GB1584332A - Implantable valvular heart prosthesis - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO AN IMPLANTABLE VALVULAR HEART PROSTHESIS (71) I, URSULA SAARIKOSKI, an Italian citizen, of Via M. Macchi, 75, Milan, Italy, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention concerns artificial heart valves and, more particularly, an implantable heart valve with a reduced lateral section obtained from the heterologous aortic valve of a pig.

Artificial heart valves that can take the place of natural ones when impaired or diseased, have already been known for some time. These artificial valves that are the most wide-spread cardiovascular protheses at present can be divided into two groups, the mechanical valves and the socalled biomorphic ones. The mechanical valves can in turn be fundamentally divided into ball valves with a freely moving component and "hinge" valves in which blood flow is regulated by the unidirectional opening of a hinged disc.

Although such artificial valves are an unreplaceable aid for heart protheses, most of them and, to be exact, the so-called ball valves, are simple from the structural and constructional point of view, but present the disadvantages of traumatic hemolysis and/or thromboembolism. For these reasons the so-called biomorphic valves made of soft material of artificial or preferably animal origin are becoming more popular.

In these such disadvantages are reduced to a minimum, thanks to their physiological functioning and, particularly in valves with flexible components of animal origin, to their anatomical and physiological affinity to the living tissues alongside which they are to function.

Among the biomorphic valves there are heart valves made of hollow cylindrical support in a firm but pliant inert textile material which encloses a more rigid structure of the same conformation having a first border provided with at least two cusps or centripetal leaflets and a second opposite border that constitutes a padded perimetrical outer rim. Both such borders are soft.

A heart valve of animal origin, preferably that of a pig, is sewn to the above-mentioned first border and constitutes the valvular component itself. Such valves are constructed after those of Hancock and are provided with characteristics features that solve various problems of construction.

manner of emplacement etc. However, they invariably have the aforesaid cusps or centripetal leaflets. These must necessarily be flexible to allow for blood flow. Therefore, owing to the presence of such cusps that constitute the commissural supports for the undulating leaflets of the aortic valve of animal origin, the prothesis must be placed in such a way that the valve itself is directed towards the ventrical. Such positioning of the prothesis, when replacing a mitral or tricuspid valve, can cause partial or total obstruction of the ventricular outflow tract. Furthermore, the protruding part may touch the interventricular septum or other intraventricular structures.

Although all Hancock valves, and those in particular those described above, are free from the disadvantages of the mechanical valves (that is to say mainly thromboembolism that requires the permanent use of anticoagulant therapy) it should be stressed that the length of life of such valves has not yet been fully ascertained.

Therefore studies have been carried out so as to obtain longer life and also improvements in connection with the side effects on patients. These studies resulted in numerous implantable protheses made from pigs' valves of different sizes being devised.

Anatomical and physiological researches with special regard to valves with a diameter between 15-25 mm. at the level of the aortic annulus or spur have been thoroughly carried out and the results supported by corresponding clinical observations.

Following these researches a new implantable artificial heart valve has been conceived and constitutes the subject of this invention. According to the present invention, there is provided an implantable artificial heart valve which comprises a hollow cylindrical support body formed of a physiologically inert pliant fabric surrounding a semi-rigid reinforcement structure of like shape formed of a physiologically inert plastics material, the cylinder housing therein a heterologous aortic valve of animal origin which retains its semilunar cusps, the distal or outflow margin of the said support body having an undulating contour. A valve constructed according to this invention allows total elimination of the above-mentioned commissural supports of Hancock valves and is free of the aforesaid inconveniences, that is to say obstructions and unwanted contact with intraventricular structures. In particular, the features of a valve constructed according to this invention as compared with valves attributable to Hancock and others are small size that allows the valve, when being implanted, contrary to the other valves, to be directed slightly towards the atrium, the direction of which is completely towards the ventricle. The features now mentioned allow for the assembling of a heterologous valve in mitral position within a support only 14 mm high.

This invention will now be described in greater detail, by way of example only with reference to the accompanying drawing, in which: Figure 1 is a side view of a valve constructed according to this invention; and Figure 2 is a topographical view of the valve shown in Figure 1 seen with its proximal border in the foreground.

Referring to the drawing, it can be seen that a valve constructed according to this invention comprises a cylindrical support (1). This is constituted by an internal semirigid reinforcement structure in plastics material suitable for medical use, such as polypropylene or polytetrafluoroethylene contained inside a soft body covering formed of a close-knit fabric, such as jersey-knit fabric formed of inert fibers suitable for medical use, for example, polyester fiber. The hollow cylindrical support (1) has an annular thickening region (2) around its circumference. The cylindrical body (1) terminates at one end in a rounded marginal region (3) that constitutes the proximal part of the bioprothesis. At its opposite end, the cylindrical body (1) is formed with a marginal region (4) of scalloped or undulating peripheral form which is intended to correspond to the undulating contour of the aortic ring of a pig's aortic valve. This marginal region (4) constitutes the distal part of the bioprothesis.

Both marginal regions are so formed as to support, by means of a stiching (5), the heart valve of pig comprising three concentric leaflets (7,8,9) making up a circular section, and separated from one another by the corresponding natural commissures.

