Artificial heart valves are mainly divided into two categories.
One is the mechanical valve, and the other is the biological valve.
The former is made of advanced synthetic materials, while the latter is made of both artificially synthesized advanced materials and biological tissue membranes that have undergone complex chemical treatments. Each has its advantages and disadvantages. The advantage of mechanical valves is good durability, but the disadvantages are that they require lifelong anticoagulation and have a higher thromboembolism rate than biological valves. The latest foreign research also suggests that if used for a long time, mechanical valves may perform better than biological valves. The advantages of bioprosthetic valves are that they do not require lifelong anticoagulation after surgery, and the thromboembolism rate is low, which improves the patient's quality of life. Therefore, patients with bleeding factors who cannot accept anticoagulation and those in rural and remote areas who are inconvenient to undergo anticoagulation can choose biological valves. The disadvantage is that the durability is not as good as that of mechanical valves. The lifespan of the valve is about ten years. If it is damaged, it will need a second treatment. Replace the valve. As for which valve is suitable for you, your doctor will recommend it to you based on your condition. A brief introduction to the various artificial heart valves currently available for clinical use is as follows:
1. Bioprosthetic valves Bioprosthetic valves include autologous pulmonary valves, allograft aortic valves, xenogeneic aortic valves and bovine pericardial xenogeneic bioprostheses. The autologous pulmonary valve is to cut out the patient's own pulmonary valve and immediately replace the damaged aortic valve. The pulmonary valve is replaced with another homologous valve to ensure the normal function of the aorta. This complicated surgery has not yet been widely used. Homogeneous aortic valves are obtained from fresh cadavers that died of other causes, and the effect is also good. Nowadays, the liquid nitrogen deep cryopreservation method can be used to preserve homogeneous valves for long-term use. However, due to the limitations of the source and the characteristics of no stent, only Can be used for aortic valve replacement. Currently, the number of applications of homogeneous bioprostheses is not as high as that of xenogeneic bioprostheses. Xenogeneic biological valves include porcine biological valves, bovine pericardial valves, and horse pericardial valves. Among them, porcine bioprosthetic valves are widely used, but their clinical effects are obviously inferior to those of bovine pericardial bioprostheses. At present, the latest research direction of foreign biological valves is to use minimally invasive technology to percutaneously implant biological valves (such as Sorin Percival), thereby making valve replacement surgery simpler, reducing patient trauma and effectively reducing surgical risks. An introduction to common biological valves is as follows:
1. Hancock valve is a porcine aortic valve treated with 0.2% glutaraldehyde and mounted on a metal stent. The valve stent is inelastic, the seat ring is round, and the right leaflet is attached. Part of the muscle tissue affects the effective area of ??the valve orifice. Subsequently, the composite trileaflet valve without muscle tissue was used. Hancock's improved Model 250 is a combined valve and uses an elastic frame, and the effective valve orifice is significantly expanded.
2. Carpentier-Edwards valve: This is the most commonly used biological valve in the world. The valve frame is made of elastic alloy steel wire and covered with sparse polyester cloth. The seat ring is not perfectly round to make it close to the valve. The attachment edge of the leaflet is reduced, and the space occupied by the muscle tissue under the right valve leaflet in the valve orifice is reduced, and the effective valve orifice area is also larger.
3. Intact valve: Its characteristic is that the valve leaflets are not subject to any tension during the treatment with glutaraldehyde. After the drug is fixed, the elastic structure within the valve leaflets still maintains a dense and wavy arrangement without being damaged. Straighten. This is called a tension-free fixation method and increases the durability of the leaflets. In addition, treatment measures to prevent calcification were adopted. From 1983 to 1987, 930 implants have been clinically implanted, with good results.
