Multicenter observational study. The study does not involve any interventions in routine clinical practice, the choice of treatment method (including the type of medical device used and the method of surgical intervention) and the methods of examination and postoperative management of patients will not differ from the standard of care for patients requiring percutaneous transcatheter edge-to-edge mitral valve reconstruction by implantation of the MitraClip clip on the mitral valve leaflets, used in the daily medical practice of a medical institution. All medical devices under study (delivery device with the MitraClip clip on the mitral valve leaflets) are registered in the territory of the Russian Federation and are used in the conditions of routine medical practice. The study will include patients who have undergone surgical intervention to correct mitral regurgitation by percutaneous transcatheter implantation of the MitraClip G4 clip on the mitral valve leaflets. It is expected to include at least 196 patients (at least 98 prospective patients and at least 98 retrospective patients). The planned number of research centers is 11 outpatient clinics, presumably in 6 regions of the Russian Federation.