-orthostatic test, test with dosed physical activity, pharmacological tests with ECG registration testify in favor of functional extrasystole. The origin of organic extrasystoles occurs as a result of damage to the myocardium or the conduction system of the heart. The main signs of organic extrasystoles:

1) permanent;

2) the general condition is usually impaired and there are signs of organic damage to the heart (rheumatism, non-rheumatic carditis, congenital heart defects).

Paroxysmal tachycardia is an attack of a sharp increase in heart rate, 2-3 times higher than the normalization of the rhythm, arising in the presence of an ectopic center capable of generating high-frequency pulses. Complaints in older children about discomfort in the heart, a feeling of tension in the neck, dizziness, fainting, pain in the epigastric region, abdomen. In young children, paroxysmal tachycardia is accompanied by convulsive and dyspeptic symptoms. With an objective examination, shortness of breath, cyanosis, pulsation of veins, congestion in the lungs, enlargement of the liver, pulse cannot be counted, low filling, decrease in blood pressure.

Allocate atrial, atrioventricular, ventricular forms of paroxysmal tachycardia. An ECG with atrial paroxysmal tachycardia reveals a long row of atrial extrasystoles with a sharp shortening of the T – P interval, the stratification of the P wave on the T wave with its deformation, the QRS complex is not changed or moderately deformed, atrioventricular paroxysmal tachycardia is characterized by repeated extratriculum of the atrious , or by shifting them to the QRS complex, or by merging with the T wave. The ventricular form of paroxysmal tachycardia on an ECG deformed, expanded complex QRS. Atrial P waves appear regularly and are superimposed on the ventricular complex of extrasystoles.

Atrial fibrillation is a violation of the correct activity of the atria in connection with the appearance in the atria of one or more foci of excitation. Complaints of deterioration of health, a sense of fear, anxiety. During auscultation, different tones, a random alternation of short and long pauses, the number of ventricular contractions depends on the form of atrial fibrillation, there is a pulse deficiency (during auscultation, the number of heart contractions is greater than pulse waves). On the ECG, the P wave is absent and slows down by waves of various sizes and shapes. The QRS complex is not changed, the S – T interval is below the isoelectric line, the T wave and the isoelectric line are deformed by flicker waves.

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Violation of the function of automatism

  1. Rhythm disturbances associated with slow channels: dependence of conduction and automatism
    The recent discovery of the incoming ion current flowing through the membrane through the so-called slow channels is of great theoretical and practical importance [76]. This current, carried mainly by calcium ions and partly by sodium ions, plays a major role in the depolarization of the cells of the sinus and atrioventricular nodes. In addition, it is able to cause depolarization of heart cells.
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