Features and advantages of the present invention will become appreciated as the same become better understood with reference to the specification, claims, and appended drawings wherein:
The present invention provides a novel annuloplasty ring for correcting pathologies associated with mitral valve prolapse, also known by a number of other names given above, including Barlow's syndrome. With this pathology, the mitral valve leaflets are distended (i.e., stretched, lengthened, swelled, thickened) or in general have become loose and floppy such that they do not properly coapt. In contrast to prior repair techniques, the annuloplasty ring of the present invention reduces or eliminates the need for a sliding annuloplasty. Furthermore, instead of attempting to constrict the mitral annulus by the addition of an annuloplasty ring that is under-sized with respect to the existing annulus, the present invention accommodates the excess material of the leaflets by providing a larger support ring than has previously been utilized. Typical annuloplasty support rings have a long or major dimension and a short or minor dimension, with the conventional ratio of the minor to major dimension being at most 3:4 (75%), and typically less. The present invention provides an annuloplasty ring that has a significantly increased minor to major dimension ratio of between about 3.3:4 (82.5%) and 4:4 (100%).
Annuloplasty rings of the present invention are desirably made of material(s) that are “generally rigid” and will initially resist distortion when subjected to the stress imparted thereon by the mitral valve annulus of an operating human heart. In this sense, “distortion” means substantial permanent deformation from a predetermined or manufactured shape; the opposite concept of which is “elastic” meaning the ability to recover the ring shape in the absence of an external force. A number of “generally rigid” materials can be utilized that will perform this function, including various bio-compatible polymers and metals and/or alloys. Certain polyesters that resist distortion and also rapid degradation within the body may be used (a material that degrades slowly may provide the required initial support). In a preferred embodiment, at least an inner core or body of the annuloplasty ring of the present invention is made of a suitable metal, such as titanium or its alloys, or ELGILOY made by Elgiloy, L. P. of Elgin, Ill., U.S.A. The core or ring body may be one piece, or may include a plurality of concentric or otherwise cooperating elements. The addition of a silicone tube or band around the ring body and a suture-permeable fabric on the exterior of the ring are also desirably to provide purchase for anchoring sutures.
In a preferred embodiment, the annuloplasty ring of the present invention comprises a continuous ring body made of a titanium alloy. A soft tubular sleeve or outer band, which may be formed from silicone, surrounds the ring body and helps conform tissue to the ring after implantation. Finally, a tubular fabric covering around the silicone sleeve provides an anchoring platform for sutures or other attachment devices such as staples. The fabric covering is typically Dacron (polyethylene terephthalate). The tubular fabric covering around the silicone sleeve provide an interface for securing the annuloplasty ring to the mitral annulus, although other interfaces are contemplated. For example, rings having outward hooks or barbs are known in the art.
With reference now to
As seen in
Looking along the flow axis 32 in
Before continuing, it is important to understand the reference directions associated with the annuloplasty ring 30. First of all, the concept of a central axis is somewhat of a misnomer as the plan view of the ring, such as in
As will be more apparent below, the annuloplasty ring 30 has a relatively complex shape for which a reference plane is difficult to define, as it is for the mitral annulus. However, for purposes of comparing the annuloplasty ring 30 of the present invention against those that preceded it, or those that might be constructed after, it is fair to say that most heart surgeons and annuloplasty ring designers recognize that early planar rings were intended to be implanted in the nominal “annular plane,” (with the understanding that anatomical differences exist from patient to patient). From there, some rings were modified to have an upward bow in the anterior side to conform to the systolic anatomical contour of the anterior aspect of most mitral annuluses. These days, physicians, designers and manufacturers understand the term upward bow when describing mitral annuloplasty rings to mean upward from the original planar design, or reference plane. Therefore, if a mitral annuloplasty ring is described in product literature as having an upward bow, the understanding is that the ring bows upward at that location from adjacent segments that define the reference plane. Likewise, if the literature describes two bows with one relatively higher than the other, it is understood to mean their respective heights parallel to the flow axis, or perpendicular to the reference plane. Otherwise, some rings can be placed on a flat surface and by dint of gravity settle into any number of orientations.
