Nonparoxysmal tachycardia in children

Non-paroxysmal tachycardia is a common heart rhythm disorder in children and occurs in 13.3% of all types of arrhythmia. Tachycardia is classified as chronic if it has been present in the patient for more than 3 months in a row (in chronic sinus tachycardia) and more than 1 month in tachycardias based on an abnormal electrophysiological mechanism. The pulse rate in non-paroxysmal tachycardia is 90-180 per 1 min, there is no sudden onset or end. Ventricular and chaotic tachycardia are much rarer in children.

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What causes non-paroxysmal tachycardia in children?

Non-paroxysmal tachycardia may occur in acute and chronic heart diseases - myocarditis, rheumatism, heart defects. The occurrence of this type of arrhythmia due to severe metabolic disorders, hypoxia, ischemia in the heart muscle is characteristic mainly of adulthood, and in children with non-paroxysmal tachycardia, this cause of arrhythmia occurs much more sharply. It has been shown that this type of arrhythmia is based on a change in the functioning of the cardiac conduction system (CCS), responsible for the formation and propagation of impulses.

What happens in non-paroxysmal tachycardia in children?

The generally accepted cardiac mechanism of non-paroxysmal tachycardia is based on the concept of ectopic focus, re-entry of excitation and trigger activity. Myocardial fibers under certain conditions exhibit the ability to spontaneously generate depolarizing impulses, thus acquiring the properties of pacemakers. For excitation to spread through the myocardium, the presence of pathways functionally isolated from the rest of the heart is necessary: accessory conduction pathways (ACP) (bundles of Kent, Mahaim, etc.). A high frequency of ACP detection in non-paroxysmal tachycardia has been noted in individuals with systemic connective tissue disorders (Marfan disease, Ehlers-Danlos syndrome and other hereditary diseases). The importance of genetic factors is emphasized by the description of familial cases.

However, the obtained facts of detection of DPT in healthy individuals without any arrhythmia indicate that the anomaly of the cardiac conduction system is a condition for the development, and not the cause of non-paroxysmal tachycardia. The basis of this rhythm disorder is a change in the neurohumoral regulation of the heart, noted in 87% of patients and realized through vagosympathetic influences. It has been established that non-paroxysmal atrioventricular tachycardia in children without signs of organic heart damage is the result of a change in the functional state of cerebral structures, which through impaired vegetative regulation leads to tachycardia.

There is no generally accepted classification of chronic non-paroxysmal tachycardia. Three main clinical and pathogenetic variants of non-paroxysmal tachycardia are distinguished: sinus, recurrent heterotopic and constant, differing in the nature and severity of disorders of the autonomic and central nervous systems. All children with non-paroxysmal tachycardia have a psychovegetative syndrome of varying severity.

Symptoms of non-paroxysmal tachycardia in children

Chronic sinus tachycardia (CST) is more common in girls than in boys. The duration of the disease before the correct diagnosis is from 6 months to 6 years. These children have an unfavorable course of the perinatal and postnatal period (70%), a high infection index (44.8), unfavorable stressful circumstances in their environment (single-parent family, parental alcoholism, conflicts at school, etc.). In addition to environmental factors, children with sinus tachycardia have family characteristics: an increased concentration of psychosomatic diseases of an ergotropic nature in the pedigree (hypertension, coronary heart disease, diabetes mellitus, thyrotoxicosis, etc.), and in parents and siblings in 46% of cases - sympathetic-tonic reactions from the cardiovascular system (increased blood pressure, increased heart rate, etc.).

Chronic tachycardia may be an accidental finding during examination, especially if the child has no complaints. As a rule, all children subjectively tolerate tachycardia well. Among the most common complaints, fatigue, excitability, abdominal and leg pain, dizziness, headache, and cardialgia prevail. Children with chronic sinus tachycardia have an asthenic constitution, low body weight, pale skin, and anxiety. Neurological symptoms are represented by isolated organic microsigns, manifestations of compensated hypertensive-hydrocephalic syndrome. Based on the totality of clinical data and the results of vegetative tests, these children are diagnosed with mixed-type vegetative dystonia syndrome in 56% of cases and sympathetic-type in 44%. In 72.4% of children, echocardiographic examination revealed prolapse syndrome and mitral valve dysfunction due to autonomic dysregulation.

It is important to note that 60% of children with chronic sinus tachycardia were observed by psychoneurologists at one time for tics, stuttering, night terrors, headaches. Children in this group are characterized by high emotional instability, anxiety, and increased aggressiveness. In intersocial contacts, their adaptation zone is sharply narrowed; they experience discomfort in almost half of all possible ordinary life situations, which is accompanied by anxious and depressive neurotic reactions. EEG shows mild changes in the form of an irregular, low-amplitude alpha rhythm, smoothing of zonal differences. There are signs of increased activity of mesencephalic structures.

Thus, chronic sinus tachycardia occurs in children with vegetative dystonia, a feature of which is the presence of a hereditary predisposition to sympathetic reactions of the cardiovascular system against the background of a protracted neurotic state. Peripheral mechanisms of arrhythmia consist in the fact that acceleration of the sinus node automatism is achieved through hypercatecholaminemia (50%) or through hypersensitivity of the sinus node to catecholamines (37.5%), less often with hypovagotonia (14.3%).