As one can see from the drawing the overall height of the implantable valve constructed in this way is about half the opening diameter that is produced when the internal commissures open.

It is evident that, in relation to the valve opening, such a valve height is a clearly reduced encumbrance and does not impair the proper functioning of the heart into which it is implanted. One should bear in mind that the stitching for the fixing of this valve unit is within the outermost circumferential margin of the valve. Ventricular penetration of the whole is therefore extremely reduced, as the bioprothesis constructed according to this invention in contrast to those known hitherto is directed slightly towards the atrium, reducing its ventricular projection to a minimum. It is evident from these explanations that, with a valve constructed according to this invention, it is possible to retain the aortic spur or annulus intact. Such an annulus is a circular formation of connective tissue from which the three commissures originate, directed towards the centre. The retention of this annulus has the very important function of stiffening the valve and excessive bending of the aortic cusps is avoided during opening, contrary to the Hancock and similar valves, for which also the sinuses of Valsalva must be eradicated.

Furthermore, the presence of the aortic annulus confers more resistance to the commissures against the trauma they undergo during closing. The preservation of the sinuses of Valsalva is considered important for the proper functioning of the aortic valve and to avoid possible abnormalities or defects of coronary artery circulation.

The preservation of the normal anatomical connections, particularly between the plane of the aortic annulus and that of the commissures, is an important benefit achieved when using a valve according to this invention. This avoids excessive traction of the commissures, which can happen when valves are provided with commissure supports. This is certainly a factor of great importance for the life of the bioprothesis.

As above-mentioned, the implantable valve constructed according to this invention represents the result of thorough anatomical and physiological studies on the valves of pigs related to corresponding clinical observations on implanted Hancock valves.

This allowed for progressive modification of the traditional valve prothesis while permitting preservation of normal functioning conditions, both for the purpose of surgical insertion of the whole commissure support, that is to say the commissures plus the aortic annulus, and for the purpose of achieving longer life. Such results are obtained thanks to a special shape and structure of this valve which is characterized by reduced lateral section, that is to say a reduced height in relation to its diameter and to the shape of its distal outflow border that follows the undulated contour of the annulus of the pig's aortic valve.

WHAT WE CLAIM IS:- 1. An implantable artificial heart valve which comprises a hollow cylindrical support body formed of a physiologically inert pliant fabric surrounding a semi-rigid reinforcement structure of like shape formed of a physiologically inert plastics material, the cylinder housing therein a heterologous aortic valve of animal origin which retains its semilunar cusps, the distal or outflow margin of the support body having an undulating contour.

2. A valve as claimed in Claim 1, wherein the heterologous aortic valve is a pig's valve and said distal margin possesses an undulating contour characteristic of that of the aortic annulus of a said pig's valve.

3. A valve as claimed in Claim 2, wherein the said reinforcement structure comprises an annular thickened region around its circumference, which thickened region is covered by a said fabric.

4. A valve as claimed in any one of the preceding claims, wherein said heterologous aortic valve retains its aortic annulus.

5. A valve as claimed in any one of the preceding claims, wherein said reinforcement structure possesses a maximum height which is substantially equal to half the maximum diameter of the opening of the semilunar cusps.

6. A valve as claimed in any of the preceding claims wherein the proximal margin is of rounded form in the radial direction.

7. A valve as claimed in any one of the preceding claims wherein said fabric is a knitted fabric 8. An implantable artificial heart valve, substantially as hereinbefore described with reference to, and as shown in, the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. achieving longer life. Such results are obtained thanks to a special shape and structure of this valve which is characterized by reduced lateral section, that is to say a reduced height in relation to its diameter and to the shape of its distal outflow border that follows the undulated contour of the annulus of the pig's aortic valve. WHAT WE CLAIM IS:-

1. An implantable artificial heart valve which comprises a hollow cylindrical support body formed of a physiologically inert pliant fabric surrounding a semi-rigid reinforcement structure of like shape formed of a physiologically inert plastics material, the cylinder housing therein a heterologous aortic valve of animal origin which retains its semilunar cusps, the distal or outflow margin of the support body having an undulating contour.

2. A valve as claimed in Claim 1, wherein the heterologous aortic valve is a pig's valve and said distal margin possesses an undulating contour characteristic of that of the aortic annulus of a said pig's valve.

3. A valve as claimed in Claim 2, wherein the said reinforcement structure comprises an annular thickened region around its circumference, which thickened region is covered by a said fabric.

4. A valve as claimed in any one of the preceding claims, wherein said heterologous aortic valve retains its aortic annulus.

5. A valve as claimed in any one of the preceding claims, wherein said reinforcement structure possesses a maximum height which is substantially equal to half the maximum diameter of the opening of the semilunar cusps.

6. A valve as claimed in any of the preceding claims wherein the proximal margin is of rounded form in the radial direction.

7. A valve as claimed in any one of the preceding claims wherein said fabric is a knitted fabric

8. An implantable artificial heart valve, substantially as hereinbefore described with reference to, and as shown in, the accompanying drawing.