Another way to look at the reference orientation of the ring 30 is that two points on opposite sides of the ring 30, typically along or near the major axis 34, are at the lowest points of the saddle shape and reside in the “reference plane.” For example, as seen in
A still further way to define the flow axis or reference plane is to note the orientation that the ring assumes relative to a delivery holder. Annuloplasty rings are conventionally mounted on holders that include a central hub for connecting to a handle, and the central hub defines an axis. Thus, to see the relative heights of the sides of a ring it may be placed so that the central hub of its holder is perpendicular to a reference surface.
With reference again to
The remainder of the ring 30 aside from the anterior segment AS between the trigone markers T1, T2 will be termed the posterior portion, shown divided into three sequential segments labeled P1, P2, and P3 (counter-clockwise from the first trigone marker T1). The precise angular dividing line between these three segments is not standardized, though they are intended to generally correspond to and abut the three visible cusps of the posterior leaflet of the mitral valve. In an exemplary embodiment, the three segments are approximately equal in angular dimension, and the middle segment P2 is symmetric about the minor axis 36. In an alternative embodiment, the ring 30 is asymmetric so as to bulge outward more toward P1 or P3, such as seen in U.S. Patent Publication No. 2005/0131533, filed Jun. 30, 2004, and entitled Annuloplasty Rings for Repair of Abnormal Mitral Valves, the disclosure of which is incorporated by reference herein.
It should be noted that annuloplasty rings are shaped and marked (e.g., with the trigone markers T1 and T2) so as to orientation-specific, such that the anterior segment is intended to be implanted against the anterior aspect of the mitral annulus, and vice versa with respect to the posterior portion. Annuloplasty rings such as those of the present invention are not rotatable within the annulus. That is, a particular orientation is indicated on the packaging, or by reference to the trigone markers T1, T2, and the ring is constructed to be specific to that orientation. A surgeon would not, for instance, implant the ring with the anterior segment AS adjacent the posterior aspect of the mitral annulus.
The exemplary annuloplasty ring 30 has a rounded isosceles triangular shape in plan view because of an outward bulge 50 centered in the middle segment P2 of the posterior portion of the ring. Stated another way, the middle segment P2 of the posterior portion of the ring has an outward curve (convexity) in comparison with the adjacent segments P1 and P3 which are relatively straight. The exemplary annuloplasty ring 30 bulges outward on the posterior side relative to a conventional 3:4 ratio “D-shaped” annuloplasty ring, such as the relaxed shape of a Carpentier-Edwards Physio® annuloplasty ring available from Edwards Lifesciences of Irvine, Calif. (www.edwards.com). The divergence from the “D-shape” essentially commences mid-way along each of the side segments P1 and P3 and spans an angle which desirably is between 90-130°, and more preferably about 128°.
As mentioned above, the outward bulge 50 preferably results in a minor-major axis dimensional ratio of 3.5:4 (87.5%), although the present invention encompasses rings having an outward bulge 50 that produces ratios of between about 3.3:4 (82.5%) and 4:4 (100%).
It is important to note that although the minor axis dimension 38a increases relative to conventional D-shaped rings, the major axis dimension 38b will remain substantially the same. Furthermore, although the outward bulge 50 is shown within the middle segment P2 of the posterior portion of the ring, the entire posterior portion below the major axis 34 may be affected. That is, the outward bulge 50 may extend into one or both of the first and third segments P1 and P3 of the posterior portion. In that case, the overall triangular shape would expand outward so as to be more “D-shaped.”
In conjunction with the outward bulge 50, the annuloplasty ring 30 also includes an upward bow 60 in the posterior portion, as seen in
The annuloplasty ring 30 further exhibits an upward bow 62 on the anterior segment AS. The magnitude of this bow 62 is given as hp in
As mentioned, and as conventional, the annuloplasty ring 30 construction includes an inner generally rigid core and an outer suture-permeable covering.
