A PROSTHETIC DEVICE FOR MITRAL VALVE REPAIR

Abstract

A prosthetic ring or band (700) for repair of a mitral valve is disclosed, having a substantially annular form or a part annular form, wherein the prosthetic ring or band occupies at least a part of a shape having: preferably, a substantially straight base portion (710), configured to align with the anterior leaflet of the mitral valve; and a central curved portion (720), arranged opposite the base portion, having a first radius of curvature, Ri, and a first and second lateral curved portions located either side of the central curved portion; wherein the first and second lateral curved portions have a second radius of curvature, R.sub.2; wherein R.sub.2>Ri; and wherein at least a portion of one of the first or second lateral curved portions is removed. Related methods of preparation of such rings or bands and repair of mitral valves in human or animal hearts with such rings or bands are also disclosed.

Claims

1. A prosthetic ring for repair of a mitral valve, the prosthetic ring forming at least part of a shape having: a substantially straight base portion, configured to align with the aortic mitral curtain; a central curved portion, arranged opposite the base portion, having a first radius of curvature, R.sub.1; and a first and second lateral curved portions, located either side of the central curved portion, wherein the first and second lateral curved portions have a second radius of curvature, R.sub.2; wherein R.sub.2<R.sub.1; and a gap in the circumference of the ring formed in at least a portion of the first lateral curved portion or the second lateral curved portion.

2. A prosthetic ring for repair of a mitral valve, having a substantially annular form or a part annular form, wherein the prosthetic ring occupies at least a part of a shape having: a substantially straight base portion, configured to align with the aortic mitral curtain; a central curved portion, arranged opposite the base portion, configured to align with the posterior leaflet of the mitral valve in the region of the middle scallop; a first lateral curved portion, located between the first end of the central curved portion and the first end of the base portion, configured to align with the anterolateral commissure of the mitral valve; a second lateral curved portion, located between the second end of the central curved portion and the second end of the base portion, configured to align with the posteromedial commissure of the mitral valve; and a gap in the circumference of the ring formed in at least a portion of the first lateral curved portion or the second lateral curved portion.

3. The prosthetic ring of any of claims 1 to 2, wherein the prosthetic ring has a substantially annular form or a part annular form, and further comprises: a posterior ring part; an anterior ring part coupled to the posterior ring part at at least one coupling point on a transverse plane defining a maximum width of the prosthetic ring; wherein the prosthetic ring comprises a gap or a removable portion located in the posterior ring part.

4. The prosthetic ring of any of claims 1 to 3, wherein the gap in the circumference of the prosthetic ring corresponds to at least the portion of the prosthetic ring configured to align with the anterolateral commissure of the mitral valve.

5. The prosthetic ring of any of claims 1 to 4, wherein the gap in the circumference of the prosthetic ring corresponds to at least the portion of the prosthetic ring configured to align with the anterior scallop of the mitral valve.

6. The prosthetic ring of any of claims 1 to 3, wherein the gap in the circumference of the prosthetic ring corresponds to at least the portion of the prosthetic ring configured to align with the circumflex branch of the left coronary artery.

7. The prosthetic ring of any preceding claim, wherein a portion of the prosthetic ring opposite the gap: a) has an increased stiffness, b) has an increased thickness, and/or c) is formed from a stiffer material, compared to at least one other portion of the prosthetic ring.

8. The prosthetic ring of any preceding claim, wherein at least a portion of the prosthetic ring comprises multiple layers of material.

9. The prosthetic ring of any preceding claim, wherein at least a portion of the prosthetic ring opposite the gap has an increased number of layers of material.

10. The prosthetic ring of any preceding claim, wherein a portion of the prosthetic ring opposite the gap comprises a material with a flexural modulus which is higher than the material of the remainder of a circumference of the prosthetic ring.

11. The prosthetic ring of any preceding claim, wherein the prosthetic ring further comprises a suture permeable coating.

12. A prosthetic ring for repair of a mitral valve, having a substantially annular form or a part annular form, wherein the prosthetic ring occupies at least a part of a shape having: a substantially straight base portion, configured to align with the aortic mitral curtain; a central curved portion, arranged opposite the base portion, configured to align with the posterior leaflet of the mitral valve in the region of the middle scallop; a first lateral curved portion, located between the first end of the central curved portion and the first end of the base portion, configured to align with the anterolateral commissure of the mitral valve; a second lateral curved portion, located between the second end of the central curved portion and the second end of the base portion, configured to align with the posteromedial commissure of the mitral valve; and wherein the prosthetic ring comprises a cut-able portion, located on the first lateral curved portion or the second lateral curved portion, which when removed, provides a gap in the circumference of the ring formed in the first lateral curved portion or the second lateral curved portion.

