1. Introduction

The congenital heart defect identified by the French physician Etienne Louis Arthur Fallot is one of the most complex malformations among all congenital heart defects. Fallot's tetralogy is manifested in the heart by pulmonary artery stenosis, interchamber barrier defect, aortic disposition and right ventricular hypertrophy. These pathological changes are manifested by specific histotopographic changes in the cardiac myocardium. Based on this, the modern classification of congenital heart disease has been proposed in many different variants of nomenclature. These classifications are explained by the frequency of regional occurrence, incomplete compliance, origin of congenital heart defects, genetic, environmental, occupational factors. Congenital heart defects account for 20.8 per cent of all heart diseases in Uzbekistan. Every 100 children in Uzbekistan have a congenital heart defect, so 0.08 per cent of them are Fallot's tetralogy and are treated only surgically. To be more precise, if 530 thousand children are born in Uzbekistan on average per year, 1% of them (5300) have congenital heart defects, 25% of them are patients who need surgery, and 8% of 5300 are Fallot's tetralogy. enough. This numerically means that 106 children with the diagnosis of Fallot's tetralogy are born in Uzbekistan every year.

The relevance of the problem is to study the distribution of Fallot's tetralogy in Bukhara region of the Republic of Uzbekistan and its peculiarities from the morphological point of view. In Bukhara oblast, the average number of diagnosed congenital heart defects per year is 32-38 Fallot's tetralogy.

The aim: It consists in studying and analysing the level of occurrence of congenital heart defects in Bukhara region, anatomical, histological and morphometric changes.

2. Material and Methods

In the Expert Bureau of Pathological Anatomy of the Bukhara region, clinical and anamnestic data of heart tissue and medical history obtained at autopsy of 65 children who died of congenital heart disease were analysed. Sections of heart tissue taken by morphological method were frozen in 10% buffered formalin for 72 hours. Then after washing in wastewater for 1 hour, they are dehydrated in ascending alcohols (70,80,90,100%). The slices are then frozen in paraffin and poured into cassettes. Using a microtome, 5-7 µm thick slices are made, deparaffinised in xylene and stained with haematoxylin and eosin. The obtained results are viewed under a light microscope, microphotographs are taken and morphometrically analysed.

3. Results and Discussion

When discussing the studied data on morphological changes of the right ventricle of the heart in Fallot's tetralogy, the following was established. Group hypertrophy of cardiomyocytes of the right ventricular myocardium was predominantly detected in the area of the anterior wall of the ventricle. Including branched hypertrophy of cardiomyocytes, large hyperchromic, well-defined cells of transverse extension were detected in the field of view 200x. The number of large cardiomyocytes was 220-255 in the field of view 200x. In comparison with the control group it was 2.25 times (up to 100-125), the size increased 2.5 times. Vessels between cardiomyocytes: capillaries and small calibre vessels were 1,75 times less than in the control group. These changes mean that compensatory mechanisms in the right heart sections are clearly developed. It was found that a large number of pale pink inclusions (glycogen) were found in the cytoplasm of atypical cardiomyocytes (pacemaker cells) located along the perimeter of the right ventricle. A cavernous appearance of lymphatic vessels of different width with cardiomyocyte inclusions was detected (see Fig. 1).

Figure 1. Fallot's tetralogy. Myocardium of the anterolateral branch of the right ventricle. The interspace reveals cavernously dilated lymphatic vessels (1), tachypneic appearance of large hyperchromatic cardiomyocytes (2), and irregular interstitial ballooning (3). V.G. Staining. Size 20x10

Due to hypertrophic changes in most cardiomyocytes of ventricular myocardium in Fallot's tetralogy, some changes in histioarchitectonics of most capillaries are observed. This, in turn, violates the laws of haemodynamics, leads to partial disruption of blood circulation in capillaries and increased permeability of the capillary wall. As a result, focal plasmorrhagia causes interstitial oedema, ruptures or dilated foci between interstitial discs that submerge cardiomyocytes, disrupting synchronous contractions. At the same time, it creates a precipitation phenomenon in the dilated capillaries. This, depending on the duration of the process, leads to activation of fibroblasts in these areas and an increase in sparse fibrous structures. As a result, this leads to atrophic changes in bundles of cardiomyocytes that have not undergone hypertrophy and have low functional activity. As a result, cardiac contractions are clinically morphologically characterised by conditions for the development of arrhythmic contractions. It is characterised by the creation of conditions for the development of necrobiotic processes in cardiomyocytes with a focus due to the formation of microthycin by sluggish erythrocytes in capillaries (see Fig. 2).

