Heart rhythm disturbances in children

Heart rhythm disorders occupy one of the leading positions in the structure of morbidity and mortality of the child population. They can be presented as a primary pathology or develop against the background of an already existing disease, usually congenital heart disease. Cardiac arrhythmias often develop at the height of infectious diseases, complicate the diseases of other organs and body systems - CNS lesions, systemic connective tissue diseases, metabolic diseases, endocrine pathology. Violations of the heart rhythm often act as one of the symptomatic complexes of many hereditary diseases. The importance of arrhythmias is due to their prevalence, tendency to chronic course, high risk of sudden death. The intensive development of childhood arrhythmology was facilitated by the development and implementation of highly informative research methods in clinical practice: Holter monitoring, high-resolution electrocardiography, surface mapping, Doppler echocardiography, and electrophysiological studies of the heart. In the absence of signs of organic defects, the basis of rhythm disturbances is considered to be the so-called idiopathic changes in the electrophysiological properties of the conduction system of the heart, understanding of their essence is the subject of numerous scientific studies.

The detection of the pathogenetic bases of arrhythmias required the expansion of our knowledge in the field of heart electrophysiology, the peculiarities of vegetative regulation of the heart rhythm, the state of extra- and intracardial sensory receptors, the role of circulating mediators of the autonomic nervous system, cellular metabolism, stress-limiting systems, molecular genetic bases of electrogenesis, autoimmune mechanisms . Such a comprehensive understanding of the problem led to significant progress in the treatment and prevention of cardiac rhythm disturbances and sudden cardiac death. The main electrophysiological mechanisms of rhythm disturbances in childhood are abnormal automatism, the mechanism of re-entry involving additional paths of impulse conduction or trigger mechanisms. Genetic mechanisms play a particularly important role in the development of a number of life-threatening arrhythmias - long QT interval syndrome, polymorphic ventricular tachycardia, Brugada syndrome. At present, a certain spectrum of mutations responsible for the development of life-threatening arrhythmias has been established. Neurovegetative regulation of the heart is also important, especially in cases of development of rhythm disturbances in children without signs of organic damage to the heart. All of the above mechanisms are specific for each type of cardiac arrhythmia, they are not isolated from each other, but are in interaction. So, for the emergence and maintenance of the electrophysiological substrate of arrhythmia, the preservation of embryonic primordia of the conduction system, the violation of the neuro-vegetative regulation of the rhythm, in some cases the main role can play anatomical conditions, for example, surgical interventions. The nervous-vegetative basis of arrhythmias is caused in infancy by disorders or features of maturation of autonomic centers of rhythm regulation, a certain role can play a hereditary predisposition.

Unlike adults in children, rhythm disturbances often occur asymptomatically and in 40% of cases it is an accidental finding that does not allow you to accurately determine the length and age of the child at the onset of arrhythmia. In some cases, for example, in the syndrome of the prolonged QT interval, the ignorance of the doctor and parents about the presence of the disease leads to tragic consequences: the first and only syncopal attack in life can lead to sudden cardiac death. Often, a chronic rhythm disturbance is diagnosed too late, when no type of therapy is able to prevent a fatal outcome. Certain difficulties exist in the clinical diagnosis of rhythm disturbances in newborns and young children. During this period of childhood, arrhythmia is most often complicated by the development of heart failure.

There are many variants of heart rhythm disturbances, differentiated on the basis of the leading clinical and electrophysiological phenomenon, as often several types of arrhythmias are revealed in the same child. In childhood, it is expedient to allocate supraventricular and ventricular tachyarrhythmias, sinus node weakness syndrome, supraventricular and ventricular extrasystoles. High degrees of AV blockade are also accompanied by rhythm disturbances. All existing disorders of rhythm are divided conditionally into two groups - tachyarrhythmias and bradyarrhythmias. The most polymorphic are tachyarrhythmias, in their differential diagnosis they encounter significant difficulties. In recent years, separately isolated group of primary electrical heart diseases, combining hereditary forms of life-threatening arrhythmias - the syndrome of an elongated and shortened QT interval, Brugada syndrome, polymorphic ventricular tachycardia.

In most cases, with the exception of paroxysmal tachycardia (sudden onset and end of an attack) and QT prolonged interval syndrome (repeated syncope), children make numerous but unspecific complaints. However, in the clinical polymorphism of various variants of rhythm disturbances, there are also regularities, they must be identified and taken into account when prescribing treatment and determining the prognosis.

The problem of differential diagnosis of syncopal conditions in childhood is often urgent, which is often caused by cardiac arrhythmias, most often by ventricular tachycardias, sinus node weakness syndrome, and high degrees of AV blockade. Among cardiogenic causes of fits of loss of consciousness, one of the leading places is occupied by primary electrical diseases of the heart, among them the syndrome of the extended interval QT (CYHQ-T) is most common. In the diagnosis of many types of arrhythmia, the role of the family electrocardiographic examination can not be underestimated, its results often become an important argument in the diagnosis. Currently, much attention is paid to molecular genetic research.

The choice of treatment tactics depends on many factors, including the mechanism of the development of cardiac arrhythmias, the age of manifestation, the frequency, severity of clinical symptoms, the representation of structural changes on the part of the heart. Treatment of children with arrhythmias includes urgent and chronic pharmacotherapy, interventional methods, including the implantation of antiarrhythmic devices (pacemakers and defibrillators). Children with supraventricular (supraventricular) paroxysmal tachycardias, life-threatening ventricular tachyarrhythmias (ventricular tachycardia, ventricular fibrillation, CYMQ-T) and bradyarrhythmias (sinus node weakness syndrome, complete AV blockades) need urgent therapy. Chronic pharmacotherapy of heart rhythm disorders in children includes correction of neurovegetative disorders of heart rate regulation, according to indications - control of abnormal electrophysiological mechanism of myocardial stimulation with the help of antiarrhythmic drugs of I-IV classes, as well as symptomatic therapy. In the last decade, the development of the method of catheter ablation pushed the role of pharmacological methods of therapy. However, in young children who do not have organic heart disease, as well as patients with heart rhythm disturbances against the background of pronounced violations of the vegetative regulation of heart rhythm, medicinal methods of treatment have an advantage. In the treatment of life-threatening cardiac arrhythmias, an important resource is the implantable antiarrhythmic device: pacemakers and cardioverter-defibrillators. However, with the implantation of a cardioverter-defibrillator for children with life-threatening arrhythmias, adequate selection of antiarrhythmic therapy is of great importance.

[1], [2], [3]