13. A method of preparing a prosthetic ring for repair of a mitral valve, comprising: removing a portion of the ring; wherein the prosthetic ring occupies at least a part of a shape having: a substantially straight base portion, configured to align with the aortic mitral curtain; a central curved portion, arranged opposite the base portion, configured to align with the posterior leaflet of the mitral valve in the region of the middle scallop; a first lateral curved portion, located between the first end of the central curved portion and the first end of the base portion, configured to align with the anterolateral commissure of the mitral valve; a second lateral curved portion, located between the second end of the central curved portion and the second end of the base portion, configured to align with the posteromedial commissure of the mitral valve; and wherein removing the portion of the ring provides a gap in the circumference of the ring formed in the first lateral curved portion or the second lateral curved portion.

14. The method of preparing a prosthetic ring for repair of a mitral valve of claim 13, wherein the prosthetic ring has a substantially annular form or a part annular form, and further comprises: a posterior ring part; and an anterior ring part coupled to the posterior ring part at at least one coupling point on a transverse plane defining a maximum width of the prosthetic ring; wherein removing the portion of the ring to provide a gap in the circumference of the ring comprises forming a gap located in the posterior ring part.

15. The method of preparing a prosthetic ring for repair of a mitral valve of claim 13, wherein removing the portion of the ring to provide a gap in the circumference of the ring comprises forming a gap in at least the portion of the prosthetic ring configured to align with the anterolateral commissure of the mitral valve.

16. The method of preparing a prosthetic ring for repair of a mitral valve of claim 13, wherein removing the portion of the ring to provide a gap in the circumference of the ring comprises forming a gap in at least the portion of the prosthetic ring configured to align with the anterior scallop of the mitral valve.

17. The method of preparing a prosthetic ring for repair of a mitral valve of claim 13, wherein removing the portion of the ring to provide a gap in the circumference of the ring comprises forming a gap in at least the portion of the prosthetic ring configured to align with the circumflex branch of the left coronary artery.

18. A prosthetic band for repair of a mitral valve, the prosthetic band forming at least part of a shape having: a central curved portion, having a first radius of curvature, R.sub.1; and a first and second lateral curved portions, located either side of the central curved portion, wherein the first and second lateral curved portions have a second radius of curvature, R.sub.2; wherein R.sub.2<R.sub.1; and a gap in the band, the gap extending over a base portion configured to align with the aortic mitral curtain and at least a portion of the first lateral curved portion or the second lateral curved portion.

19. A prosthetic band for repair of a mitral valve, having a substantially part annular form, wherein the prosthetic band occupies at least a part of a shape having: a central curved portion, configured to align with the posterior leaflet of the mitral valve in the region of the middle scallop; a first lateral curved portion, located at the first end of the central curved portion, configured to align with the anterolateral commissure of the mitral valve; a second lateral curved portion, located at the second end of the central curved portion, configured to align with the posteromedial commissure of the mitral valve; and a gap in the band, the gap extending over a base portion configured to align with the aortic mitral curtain and at least a portion of the first lateral curved portion or the second lateral curved portion.

20. The prosthetic band of claim 18 or 19, wherein the gap in the prosthetic band extends over at least the portion of the prosthetic band configured to align with the anterolateral commissure of the mitral valve.

21. The prosthetic band of any of claims 18 to 20, wherein the gap in the prosthetic band extends over at least the portion of the prosthetic band configured to align with the anterior scallop of the mitral valve.

22. The prosthetic band of any of claims 18 to 21, wherein the gap in the prosthetic band extends over at least the portion of the prosthetic band configured to align with the circumflex branch of the left coronary artery.

23. A prosthetic band for repair of a mitral valve, having a substantially part annular form, wherein the prosthetic band occupies at least a part of a shape having: a central curved portion, configured to align with the posterior leaflet of the mitral valve in the region of the middle scallop; a first lateral curved portion, located at the first end of the central curved portion, configured to align with the anterolateral commissure of the mitral valve; a second lateral curved portion, located at the second end of the central curved portion, configured to align with the posteromedial commissure of the mitral valve; and wherein the prosthetic band comprises a cut-able portion, located on the first lateral curved portion or the second lateral curved portion, which when removed, provides a gap in the band extending over the first lateral curved portion or the second lateral curved portion.

