WO2004071333A2

WO2004071333A2 - A prosthetic ring for mitral valves

Info

Publication number: WO2004071333A2
Application number: PCT/IB2004/000539
Authority: WO
Inventors: Carlo Fucci; Daniele Obino
Original assignee: St. Jude Medical, Inc.
Priority date: 2003-02-12
Filing date: 2004-02-11
Publication date: 2004-08-26
Also published as: WO2004071333A3; ITRM20030060A1; ITRM20030060A0

Abstract

A prosthetic ring to be used for the surgical correction of insufficiencies of the mitral valve has the shape of a capital D and is made of a material with plastic properties such as to be deformable up to a pre-set limit of deformation with the application of forces in chosen points of the perimeter of the ring by the surgeon so that, in the installed position, it remains shaped according to the anatomical shape of the mitral valve.

Description

A PROSTHETIC RING FOR MITRAL VALVES Field of the invention

The present invention relates to a prosthetic ring to be used for surgical correction of insufficiencies of the mitral valve. Clinical experience has demonstrated the superiority of reconstructive surgery as compared to replacement surgery in terms of lower risk of thrombo-embolitis, endocarditis and ventricular dysfunction. State of the art

Mitral insufficiency is a cardiopathy corresponding to an anomalous dilatation of the fibrous ring of the mitral valve and to a deformation thereof. Remodelling of the fibrous ring is consequently a crucial step in the majority of methods of reconstructive surgery of the mitral valve. One of the most effective methods of treatment of this pathological condition is surgery with the insertion of rings in the mitral valve. Prosthetic rings for reparative surgery of the mitral valve, which have been known for years, albeit in their diversity of shape, dimensions and structure, share the common aim of achieving, among other things, the following purposes: i) preserving the normal distance between the two fibrous trigons in order to prevent any obstruction of outflow from the left ventricle; ii) restricting and reshaping adequately the native ring in the posterior part by bringing forward the posterior leaflet and favouring co-optation of the leaflets; and iii) stabilizing the ring and the sutures in order to prevent any dehiscence of the sutures themselves and renewed annuiar dilatations.

There exist various known types of prosthetic rings for plastic surgery of the mitral valve, which may be classified schematically according to two criteria. The first criterion of classification is the one based upon the choice of the material used, whereby the materials are classified as rigid materials and elastic materials (i.e., ones that recover their initial shape after removal of a stress). It is known practice to define the degree of flexibility of the ring by means of insertion or otherwise of a rigid core inside a coating made of a fabric that is compatible with human tissue.

Also known to the art is a variant consisting of a flexible ring having wires or strands inside it, which enable modulation of the diameter and shape of the ring according to the tension to which the strands are subjected in order to render the ring more conformable to the size and shape of the mitral valve. In the case of rings characterized by high rigidity, the reduction of the dilatation of the native ring is achieved, but said high rigidity presents the disadvantage of opposing the natural flexibility, by resisting the natural movements of the wall of the heart.

On the other hand, very flexible rings do not prevent sufficiently the deformation of the fibro-muscular ring and do not enable satisfactory co-optation of the valve to be re-obtained. The second criterion of classification is the one based upon the shape, whereby the rings are classified as closed rings and open rings (the latter also being referred to as posterior rings).

A typical example of a closed ring according to the state of the art is illustrated in Figure 1. It substantially presents the shape of a capital D, designed to be set with its substantially rectilinear portion in the anterior part of the mitral valve with reference to the human body . The portion that is to be implanted at the rear, which presents a curvilinear shape, has two end segments with marked curvature, each connected, with a first end, to an end of the rectilinear portion, whilst the two respective second ends of the two portions with marked curvature are connected together by a portion presenting a smaller curvature and a length that is substantially equal to the portion that is to be implanted at the front. An example of an open ring according to the state of the art is illustrated in Figure 2. This open ring substantially has the shape of a capital C. As compared to the previous ring, this is without the substantially rectilinear portion that is to be implanted at the front.

