What Are the Different Types of Prosthetic Valves?

Heart Valve Prothesis is an artificial organ that can be implanted in the heart instead of heart valves (aortic valve, tricuspid valve, mitral valve), which can make blood flow in one direction and has the function of a natural heart valve. When the heart valve disease is severe and cannot be restored or improved by valve separation surgery or repair surgery, artificial heart valve replacement must be used. Valve replacement cases are mainly rheumatic heart disease, congenital heart disease, Marfan syndrome and so on.

Chinese name: Artificial heart valve
Foreign name: Heart Valve Prothesis

Use: Heart valve
Species: Biological valve, mechanical valve

Application and development of artificial valve

The trial production of artificial heart valves began in the late 1940s, when it was only in the experimental stage and had not been practically used. In 1960, Surgeon Starr and his collaborator Edwards of Portland, Oregon, first implanted a rheumatic heart valve with an artificial spherical valve, a silicone ball artificial heart valve, for a mitral stenosis heart disease patient. Patients with mitral stenosis due to heart disease have long-term survival after surgery, which has created a history of artificial heart valve replacement. By 1981, there were as many as 350,000 cases of artificial valve replacement worldwide.

With the advancement of science and technology, artificial heart valves have undergone such an evolutionary process as globe valves, single leaf disc valves, biological valves, and double leaf disc valves (see the figure below). Current research on artificial heart valves is aimed at improving durability, reducing comorbidities, and improving valve function.

At present, the mortality of valve replacement is even lower than that of major abdominal surgery in many places. Millions of cases of clinical practice have proven that under normal circumstances, patients' lives have been extended and their health has also improved significantly. So far, more than 100 kinds of artificial heart valves have been made, and most of them have been eliminated, leaving only a few valves. Artificial heart valves are classified into mechanical valves and biological valves. The hard metal materials used as mechanical valves are mainly cobalt-chromium-nickel alloys and titanium steel; the non-metallic hard materials are mainly low-temperature isotropic carbon; the elastomer material was originally used as the silicone of the valve ball valve body The rubber has developed into a "low vulcanized" silicone rubber that is not easily denatured; the textiles of the seam loop are polytetrafluoroethylene and polyester filament fabrics. Biological valves are mainly composed of the same type and heterogeneous type. There are two kinds of the same kind of aortic valve and the same kind of dura mater; the two kinds of different kinds of valve include pig valve and bovine pericardial valve. The mechanical valve is characterized by good strength, but needs anticoagulation for life; the biological valve is characterized by no anticoagulation, but its life is not as good as the mechanical valve. In recent years, research on artificial heart valves has mainly focused on solving the problems of mechanical valve anticoagulation and biological valve anticalcification, but no breakthrough has been achieved. The UK is using soft composites to make bionic artificial heart valves. Many countries are also studying tissue-engineered heart valves, but they are still in the laboratory stage. There are about 20,000 replacements of artificial heart valves in China each year, of which 70% to 80% are imported valves. Domestic Beijing Star Medical Devices Company and Lanzhou Flight Control Group Company produce roll butterfly flaps. Recently, these two companies and Shanghai Jiuling Medical Device Co., Ltd. have developed a double-leaf mechanical valve, which is in the clinical research stage. At the same time, Beijing Bairensi Bioengineering Co., Ltd. has developed a central flap and a pig heart flap, and strives to change the phenomenon that the use of biological flaps in our country is very low (about 5%). Southwest Jiaotong University is studying to improve the anticoagulant performance of mechanical flaps by spraying TiN ₂ and TiO on an isotropic carbon surface.

Type of artificial valve

Artificial valves are divided into two categories according to the materials used: one is called mechanical valves made entirely of artificial materials; the other is called biological valves made entirely or partially of biological tissues. Whether it is a mechanical valve or a biological valve, its basic structure includes a metal valve frame, an obstructing body and a suture ring. The metal valve frame is generally made of stainless steel, titanium, cobalt-nickel alloy or other super-hard metals. The suture ring is the part that sew the artificial valve to the human heart annulus. It is made of knitted material. Polypropylene and polyester have been used. , Teflon, and carbon fiber in recent years. Biological valves are generally made of porcine aortic valve and bovine pericardial valve.

Mechanical prosthetic valve

Mechanical valves are all made of artificial materials, including spherical valves, oblique disc valve and two-leaf valve. The spherical valve is a valve that is moved by the ball in the stent. In 1952, Huf nagel was first applied to clinical patients, which is a spherical valve. The spherical valve has a simple structure and few failures, and it can receive good clinical results in the early stage. Therefore, the clinical application of artificial valves can be considered to be started with a spherical valve. However, in the late 1960s, due to the development of the oblique disc valve, and the development of the two-lobed valve in the late 1970s, spherical valves are now almost no longer used.

At present, there are two types of mechanical valves: double leaf valve and single leaf valve, both of which are disc valves. The imported valve is generally a double-leaf valve, while the domestic valve is a single-leaf valve, that is, an oblique disc valve. The oblique disc valve is a door that opens and closes like a gate. It can get more central mainstream than the spherical valve, and the fluid resistance is also small. The disc is supported by the stainless steel bolt that can not fall off. The circular plate is made of graphite coated with carbon and treated with hot carbon, which has excellent antithrombotic properties, and is superior to spherical valves in terms of antithrombotic properties. The representative of the oblique disc valve is the Bjork-Shiley valve, which has been used since the late 1960s. After several model experiments, Monostrut valve is now its main representative. In addition, this valve also has Omnicarbon valve and Medtronic-Hall valve.