24. A method of preparing a prosthetic band for repair of a mitral valve, comprising: removing a portion of the prosthetic band; wherein the prosthetic band occupies at least a part of a shape having: a central curved portion, configured to align with the posterior leaflet of the mitral valve in the region of the middle scallop; a first lateral curved portion, located at the first end of the central curved portion, configured to align with the anterolateral commissure of the mitral valve; a second lateral curved portion, located at the second end of the central curved portion, configured to align with the posteromedial commissure of the mitral valve; and wherein removing the portion of the band provides a gap in the band extending over the first lateral curved portion or the second lateral curved portion.

25. The method of preparing a prosthetic band for repair of a mitral valve of claim 24, wherein removing the portion of the band to provide a gap in the band comprises forming a gap in at least the portion of the prosthetic band configured to align with the anterolateral commissure of the mitral valve.

26. The method of preparing a prosthetic band for repair of a mitral valve of claim 24, wherein removing the portion of the band to provide a gap in the band comprises forming a gap in at least the portion of the prosthetic band configured to align with the anterior scallop of the mitral valve.

27. The method of preparing a prosthetic band for repair of a mitral valve of claim 24, wherein removing the portion of the band to provide a gap in the band comprises forming a gap in at least the portion of the prosthetic band configured to align with the circumflex branch of the left coronary artery.

28. A method of repairing a mitral valve using a prosthetic ring of any of claims 1 to 12, or a prosthetic band of any of claims 18 to 23, comprising the steps of: suturing the prosthetic ring, or the prosthetic band, to a mitral valve to remodel its shape.

29. A method of repairing a mitral valve comprising the steps of: preparing a prosthetic ring according to the method of any of claims 13 to 17, or preparing a prosthetic band according to the method of any of claims 24 to 27; and suturing the prosthetic ring, or the prosthetic band, to a mitral valve to remodel its shape.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0041] Some embodiments of apparatus and/or methods in accordance with embodiments of the present invention are now described, by way of example only, and with reference to the accompanying drawings, in which:

[0042] FIG. 1 shows a cross-section representation of a human heart

[0043] FIG. 2 shows a cross-section representation of a healthy human mitral valve during systole;

[0044] FIG. 3 shows a cross-section representation a misaligning mitral valve during systole;

[0045] FIGS. 4A to 4F show plan views of mitral valve prosthetics known from the prior art;

[0046] FIG. 5 shows a plan view of a mitral valve prosthetic known from the prior art;

[0047] FIG. 6a shows a cross-section representation of mitral valve repaired by fixation of a prior art mitral valve prosthetic;

[0048] FIG. 6b shows an enlarged representation of the repaired mitral valve of FIG. 6a;

[0049] FIG. 7 shows a mitral valve prosthetic according to the present invention;

[0050] FIG. 8 shows a cross-section representation of mitral valve repaired by fixation of a mitral valve prosthetic according to an embodiment of the present invention;

[0051] FIG. 9a shows a mitral valve prosthetic according to the present invention;

[0052] FIG. 9b shows a mitral valve prosthetic according to the present invention;

[0053] FIG. 10 shows a mitral valve prosthetic according to the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

[0054] To aid the skilled person's understanding, where appropriate, an imaginary x-axis and y-axis has been included in the figures. Where included, the x-axis is marked x, and the y-axis is marked y.

[0055] The applicant has identified that 3% to 5% of patients will suffer some degree of circumflex artery distortion or injury, during a mitral valve annuloplasty. Circumflex artery damage may lead to a myocardial infarction (a heart attack), generally due to unrecoverable left ventricular infarction, unless quickly diagnosed and treated.

[0056] One difficulty faced by surgeons performing mitral heart valve annuloplasties is that the surgeon may not know beforehand the relative location of the heart vasculature to the operation site. The surface of the heart is covered by a complicated vasculature system, as can be seen, for example, in FIG. 6a.

[0057] The applicant has also identified that a significant potential cause of complications during or after mitral valve annuloplasty can be the surgical impingement of the vasculature in proximity to the mitral valve. These problems are particularly acute in patients who, through natural anatomical variation, are considered to have a higher risk anatomy. In particular, the applicant has identified that patients with heart vasculature in which the circumflex branch of the coronary artery lies close to the mitral valve are particularly at risk of operative complications during and following a mitral valve annuloplasty. Therefore, there exists a need for an improved mitral valve prosthetic which mitigates some of the causes of complications experienced in mitral valve annuloplasty procedures for those patients where natural variation has caused particularly high risk location of the vasculature in proximity of the mitral valve. Particularly, it has been identified that certain patients can be identified as at a high risk of operative circumflex artery damage.