The open ring consists only of the part that is to be implanted at the rear, which has a curvilinear shape with two end areas having marked curvature, the first ends of each area with marked curvature of which constitute the ends of the open ring, whereas the two respective second ends of the two parts with marked curvature are connected together by a segment having a smaller curvature and a length that is substantially equal to the portion that is to be implanted at the front. A deformation of some segments of the ring that is gradual, selective and reversible and can be performed once the ring has been implanted in the human body, in the case where such a deformation is required, is not made possible by currently known rings. This renders any surgical operation more complicated because, in many cases, the configuration of the mitral valve is identified exactly only when the surgical operation is in progress, and, consequently, the surgeon is pushed to seek the best solution for correction or elimination of the pathological condition, possibly having at his disposal a series of standard rings from which he must choose the one that seems to be the most suitable for the given purpose. Furthermore, the very conformation of the mitral valve depends upon the anatomy of the individual patient. The rings available cannot at the same time meet all these needs, except at the expense of a complexity of structure or difficulty of manipulation

The ring according to the invention provides the surgeon with a device that enables an increased adaptability to the shape of the mitral valve in question in that the ring can be moulded during the surgical operation thanks to the use of a set of means purposely designed to achieve the specific shape sought.

Given that these operations of annuloplasty call for an intense and complex commitment on the part of the equipe of surgeons, the possibility of obtaining a good adaptability to the shape sought also facilitates the operation and in part eliminates the drawback represented by the need to replace the prosthesis in order to remedy possible unsatisfactory discrepancies. Summary of the invention

One object of the present invention is hence to overcome the drawbacks described above, by means of the features specified in Claim 1. This and other object of this invention are achieved by means of a ring according to the invention whose features guarantee an "adjustable" annuloplasty both in the centre and in the paracommissural site. Ensured by said ring are both the graduality of -adjustment- and the reversibility of -adjustment-_and return to the original shape. The ring makes possible, in a simple way, the gradual adjustment of the shape in every area of the mitral valve to be obtained after implantation of the ring, and hence by evaluation, on the part of the surgeon, of the effectiveness of the reconstruction, either intra-operatively or at the moment of possible subsequent operations. Added to this important characteristic is the reversibility of the deformation of the ring, which also enables correction of any possible excesses of deformation thereof, which could have serious consequences for the patient. Amongst the other advantages provided by the ring according to the present invention, in addition to the ones already referred to, there are also the following: - further reducing the area of the leaflets that is subject to the left-ventricular pressure (systolic pressure), with a consequent reduction in the stress on the leaflets and on the sutures;

- reducing the diastolic stress in the case of use of the_so-called "edge-to-edge" technique,_thus contributing to counteracting tethering of the leaflets with incomplete co-optation; and

- counteracting tethering of the leaflets, even without applying the edge-to-edge technique.

All the above advantages can be achieved thanks to the good deformability in every perimetral area of the ring, guaranteeing to the surgeon optimal selectivity of the area of intervention on the mitral valve, for example both in the event of the presence of a central jet of regurgitation and in the case where said jet is in a paracommissural site, as illustrated in Figure 3.

In summary, the ring according to the invention is innovative in that it is made of a material that is sufficiently rigid to maintain the mitral valve in the desired shape once the surgical operation is completed, but at the same time sufficiently deformable under the action of forces that are commonly exerted by a surgeon during use of normal manual surgical instruments to cause the ring to take on any shape that might be necessary for correcting the pathological condition of the patient and then to maintain permanently the shape assumed during the surgical operation.

