Objective: study of structural and geometric myocardium changes in children with extrasystoly and connective tissue heart dysplasia (CTHD). Material and methods. We studied 159 children at the age 0-17 years old, the average age 8,2 ± 5,7. The first group of patients included children with ES, the second one – 70 patients with ES in the course of CTHD. The third group included 54 kids with CTHD. Echo data were estimated: left ventricular end-diastolic diameter (LLVIDd), interventricular septum thickness (IST), left ventricular posterior wall thickness (LVPWT) left ventricular ejection fraction (EF), left ventricular mass (LVM), left ventricular mass index (LVMI – LVM to the standing height (m) raised to the 2,7 power, which was interpreted according to the percentile table LVMI, g/m2,7 by S.R. Daniels еt al.) and left ventricular relative wall thickness (RWT). Results. The most part of children with ES had CTHD. The average values of left ventricular sizes in diastole and systole were much bigger in children with ES at the school age. On the other side preschool children had maximum meanings in cases without arrhythmia. Left ventricular myocardium hypertrophy occurred significantly more often in children with ES in preschool age. Being the most complicated kind of remodeling concentric hypertrophy was in 3% of children of preschool age with ES both without CTHD and in the course of it. Conclusion. Extrasystoly is a leading reason in myocardium remodeling in children. In this case it is important to estimate intracardial hemodymanic with indexes calculation. If some indexes have deviations it is necessary to prescribe vigorous treatment of arrhythmia as well as in course of good contractive myocardium capability.