[0058] A first embodiment of the invention will now be described with reference to FIG. 7. FIG. 7 shows a mitral valve prosthetic 700. The shape of the prosthetic 700 conforms to an annular, kidney-shaped form. Thus, the shape of the prosthetic 700 can be divided into four sections. The shape of prosthetic 700 has a substantially straight base portion 710, a central curved portion 720 located opposite the base portion 710, and two lateral curved portions 730, 740 located between the base portion 710 and the curved portion 720.

[0059] Mitral valve prosthetic 700 may be made of a resilient bio-compatible material. The resilience of the material allows the prosthetic 700 to be at least partially deformed during surgery and provides a force to the mitral valve which restores the natural anteroposterior diameter to transverse diameter ratio geometric ratio. Bio-compatibility ensures that the prosthetic 700 does not promote blood clotting or bacterial growth. Many suitable resilient bio-compatible materials are known in the art, including bio-compatible polymers, metals and metal-alloys. Preferably, at least part of the prosthetic 700 is made of titanium or a titanium alloy.

[0060] The mitral valve prosthetic 700 may be covered in suture-permeable covering 750. The suture-permeable covering can aid the surgeon in fixing the prosthetic 700 to the mitral valve. Suture-permeable coverings for prosthetics are well known in the art and the prosthetic 700 may use any such suitable covering. Preferably, the suture-permeable covering is Dacron (polyethylene terephthalate) coated silicon.

[0061] The mitral valve prosthetic 700 has a gap 760 in its circumference. The gap 760 corresponds to the region of the mitral valve close to the circumflex artery and represents either a manufactured gap or removed portion in the circumference of the prosthetic. Since gap 760 is provided in the prosthetic 700, in use, no sutures can be placed within the region of the mitral valve closest to the circumflex artery. This reduces the likelihood of circumflex artery impingement or damage. This goes against the strongly held prejudice in the art to provide as much support as possible to the circumference of the mitral valve; or in cases where the anterior leaflet of the mitral valve is unaffected by the underlying pathology, to provide as much support as possible to at least the entirety of the posterior leaflet of the mitral valve. Evidence of this prejudice in the art can be seen, as discussed previously, in prior art prostheses such as those shown in FIGS. 4A to 4F.

[0062] FIG. 8 illustrates the mitral valve prosthetic 850 once it has been fixed to a mitral valve 890. As can be seen from FIG. 8, parts of the circumflex artery 891 (otherwise known as the circumflex branch of the coronary artery) are located close to the mitral valve 890. Therefore, the gap 760, 860 corresponds to, at least, the anterior commissure 670, 870, i.e. zone 655, 855. Furthermore, FIG. 8 also illustrates that the region of the circumflex artery 891 in close proximity to the mitral valve 890 may extend from the region of the anterior commissure 670, 870 to at least partially surround the region of the anterior scallop 621, 821. Consequently, the gap 760, 860 may also correspond to, at least part of, the anterior commissure 670, 870 and the anterior scallop 621, 821 i.e. zone 655, 855 and zone 656, 856.

[0063] As will be appreciated, the gap 760, 860 in the mitral valve prosthetic 700 will reduce the overall stiffness of the mitral valve prosthetic 700. To compensate, the mitral valve prosthetic preferably comprises a material with a stiffness higher than a prior art mitral valve prosthetic. Increased stiffness can be achieved by any suitable method of stiffening an object, including using a material with a higher stiffness, combining multiple layers of material, thickening at least a portion of the ring and/or incorporating multiple materials of differing stiffnesses into the ring. This is preferably implemented in an area substantially opposite or adjacent to gap 760, 860.

[0064] The applicant recognises that omitting or removing a portion of the mitral valve prosthetic 700 may decrease the durability of the prosthetic 700 due to increased flexing under contraction of the heart. This is a further reason for which the configurations of the present invention have been avoided in the prior art. However, in conceiving the invention, it has been recognised that clinically, the potentially lower durability of the prosthetic 700 may be preferable to the risk of damage to heart vasculature through infarction of the lateral wall of the heart for certain patients due to damage caused to vasculature in close proximity to the area of suturing.

[0065] In FIG. 7, mitral valve prosthetic 700 is shown as being substantially symmetrical along a central midline. The skilled person will understand that the shape of mitral valve prosthetic 700 can deviate from being perfectly symmetrical whilst still conforming to the shape of the mitral valve. In fact, the mitral valve prosthetic must be at least partially deformable in order to be installed by common key-hole surgical methods. Furthermore, the mitral valve prosthetic is sutured onto a mitral valve which continuously deforms as the heart beats. Thus, in use, the mitral valve prosthetic 700 must resiliently correct the shape of the mitral valve whilst allowing for the natural cycle of movement of the valve.