Bilobular valves are two semicircular valves that are opened and closed by folding leaves, which increases the opening area more than oblique disc valves. The blood flow of the double leaflet is advection, and the effective opening area is relatively larger. The single leaflet is eccentric blood flow, and the noise of the double leaflet is generally smaller than that of the single leaflet. In order to get closer to the central mainstream, the St-Jude Medical (SJM) valve, which was designed and used in 1977, is its representative. Later, it developed Edwards Duromedieus valve and Carbomedics valve for clinical application.

Bioprosthetic valve

There are three types of biofilms: homogeneous valve, heterogeneous valve and tissue valve. The same kind of valve is a cryopreserved human aortic valve, and it is now considered to have antithrombotic and anti-infective properties; a heterogeneous valve is used to fix porcine aortic valves with malondialdehyde, and it has been used clinically since the 1970s. Clinical follow-up has confirmed that the biological valve has better antithrombosis than the mechanical valve, but it is easy to cause calcification, and the mechanical strength is not as good as the mechanical valve. Therefore, the second-generation biological valve developed using low-pressure fixation methods, improved valve installation methods, and inhibition of calcification has also been clinically applied. On the other hand, the tissue valve is a heterogeneous valve that sutures the bovine pericardium to a graft stent, and can obtain excellent valve function. However, it is known to have lower performance than the heterogeneous valve in terms of durability time and valve calcification. .

At present, artificial heart mechanical valves have good durability but they are prone to thrombosis, and patients need anticoagulation for life after operation. Although patients with biological valves do not need to take anticoagulants, due to the calcification problem of biological valves, Short life. The crux of these problems is precisely to find a material for making heart valves that does not require anticoagulation and has a long service life. Tissue engineered heart valves are still only in animal experiments. Their clinical effects are still difficult to determine. There is still a long way to go to research the materials for making ideal heart valves.

Pros and cons of prosthetic valves

The use of mechanical or biological valves during valve replacement is an important choice. Generally, there is no big difference between the two in terms of valve function. In terms of antithrombotic properties, biological valves are significantly superior, and mild anticoagulation can be used. For its advantages. However, the bioprosthetic valve can be damaged and calcified 6 to 7 years after its use. The mechanical valve has excellent durability and does not need to worry about calcification. For example, if strict anticoagulation therapy is not used, the high incidence of thrombosis may also cause the risk of cerebral hemorrhage due to the use of anticoagulants. In addition, due to the structure of the valve, the mechanical valve has a reverse flow when the valve is closed, so there is also a problem of progressive anemia due to hemolysis.

It can be seen that mechanical valves and biological valves each have different lengths. Nowadays clinically, they are often selected and used according to the state of the patient. Although biological valves are the first choice for young women who wish to give birth and patients older than 70 years of age who are unable to undergo adequate anticoagulation therapy, mechanical valves are also the first choice. Japan now uses more than 5,000 artificial valves each year, and more than 94% of them are mechanical valves.

Precautions for Prosthetic Valve Surgery

The first three months after prosthetic valve replacement surgery is an important stage to overcome surgical trauma and recover physical fitness. Pay attention to the following:

Continue to take a variety of drugs prescribed by your doctor on time. Commonly used drugs include anticoagulants, cardiac diuretics, and antiarrhythmic drugs.

Learn to adjust the dose of anticoagulant medicine yourself. Due to individual differences, the dose of anticoagulant required by each patient is different. The doctor has already figured out the anticoagulant dose of the patient at the time of discharge. The patient should be tested regularly after discharge to further adjust his anticoagulation treatment.

(3) Prevention of infection, especially respiratory tract inflammation, periodontitis, bloated skin, urinary tract infection, etc. Once found, it should be controlled in time. For intermittent or persistent fever of unknown cause, do not confuse doctors and use antibiotics arbitrarily. Seek medical attention in time to avoid delay in treatment.

Proper activity should be maintained after surgery in order to improve physical fitness and quality of life while recovering heart function. The amount of activity should pay attention to capacity and action, step by step, it is appropriate not to cause panic shortness of breath, it is not allowed to stay in bed all day.

Arrange your early self-cultivation life, keep your spirit happy, feel comfortable, optimistic and confident.

Do not eat in diet, pay attention to increase nutrition, supplement protein and vitamins. Should not eat too salty food. Patients with poor heart function should limit the amount of water they drink. It is not advisable to eat a lot of porridge and soups to avoid excessive fluid intake, increase the heart burden, and treat foods affected by anticoagulant drugs, such as spinach, carrots, and pig liver. Do not consume too much or for a long time.

Three months after the operation, you should go to the hospital for a detailed examination (including physical examination, electrocardiogram, chest X-ray, echocardiography, etc.), adjust the medication according to the results, and make health guidance for future life and work.

Prosthetic valve extended reading

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