APPARATUS FOR SELECTING A SUITABLY DIMENSIONED BUTTRESS FOR A MITRAL VALVE
The present invention relates to an apparatus for selecting a suitably dimensioned buttress for reconstruction of the annulus of a mitral valve.
The mitral valve is located in the left atrioventricular opening of the heart and serves to prevent regurgitation of blood from the ventricle into the atrium when the ventricle contracts during systole.
The mitral valve, which is surrounded by a dense fibrous ring known as the annulus, comprises two valve leaflets or cusps of unequal size, the large or anterior leaflet adjacent the aortic opening and the smaller posterior leaflet. The line at which the leaflets come together is called the commissure.
The most common defect leading to mitral valve dysfunction is a dilation of the posterior two-thirds of the annulus which corresponds to the posterior leaflet. Thus, in repairing a mitral valve, it is sometimes necessary to repair the dilated posterior two-thirds of the mitral valve, by reducing the physiological dimensions of the annulus. This is known as annuloplasty .
It is known to provide an annuloplasty buttress for mitral valve reconstruction, the buttress comprising an
elongate member formed from a fabric bendable, in use, into an open substantially ring-shaped configuration dimensioned to fit against the base of the cusps of the mitral valve. Such a buttress is normally offered to the mitral valve in an extended condition, as is taught in WO 97/03625, the whole contents of which are incorporated herein by reference.
It is an object of the present invention to provide an apparatus for selecting a suitably dimensioned buttress for mitral valve reconstruction.
According to the invention there is provided an apparatus for selecting a suitably dimensioned buttress for reconstruction of an annulus of a mitral valve, the mitral valve including an anterior mitral leaflet and a posterior mitral leaflet; the buttress being bendable, in use, into an open substantially ring-shaped configuration, the buttress being longitudinally extendable to no more than about 110% of its unextended length; and the buttress being offered to the mitral annulus, preferably in its extended condition, the apparatus comprising a segment member having a chord to arc length ratio of about 1:2, the chord length approximately relating to the maximum depth of the anterior mitral leaflet from its base to its commissure with the posterior mitral leaflet.
Preferably, the length of the chord approximates twice the maximum depth of the anterior mitral leaflet from its base to its commissure with the posterior mitral leaflet and the length of the arc approximates the length of the buttress in its unextended condition.
More preferably, the apparatus includes a substantially semi-circle-shaped member defined by a second arc and a second chord, the chord of the segment -shaped member and the second chord of the substantially semi-circle- shaped member being co- linear.
Alternatively, the substantially semi-circle-shaped member is substantially parallel to, and spaced-apart from, the segment -shaped member; and a flange is provided extending between the chord of the segment - shaped member and the second chord of the substantially semi-circle-shaped member, the chord, the flange and the second chord being coplanar.
Advantageously, a gripping means is provided, preferably on the substantially semi-circle-shaped member .
One embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:-
Figure 1 is a plan view of an apparatus for selecting a suitably dimensioned buttress according to the present invention;
Figure 2 is a side view of the apparatus of Figure 1 ; and
Figure 3 is an isometric view of the apparatus of Figure 1.
Referring now to Figures 1-3 of the accompanying drawings, there is illustrated an apparatus for selecting a suitably dimensioned buttress for mitral valve reconstruction, the apparatus being generally indicated as 10.
The apparatus 10 comprises a segment -shaped member 12, defined by an arc 14 and a chord 16. The chord 16 to arc 14 length ratio is about 1:2.
The apparatus 10 also comprises a substantially semicircle-shaped member 18, which is defined by a second arc 20 and a second chord 22. The length of the chord 16 approximates the length of the second chord 22.
The substantially semi-circle-shaped member 18 is substantially parallel to, and spaced-apart from, the segment-shaped member 12. A flange 24 is provided extending between the chord 16 of the segment -shaped
member 12 and the second chord 22 of the substantially semi-circle-shaped member 18. As will be evident from, for example, Figure 1 of the accompanying drawings, the chord 16, the flange 24 and the second chord 22 are coplanar.
It will be appreciated that the substantially semicircle-shaped member 18 could, alternatively, be integral with the segment -shaped member 12 (not shown) and, in that event, the second arc 20 of the substantially semi-circle-shaped member 18 would be indicated on the surface of the segment -shaped member 12. In that event, the second chord 22 and the chord 16 would be co-linear.
A gripping means 26 in the form of a boss is provided on the substantially semi-circle-shaped member 18. It will of course be appreciated that, in the above- mentioned alternative embodiment (not shown) , the gripping means 26 would be provided on the segment - shaped member 12.
The apparatus 10 according to the present invention, may be formed from any suitable bio- inert material such as, for example, polysuphone .
It is envisaged that a series of apparatus 10 according to the invention, of graduated chord lengths, will be provided as a kit of parts to a cardiac surgeon for use
in selecting a suitably dimensioned buttress for mitral valve reconstruction for an individual patient.
In use, the cardiac surgeon offers a series of apparatus 10 according to the invention, to the annulus of a particular patient, until he identifies the specific apparatus 10 according to the present invention, whose substantially semi-circle-shaped member 18 most closely approximates the dimensions of the anterior mitral leaflet of that particular patient.
It will be appreciated that the apparatus 10 according to the present invention is used to select an appropriately sized buttress. The substantially semi- circle-shaped member 18 approximates the clear area of the anterior mitral leaflet, whilst the segment -shaped member 12 approximates the effect on mitral orifice area upon completion of mitral valve reconstruction. The segment -shaped member 12 also approximates the total surface area of the anterior mitral leaflet which, in turn, approximates the area of the mitral valve during systole, that is, during dynamic contraction. Preferably, the length of the arc 14 is twice the length of the chord 16 and four times the radius of the substantially semi-circle-shaped member 18. Thus, the apparatus 10 according to the present invention, identifies a length of buttress proportional to a particular anterior mitral leaflet measured, in vivo , in a particular patient.
It will, therefore, be appreciated that the apparatus 10 according to the present invention identifies a desired length of buttress for mitral valve reconstruction in a particular patient, the buttress being pre- formed using an apparatus for cardiac valve reconstruction as disclosed in WO 97/03625.
The surgeon then selects an annuloplasty buttress whose unextended length approximates the arc 14 of the segment-shaped member 12 of that specific apparatus 10.
The cardiac surgeon then offers the annuloplasty buttress to the mitral annulus in an extended condition and sutures the annuloplasty buttress to the mitral annulus, preferably in the extended condition. If, as is preferred, the length of the chord 16 approximates twice the maximum depth of the anterior mitral leaflet so that the length of the arc 14 approximates the length of the buttress in its unextended condition, the cardiac surgeon can then re-offer the apparatus 10 to the mitral annulus, to confirm that the terminal sutures of the buttress have been correctly positioned.
Alternatively, a single buttress 10 according to the invention could be provided to the cardiac surgeon, provided that the arc 14 and chord 16 of the segment- shaped member 12 and the second arc 20 of the substantially semi-circle-shaped member 18 are suitably graduated.