Hospital pediatrics. Heart rhythm disturbances in children. Clinic, diagnosis, treatment (lecture notes)

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Hospital pediatrics. Heart rhythm disturbances in children. Clinic, diagnosis, treatment (lecture notes)

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LECTURE No. 6. Heart rhythm disturbances in children. Clinic, diagnosis, treatment

Arrhythmias are disorders of heart rhythm and conduction that occur with congenital heart defects, acquired heart diseases, and dysfunction of the central and autonomic nervous systems.

Classification of cardiac arrhythmias.

1. Violation of the function of automaticity - consists of a change in the number of pulses rotating in the sinus node (violation of the formation of an excitation impulse):

1) nomotopic rhythm disturbances (impaired impulse formation in the sinus node - sinus arrhythmia, sinus tachycardia, sinus bradycardia;

2) heterotopic rhythm disturbances (the impulse originates outside the sinus node).

2. Passive ectopic rhythms:

1) nodal rhythm;

2) migration of the pacemaker (from the sinus node to the atrioventricular connection).

3. Active ectopic rhythms:

1) extrasystole;

2) paroxysmal tachycardia;

3) atrial and ventricular fibrillation;

4) flutter of the atria and ventricles.

4. Disorders of the conduction function (blockade), slowdown, complete delay in the conduction of excitation through the conduction system:

a) sinoauricular blockade;

b) atrioventricular blockade;

c) intra-atrial blockade;

d) intraventricular blockade;

e) blockade of the legs of the bundle of His.

1. Violation of the function of automatism

Nomotopic rhythm disturbances. Sinus arrhythmia manifests itself in periodically occurring increases and decreases in heart rate. The patients do not make any complaints. Sinus arrhythmia is often associated with respiratory phases and can occur in healthy children. Respiratory arrhythmia occurs when the heart rate increases during inhalation and the heart rate decreases during exhalation. It is caused by inhalation by a reflex decrease in the tone of the vagus nerve, and on exhalation by an increase in vagal tone. The ECG shows changes in heart rhythms (RR or P-P intervals of varying duration due to an increase in diastolic T-P intervals).

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

Sinus tachycardia - an increase in the number of heart contractions. Associated with the effect 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 during physical and emotional stress, increased body temperature, organic heart disease, various infections and intoxications, and thyrotoxicosis. On the ECG, the atrial and ventricular complexes are not changed, the RR (cardiac cycle), T-P (cardiac diastole) intervals are shortened.

Heterotopic rhythm disturbances. Nodal rhythm - an increase in the automatic function of the atrioventricular node and a decrease in the automatic ability of the sinus node due to functional or organic changes. There are no complaints, sometimes complaints about pulsation in the neck, which is noted with simultaneous contraction of the atria and ventricles. Auscultation of the heart reveals an increase in 1 tone. On the ECG, a negative P wave precedes the QRS complex, the RR interval is shortened.

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

Extrasystole is a premature contraction of the entire heart or a separate part of it, occurring under the influence of an additional source of excitation emanating from the sinus node. Causes: inflammatory, dystrophic, degenerative, toxic, mechanical damage and neurogenic disorders. Depending on the place of origin, they distinguish between ventricular, atrial, and atrioventricular. Extrasystoles can be single, multiple, and can occur after each contraction in a certain sequence (bigemia) or after two contractions (trigemia). Extrasystoles occurring in various ectopic centers are called polytopic. Most often there are no complaints, sometimes there are unpleasant sensations in the heart area (freezing, stopping, strong shock). During auscultation of the heart, additional pulse beats and 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 long, incomplete compensatory pause occurs. On the ECG - a deformed P wave is premature or overlaps 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 retrogradely, from bottom to top, and the excitation of the ventricles occurs normally. On the ECG - a negative P wave in a different location in relation to the QRS complex, either before the complex, or merges with it, or comes after it, the shape of the QRS complex is not changed, the T-P interval is equal to two normal heartbeats (full compensatory pause). With ventricular extrasystoles, the sequence of cardiac excitation changes, the impulse arising in the ventricles does not propagate retrogradely, and the atria are not excited. The excitation of the ventricles occurs alternately, and not simultaneously, as is normal, which depends on the localization of the ectopic focus.

