MX2011013866A - Bioprosthesis of bovine pericardium. - Google Patents

Abstract

The present invention refers to a bioprosthesis of bovine pericardium for human use with a support or ring of titanium coated with a textile material, which is resistant, biocompatible and bioimplanted. The bioprosthesis of the present invention reaches a higher valvular area, since the biological tissue is not fixed to the poles of the titanium ring, thus avoiding ruptures, the fixation and sterilization of the biological tissue (bovine pericardium) being performed with a special aldehyde for sterilizing and fixing the tissue intended to align the collagen fibres, increasing the stress strength and the ductility thereof. The bioprosthesis is coupled in order to form a valve similar to the native valve and therefore having a behaviour similar to a natural valve, in such a manner that it is opened in a single direction for preventing the blood volume from escaping. The invention also comprises a method for manufacturing the bioprosthesis where a strategic step of the manufacturing meth od implies treating the bovine tissue with an amino acid solution specific for removing the aldehyde used for the sterilization, this preventing calcium from being adhered to the biological tissue of the prosthesis and delaying the calcification, this means that the amplitude of the valve is not reduced with the use.

Description

BIOPRÓTESIS DE PERICARDIO BOVINO Field of the Invention The present invention is situated in the field of cardiac prostheses. More specifically, the invention relates to those prostheses called "bioprostheses", which are made partially based on organic tissues (the leaflets, which are the moving part) and which are useful and suitable to be used to correct the haemodynamic problem caused by injury to any of the natural valves in humans.

Background of the Invention Bioprosthesis placement is one of the procedures used as a substitute for damaged natural valves. For hundreds of years, the clinic was able to diagnose valvular disease, even found, even without the research resources of today, the etiology of several of these diseases, such as rheumatic fever, but without finding any medical treatment at the time , nor less the surgical one. In his time, Leonardo da Vinci had observed the perfection of the aortic valve and even devised a glass model of said valve and its operation.

In the last century, the situation finally evolved, penicillin and other antibiotics were discovered and widely used, and anesthetic methods, blood banks and other advances that allowed more advanced surgeries were developed; thus the inventiveness and the technical resources, allowed later the development of ingenious methods to replace the diseased valves. Among these methods is precisely the use of cardiac prostheses for patients with valvulopathy. The first prosthesis that was used (1960) was a mechanical prosthesis -the one of Starr-Edwards-, large, bulky and that although it solved the hemodynamic problem, it subjected the patient to a series of complications that soon manifested, - in acute form, sometimes in two or three days - as thrombi formation on the prosthesis that could hinder the movement of the occlusion system or even close it completely, which was incompatible with life. Or that the aforementioned thrombus migrated and embolized to any place in the body (brain, abdominal, kidney, liver organs, etc.). In addition, the occlusal system of this first medium and long term prosthesis presented structural failures, because the cage that contained it fractured and migrated the sphere of that occluder or fractured the own sphere and also gave embolisms to diverse organs, and of course the valve was totally insufficient and the blood, instead of advancing backwards and this also was a mortal contingency. The immediate solution was to anticoagulate the patient, which in effect prevented the formation of thrombi, but this did not improve at all the mechanical problem of fatigue of the materials and these were still fracturing, in addition to the side effects of using anticoagulants they were also -and are- very important and if these are uncontrolled, in excess they can produce hemorrhages in any part of the organism or if on the contrary they are insufficient, in any case produce the described thrombotic phenomena.

Due precisely to these important problems that made the use of mechanical prostheses very risky, an alternative was sought. This was found in the first instance in the valvular homografts -of corpses- designed precisely to avoid the use of anticoagulants, but this did not turn out to be the ideal solution, since one of the problems was technical, since almost 20% of the patients were left with insufficiency. valvular, in addition to other very serious problems, such as the large number of patients who required this treatment and the small proportion of donors that were useful for that purpose, in addition to its rapid structural deterioration by calcification. To this it had to be added that the surgical technique for placing said grafts was more complex than placing a prosthesis and the learning curve takes time.

In the 70s there is a radical change and biological tissues are used with the use of artificial prostheses of this material, especially to shape the valves. This alternative had great worldwide acceptance because its manufacture was relatively simple and its reproduction and immediate results were good, but it always had against, like all the tissues used for heart valves at this time, not having a basic preparation that allowed to maintain its conditions of elasticity and strength, a situation that was unknown at that time.

