The aim of the research. To study structural and functional parameters of the heart in patients with polycythemia vera. Material and methods. A total of 63 patients with stage I-IIB polycythemia vera (27 male and 36 female) and 52 healthy subjects underwent echocardiography, dopplerography, tissue dopplerography of fibrous rings of atrioventricular valves as well as evaluation of longitudinal strain of the left ventricular myocardium. Results. In patients with polycythemia vera, there is enlargement of heart chambers, interventricular septum hypertrophy develops in 20.6% of the cases, pulmonary hypertension in 39.7% of the cases, global diastolic dysfunction of the left ventricle in 84.1% of the cases, as well as diastolic dysfunction of the fibrous rings of the mitral and tricuspid valves and a decrease in longitudinal strain parameters of the left ventricle indicating impairment of its contractile function. Conclusion. The decline in parameters of tissue dopplerography of the fibrous rings of the atrioventricular valves and longitudinal strain of the left ventricular myocardium may serve as early criteria for diagnosis of myocardial dysfunction in patients with polycythemia vera.