Classification of sick sinus syndrome

Most of the sinus node weaknesses in the syndrome classification suggested the use of the presence or absence of clinical manifestations, ECG patterns on a standard ECG or Holter monitoring, an increase in heart rate when carrying out samples with physical activity. Since the beginning of the 90s, the division of this pathology into clinical and electrocardiographic variants of the sinus node weakness syndrome in children, depending on the nature, sequence of growth and the degree of manifestation of changes in the conduction system of the heart, taking into account a stable combination of ECG manifestations, circadian changes rhythm according to the holter monitoring, the response of the heart rhythm to the load and the concomitant lesions of the conduction system of the heart.

Clinical and electrocardiographic variants of sinus node weakness syndrome in children

Violations of functions

Sinus node	Lower levels of the conduction system of the heart
I option. Sinus bradycardia with heart rate less than 20% below the age limit, rhythm migration. Pause of the rhythm in Holter monitoring up to 1.5 s. Adequate frequency of sinus rhythm during exercise	Delay AV holding to AB-blockade 1 degree. Alternative of AV-conduction
II option. Sinoatrial blockade, slip cuts and accelerated rhythms. Pauses of rhythm in Holter monitoring from 1.5 to 2 seconds. Inadequate increase in heart rate during exercise	AV dissociation, AV blockade of II-III degree
III option. Syndrome of tachycardia-bradycardia. Pause of the rhythm in holter monitoring from 1.5 to 2 s	AV-dissociation, AV blockade of II-III degree
IV option. Rigid sinus bradycardia is less than 40 per minute, ectopic rhythms with single sinus contraction, flicker-atrial flutter. Lack of restoration of a stable sinus rhythm and its adequate increase in physical activity. Pause of the rhythm in Holter monitoring for more than 2 seconds	Violations of AV and intraventricular conduction. Secondary extension of the QT interval . Violation of the process of repolarization (depression of the ST segment, reduction of the amplitude of the T wave in the left thoracic leads)

Four stable clinical-electrocardiographic variants of the sinus node function were identified in children:

• I variant includes minimal manifestations in the form of sinus bradycardia and rhythm migration;
• II variant - substituting rhythms, stops of the sinus node, sinoatrial blockade against a background of more pronounced depression of the main rhythm;
• III variant - combination of sinus bradycardia with supraventricular heterotopic tachycardia;
• IV variant - cardioneuropathy with a rigid pronounced sinus bradycardia, a set of replacing rhythms, asystole and a violation of repolarization of the myocardium.

Each of these variants in a sufficiently high percentage of cases is characterized by the addition of violations of AV-conduction. The staging of sinus node function disorders in children was confirmed: from I to II (or III depending on the presence of electrophysiological conditions for the development of tachyarrhythmias) and IV variants.

Experimental studies. Pokrovsky and co-authors in 2007 the model of sinus node weakness syndrome was developed, in which the progressive increase in the expression of electrocardiographic changes was associated with the weakening of the central nervous system's influence on rhythmogenesis. It has been confirmed that the decrease in the functionality of the sinus node occurs consistently. At the first stage there is a migration of the rhythm, on II - slipping cuts, on III the syndrome of tachycardia-bradycardia is formed. And the maximum decrease in the functional activity of the sinus node occurs in conditions of a significant decrease in central influences and is manifested by rigorous bradycardia. Thus, the stages of the progression of the violation of pacemaker activity in the sinus node in the experimental study correspond exactly to the stages of development of the sinus node weakness syndrome in children, which confirms the scientific and clinical significance of the classification proposed for pediatrics.

[1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14]