[0066] FIG. 7 also illustrates only a 2-dimensional representation of mitral valve prosthetic 700. This should not be taken to mean that mitral valve prosthetic 700 is flat in the third dimension (i.e. a z-axis which is normal to both the marked x-axis and y-axis). In fact, mitral valve prosthetic 700 may be formed to have a substantially curved profile along the z-axis, as is used in some prior art mitral valve prosthetics.

[0067] Mitral valves come in many different sizes and consequently, the mitral valve prosthetic 700 may be supplied in a series of differing sizes, all conforming to the same shape of the claimed invention, to fit differing sizes of mitral valves. The larger mitral valve prosthetics 700 may require increased stiffening in order to sufficiently correct the abnormal geometric ratio of the damaged mitral valves. This increased stiffening may be performed by any of the methods described above. Conversely, the smaller sizes of mitral valve prosthetic may require less stiffening in order to adequately correct the mitral valve.

[0068] Whilst mitral valve prosthetics with removed sections are known from the prior art, generally termed mitral bands (see for example FIG. 4D of the present application), all of these prior art mitral valve prosthetics define a removed or removable section within the substantially straight base portion (710) of the mitral valve prosthetic; i.e. the prior art mitral valves with a gap are effectively C shaped. These C shaped mitral valves are so shaped in order to preserve the natural shape and function of the anterior leaflet of the mitral valve, whilst providing full support around the circumference of the posterior leaflet. Consequently, these prior art mitral valve prosthetics should only be used where the anterior leaflet of the mitral valve is unaffected by the underlying pathology requiring treatment. Thus, these prior art mitral valve prosthetics are aimed at solving a different technical problem to the presently claimed invention, that of providing a mitral valve prosthetic which does not alter or restrict the shape and movement of the anterior leaflet of the mitral valve. Differently to the present invention, all prior art mitral valve prosthetics have until now provided support to the whole of the posterior leaflet of the mitral valve.

[0069] Further embodiments will now be further described in relation to FIG. 9a. The mitral valve prosthetic 900 conforms to mitral valve 700, shown in FIG. 7, but is defined geometrically rather than by reference to anatomical features. Mitral valve prosthetics are commonly described geometrically in the prior art, as can be seen in EP 1258232 A2 and U.S. 2011/0224786 A1. Mitral valve 900 is thus described, where possible, using equivalent geometric terms as those used in the prior art.

[0070] Mitral valve prosthetic 900 comprises an anterior half-ring 910 which is substantially straight, and a curved posterior half-ring 920. The posterior half-ring 920 and anterior half-ring 910 are coupled at one point 950 located substantially on a lateral plane 930 that defines a maximum width section of the prosthesis. In addition, a longitudinal plane 940 is also defined, that intersects the prosthesis substantially at points 970 and 980, that is arranged substantially perpendicular to the lateral plane 930 and substantially bisects the anterior half-ring 950 at point 980. The posterior half-ring 920 is thus subdivided in to a first lateral zone (left) 990 located between the points 950 and 970, and a second lateral zone (right) 995 located between the points 965 and 970.

[0071] The intersection points 950, 970 and 980 of the prosthesis respectively with the planes 930 and 940 define geometric points used for the calculation of the dimensions of the prosthesis. In accordance with the prior art, the distance between the points 970 and 980, defines the height of the prosthesis. The length of the anterior half-ring 910, defines a width of the prosthesis. Typically, the ratio of the height of the mitral valve prosthesis to the width of the prosthesis is approximately 3:4.

[0072] Mitral valve prosthetic 900 is made of a resilient bio-compatible material. The resilience of the material allows the prosthetic 900 to be at least partially deformed during surgery and provides a force to the mitral valve which restores the natural anteroposterior diameter to transverse diameter ratio geometric ratio. Bio-compatibility ensures that the prosthetic 900 does not promote blood clotting or bacterial growth. Many suitable resilient bio-compatible materials are known in the art, including bio-compatible polymers, metals and metal-alloys. Preferably, at least part of the prosthetic 900 is made of titanium or a titanium alloy.

[0073] The mitral valve prosthetic 900 is covered in suture-permeable covering 955. The suture-permeable covering aids the surgeon in fixing the prosthetic 900 to the mitral valve. Suture-permeable coverings for prosthetics are well known in the art and the prosthetic 900 may use any such suitable covering. Preferably, the suture-permeable covering is Dacron (polyethylene terephthalate) coated silicon.