A further purpose of the present invention is to provide both an instrument for setting the ring described above in place, as well as a pair of forceps for deforming the ring in the required points of the perimeter, which can be used also for enabling the ring to recover part of the applied deformation, or for reducing the amplitude of the deformations whenever necessary, with an application of force from inside the ring. Brief description of the figures Further characteristics and advantages of the invention will emerge more clearly from the ensuing detailed description of preferred non-limiting embodiments of a prosthetic ring, provided purely by way of non-limiting example, with the aid of the annexed drawings, in which: - Figure 1 is a view of a closed prosthetic ring for reparative surgery of the mitral valve according to the state of the art;

- Figure 2 is a view of an open prosthetic ring for reparative surgery of the mitral valve according to the state of the art;

- Figure 3 is a view of a prosthetic ring for reparative surgery of the mitral valve according to the invention, in which two alternative types of deformation of the ring are indicated according to two regurgitation jets located in different positions;

- Figure 4 is an anatomical view of a prosthetic ring for reparative surgery of the mitral valve according to the invention, located in the implantation site;

- Figure 5 is a view of an instrument for setting the ring in place, said instrument having the shape of a plate;

- Figure 6 is a view of an embodiment of the instrument of Figure 5; and

- Figure 7 is a perspective view of an instrument which has the purpose of deforming the ring in association with the instrument of Figures 5 and 6 and which is capable of causing return of the ring according to the invention to its original shape in order to correct any deformation.

Detailed description of preferred embodiments of the invention

With particular reference to Figure 3, the prosthetic ring 1 according to the invention has the typical basic D shape.

The ring is made of a continuous_structure and_of a material_such as to ender it deformable notjn the sense of a widening of the diameter and hence of the area thereof, but in the_sense_of a_change e in the_shape by bringing closer together different portions of its perimeter and thus causing it to assume atfshapes different from the original shape. T-ali-The_shapes that_it_can assume_are different as the degree and the site of the deformation vary according to the different valve problems requiring correction.

As indicated in Figure 3, starting from the original shape, the ring is deformed by the application of a force to obtain the configuration capable of solving the pathological problems that call for implantation of the ring. If the surgeon applies a force F or F1 in a position corresponding to the points A and B of the ring, there is obtained a displacement of said points into the positions A1 and B1 , indicated by the dashed lines in Figures 3 and 4, so bringing about the desired configuration. Should it be deemed necessary, if a force of equal intensity but having opposite direction is applied, the original shape of the ring is restored. This renders the surgical operation safer, guaranteeing reversibility of the intervention at a point of the valve that would be deformed more than necessary on account of the elimination of the pathological condition, for example of the regurgitation jet. The ring_is_made of a_material_that is particularly_suited for_guaranteeing_all_the advantages_sought.

Advantageously^the_materialjs_chosen_fπ-)m among_metals_such as_mild_non-alloy steels, for example C2, and C45. namely, steels_presenting marked characteristics of elasticity._Also aluminium alloys^fo^example AIMnl ,2/AIMg4,5//AIMnSi. or copper alloys Or_example CuAI8. CuZn40, are suitable materials for the ring., Further_advantageous_materials_are_biocompatible polymers^such as_polyurethane resins (PURs), polymethylmethacrylate copolymers (PMMAs), polvamides (PAs), acetal resins,_or cross-linked polyethylenes (XPEs), preferably activated with cross-linking agents used for_modifying their_characteristics of elasticity by varying the_percentage_of the cross-linking additive. The physical characteristics of said materials_satisfy_two_opposed requirements^

In the initial_step_of_implantation_of the ring^the latter affords_a_convenient deformability such as to enable the_desired shape_to be bestowed thereon_A following upon_manipulation_by the_surgeon_J_whereas, after_resumption_of cardiac activity,_the ring affords the capacity of maintenance of the_shape_bestowed thereon^Further_advantages_of the_material_chosen_for the ring_are its fatigue resistance, given the_number_of_loading cycles_to_which_the ring_is_subjected, and the absence.of toxicity..