However, faced with the evidence that biological tissues end up calcifying, for several years, many groups have been given the task of investigating the causes of it and therefore, the shorter duration of bioprostheses.

With the massive use in the 60 's and 70' s of mechanical prostheses and to a lesser degree biological, it was notorious that the bioprostheses had an undoubted advantage since they were more similar in their operation to the normal than the mechanical ones, especially of their first models, since these were very large and very thrombogenic, which forced from the beginning to use anticoagulants for life for the carriers of these prostheses. However, even the following two versions of mechanical prostheses, although improved in their design are still very thrombogenic and therefore their use is increasingly limited, being now the best indication for a valve change when required, to do so with a bioprosthesis. .

The main reason that mechanical prostheses are thrombogenic is that they alter the blood flow through the valves of the heart. Normally this flow is unique and central and mechanical prostheses transform it into multiple and therefore very turbulent, which favors the initial phenomenon of platelet aggregation whose result in a few minutes is the formation of a thrombus, followed by a clot, with the consequences already noted. Biological prostheses, on the other hand, maintain a more normal flow, also central and unique and therefore are not turbulent and do not necessarily require anticoagulation. The final result, from the hemodynamic point of view, is excellent and the quality of life of the patient also despite being a cardiologist, not being exposed to the risks of anticoagulation.

As already known, mechanical prostheses give three or more flow channels (depending on the model and brand) and a lot of turbulence when tested with contrast medium, while biological prostheses always give a large central flow with minimal turbulence.

In this regard, there are documents such as PA / a / 2002/010798, which describes a system and method for covering a heart valve prosthesis with splint with biological tissue, such as pericardium. The prosthesis includes a splint that is covered with a cloth material. A heart valve is placed inside the splint, with sutures the heart valve is secured to the fabric cover. One or more sheets of biological tissue are applied to the prosthesis with splint to cover all areas exposed externally of the fabric material. This type of prosthesis is coated with biological tissue such as pericardium and one or more sheets of said tissue are placed. However, the shape of the prosthesis or the origin of the tissue with which it is coated is not described. This model is only experimental and has never been used for clinical application, it is a purely mechanical model as shown in a photo of the scheme of that patent and it is so voluminous that it would be difficult if it were used in a human heart. One of the characteristics that have marked the advance in the design of cardiac prostheses, is to try to make them as small as possible, precisely so as not to be themselves an obstacle. In addition, as seen in the scheme of that patent, there is no definition in the proposed valve, because the ring is used interchangeably in a prosthesis with a metal disc, the same ring with two metal discs (in both straight situations) and finally in another with a curved metal disc, that is to say it is a ring of multiple uses, but of mechanical prostheses.

Also, document MX 284479 discloses a biodesigned vascular graft support prosthesis, prepared from clean tissue material derived from animal sources; the bioengineered vascular graft prostheses of the invention are prepared using methods that preserve the compatibility of the cells, resistance and bioremodelation capacity of the processed tissue matrix; Bioengineered graft prostheses are used for implantation, repair or in a host mammal. This type of bio-designed prosthesis is prepared from tissue derived from animal sources, however it is not specified what kind of animals are used, nor the risks or advantages of using one or the other in a preferential way. Likewise, patents X284480 and MX280238 disclose tubular graft prosthesis and flat blade graft with very similar characteristics.

Furthermore, US 7,972,376 protects a method for attenuating calcification in a bioprosthesis. However, there are two important points to consider: 1) the method consists of two parts, the treatment with a limiting agent such as an amine, an amino acid and aminosulfonate in combination with a reducing agent such as sodium borohydride and the dehydrating process the tissue with a glycerol ethanol solution. 2) The tissue used in the bioprosthesis is bovine pericardium tissue, therefore the novelty characteristic is lost in this last aspect. In this same sense the patent US 7,914,569 also protects the use of bovine, porcine, equine or other mammalian pericardial tissue, as well as synthetic or polymeric material. This document refers to an experimental technology and explicitly suggests not placing it in the heart, but in the ascending aorta. This type of placement of a prosthesis -not cardiac- has a unique antecedent in one that was placed by a German surgeon named Hupfnagel in the 50s before the advent of extracorporeal circulation who placed it in the descending aorta. The patient survived for a while, but eventually died. This example was not repeated anywhere. In addition, who made that drawing, lacks elementary anatomical knowledge, because it shows 4 vessels emerging from the aortic arch, when there are only three. It also shows 3 coronary arteries when there are only two, finally it shows three venae cavae - two inferior ones - when there are only two. Also this document does not refer to a valve for cardiac use, but as the same patent mentions, it is for vessels; the fact that he mentions that it can be used with any material to form the valves, means that none has been experienced and specified in a prosthesis that has had clinical use. As mentioned a little before, never again after Hupfnagel has such a prosthesis been used, so there is no evidence of its chances of success or failure.

