MORPHOMETRIC ANALYSIS OF THE STRUCTURE OF DIFFERENT MYOCARDIAL DEPARTMENTS OF LEFT VENTRICULAR IN HYPERTROPHIC CARDIO-MYOPATHY

Hypertrophic cardiomyopathy (HCM) is inherited myocardial disease characterized by hypertrophy of the left ventricle (LV) of the heart in the absence of other causes of hypertrophy. HCM is the most common cause of sudden cardiac death in young people. The etiological factors of the disease remain unknown, the genetic nature of HCM development is the most discussed theory. According to many studies, histological changes in HCM are the basis of hemodynamic and clinical manifestations of the disease. They are presented by the triad of structural myocardial remodeling: hypertrophy of сardiomyocites (CMCs), violation of the of muscle fibers orientation with the formation of disarray (DS) and varying degrees of fibrosis. There is no consensus among the histologists regarding the quantitative characteristics of the DS required to establish a morphological criterion for diagnosis of HCM. The aim of the morphological study was to deter-mine the relationship between the DS and topographic disor-ders of the myocardial structures of IVS whith HCM, as well as to quantify it in comparison with hypertrophy of the myo-cardium of patients with aortic valve (AV) stenosis. Studies were performed on the hearts of three patients who died from HCM (2 cases - obstructive and 1 - nonobstructive HCM) and 3 patients with AV stenosis (comparison group). Eight intact hearts of newborns and two hearts of young people, who died of accidents, were used as a control. The LV at the basal, middle and apex levels was cut into small pieces. Tissue specimens were prepared for histological and a morphometry examination. The areas of branching zones of CMCs were determined in the IVS and free walls of the LV. These in-cluded centers with chaotic placement of CMCs (disorientation of the myocardium) and the deviation zones from the parallel orientation of muscle fibers due to the intersection of multi-directional myocytic bundles or the meeting with interstitial structures. The total area of sections of the IVS and the free walls of the LV was measured, and then the percentage content of the CMCs branching was calculated. An analysis of the prevalence of the focuses of CMCs disorganization (isolated) and the centers of DS was carried out in the same way. The results showed that a large number of foci of chaotic CMCs location is a characteristic histological feature of HCM. Such foci of disorganization turn into DS with peculiar signs of destruction of CMCs (focal lysis with dissociation and a decrease in the number of myofibrils). Replacement fibrosis develops in the DS areas. We have shown the association of such changes with deformation of myocyte fragments in the zones of branching myocardial fibers. Estimation of the areas of branching and disorientation of the myocardium showed that these parameters were significantly higher in HCM than in normal hearts and in myocardial hypertrophy associated with AV stenosis. In normal structure of the myocardium DS develops much less frequently, but also in the zones of deformation of muscle fibers. This suggests that genetic factors play a negative role already at the stage of embryogenesis, preventing the proper organization of muscle fibers in bundles of a particular direction. At the same time, many deforming angles have formed and contribute to the destruction of the CMCs with the formation of DS, therefore, in patients with AV stenosis, DS develops much less frequently. However, in patients with HCM, cellular changes of DS can develop even in bundles of parallel-oriented CMCs.