Figure 2. Fallot's tetralogy. Myocardium of the middle branch of the right ventricle. Sludge phenomenon in most capillaries (1), tachy-shaped appearance of large hyperchromic cardiomyocytes (2), and irregular interstitial swelling in the interstitium (3) are determined. V.G. staining. Size 40x10

In the cytoplasm of cardiomyocytes of papillary muscles of the right ventricle, various drop-shaped focal dystrophies continue to develop, leading to sharp hypertrophy of morphofunctionally active cardiomyocytes, and macroscopically, rough fibrous surfaces with uneven appearance appear on the surface of papillary muscles. As a result, atrophic changes of cardiomyocytes continue with endocardial thickening and development of fibroelastosis foci on surfaces close to the endocardium of the heart (see Fig. 3).

Figure 3. Fallot's tetralogy. Part of the papillary muscle of the right ventricle. In most cardiomyocytes, fatty dystrophy has medium to small drop-shaped foci (1), smooth interstitial oedema in the subendocardial region (2), and the cytoplasm of morphofunctionally active cardiomyocytes is dark pink in colour (3). V.G. staining. Size 40x10

Figure 4. Fallot's tetralogy. Subvalvular branch of the right ventricle. Foci of mysclerosis (1), interstitial oedema (2), destructive changes of fibrous structures (3) are defined. G.E. Staining. Size 40x10

In particular, right ventricular branches close to the lower left ventricle develop, with the appearance of various granular basophilic inclusions in the endocardium, foci of fibroelastosis and cytoplasm of Purkinje cells. This in turn continues with the development of interstitial oedema around foci of fibroelastosis, scar processes infiltrating the myocardium. Macroscopically, it continues with the appearance of foci characterised by the detection of uneven non-smooth surfaces on the surface of the inferior branch of the right ventricle and facing the area of the interventricular septum.

Figure 5. Fallot's tetralogy. Subvalvular region of the right ventricle. Foci of fibroelastosis (1), intermediate edema (2), destructive changes of fibrous structures (3) are determined. Hydropic dystrophy of Purkinje cells (4). V.G. staining. Size 40x10

In the left ventricle, abrupt changes do not develop, on the contrary, most of the cardiomyocytes remain homogeneous in size, and they are characterised by relatively low development of interstitial tumours in the capillary network. Most endocardially located cardiomyocytes have the same appearance and histioarchitectonics, and cardiomyocytes of fatty dystrophy are practically not detected, which means an ordered arrangement of cardiomyocytes of the same morphofunctional size. Cardiomyocytes of subpericardial branches reveal the same changes, mainly changes in functionally active foci of cardiomyocytes located near the subvalvular branch: hypertrophied cardiomyocytes, irregular interstitial oedema, sludge phenomenon is detected in capillaries. The primary cause of these changes is endocardial thickening in periva-subvalvular branches affected by fibroestosis and asynchronous contractions of cardiomyocytes due to developed hydropic dystrophy in the majority of Purkinje cells. At the same time, the development of sparse fibrous structures between cardiomyocytes and the appearance of sclerotic changes around small-calibre vessels in these areas are determined.

Figure 6. Fallot's tetralogy. Subvalvular region of the left ventricle. Foci of fibroelastosis (1), intermediate edema (2), destructive changes of fibrous structures (3) are determined. Hydropic dystrophy of Purkinje cells (4). V.G. staining. Size 40x10

4. Conclusions

Thus, characteristic aspects of morphological changes occurring in congenital heart defects, focal hypertrophy of cardiomyocytes, sclerotic changes around vessels, interstitial oedema and foci of fibroestosis have been determined. The most pronounced changes include focal endocardial thickening, group atrophic changes in subendocardial cardiomyocytes, lipomatous foci in the pericardium, and medium to small fatty dystrophic changes in right ventricular cardiomyocytes. These changes are determined in Fallot's tetralogy, among the combined types of congenital heart disease, in defects of the interventricular barrier, in transposition of the main vessels of the heart. These changes manifest themselves differently in different parts of the heart (frontal, inferior and interventricular septum) depending on the localisation of congenital heart defects. It has been established that the main part of cardiomyodestructive changes falls on the right ventricle in the blue type of heart defects from the clinical and morphological point of view of most congenital heart defects. These changes continue with the development of chronic venous stasis in the great circle of circulation. As a result, the heart lesion ends with the rapid development of right ventricular failure.