Finally, documents WO / 1998/032400, WO / 2011/058385, US 6,719,790 and WO / 2010/042021 also refer to various types of prostheses such as those having an opening and closing mechanism, in which animal tissues are not used and which are used in or adjacent to blood vessels to improve blood flow; or those that increase the valvular lumen and serve as a mitral and aortic valve prosthesis, covered with any material compatible with the blood; or those that include valves made of fabric which are attached to the posts; or those that use valves made with any material biocompatible with the blood flow and that may or may not use a support in which the valves are sewn on the outside of said support. These patents reveal models proposed experimentally for no definite purpose, since it can not be said that they can be made of any material that is biocompatible, be it metallic or biological, just as they do not try to demonstrate their benefits or limitations. This type of patent reveals technologies that refer only to laboratory hypotheses without any practical application.

Summary of the Invention Given the aforementioned, it is an objective of this invention to present a bioprosthesis for use in human patients made of bovine pericardium, comprising a titanium support ring, which, being thin on its posts, allows a certain degree of flexibility that counteracts the stress of the blood pressure on the biological tissue, improving with this its resistance to structural deterioration and therefore, improving its useful life time. This ring is lined with a polymer textile material that has the advantages that it is resistant, biocompatible and bioimplantable, in addition to an improvement made by not fixing in the corners of the prosthesis a point that was technically designed to prevent failure valvular, but what produced was a decrease in the opening area of the valve by limiting the excursion of the leaflets, but which was also a risk point, because when drilling each valve in two places next to the commissures, it favored the possibility of that in the medium or long term, there would be a rupture of the tissue in that place. By placing said point not in front of the post, but behind it, a much larger valvular area is achieved, also avoiding a possible rupture since the valves are never pierced in the area exposed to blood stress.

Another objective of the present invention is to provide a bioprosthesis for use in human patients made from bovine pericardium, where the fixation and sterilization of the biological tissue is done with an already polymerized aldehyde, thereby achieving that the preparation of the tissue is optimal making that the collagen fibers are aligned, that bridges are formed between the various layers of the collagen of the pericardium, thereby increasing their resistance to stress and their ductility, in addition to avoiding rejection reactions.

Another objective of the invention is to provide a bioprosthesis for use in human patients made from bovine pericardium, which resembles a valve more similar to the native one and, therefore, have a behavior similar to a natural valve, both in relation to the type of flow that produces, as their hemodynamic conditions of pressure gradients, volume of both expenditure and leakage.

A further objective of the present invention is to reveal a bioprosthesis that faithfully reproduces the flow mechanism of the natural heart valves, that is to say that unlike - - of the prosthesis that totally disrupt the blood flow turning it turbulent, our prosthesis does maintain the unique and central cardiac flow, which makes its behavior natural and hence it is not necessary to anticoagulate the patient.

Description of the Drawings of the Invention Figure 1 shows the titanium support or ring that functions as a support for the bioprosthesis according to the present invention.

Figures 2a and 2b show the fixation of the liner based on polymeric material on the titanium support or ring and the introduction of said polymeric lining into the titanium ring.

Figures 3a and 3b show the bioprosthesis according to the present invention, wherein the bovine pericardium tissue has already been placed in the titanium support or ring (3a) and where the silicone ring that fits the bioprosthesis is shown if the prosthesis is mitral type (3b).

Figure 4 shows an embodiment of the bioprosthesis according to the present invention of the aortic type.

Figures 5a and 5b show an example of the application of the bioprosthesis according to the present invention, where a large cardiac growth is observed on the day of surgery (5a) and several months of use of the second prosthesis (5b), decrease in size from the heart.

