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.

Mitral regurgitation (MR) may result from either degenerative lesions of the mitral valve (MV) leaflets - degenerative MR (DMR) - or pathological dilation of the left ventricle (LV) - functional MR (FMR). In DMR, the MV apparatus itself is compromised by affected leaflets, chords, etc. In contrast, FMR is usually associated with cardiomyopathy (usually of ischemic etiology), with this type of MR being secondary to LV dysfunction. In both cases, there is a violation of leaflet co-optation and reverse blood flow from the LV into the left atrium. According to existing guidelines, surgical reconstruction (plastic surgery) is the preferred treatment option for DMR. Indications for invasive treatment of FMR are not so clear-cut due to the high rate of postoperative MR recurrence and the lack of reliable evidence of a positive effect of FMR correction on long-term survival. The greatest complexity is presented by the group of patients with severe MR and high or unacceptable surgical risk of open surgery.

For the treatment of severe MR in such patients, the method of transcatheter MV repair was proposed, which is an endovascular analogue of the suture "edge-to-edge" repair according to Alfieri. MitraClip system is approved in the European Union, the USA, the Middle East and the CIS (Kazakhstan, Belarus) for the treatment of high surgical risk patients with DMR and FMR with symptomatic heart failure of II-IV functional class according to the classification of the New York Heart Association (NYHA), persisting despite optimal drug therapy.

The aim of this study is to evaluate the safety and effectiveness of the procedure of percutaneous transcatheter implantation of the MitraClip G4 clip on the mitral valve leaflets in a population of patients from the Russian Federation for the treatment of mitral regurgitation. Information on the health status of patients who have undergone the procedure of percutaneous transcatheter edge-to-edge mitral valve reconstruction by implanting the MitraClip clip on the mitral valve leaflets will be of high scientific and practical interest.

Cohort 1 (prospective patients)

Inclusion Criteria:

1. Patients who are indicated for cardiac surgery to correct mitral regurgitation using transcatheter edge-to-edge reconstruction of the mitral valve by implanting the MitraClip G4 on the cusps of the mitral valve.
2. Age 18 years and older.
3. Understanding and voluntarily signing the informed consent form for the processing of personal data.

Exclusion Criteria:

1. The expected life expectancy of the patient is less than 12 months (contraindication to surgical intervention).
2. The presence of concomitant diseases that limit the patient's ability to carry out visits according to the study protocol.
3. Conditions that limit the patient's ability to comply with the study requirements (dementia, psychoneurological diseases, drug addiction, alcoholism, etc.).
4. Simultaneous participation in other clinical trials or previous participation in this trial.

Cohort 2 (retrospective patients)

Inclusion Criteria:

1.Patients who underwent cardiac surgery to correct mitral regurgitation using transcatheter edge-to-edge mitral valve reconstruction with MitraClip G4 clip implantation on the mitral valve leaflets.

Exclusion Criteria:

1. Patients for whom the physician-researcher cannot access primary medical documentation (medical records, outpatient cards) to collect complete and reliable information about the patient in the volume required by the study protocol.
2. The surgery must have been performed no earlier than January 1, 2022.
3. Age 18 years and older.

Adult patients aged 18 years and older with heart failure and implanted MitraClip G4 mitral valve clips.