An_essential_characteristic_of the ring_is_that_of_enabling recovery of the original shape by the deformed ring_or else eduction in the ampiitude_of the deformations in given points_of its_circumference_by applying_a_pre-set force thereon_^which is compatible with the force_that_a_surgeon_can_apply_J_without_leaving_any residual trace of the initial deformation. It has been found that_other_types_of_materials_can_also_be_used, such as_the composite_materials_consisting of a combination of a_metal wire_embedded in a polymer. The metal and polymer are advantageously chosen in an appropriate_way to meet the specific needs of the surgical operations to be carried out Advantageously,_a variant_of the ring_envisages a_biocompatible-fabric coating envelopingjt

Represented in Figure 5 is a plate 3 made of appropriate material suitable for surgical operations, for example Plexiglas, which is used to define the shape that the ring is to assume at the end of the operation of deformation. The plate has a central hole, into which a rod 4 is inserted to enable gripping and manipulation of the instrument 2. The ensemble constitutes a surgical instrument designed to set the ring according to the invention described above in place in a convenient and reliable way. This non-limiting embodiment is particularly suitable for correcting other pathological conditions of the mitral valve, for example for correcting the regurgitation jet 6 represented in the left-hand part of Figure 3.

Represented in Figure 6 is a plate 3', having an alternative shape, which is also designed to be used to bring about deformation of the ring 1 and is suitable for correcting other pathological conditions of the mitral valve, for example for correcting the regurgitation jet 7 represented in the right-hand part of Figure 3. Figure 7 illustrates a perspective view of an instrument for deforming the ring, substantially consisting of a pair of forceps 5 to be gripped and manipulated by the surgeon during the surgical operation to bring about deformation of the ring 1. The pair of forceps 5 has jaws constituted by plates or similar elements, made of holder material with a profile of appropriate shape and such as to be able to bestow on the ring the deformation necessary for eliminating the anatomical pathological condition of the mitral valve. The forceps 5 can also perform another function, which is that of correcting or recovering part of the deformations imparted on the ring 1 , for instance in a position corresponding to the point A1 or else the point B1 , in the direction of a shape recovery towards the positions indicated by A or B, respectively. In extreme cases, said forceps 5 are designed to be used for causing the ring 1 to return to its original shape by application of a force from inside the ring. The ringjs inserted in the_envisaged anatomical sitejn the_way_described in what follows. After the thoracic cavity and the left atrium have been opened, the_surgeon implants the ring 1 on the mitral valve^He inserts the plate 3 within the ring 1. holding it_by the_handle provided^The_pIatejs_previously_chosen_with_the_particular shape_that_the ring_must_assume to correct_the individual lesions; the plate is chosen also according to its size corresponding to the size of the ring._Using the forceps_5,_the_surgeon_acts_on_particular points_of the ring 1 to confer onjts perimeter the deformations required. for_example, to_reduce_regurgitation jets.. Given the_advantageous characteristic_of the ring^in the_course_of the surgical operation, the_surgeon_canjntervene_further on the deformations that he has made in the_case_where they_are_insufficient for_particular points_or else are_too_marked for the purpose_of_perfect_operation_of the_mitral valve_in order to achieve_an optimal shape for the ring

Claims

1. A prosthetic ring for mitral valves defining a closed profile, substantially having the shape of a capital D, with a portion having a convex curvilinear shape, designed to be implanted at the rear, and a portion having a substantially straight shape, designed to be implanted at the front, with reference to the human body, in a position corresponding to a mitral valve, characterized in that the ring is made of a material with plastic properties such as to be deformable up to a pre-determined limit of deformation with the application of forces in chosen points of the perimeter of the ring itself and to preserve the shape corresponding to said pre-determined limit of deformation after the removal of the force so that, in the installed position, it remains shaped according to the anatomical shape of the mitral valve.

2. The ring according to Claim 1 , wherein the material has plastic and elastic properties such as to satisfy predetermined requirements.

3. The ring according to Claim 2, wherein the material is a metal_comprised_among high-elasticity steels_i

4. The ring according to Claim 2, wherein the material is a polymer

5. The ring according to Claim 2, wherein the material is a metal/polymer compositei

6. The ring according to any one of Claims 3 to 5, wherein a biocompatible-fabric coating is provided.

7. A pair of forceps having, at the gripping end, appropriately shaped plates, designed to produce -deformations on the_perimeter_of the ring (1) according to Claim 1 , characterized in that the plates are made of Plexiglas.