1981-01-22
1983-11-22
Frinks, Ronald L.
A61F 124
Patent
active
044160283
DESCRIPTION:
BRIEF SUMMARY
This application is based upon International Application No. PCT/SE80/00161, filed June 4, 1980.
The present invention relates to a new type of blood vessel prosthesis for permanent or long-term implantation, which has clearly improved properties compared to previously used substitutes.
A variety of substitutes for pathologically changed, functionally important arteries and veins have been utilized in surgical treatment. Thus, either autologous material (such as superficial veins from the lower extremities), non-autologous biological material (such as chemically or physically treated blood vessels from other persons or from animals) or synthetic materials (such Dacron and Teflon.RTM. tubes having varying structures depending on method of preparation) have been commonly used. As substitutes for aorta and large branch arteries the synthetic materials have proved to give acceptable results. As substitutes for extremity arteries or arteries of a corresponding dimension the body's own veins have proved to give by far the best results. In many cases, however, the patient has no suitable vein material, and attempts have therefore been made to use a non-autologous material or a completely synthetic material. Such arterial reconstructions have, however, given inferior results. The factor above all contributing to the less favourable result is the absence of development of the specific inner coating characterizing a blood vessel, the intimal layer. The normal intimal layer consists of a cell layer, whose functions are on one hand to prevent the formation of intravascular thrombi (anti-thrombogenic effect), and on the other hand to provide for exchange of metabolic products between the blood and smooth muscle cells in the vascular wall. On the inner aspect of the hitherto used vascular substitutes no endothelium is developed, but it is coated by a layer of fibrin and sometimes connective tissue. The resulting surface certainly appears to be smooth but lacks potent anti-thrombogenic properties. There is therefore a risk for formation of a thrombus, which may obstruct the inserted prosthesis completely with serious ischemic consequences for the patient. Essentially the same conditions will apply when replacing pathologically changed veins.
Previous attempts to attain an inner endothelial coating on synthetic vascular prostheses have been unsuccessful. This problem has now been solved through the present invention.
It has been found that such an endothelial coating can be obtained by implantation of a vascular prosthesis composed of a completely or partially non-resorbable synthetic material, the inside of which is essentially covered by an inner wall construction of a resorbable material. To obtain the endothelium layer, the resorbable inner wall material should have such a porous structure that blood cells, such as erythrocytes and thrombocytes, may pass into or through it, so that it can serve as or define a growth zone or zones for the new tissue. Hereby a relatively thick and uniform layer of thrombotic material can be formed, building a scaffold for the proliferation of a endothelium coated muscle layer. Preferably the resorbable material is arrranged so that more or less continuous interspaces are formed within the resorbable material and/or between the resorbable and the at least partially non-resorbable materials. This can, for example, be achieved by spacing, preferably large, parts of the resorbable material from the non-resorbable material.
The resorbable layer or covering can be designed and applied in different ways. Thus, the resorbable material may, for example, be an inner tubular member, which is inserted into and fixed to the outer tubular prosthesis element of non-resorbable material. The inner tube may be formed of a coarse-to fine-meshed net, or may be a tube with perforated walls or walls having pores, etc. The resorbable structure may e.g. further consist of a fine wire structure protruding from or fixed to the outer tubular member or be another correspondingly porous structure of a resorbable ma
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patent: 3105492 (1963-10-01), Jeckel
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patent: 3463158 (1969-08-01), Schmitt et al.
patent: 4130904 (1978-12-01), Whalen
Bowald Staffan
Busch Christer
Eriksson Ingvar
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