Aim. To compare the results of mitral valve replacement with the full-flow mechanical valve MedInzh-ST and the classical prosthesis MedInzh-2, to learn the structural and functional parameters of the heart depending from the prosthesis in the long-tern period. Material and methods. From 2015 to February 2020 years an the basis of the cardio-surgical department of the Regional clinical Hospital 116 patients, in order to correct defects, were underwent mitral prosthetics with MedInzh valves. Of these 55 patients received a new full-flow valve MedInzh-ST. 61 patients a classical MedInzh-2. Before surgery and in the long-term period all patients were underwent transthoracic echocardiography with using expert-class devices. In the long-tern postoperative period 34 patients were underwent echocardiographic research after implantation full-flow valves and 40 patients after prosthetics of classical prosthesis. Results. The choice of the prosthesis model did not affect the incidence of postoperative complications and the rate of hospital mortality. In all cause of death is not associated with impaired function of the prosthesis. All patients before the discharge from hospital were fixed the positive effect from surgical treatment. In the long-term postoperative period between patients after implantation of full-flow valves, the cases of prosthetic platelets were not registered. One patient was diagnosed with prosthetic thrombosis after implantation of a classical prosthesis, which required further reprosthetics. There were no signs of prosthetic endocarditis and paraprosthetic fistula in both groups. There were no significant differences in the structural and geometric parameters of the heart in all patients. Conclusion. Analysis of the functional characteristics of the new full-flow valve MedInzh-ST in the long-term period allows us to conclude that the new valve model meets modern requirements for efficiency and safety.