[0074] The mitral valve prosthetic 900 has a gap 960. The gap 960 is provided in, or omitted from, at least a portion of the first or second lateral curved portions 990 or 995. Since portion 960 is removed from the prosthetic 900, in use, no sutures can be placed within these regions. This portion 960 corresponds to the region of the mitral valve closest to the circumflex artery, thus reducing the likelihood of circumflex artery impingement or damage.

[0075] As will be appreciated, removing a portion 960 of the mitral valve prosthetic 900 will reduce the overall stiffness of the mitral valve prosthetic 900. To compensate, the mitral valve prosthetic is preferably made of a material with a stiffness higher than a prior art mitral valve prosthetic. Increased stiffness can be achieved by any prior art method of stiffening an object, including using a material with a higher stiffness, combining multiple layers of material, thickening at least a portion of the ring and/or incorporating multiple materials of differing stiffnesses into the ring. This is preferably implemented in an area substantially opposite or adjacent to gap 960.

[0076] The applicant recognises that omitting or removing a portion of the mitral valve prosthetic 900 may decrease the durability of the prosthetic 900 due to increased flexing under contraction of the heart. However, it has been recognised that clinically, the potentially lower durability of the prosthetic 900 may be preferable to the risk of damage to heart vasculature through infarction of the lateral wall for certain patients.

[0077] In FIG. 9a, mitral valve prosthetic 900 is shown as symmetrical along a central midline. The skilled person will understand that the shape of mitral valve prosthetic 900 can deviate from being perfectly symmetrical whilst still conforming to the shape of the mitral valve. In fact, the mitral valve prosthetic must be at least partially deformable in order to be installed by common key-hole surgical methods. Furthermore, the mitral valve prosthetic is sutured onto a mitral valve which continuously deforms as the heart beats. Thus, in use, the mitral valve prosthetic 900 must resiliently correct the shape of the mitral valve whilst allowing for the natural cycle of movement of the valve.

[0078] Mitral valves come in many different sizes and The mitral valve prosthetic 900 may be supplied in a series of differing sizes, all conforming to the same shape of the claimed invention, to fit differing sizes of mitral valves. The larger mitral valve prosthetics 900 may require increased stiffening in order to sufficiently correct the abnormal geometric ratio of the damaged mitral valves. This increased stiffening may be performed by any of the methods described above.

[0079] Further embodiments will now be described in relation to FIG. 9b. FIG. 9b illustrates the mitral valve prosthetic 900 of FIG. 9a in a prosthetic band configuration. As has been described previously, prosthetic bands (or mitral bands) are known in the art. These known prosthetic bands can comprise a removed or removable section within the previously defined substantially straight base portion (710) of the mitral valve prosthetic. These known prosthetic bands are shaped in order to preserve the natural shape and function of the anterior leaflet of the mitral valve. Therefore, these prosthetic bands are preferably only used when the anterior leaflet of the mitral valve is functionally normal and does not require further support.

[0080] There are patients who would otherwise be suitable for a prosthetic band, but have an anatomy which gives rise to a high risk of surgical impingement of the vasculature in proximity to the mitral valve. Hence, they are not suitable for traditional prosthetic bands. As will be appreciated from the discussion above, the presently described novel features of the invention can be equally applicable to a prosthetic band arrangement. For illustration, an example is shown in FIG. 9b. Thus, FIG. 9b shows a prosthetic band, in accordance with embodiments of the present invention, which are particularly suitable for patients with high risk anatomies, but a fully functioning anterior leaflet of the mitral valve.

[0081] As described earlier in relation to mitral bands, in FIG. 9b, mitral valve prosthetic 900 does not comprise an anterior half-ring 910, but otherwise corresponds in shape to the mitral valve prosthetic 900 of FIG. 9a. That is, in FIG. 9b, mitral valve prosthetic 900 comprises a curved posterior half-ring 920. FIG. 9b also illustrates that mitral valve prosthetic 900 comprises a gap 960 which extends over the base portion (not shown), i.e. the missing anterior half-ring 910 of FIG. 9a.

[0082] As with the example of FIG. 9a, the mitral valve prosthetic 900 of FIG. 9b is also made of a resilient bio-compatible material. The resilience of the material allows the prosthetic 900 to be at least partially deformed during surgery and provides a force to the mitral valve which restores the natural anteroposterior diameter to transverse diameter ratio geometric ratio. Bio-compatibility ensures that the prosthetic 900 does not promote blood clotting or bacterial growth. Many suitable resilient bio-compatible materials are known in the art, including bio- compatible polymers, metals and metal-alloys. Preferably, at least part of the prosthetic 900 is made of titanium or a titanium alloy.