4. Ionescu-Shiley valve: Ionescu's was first used in 1971. This flap is made from calf pericardium aged 6 to 18 months. After fixation with glutaraldehyde solution, a whole piece of bovine pericardium with uniform thickness was selected and wrapped around the stent to make three equal-sized valve leaflets. The elastic low valve frame is superior to the porcine aortic valve in hydrodynamic tests and fatigue tests. Beijing BN valve: The self-made bovine pericardial valve made by Fuwai Hospital is similar to the standard Ionescu valve and was used clinically in 1976. By 1987, more than 800 such valves had been clinically implanted. The valve integrity rate at ten-year follow-up was 74.5%. Currently, there are Mitroflow, Edwards, Sorin and other bovine pericardial valves on the international market, all of which have significantly improved in terms of preventing calcification.
⒌ Sorin Mitroflow valve and Solo valve: In 1985, the first generation Sorin bovine pericardial bioprosthetic valve was launched for clinical use and was treated with glutaraldehyde. After 15 years of clinical research abroad, its hemodynamic performance is satisfactory.
The latest Mitroflow and Solo valves have been detoxified to avoid the toxicity of glutaraldehyde to heart tissue, effectively prevent valve calcification, and significantly improve the durability of the valve. Among them, Mitroflow is designed with a valve frame, making it easier to implant. Solo is a stentless valve with better hemodynamics and postoperative clinical effects.
2. Mechanical valves currently include two categories: single-leaf valves and bi-leaflet valves. Since the hemodynamic performance of bileaf valves is significantly better than that of single-leaf valves, single-leaf valves have basically withdrawn from clinical use. Representative ones include:
1. St. Jude double-leaf mechanical valve: the blade is a thin rectangular shape, made of pyrolytic carbon as the basic material, and the two ends of the blade are in the oblique groove of the valve ring. slide. When the valve orifice is open, the leaves reach above 80°C and are almost parallel to the blood flow. Therefore, it can also be considered as a central blood flow mechanical valve. Its hydrodynamic performance is better than that of the inclined-leaf mechanical valve.
2. Medtronic ATS bileaflet mechanical valve: It adopts a valve frame protruding ball shaft design, which originated from the original Carbomedics company (now Sorin company). The clinical manifestations are similar to the St. Jude mechanical valve. However, due to its ball-shaft design, the incidence of blood clots may be higher than that of other similar valves.
3. Sorin bileaf mechanical valve: There are two series: Carbomedics and Bicarbon. Carbomedics has been used clinically for more than 25 years, and has been implanted in more than 600,000 cases worldwide, without a single case of structural-related failure. The Bicarbon series adopts streamlined valve leaflet and valve frame designs to effectively reduce valve orifice resistance and improve postoperative results. At the same time, the durability of the valve is improved due to the use of patented carbon plating technology. More than 10 years of clinical data show that its incidence of various postoperative complications is lower than similar products.
4. On-X double-leaf mechanical valve: This product is made of pure non-alloyed pyrolytic carbon. The surface is covered with graphite enzymatic hydrolyzate. The enzymatic hydrolyzate of the valve leaflets is made of 10% Tungsten infusion, the outer ring is made of titanium alloy, and the suture ring material is polytetrafluoroethylene. The design of the On-X valve is unique. Pure pyrolytic carbon has good biocompatibility, smoother surface, and stronger anti-thrombotic effect. The leaves open at 90°C parallel to the blood flow, increasing the effective valve area, reducing turbulence, and the valve axis. Comprehensive flushing prevents thrombosis and greatly improves clinical effects. FDA statistics show that compared to other valves, the On-X valve can reduce the incidence of adverse events by 50-60%. Therefore, On-X, as the first and only heart valve product, was approved by the US FDA in June 2006 to conduct a multi-center (40 centers) clinical trial of artificial heart valves with anticoagulant effects: the PROACT study for short. The On-X valve is the result of more than 40 years of painstaking research by Dr. Jack Bokros and his team using pyrolytic carbon research. Dr. Jack Bokros, the discoverer of pyrolytic carbon, received the Biomaterials Surface Science Foundation Lifetime Achievement Award in recognition of his contribution to the development of isotropic pyrolytic carbon materials.