Mechanical flaps are artificial flaps made of non-metallic and metallic materials that resemble familiar “doors”, except that the door frame is circular and contains one or two “doors”. The “single-leaf door” and the “double-leaf door” are single-leaf flaps for a single door and double-leaf flaps for two doors. Most of the mechanical flaps are made of pyrolytic carbon material, with strength and wear resistance equivalent to diamond, thus very strong and durable. In terms of annular size: in patients with larger annuli (especially aortic annuli), there is no significant difference between single- and double-lobe valves, and there are individual reports in the literature that single-lobe valve hemodynamics seem to be more in line with physiological requirements; in patients with smaller annuli, double-lobe valves have a larger opening area and better hemodynamics; in terms of anticoagulation therapy, the incidence and consequences of thrombosis in mechanical valves are better with double-lobe valves than with single-lobe valves. Therefore, the clinical use of bileaflet valves is significantly higher than that of unileaflet valves, especially in the tricuspid position, where bileaflet valves are recommended. Mechanical valves have good durability but require lifelong anticoagulation Advantages: The greatest advantage of mechanical valves is their good durability. Based on experimental data alone, modern mechanical valves have a theoretical service life of 50 years or more, and thus have a service life that can accommodate patients of all ages. In addition, smaller mechanical valves (e.g., 19- or 21-gauge) have a significantly larger opening area than stented bioprosthetic valves of the same type, making them ideal for implantation in patients with smaller aortic rings; in addition, mechanical valves have a significantly lower frame structure than bioprosthetic valves. Disadvantages: The biggest disadvantage of mechanical valves is the need for lifelong anticoagulation, which means that a daily dose of warfarin is required and the dose of the drug is adjusted according to the anticoagulation test results (INR). Daily anticoagulation is cumbersome, and inadequate medication adjustments can predispose to bleeding (over-anticoagulation) or thrombosis (under-anticoagulation). In addition, warfarin can cause fetal malformations through the placenta, which is also a cause for serious concern. Doctors suggest that prosthetic valves are divided into biological and mechanical valves, each with its own characteristics, so patients should choose prosthetic valves according to their own situation, through in-depth communication with the doctor to determine, do not blindly “worship” any one of them, suitable is the best.