[0083] As with the example of FIG. 9a, the mitral valve prosthetic 900 of FIG. 9b is also covered in suture-permeable covering (not shown). The suture-permeable covering aids the surgeon in fixing the prosthetic 900 to the mitral valve. Suture-permeable coverings for prosthetics are well known in the art and the prosthetic 900 may use any such suitable covering. Preferably, the suture-permeable covering is Dacron (polyethylene terephthalate) coated silicon.

[0084] As with the example of FIG. 9a, the mitral valve prosthetic 900 has a gap 960. The gap 960 is provided in, or omitted from, at least a portion of the first or second lateral curved portions 990 or 995. Since portion 960 is removed from the prosthetic 900, in use, no sutures can be placed within these regions. This portion 960 corresponds to the region of the mitral valve closest to the circumflex artery, thus reducing the likelihood of circumflex artery impingement or damage.

[0085] As will be appreciated, the removed portion 960 of the mitral valve prosthetic 900 of FIG. 9b will further reduce the overall stiffness of the mitral valve prosthetic 900. To compensate, the mitral valve prosthetic is preferably made of a material with a stiffness higher than a prior art mitral valve prosthetic. Increased stiffness can be achieved by any prior art method of stiffening an object, including using a material with a higher stiffness, combining multiple layers of material, thickening at least a portion of the ring and/or incorporating multiple materials of differing stiffnesses into the ring. This is preferably implemented in an area substantially opposite or adjacent to gap 960 or the overall gap between ends of the band.

[0086] The applicant recognises that omitting or removing a greater portion of the mitral valve prosthetic 900 may decrease the durability of the prosthetic 900 due to increased flexing under contraction of the heart. However, it has been recognised that clinically, the potentially lower durability of the prosthetic 900 may be preferable to the risk of damage to heart vasculature through infarction of the lateral wall for certain patients.

[0087] In FIG. 9b, mitral valve prosthetic 900 is shown as substantially symmetrical along a central midline. The skilled person will understand that the shape of mitral valve prosthetic 900 can deviate from being perfectly symmetrical whilst still conforming to the shape of the mitral valve. In fact, the mitral valve prosthetic must be at least partially deformable in order to be installed by common key-hole surgical methods. Furthermore, the mitral valve prosthetic is sutured onto a mitral valve which continuously deforms as the heart beats. Thus, in use, the mitral valve prosthetic 900 must resiliently correct the shape of the mitral valve whilst allowing for the natural cycle of movement of the valve.

[0088] Mitral valves come in many different sizes and the mitral valve prosthetic 900 may be supplied in a series of differing sizes, all conforming to the same shape of the claimed invention, to fit differing sizes of mitral valves. The larger mitral valve prosthetics 900 may require increased stiffening in order to sufficiently correct the abnormal geometric ratio of the damaged mitral valves. This increased stiffening may be performed by any of the methods described above.

[0089] In a second embodiment of the present invention, with reference to FIG. 10, there is provided a mitral valve prosthetic 1000. The shape of the prosthetic 1000 conforms to the annular, kidney-shaped form of the prosthetic 700, 800 of the first embodiment. That is, the shape of the prosthetic 1000 can be divided into four sections; a substantially straight base portion 1010, a central curved portion 1020 located opposite the base portion 1010, and two lateral curved portions 1030, 1040 located between the base portion 1010 and the curved portion 1020. Alternatively, the shape of the prosthetic 1000 could be considered to comprise a posterior half-ring 1080 and an anterior half-ring 1070 which is coupled to the posterior half ring at at least one coupling point on a first lateral plane.

[0090] Mitral valve prosthetic 1000 may also be made of a resilient bio-compatible material. The resilience of the material allows the prosthetic 1000 to be at least partially deformed during surgery and provides a force to the mitral valve which restores the natural anteroposterior diameter to transverse diameter ratio geometric ratio. Bio-compatibility ensures that the prosthetic 1000 does not promote blood clotting or bacterial growth. Many suitable resilient bio-compatible materials are known in the art, including bio-compatible polymers, metals and metal-alloys. Preferably, at least part of the prosthetic 1000 is made of titanium or a titanium alloy.