On the ECG, ventricular extrasystoles appear:

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

2) QRS complex with high voltage, widened, split, jagged, passing T wave without S-T interval;

3) the discoordinate direction of the T wave in relation to the maximum wave of the QRS complex of the extrasystolic;

4) prolongation of the compensatory pause after the extrasystole; the distance between two RR intervals, including the extrasystole, is equal to two normal cycles. There are right and left ventricular extrasystoles: with right ventricular extrasystoles in lead 1 the largest R wave of the QRS complex is, the extrasystoles are directed upward, and in lead 3 the largest is the S wave directed downward.

With the left ventricular type, in lead 1 the largest S wave of the QRS complex of extrasystoles is directed downward, in lead 3 the largest R wave is directed upward. The origin of functional extrasystole is due to a violation of extracardiac, often autonomic, regulation.

The main signs of functional extrasystole (most often found in prepubertal and pubertal age):

1) labile during the day, changes with changes in body position and physical activity;

2) children show signs of vegetative-vascular dystonia, foci of chronic infection, endocrine disorders;

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

1) permanent character;

2) the general condition is usually disturbed and there are signs of organic heart damage (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 normal rhythm, which occurs in the presence of an ectopic center capable of producing high-frequency impulses. Complaints in older children include discomfort in the heart area, a feeling of tension in the neck, dizziness, fainting, pain in the epigastric region and abdomen. In young children, paroxysmal tachycardia is accompanied by convulsive and dyspeptic symptoms. On objective examination, shortness of breath, cyanosis, pulsation of the veins, congestion in the lungs, enlarged liver, pulse cannot be counted, low filling, decreased blood pressure.

There are atrial, atrioventricular, and 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, layering 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 multiple repetitions of atrioventricular extrasystoles having negative P waves, or their displacement onto the QRS complex, or merging with the T wave. The ventricular form of paroxysmal tachycardia on the ECG is a deformed, dilated QRS complex. Atrial P waves appear regularly and overlap the ventricular complex of the extrasystole.

Atrial fibrillation is a violation of the proper activity of the atria due to the appearance of one or more foci of excitation in the atria. Complaints about deterioration in health, feelings of fear, anxiety. During auscultation, there is a different sonority of 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 is slowed 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.

2. Disorders of the conduction function

Blockades are manifested by a slowdown (incomplete blockade) or complete cessation (complete blockade) of the conduction of impulses from the sinus node to the final branches of the conduction system of the heart.

Classification.

1. Sinoauricular blockade.

2. Intra-atrial blockade.

3. Atrioventricular blockade degree).

4. Intraventricular block (bundle branch block). Sinoauricular block is a violation of the conduction of excitation from the sinus node to the atrial myocardium.

Causes: autonomic dysfunction with vagotonia, immaturity of the sinus node in newborns, hyperkalemia, drug intoxication, degenerative and inflammatory changes in the sinus node and myocardium. No complaints. Periodic loss of individual heart contractions (complete R-R cycles) appear on the ECG and in their place a pause is recorded equal to the double R-R interval.

Intraatrial blockade is a violation of the conduction of impulses along the interatrial pathways, as a result of which the synchronicity of the activity of both atria is disrupted. Occurs in diseases with enlarged atria due to rheumatism, cardia, heart defects. The ECG shows a change in the amplitude and duration of the P wave, which can be split, bifurcated in lead I, double-humped in leads 1, 2 and 5.

Atrioventricular block (degree) appears as a result of a slowdown or complete cessation of the conduction of excitation from the atria to the ventricles.

