Early Feasibility Study of Surgical Implantation of a Polymer Prosthetic Mitral and Aortic Valve

The goal of this clinical trial is to explore the early feasibility, initial safety, and efficacy of surgical implantation of a polymer prosthetic heart valve in patients requiring either mitral valve replacement or aortic valve replacement. The main question it aims to answer is: \-- What is the rate of valve-related complications, including thromboembolism, valve thrombosis, severe perivalvular leak, severe bleeding, and endocarditis, at 12 months post-operation? Participants will undergo: * Surgical implantation of a polymer prosthetic valve (mitral valve replacement for mitral valve group and aortic valve replacement for aortic valve group). * Regular follow-up visits at 30 days, 3-6 months, and 12 months post-operation to evaluate clinical outcomes, including echocardiographic assessment and clinical event monitoring.