[0091] The mitral valve prosthetic 1000 may also be covered in suture-permeable covering 1050. The suture-permeable covering can aid the surgeon in fixing the prosthetic 1000 to the mitral valve. Suture-permeable coverings for prosthetics are well known in the art and the prosthetic 1000 may use any such suitable covering. Preferably, the suture-permeable covering is Dacron (polyethylene terephthalate) coated silicon.

[0092] The mitral valve prosthetic 1000 has a removable portion 1060. The removable portion 1060 corresponds to the region of the mitral valve close to the circumflex artery. The removable portion 1060 is weaker, and hence more easily cut-able, than the rest of the mitral valve prosthetic. I.e. the material making up the removable portion 1060 is less resistant to shear stresses than the material making up the rest of the mitral valve prosthetic. Any suitable method of providing a material less resistant to shear stress may be used, for example, using a different material in the removable portion 1060, using less layers of material in the removable portion 1060 and/or using thinner layers of material in the removable portion 1060.

[0093] The removable portion 1060 may be removed in use by the surgeon to provide a gap 1060 corresponding to the region of the mitral valve close to the circumflex artery. The removable portion, may be made in any portion of the posterior half-ring. The removable portion 1060 may be removed in its entirety or partially. When portion 1060 is removed from the prosthetic 1000, in use, no sutures can be placed within the region of the mitral valve closest to the circumflex artery, thus reducing the likelihood of circumflex artery impingement or damage. The removable portion 1060 may be made of a different material to the rest of the mitral valve prosthetic. Preferably, the removable portion 1060 is made of a material that is less tough than the rest of the ring, to aid the removal of the removable portion. The removable portion 1060 may further be segmented to aid its partial removal.

[0094] The suture-permeable covering 1050 may be marked to illustrate the extent of the removable portion 1060. Any bio-compatible marking may be used, such as changing the colouration of the suture-permeable covering, the addition of further bio-compatible threads.

[0095] As will be appreciated, removing a portion 1060 of the mitral valve prosthetic 1000 will reduce the overall stiffness of the mitral valve prosthetic 1000. To compensate, the mitral valve prosthetic preferably comprises a material with a stiffness higher than a prior art mitral valve prosthetic. Increased stiffness can be achieved by any prior art method of stiffening an object, including using a material with a higher stiffness, combining multiple layers of material, thickening at least a portion of the ring and/or incorporating multiple materials of differing stiffnesses into the ring.

[0096] The applicant recognises that removing a portion of the mitral valve prosthetic 1000 may decrease the durability of the prosthetic 1000 due to increased flexing under contraction of the heart. However, in conceiving the inventions, it has been recognised that clinically, the potentially lower durability of the prosthetic 1000 may be preferable to the risk of damage to heart vasculature through infarction of the lateral wall of the heart for some patients.

[0097] In FIG. 10, mitral valve prosthetic 1000 is shown as being substantially symmetrical along a central midline. The skilled person will understand that the shape of mitral valve prosthetic 1000 can deviate from being perfectly symmetrical whilst still conforming to the shape of the mitral valve. In fact, the mitral valve prosthetic must be at least partially deformable in order to be installed by common key-hole surgical methods. Furthermore, the mitral valve prosthetic is sutured onto a mitral valve which continuously deforms as the heart beats. Thus, in use, the mitral valve prosthetic 1000 must resiliently correct the shape of the mitral valve whilst allowing for the natural cycle of movement of the valve.

[0098] FIG. 10 also illustrates only a 2-dimensional representation of mitral valve prosthetic 700. This should not be taken to mean that mitral valve prosthetic 1000 is flat in the third dimension (z-axis). In fact, mitral valve prosthetic 1000 may be formed substantially curved along the z-axis, as is used in some prior art mitral valve prosthetics.

[0099] The removable portion 1060 can also be applied to the prosthetic band-type embodiment of FIG. 9b, to provide a removable portion at the location of the gap or omitted portion 960. As can be seen from FIG. 9b, mitral valve prosthetic 900 already comprises a gap 960 which extends over the base portion (not shown), i.e. the missing anterior half-ring 910 of FIG. 9a. The removable portion 1060 extends gap 960 over a portion of the first or second lateral curved portions 990 or 995.

[0100] Mitral valves come in many different sizes and consequently, the mitral valve prosthetic 1000 may be supplied in a series of different sizes, all conforming to the same shape of the claimed invention, to fit differing sizes of mitral valves. The larger mitral valve prosthetics 1000 may require increased stiffening in order to sufficiently correct the abnormal geometric ratio of the damaged mitral valves. This increased stiffening may be performed by any of the methods described above. Conversely, the smaller sizes of mitral valve prosthetic may require less stiffening in order to adequately correct the mitral valve.