Response of autonomic nervous system in children with mitral valve prolapse to physical exercises

Abstract

The problem of cardiovascular diseases diagnosing is topical. The prevalence of mitral valve prolapse (MVP) has been increasing over the past decades, which requires a differentiated study to prevent its complications in children. Purpose - to explore the reaction of the autonomic nervous system to physical exercises in children with MVP, taking into account the mitral regurgitation (MR). Materials and methods. 44 children with MVP were examined and divided into two groups considering MR aged from 13 to 17 years old. The Group 1 consisted from 20 (45.5%) children with MVP without MR, the Group 2 - 24 (54.5%) children with MVP without MR. It were studied the influence of physical activity on the state of vegetative homeostasis in these children. The estimation of autonomic system state and heart rhythm variability parameters, including spectral and frequency analyses were conducted by cardiointervalography. Estimation of these parameters was performed after physical exercises and compared with primary results. Results. Increasing of VLf (Very low frequency) and Lf (Low frequency) data parameters on 32.7% and 65.6% in children with MVP without MR was noted which shows the prevalence of sympathetic part of autonomic nervous system (ANS), while in children with MR - on 40.5% and 85%, respectively, that is 7.8 and 19.5% more than in children without MR. This can be associated with increased sympathicotonia against the background of the MR presence. Among the parameters which describe the parasympathetic part of the ANS, there was an increase in Hf (High frequency) by 67.0% in children without MR, when it appears, this parameter decreases by 9,1% - we observe an increase in relative sympathicotonia. Increase of sympathetic tonus was also noted in Lf/Hf elevation by 3.8% (without MR) and by 28% (with MR). The analysis of heart rate variability (HRV) time parameters expectedly had changes within reducing of SDNN (Standard deviation of the NN (R-R) intervals) by almost half (p<0.05) in children of both subgroups and the increase of rMSSD (root mean square of successive R-R interval differences) by 23.2% in children without MR (р<0.05), and with the appearance of MR decrease of this parameter by 24.3% was noted. Therefore, in children with MVP, with the appearance of MR, changes in the parameters that characterize the state of ANS with sympathicotonia increasing and parasympathicotonia weakening. Conclusions. In children with MVP, against the background of physical exertion, there is an increase in changes in the balance of the ANS, regardless to the presence or absence of MR. In children with MVP, against the background of MR, the influence of the sympathetic division of the ANS increases almost twice after physical exertion. These children should be under the close supervision of pediatricians, pediatric cardiologists and family doctors. The research was carried out in accordance with the principles of the Helsinki Declaration. The study protocol was approved by the Local Ethics Committee of all participating institutions. The informed consent of the patient was obtained for conducting the studies. No conflict of interests was declared by the authors.