- Figures 5c and 5d show an example of a patient before and after using the bioprosthesis according to the present invention.

Figure 6 shows the flow in a hydrodynamic test during the operation of the bioprosthesis according to the present invention.

Detailed description of the invention For the manufacture of the bioprosthesis according to the present invention, a one-piece titanium support or ring is selected as shown in Figure 1, and it must be lined with a dacron-polymer.

This ring is made up of the following elements that are identified in Figure 1 as follows: 1- Posts 2- Valley curved between the posts 3- Holes to fix the Teflon and the pericardium to the post, to the external part of the prosthesis 4- Orifice at the end of the post to fix the Teflon and the pericardium to the post 5- Side holes in each base of the valleys, to fix the pericardium to the post 6- Bottom edge The particularly dacron polymer material uses its weft in the vertical direction. To fix the pericardium to the post, a teflon strip is used, slightly less wide than the post, as can be seen in Figure 2.

The dacron, which is originally a plate and which is a synthetic fiber based on polyesters obtained by the action of an acid on an alcohol, is joined at its ends to form a cylinder, this is bent at one end 2.5 cm. , as shown in Figure 5, on itself, leaving the rest of 2.5 cm to form the mitral fixation ring, this is the one that will fasten, with a suture, the prosthesis to the patient's ring; This measure of 2.5 cm is the same for all prosthesis sizes.

Then the metal ring is placed in the middle of the 2 fabrics of the folded segment, with the ends of the poles directed to the blind part of the fold, the outline of the ring is marked, achieved which is removed and proceeds to close, with a suture the two fabrics following the marked outline of the posts. Once this maneuver is completed, the excess is cut between the posts giving the shape of the ring, the dacron is inverted, which already has the ring shape, leaving the seams inside (Figure 2a).

The titanium ring is introduced into the dacron lining by placing and adjusting each post one by one carefully, once adjusted, proceed to make a suture line at the base of the ring to close the cover, as shown in Figure 2b.

To make an aortic ring, the dacron is cut with the horizontal frame, the same procedure is performed as for - - the mitral ring until the closure of the sheath, leaving for the 7 mm aortic support ring, placing a suture line on the edge of the dacron, once the lining of the ring, mitral or aortic, is finished, it is washed with enzymatic soap and water demineralized, dried, packed and sterilized in ethylene oxide.

The bovine pericardium with which the valves are made, is obtained from the authorized and controlled trails by corresponding sanitary authorities, which ensures that it fills the cleaning and quality requirements. They are obtained by personnel trained for this purpose; The first trace of the grease and other impurities that could have been washed with sterile saline is done on the trail itself. It is transported in a container treated with special antiseptics and immersed in sterile cold saline at 4 ° C. Afterwards, in a clean room with sterile clothes and gloves, he does a deep cleaning, discarding the pericardies that present irregularities and preserving only those that are in good condition. Once clean, they are placed in sterile containers with the 0.6% glutaraldehyde (GA) solution, placing each pericardium in a single frame, so that the tissue is always on both sides in contact with the GA, since To be very thin (between 250 and 500 microns), there is the possibility that some of their faces are not always in contact with the GA and 30 minutes are left in said frame, after which the edges are cut that are always irregular before removing them from the aforementioned frame and this leaves very regular plates of the pericardium; the total time of stay in glutaraldehyde is 44 hours. After this time, they are removed from the GA solution, washed three times in sterile saline in a laminar flow hood, of course all in a sterile environment and subjected to the anticalcifying system solution (0.05 molar glycine). for an hour. Rinse again - always in the laminar flow hood - three times with sterile saline solution, place in sterile containers (in groups of 5) in the 50% glycerin preservative solution and store until used. for the manufacture of prosthesis.

Subsequently, the biological tissue is placed in the ring or titanium support to form the valvular mechanism, composed of three symmetric valves. This procedure is performed in sterile area and of course with sterile techniques.

The biological tissue is selected, which is homogeneous, making sure that it has no defects; The biological tissue is cut according to the diameter of the selected ring.

