The purpose of the research was to study the state of autonomic regulation in prepubertal children with mitral valve prolapse during an orthostatic test Materials and methods. The study involved 2 groups: the main – 26 children aged 10-11 years with mitral valve prolapse, and a control group – 22 relatively healthy children. The adaptive mechanisms were monitored by analyzing heart rate variability. All children participated in a cardiorhythmic examination at rest lying down and during an active orthostatic test. Results and discussion. Among the indicators that had significant differences, the indicators of regulatory process adequacy index and mode amplitude should be noted. In the group of children with mitral valve prolapse, an increase of the regulatory process adequacy index indicated the predominance of the functioning of the sinus node over the activity of the sympathetic division of the autonomic nervous system. An increase in the adequacy index and mode amplitude indicates the connection of the central structures of rhythm control (subcortical rhythms) during a change in body position. Stress index also increased. This index of tension of regulatory systems shows the activity of the mechanisms of sympathetic regulation, the state of central regulation. Children in the control group had a well-coordinated response of the sympathetic nervous system to the orthostatic test: the low frequency spectrum and very low frequency indicators increased. While in main group, the value of low frequency spectrum (the work of the sinus node) increased, the value of very low frequency (the reaction of the central structures of the nervous system) decreased. This indicates dysfunction of the most important reactions, which also affects the daily activities of children, increases the risk of mitral valve prolapse complications. Conclusion. In children with mitral valve prolapse, the absence of a pronounced typical reaction to an ortho test is a reflection of an adaptive-regulatory overstrain in conditions of morphological determinacy of connective tissue dysplasia, which are trying to ensure the adequacy of intracardiac hemodynamics. The data obtained will be useful for predicting the reaction of the body of children with mitral valve prolapse to physical activity of varying intensity

Keywords: autonomic nervous system, heart rate variability, mitral valve prolapse, orthostatic test, pediatric patients

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