Blockade classification:

1) incomplete (I, II degree);

2) complete (III degree);

3) functional, congenital, acquired. Causes of vegetative-vascular dystonia of the vagotonic type:

1) congenital malformations of the conduction system of the heart, combined with congenital heart defects;

2) rheumatism;

3) tachyarrhythmias;

4) progressive muscular dystrophy;

5) injuries;

6) embolism;

7) collagenosis;

8) drug intoxication (digoxin). Atrioventricular block of the first degree is manifested by increased fatigue, dizziness, pain in the heart, upon an objective examination there is an expansion of the borders of the heart to the left, upon auscultation of the heart there is a muffled first tone at the apex. An ECG shows a prolongation of the P-Q (R-P) interval. The FVD shows a pronounced atrial sound, the first sound is split or bifurcated.

Second degree atrioventricular block manifests itself in the form of a pause that occurs due to loss of heart contractions. On the ECG, the P-Q interval increases, the QRST complex periodically falls out, followed by a normal P-Q interval, which gradually lengthens and ends with the QRST loss.

Third degree atrioventricular block, when conduction disturbances record independent contractions of the atria and ventricles. The atria contract in a rapid rhythm under the influence of impulses from the sinus node, the ventricles contract in a rare rhythm under the influence of impulses from automatic centers of the second and third order. Complete atrioventricular block is often congenital and is clinically manifested by bradycardia, a flapping sound at the apex of the heart, hypertrophy of the right and left parts of the heart due to hemodynamic disturbances. The ECG shows the appearance of positive P waves, not associated with the QRS complex and located at different distances from it, the RR intervals are constant, and the P-P intervals are shorter than the RR intervals and change in the presence of sinus arrhythmia. Intraventricular block (blockade of the bundle branches) occurs as a result of an anatomical interruption (malformation, inflammation, sclerosis) or a functional block (supraventricular tachyarrhythmia, extrasystole). When one of the bundle branches is blocked, the excitation normally covers the ventricle with an intact leg and is retained in the ventricle with a damaged one. leg. As a result, the ventricles contract at different times. Patients do not make any complaints. During auscultation of the heart, dullness of tones and often their splitting are heard (gallop rhythm due to non-simultaneous contraction of the right and left ventricles).

The following changes are recorded on the ECG.

1. A tall, widened, deformed, jagged QRS complex, preceded by a normal P wave with a normal or slightly elongated P-Q interval.

2. The QRS complex and the widened T wave in each lead have a discordant direction.

With blockade of the left bundle branch in lead I, the QRS complex is directed upward, and with blockade of the right bundle branch, the QRS complex in lead I is directed downward. Blockade of the terminal branches of the conduction system occurs with severe myocardial damage (diffuse myocarditis, myocardiosclerosis). An ECG with this disease reveals a low voltage of the teeth of the complex and their widening. The T wave is flattened or negative. Intraventricular block is combined with a shortened atrioventricular interval, called Wolff-Parkinson-Watt syndrome, more often observed in children suffering from rheumatism, but can also occur in healthy children. There are no complaints, no clinical manifestations. On the ECG, the P-Q interval is shortened, the QRS complex is lengthened and jagged.

Treatment.

In the absence of vital indications, antiarrhythmic drugs should not be used. Of particular importance among antiarrhythmic drugs are: 10% solution of calcium chloride, 1 tsp., dec., tbsp. l. depending on age 3-4 times a day, novocainamide 0,1-0,5 g 2-3 times a day, /? - adrenergic blockers. During an attack of paroxysmal tachycardia, means of mechanical stimulation of the vagus nerve are used (pressure on the sinuses of the carotid artery, eyeballs, inducing a gag reflex by pressing on the root of the tongue), isoptin is used intravenously in a dose of 0,3-0,4 ml for newborns up to 1 year - 0,4-0,8 ml, 1-5 years - 0,8-1,2 ml, 5-10 years - 1,2-1,6 ml, 10 years and older - 1,6-2,0 ml and digitalis preparations.

Author: Pavlova N.V.

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