A rectangle is cut in one piece (Figure 2) once the fabric is cut it is divided into equal thirds and a reference is placed in each third, the rectangle is joined by suturing the fabric forming the short ends and a cylinder is formed, this It is placed on the ring covered by the external part forming 3 valves (Figure 2b), fixing the pericardium on each post with Teflon tape on the outside. At the top of each post-external side-a fixation point is placed taking teflon, pericardium and dacron from the lining of the ring, fixing this set to the post; The same procedure is performed for the 3 posts.

This procedure to fix the points by the external part, is one of the points in which it has been improved and which are innovative and vital to make this prosthesis have a better hemodynamic behavior and to increase its useful life time. First, because the point that was made in these prostheses to prevent the poles from leaking (insufficiency), limited the total opening of the prosthesis (effective valvular area) and as mentioned before, it was a risk point, because when crossing with a point (double) each leaflet, the tissue was perforated and with the constant stress of the blood flow it sometimes came to break, which made it urgent to reoperate the patient. With the point on the outside, the effective valvular area is automatically increased and the possibility of rupture is definitely avoided.

Once the fixation of the 3 posts is completed, the valves are adjusted by the external part of each post, a suture line is made at the base of the ring, fixing the pericardium to the ring, to cover the suture line, the Teflon tape on each post, fixing it with stitches on each side of it, the dacron and the remaining pericardium are trimmed and the pericardium is attached to the dacron at the base of the ring (Figure 3a).

If the prosthesis is a mitral type, a preformed silicone ring is placed around the ring and wrapped with the dacron, adjusted and fixed with a suture line taking pericardium and dacron as shown in Figure 3b. This ring is parallel to the lower edge of the prosthesis which, as already specified, is flat.

If the ring is for manufacturing an aortic prosthesis, the procedure is similar, but the ring is not on the lower edge of the prosthesis, but a little above the lower edge, this in order that the remainder of the ring the prosthesis, fits inside the patient's ring and it is not above that plane as shown in Figure 4.

Subsequently, for both types of prosthesis, a pericardial strip of .5 cm is cut. and it is fixed to the clamping ring as a control for taking cultures, it is packed in a bottle with a conservative solution, it is closed well and it is kept in a sterile bag, sealed and the label containing the data corresponding to the prosthesis is placed manufactured, the log must contain the same data.

Specifically, the innovations that can be proven in this bioprosthesis are four fundamentally: The first, that the poles are narrower than in the biological prostheses with metal ring of previous models, which allows some flexibility to reduce the pressure stress of the blood flow. This phenomenon has managed to increase the useful life of the prosthesis in several years. This is a phenomenon that has been demonstrated in clinical practice, since the implementation of this model (1983), in more than 3900 prostheses, the useful life went from 8 to 10 years on average, to be currently 14 to 15 years.

The second innovation derived from the effect of removing the point in the leaflets in the vicinity of the poles, is to avoid that at that site with the permanent stress of blood flow and pressure, the tissue undergoes structural deterioration and fracture. Since this change (more than 1200 prostheses) has been used, none has been broken due to the aforementioned stress.

A third innovation is to significantly increase the effective valvular area, as mentioned above. The increase can be quantified in a figure between 5 and 10%, which is a very positive effect, especially when prostheses are placed in normally small areas such as the aorta, since the increase of the valvular area in this site is essential to avoid well-known phenomenon - and feared by surgeons - the so-called "patient-prosthesis disproportion" in which a patient is placed a small prosthesis for their needs and the prosthesis can not provide the necessary blood flow for their weight, age and activities .

When this happens, a more complex and risky operation has to be done to increase the size of the aortic annulus that will receive a prosthesis, with this procedure, larger. With the expansion of the valvular area with this innovative modification, this is avoided, giving the patient a larger valvular area without the need for more complex surgeries.

The fourth is that of presenting, in addition to an effective valvular area larger than the generality of the prosthesis, it is that above all, it allows and maintains always a unique and central flow as in natural valves, which is why anticoagulation is not necessary. .

Application examples Figures 5a and 5b show an example of the application of the bioprosthesis according to the present invention several months after surgery, where Figure 5a shows a large cardiac growth on the day of surgery (the esophagus is very deviated by the growth of the heart) and in Figure 5b several months later, in addition to the prosthesis, decreased heart size. In figures 5c and 5d another example of a patient with large cardiomegaly is shown and at 10 months, said cardiac growth has decreased markedly, which results in significant improvement in the patient's symptomatology. See also Figure 6 where the performance of a bioprosthesis in a tester is shown in a hydrodynamic test demonstrating how it produces a single flow.

