Vascular prosthesis

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A vascular prosthesis is an implant , i.e. a medical product that is permanently inserted into the body for therapeutic purposes , to replace natural blood vessels . It is usually used as a so-called interposal to replace severely damaged vessel sections, for example in the event of injuries ( trauma ), chronic narrowing or blockage of vessels due to arterial occlusive disease , pathological severe enlargement ( aneurysm ), or an aortic dissection . In addition, vascular prostheses are also used for bypass operations when a sufficiently large endogenous blood vessel cannot be used. They are primarily used to treat damage to arteries , and less often to replace veins .

Material and application

Aortic endoprosthesis ( MS-CT image)

Vascular prostheses are usually made of plastics such as polyethylene terephthalate (PET, brand name Dacron ) or polytetrafluoroethylene (PTFE, brand name Gore-Tex®). PET prostheses are mainly used for large vessels with a high flow rate and low resistance, such as the aorta , the inner and outer pelvic arteries and the femoral arteries , while PTFE prostheses are used in particular for smaller vessels and as a bypass. Vascular prostheses are designed in the form of tubes , prostheses made of PET have a folded structure that is comparable to the bellows of an accordion . This ensures a corresponding flexibility of the prosthesis, through which the Windkessel effect of natural arterial vessels is mimicked.

In the early days of vascular prostheses in particular, they had to be soaked with the recipient's blood to seal them before the operation , which is known as preclotting . This step is not necessary with PTFE-based prostheses or with PET prostheses that have already been sealed by the manufacturer by applying a protein layer . For example, albumin , collagen or gelatin are used as their denatured form. In the period after implantation, the inside of the prosthesis is lined with a layer of blood platelets and fibrin , which is called pseudointima, analogous to the intima of natural blood vessels. In about ten to 15 millimeters long area of the anastomosis called stitched connection between the prosthesis and the natural vessel beyond a called neointima formed endothelial layer .

Chances of success

Five to ten years after implantation, around 90 percent of the prostheses in the area of ​​the aorta and the adjacent vessels still work, while prostheses with a diameter of less than six to eight millimeters have a success rate of less than 50 percent after five years. The prospects for short-term and long-term functioning are generally lower, the higher the flow resistance in the implant area.

The most common complications after the use of vascular prostheses are their blockage ( occlusion ) due to excessive tissue formation in the area of ​​the neointima ( hyperplasia ) or due to the detachment of parts of the pseudointima, infections of the implant, problems with the material structure, and the development of aneurysms and pseudoaneurysms in the area of ​​the anastomosis.

Historical information

The first successful use of vascular prostheses in humans took place in 1952. They have been used routinely in vascular surgery since around the mid-1960s . Currently, vascular prostheses in medicine represent one of the most successful applications of implants made of biomaterials in terms of their therapeutic benefits .