How is non-paroxysmal tachycardia diagnosed in children?

Heterotopic chronic tachycardia of functional genesis is detected accidentally during a medical examination in 78% of cases. Ignorance of this form of autonomic dysregulation of the heart rhythm in 54.8% of the examined children was the reason for the erroneous diagnosis of myocardium, rheumatism with the prescription of hormones, antibiotics without any effect, which led to unjustified regime restrictions, neurosis of children. A feature of the ECG of this type of arrhythmia is the presence of two types of rhythm disturbance: a permanent form of non-paroxysmal tachycardia, in which the ectopic rhythm is not interrupted by sinus contractions (chronic tachycardia of a permanent type - CPTT), and a recurrent one - when ectopic contractions alternate with sinus contractions (the so-called chronic non-paroxysmal tachycardia of a recurrent type - CPTT). The transformation of a permanent form of chronic tachycardia into a recurrent one and, in turn, the transition of non-paroxysmal tachycardia into paroxysmal tachycardia indicate the presence of common pathogenetic links in these rhythm disturbances.

Treatment of non-paroxysmal tachycardia in children

Unlike organic forms of rhythm disturbance, treatment of non-paroxysmal tachycardia with antiarrhythmic drugs is completely unsuccessful in 81% of cases. Like sinus tachycardia, heterotopic tachycardia can exist for many years without treatment. At the same time, prolonged tachycardia (especially with high heart rate) can lead to arrhythmogenic cardiomyopathy (in the form of myocardial hypertrophy, enlarged heart size, decreased contractile ability of the heart muscle) and even heart failure. Thus, arrhythmia in children with vegetative dystonia is far from a safe manifestation, requiring timely and correct correction.

In this group of patients, no gender predominance was noted. Of note is the lag in physical development of patients (in 85%) - by 2-3 years against the age standard, delayed puberty (75% of children) - in girls over 10 years old and in boys over 12 years old.

The early history of children with chronic sinus tachycardia and chronic nonparoxysmal tachycardia differs little from the group of children with nonparoxysmal tachycardia in terms of the frequency of pathology, but prematurity is more common, the percentage of asphyxial disorders during labor is higher (chronic sinus tachycardia - 28%, heterotopic tachycardia - 61%). When studying the family history, a predominantly trophotropic orientation of diseases in relatives of children is revealed (84%), especially arterial hypotension.

Children with this type of chronic non-paroxysmal tachycardia differ significantly in appearance from children with chronic sinus tachycardia: as a rule, these are sluggish, asthenic children with normal or overweight body weight, presenting numerous complaints of anxious-depressive and hypochondriacal content. Despite the fact that in general the frequency of psychotraumatic situations in this group of children is sharp, they have their own specifics in the form of pathological forms of upbringing - with hypersocialization of the child, upbringing in the "cult of illness", in families with anxious-phobic type of parents, with early formation of the iatrogenic beginning in the structure of the child's disease.

Pronounced vegetative dysfunction was noted in all children with heterotopic tachycardia, while in 86% of cases with HNTVT and 94% with HNTPT there was a developed syndrome of vegetative dystonia, while the remaining children had vegetative lability. In terms of vegetative tone, parasympathetic influences predominated in more than half of the children, and mixed tone in 1/3 of the children. Vegetative support of activity was insufficient in 59% of children with HNTVT and in 67% with HNTPT. This indicates a functional insufficiency of the sympathoadrenal system, which is confirmed by biochemical indicators.

Children with heterotopic tachycardia often have various psychoneurological abnormalities: stuttering, enuresis, tics, delayed development of psychomotor skills, convulsive syndrome. During neurological examination, more than 85% of children have microorganic symptoms similar to those found in other forms of vegetative dystonia, but they are more distinct, combined with signs of hypertensive-hydrocephalic syndrome in 76% of patients.

Children with this type of tachycardia are characterized by high anxiety, difficulties in adaptation at school, among peers, and the presence of conflicts, as a rule, is predetermined by the existence of the disease and the child's attitude to it. In children of this group, the formation of the internal picture of the disease is associated with hypertrophied ideas about the danger of arrhythmia for life, long-term hypochondriacal "processing" of neurotic information. The use of EEG in children with heterotopic tachycardia showed the presence of functional shifts characterized by an increased representation of slow-wave oscillations (6-8 range), general immaturity of rhythm. Electrophysiological shifts reflect the dysfunction of the diencephalic-stem structures of the brain and in children over 11 years of age indicate a delay in the morphofunctional maturation of cortical-subcortical relationships. The functional state of the brain is characterized by insufficient mobilization of the activation systems included in the limbic-reticular complex. Taking into account the peculiarities of the cerebral organization of children with heterotopic tachycardia, the presence of signs of partial delays in maturation, the existence of autonomic dysfunction with a predominance of the parasympathetic link and pronounced neurotic personality changes, basic therapy has been developed for the treatment of rhythm disturbances, taking into account these features, including drugs with a stimulating effect on metabolism (pyriditol, glutamic acid, etc.), psychotropic and vascular agents.