The native valves, which are four, of the heart work in a similar way, since they open in only one direction, allowing the blood volume to advance, but not backing up. Two of them are totally intracardiac - the mitral and the tricuspid - and are called atrioventricular valves because they communicate the upper part of the heart -auricules- with the lower one -ventricles-. The mitral valve consists of two valves and the tricuspid valve of three. The other two valves are located at the exits of the heart towards the great vessels, the aorta and the pulmonary; both are composed of three valves. When the atrioventricular valves open to let the blood that has collected in the atria pass through, the second, those of the great vessels remain - - closed, to let the right and left ventricles fill with blood. When the atria are full, they are emptied into the ventricles by two mechanisms, one by gravity and the other by contraction of the atria. When the ventricles are full, the contraction mechanism of them is activated, which automatically closes the mitral and tricuspid valves and opens those of the great vessels, allowing the blood to leave the heart. This is called cardiac cycle in general and this happens to each other with a duration of about 780 milliseconds and with a heart rate of 70 to 80 cycles per minute. When one of these valves gets sick, it can follow two paths, become smaller (stenosis) or larger (insufficiency).

Between these two forms of valvular pathology, there are all possible ranges of these two forms of injury, but the result is that in both or the blood is returned (insufficiency) and passes in a small amount and with difficulty (stenosis), and therefore the volume that the heart can expel decreases proportionally to the degree of injury of these valves, resulting in a series of clinical manifestations and, of course, compromising the health and life of the patient with this condition.

The way to surgically correct these injuries has gone through several stages, but one of them remains as fundamental, the reconstructive valvular surgery, which had its peak when it was already possible to have access to the interior of the heart (1953) and as there were no prostheses It was indispensable to invent reconstruction techniques. The other way, when the valves are so damaged that they can not be repaired, it is - - to replace diseased valves with a prosthesis. Between the two varieties of prostheses the mechanical and biological, time has been the best decanter and although the first prostheses were mechanical, over time the biological ones have been shown to be very superior in many aspects, such as hemodynamics, since the biological ones simulate the natural flow of heart valves, single flow, central that the mechanics sometimes produce up to 6 channels of flow and therefore cause a phenomenon called shear stress (known generally as turbulence) whose final result is a chaotic flow that ends up producing a thrombus and a clot.

In general terms, all current biological prostheses have a similar shape and situation, but the details that allow improving the benefits are those that can make them more efficient and make them last longer.

Prostheses that have a metallic or polymeric support ring are generally more rigid and this means that the stress they undergo during millions of cardiac cycles over time, in certain well-known places, suffer a certain degree of structural deterioration that can reach to the rupture, especially when points are placed in the corners to prevent insufficiency in those places.

If the posts are thinner, as is the case with the prosthesis according to the present invention, they have a certain mobility in each cardiac cycle, which allows to reduce that stress. It has been proven to make these biological valves with various materials, such as complete porcine valves - mounted on a support ring, but these calcify faster than those of pericardium and also their hemodynamic behavior is not as good as they offer more resistance and a quality test parameter, the gradient that produces this type of valve is usually higher than the pericardium. The normal gradient in a normal heart valve is around 3-5 mm of mercury. Mechanical prostheses produce gradients of 8-10 mm (depending on the size, because the smaller a prosthesis, the greater the gradient); Biological prostheses also produce gradients of 3-5 mm, that is, the same as a natural valve. The prosthesis according to the present invention, even after several years of use, maintains equal figures, a sign that they do not suffer calcification in the medium and long term.

