Heterologous Arterial Biograft and Biological Material Treating Process

This invention generally concerns a biological graft and more particularly concerns the replacement of arteries and human veins by a heterologous arterial biological material-made tubular graft.

Two types of arterial grafts are currently known:

(a) biological grafts, comprehending: (i) saphena vein autografts and (ii) umbilical cord homografts and

(b) bovine carotid artery heterografts.

The saphena vein autograft is mostly used as its elastic structure, inner surface and inner diameter proportion remain unaltered. Saphena veins however not always can be used. The umbilical cord vein homograft is thicker and not so elastic and so is the bovine carotid artery heterograft.

We further have:

(c) DACRON (DU PONT's trademark) tubular prothetic and similar grafts, the patency of which (permeability or disobstruction condition) is highly inconvenient on account of inner smaller diameters.

To date, there is no arterial graft that may meet the requisites of patency, proportion, flexibility, etc., with the exception of the saphena vein autograft that not always is the most suitable solution (varices) nor always can be used by reason of saphenectomies formerly performed on the patient. Thus, a synthetic or heterologous arterial biograft to compensate for such deficiencies is needed, particularly a graft having a caliber comparable to the medium and small-sized caliber human arteries as a replacement for coronary arteries, should arterial autografts be not available.

This invention aims at overcoming the disadvantages of the above conventional technique, through a heterologous, arterial biological material tubular graft having characteristics of flow, patency, flexibility, inner wall surface homogeneity, inner diameter caliber and proportion to the wall thickness comparable to those of the receiving patient.

This invention also aims at covering the biological material treating process applicable to the preparation of the graft.

The detailed description below related to the attached drawings shall contribute towards making the invention known better:

FIG. 1: upper schematic diagram of the invented graft; and

FIG. 2: cross section schematic diagram through the FIG. 1's 2--2 line.

As FIGS. 1 and 2 show, the arterial biograft comprehends a smooth arterial duct (1) without internal valves, made of a heterologous biological artery, the branches (2) of which are bound together (3). The preferred heterologous biological artery pursuant to this invention is an animal internal mammary artery, preferably swine's or bovine's depending on the desired arterial caliber. Typically, the artery treated by the below described process keeps a natural elasticity ranging from 40% to 60%; an inner wall (4) homogeneity ranging from 0.5 mm to 1,00 mm and an inner diameter proportion to the wall thickness kept within a 9:0.5 mm to 7:1.5 mm range.

The biological material treating process as contemplated by this invention comprehends the taking of an animal artery--preferably a swine or bovine internal mammary artery--followed by the immediate binding (through micro technique) of every arterial branch, the duct as thus treated to be left to complete curing in an aqueous diabasic acid (succinic or glutaric--the glutaric acid to be preferred) aldehyde balanced solution. The aldeheyde solution concentration range shall extend from 0.001% to 3% approximately. The solution of this invention shall preferably comprehend both monomeric and polymeric free anhydride glutaric aldehydes, so that the monomer-polimer unsaturated alpha and beta polimer-free ratio be 3:1. The solution is them tamponed with Mg group ions--preferably Mg.sup.+ S.sup.- O.sub.4 ion--until a physiological pH (preferably above 7) is reached. This is a rather important feature for controlling the invention for it has been ascertained that, to keep the biological tissues duly preserved, the ionic power of the solution should be such that the existing ions--as spetrophotometrically proven--be kept between 230 .ANG. and 300 .ANG. approximately.

In addition, an ammoniated chlorined oxyde from an element--preferably iron or ruthenium--of the Periodic Table's group 8 meant to act as a biological tissue fixative is considered to specifically preserve the polysaccharide mucus and the proteoglycogen in the matrix and in the basal membrane, thus contributing to increasing the durability of the biological tissue. The invention concerns the application of an amount ranging from 0.02% to about 3% of the desired oxychlorate weight solution at a temperature higher than 10.degree. C. but less than the degradation temperature of the solution components and the biological material is to be left in the solution to curing until a satisfactory histopathologically controlled curing of the material is obtained. It should be clear that any improvement may be made to the material provided, however, that no deviation from the original inventive concept as above described and as hereafter claimed occurs.