The Study on the Use of "UniLine" Bioprosthesis in the Treatment of Isolated Aortic and Mitral Valve Diseases

Inclusion Criteria: 1. Provided informed consent to participate in the study. 2. Must be aged 18 years and older. 3. Patients with isolated acquired mitral or aortic valve disease. 4. No prior heart valve replacement, current replacement must be planned (not conducted in an urgent/ emergency manner), using the "UniLine" biological prosthesis made from xenopericardium. 5. Patient must be able to visit the Research Center. Exclusion Criteria: 1. Mechanical or biological prosthesis in another position. Patients with tricuspid valve repair may be included in the study. 2. Prior heart valve replacement. 3. Concomitant interventions on the heart (coronary artery bypass grafting, coronary heart disease treatment, surgical reconstruction of a left ventricular aneurysm) and thoracic aorta. 4. Patients with cancer in history. 5. Patients with musculoskeletal conditions with severe movement disorders and diseases of the central nervous system, accompanied by cognitive disorders (disorientation, inability to independently reach the destination). 6. Acute or subacute stages of infective endocarditis. 7. Class IV heart failure according to the New York Heart Association Functional Classification with ongoing therapy, left ventricular ejection fraction less than 40%, myocardial infarction less than 90 days old, angina pectoris grade 4. 8. The presence of severe somatic, neurological, mental and infectious diseases that worsen the prognosis of long-term survival: tuberculosis, human immunodeficiency virus, Alzheimer's disease, epilepsy, chronic kidney disease stage 3b (Glomerular Filtration Rate less than 30 mL/ min / 1.73 m²), chronic lung diseases requiring constant intake of corticosteroids and bronchodilators, multifocal atherosclerosis (grade 3 chronic lower limb ischemia, stenosis of the carotid arteries more than 50%, prior and planned interventions on the abdominal aorta, carotid arteries or arteries of the lower extremities).