The phenomenon of structural failure by calcification is also a generic problem for bioprostheses. This phenomenon is inherent to humanity and occurs in general with age as many other phenomena of aging occur. This process of calcification occurs in virtually all arteries of the human economy (brain, peripheral arteries, heart, abdominal organs, etc.). Thus, if a foreign attachment is placed on the organism, as in the case of cardiac prostheses, especially if it has biological elements, it is normal that this phenomenon occurs over time. Therefore, all the studies of the groups that produce bioprostheses, are aimed at improving the hemodynamic performance and above all to reduce or avoid this dreaded phenomenon of calcification. This is achieved in several ways. The first and most important, which has been mentioned before, is to make the prosthesis produce a flow similar to the normal one in the bloodstream, that is, a Newtonian flow, a laminar flow. Until now, a mechanical prosthesis has never achieved it, but bioprostheses have. To do so, we must make the leaflets (three in all current models) behave like the natural leaflets (the heart has four valves and of them, three have three valves and only one, the mitral, has two). Therefore these leaflets have to make their complete excursions, both to open and close and for that they have to have the exact size according to the diameter and height of the prosthesis (of course this is variable for each size of prosthesis). Therefore it is important that the prosthesis have no obstacles in the leaflets that limit these movements and therefore the fixation points should not be placed in the corners in front of the post, but on the outside of these and therefore of the prosthesis, such and as proposed by the bioprosthesis according to the present invention.

Finally, the internal diameter of the prosthesis should be as wide as possible (effective valvular area) and if there are internal points in the corners, this area will not reach the indicated.

Claims (8)

REIVI DICACIO ES Once the invention is described, what is considered novel and therefore its property is claimed is the following:

1. A cardiac bioprosthesis made with a biological tissue sterilized with an aldehyde, characterized in that it comprises a titanium support ring on which the biological tissue is fixed and which is lined with a synthetic fiber material based on polyesters that is resistant, biocompatible and bioimplantable; and that also includes thin posts, a curved valley between the posts; holes to fix the biological tissue to the post using Teflon on the outside of the prosthesis; a hole at the end of the post to fix the biological tissue to the post using Teflon; lateral holes in each base of the valleys to fix the pericardium to the post and a lower edge.

2. The bioprosthesis according to claim 1 wherein the biological tissue is bovine pericardium and the synthetic fiber is dacron.

3. The bioprosthesis according to claim 1 wherein the biological tissue is previously sterilized with glutaraldehyde (GA), thereby also achieving that the collagen fibers in the biological tissue are aligned and bridges are formed between the various layers of the collagen of the pericardium, increasing with this its resistance to stress and its ductility, also avoiding reactions of rejection in the organism.

4. The bioprosthesis according to claim 1 wherein the biological tissue is fixed with a point behind the posts of the titanium support ring, thus achieving a much larger valvular area, also avoiding a possible rupture since the valves of the bioprosthesis are not perforated in the area exposed to blood stress.

5. The bioprosthesis according to claim 1 wherein the titanium support ring, being thin in its posts, allows a certain degree of flexibility that counteracts the stress of the arterial pressure on the biological tissue, improving with this its resistance to structural deterioration and for both, improving its useful life time.

6. The bioprosthesis according to claim 1, characterized in that it faithfully reproduces the flow mechanism of natural heart valves and therefore has a behavior similar to a natural valve, both in terms of the type of flow it produces, and its hemodynamic conditions. pressure and volume gradients, both of expense and leakage.

7. The bioprosthesis according to claim 1, characterized in that it does not disrupt the blood flow since it maintains the non-turbulent laminar flow as it resembles the natural heart valves, being suitable for use in human patients.

8. The bioprosthesis according to claim 1, characterized in that it faithfully reproduces the flow mechanism of the natural heart valves, since it maintains the single and central cardiac flow, which makes its behavior natural, making it unnecessary to supply anticoagulants to the patient who carries it. SUMMARY OF THE INVENTION The present invention relates to a bioprotesis of bovine pericardium for use in human patients with a support or ring of titanium lined with a textile material, which is resistant, biocompatible and bioimplantable. The bioprosthesis according to the present invention achieves a much larger valvular area since the biological tissue is not fixed on the posts of the titanium ring, thus preventing ruptures and the fixation and sterilization of the biological tissue (bovine pericardium) is done with a special aldehyde for sterilize and fix the tissue causing the collagen fibers to align, increasing their resistance to stress and their ductility. The bioprotesis according to the present invention is coupled to form a valve similar to the native one and thus have a behavior similar to a natural valve, in such a way that it opens in only one direction and does not let the volume of blood escape. The invention also comprises a method of manufacturing the bioprotesis wherein a strategic step of the manufacturing method involves treating the bovine tissue with a solution of a specific amino acid to remove the aldehyde used for sterilization, thereby preventing it from being fixed. calcium in the biological tissue of the prosthesis and delaying calcification, which means that the amplitude of the valve is not diminished with its use.