Aim. To evaluate the change in the parameters of systolic and diastolic myocardial functions in patients with severe obstructive sleep apnea (OSA) syndrome before and after CPAP therapy.
 Materials and methods. Forty eight patients with severe OSA aged 4574 years were examined. All patients underwent questionnaires, echocardiography with tissue Dopplerography, speckle-tracking echocardiography. At the end of the three-month course of CPAP therapy, the patients were re-examined, followed by a comparative analysis of the data obtained.
 Results. In patients with severe OSA after CPAP therapy, the ejection fraction of the left ventricle and the amplitude of systolic displacement of the fibrous ring of the tricuspid valve significantly increased, which indicated an increase in the relative capacity of the ventricular myocardium. The performed CPAP therapy had a positive effect on the diastolic function of the myocardium of both ventricles, which was manifested in an increase in the ratio of peak rates of early and late transmitral and transtricuspidal diastolic flows. The rate of transtricuspidal regurgitation and systolic pressure in the pulmonary artery decreased in dynamics.
 Conclusion. The use of CPAP therapy improves systolic and diastolic heart function, leads to a decrease in systolic pressure in the pulmonary artery in patients with severe OSA. The results obtained substantiate the importance of early initiation of CPAP therapy in the complex treatment of patients with OSA.