Loss of Myofibrils in Cardiomyocytes as a Morphological Indicator of Reduced Compensatory Capabilities of Hypertrophied Myocardium

The functioning of the ventricular myocardium in hypertrophic cardiomyopathy (HCM) under high hemodynamic load leads to depletion of its resources and is associated with the risk of developing a dilated stage. In patients with HCM, the cardiomyocytes of the interventricular septum are hypertrophied, the proportion of cardiomyocytes in which myofibrils constitute less than 50% of the sarcoplasm volume increases with increasing the cardiomyocyte length and correlates with echocardiographic signs of left ventricular obstruction. These cardiomyocytes are characterized by ultrastructural signs of synthetic activity. In the myocardium of patients with HCM, single cardiomyocytes with “critical” loss of myofibrils and nonspecific degenerative changes corresponding to the picture of irreversible changes in the cardiomyocyte ultrastructure were revealed. The presence of cardiomyocytes with this ultrastructural phenotype is an early marker of exhaustion of the compensatory capabilities of the myocardium in HCM.