With reference now to
The annuloplasty ring body 70 has a rounded isosceles triangular shape in plan view and is oriented about a central flow axis 82. The flow axis 82 defines an upward direction and a downward direction, corresponding to the top and bottom of the page relative to the ring body 70 as seen in
The annuloplasty ring body 70 has a rounded isosceles triangular shape in plan view with a relatively straight anterior segment AS extends around the upper portion of the ring body 70 in
The outline of an isosceles triangle is seen with its sides coinciding with an inner edge of the three relatively straight sides of the ring body 70. The triangle has a long side along the relatively straight anterior segment AS and two equal slightly shorter sides along the side segments 94a, 94b. Two equal anterior corner angles α supplement a posterior vertex angle β. Desirably, the ring body 70 has a shape in which 50°>α>60°, and 60°>β>80°. In a preferred shape, 55°>α>56°, and 68°>β>70°.
The extent of the outward bulge 90 of the ring body 70 has been discussed above in general terms. However, it is important to understand that the major and minor axes can be measured at different points on the ring body 70, and with respect to the completed ring 30 as seen in
The ratio of the minor axis to the major axis desirably falls within a range of 3.3:4 to 4:4 (82.5%-100%), more preferably between about 3.44:4 to 3.6:4 (86%-90%), and most preferably 3.5:4 (87.5%). It should be understood that the dimensional parameters set forth herein with respect to the ring body 70 correspond closely with those of the completed ring 30, though the outward bulk of the outer suture-permeable covering seen in
The exemplary annuloplasty ring body 70 bulges outward on the posterior side relative to a conventional 3:4 ratio “D-shaped” annuloplasty ring body, such as the relaxed shape of a Carpentier-Edwards Physio® annuloplasty ring available from Edwards Lifesciences of Irvine, Calif. (www.edwards.com). A dashed outline 96 of such a conventional 3:4 ratio “D-shaped” annuloplasty ring body is shown to illustrate the more pronounced outward bulge 90 of the present ring body 70.
It is important to note that although the minor axis dimension 88a increases relative to conventional D-shaped ring bodies (i.e., dashed outline 96), the major axis dimension 88b will remain substantially the same (for a given ring size). Furthermore, although the outward bulge 90 is shown centered within the middle of the posterior portion of the ring, the entire posterior portion below the major axis 84 may be affected. That is, the outward bulge 90 may extend into one or both of the side segments 94a, 94b of the posterior portion. Preferably, the divergence from the “D-shape” essentially commences mid-way along each of the side segments 94a, 94b and spans an angle λ which desirably is between 90-130°, and more preferably about 128°.
In the illustrated embodiment, the ring body 70 exhibits two opposed lower flats 100a, 100b located in the side segments 94a, 94b that, as seen in
The exemplary ring body 70 of the present invention includes an upward bow 102 in the posterior portion, as seen in
The upward bow 102 may or may not be formed in the ring body 70 around the same angular extent as the outward bulge 90. In a preferred embodiment, both the outward bulge 90 and upward bow 102 are centered along the minor axis 86, although one or both may be asymmetrically offset as mentioned above. The upward bow 102 may span a peripheral extent of the ring body 70 that is larger than the outward bulge 90. For example, the upward bow 102 may be centered about the minor axis 86 and commence at symmetric locations on both sides of the posterior portion mid-way along each of the side segments 94a, 94b, as indicated in
As seen in
An important aspect of the present invention is the existence of an enhanced anterior bow in combination with a somewhat reduced posterior bow. This is distinct from an earlier ring designed to correct similar pathologies disclosed in co-pending U.S. Patent Publication No. 2006/0129236, filed Feb. 2, 2006, and entitled Annuloplasty Ring for Mitral Valve Prolapse, the disclosure of which is incorporated by reference herein. The earlier ring disclosed a posterior bow, and an anterior side that could be planar or bowed. None of the embodiments described an enhanced anterior bow 104 as discussed above, or an anterior bow that rises higher than a posterior bow 102. It is believed that in some cases a reduced posterior bow is necessary to avoid dehiscence, the likelihood of which tends to increase with higher posterior bows. At the same time, in some cases an enhanced anterior bow is believed to more faithfully match the systolic anatomy of the certain mitral annuluses than previous rings with anterior bows.
The present invention contemplates an annuloplasty ring with an upward and outward posterior bow 102, and an enhanced anterior bow 104, but also with particular dimensions, ratios, and contours to optimize performance. One such dimensional configuration is the cross-sectional shape.
The particular shape shown, a vertically-oriented oval, is believed most desirable because of its rounded contours and consequent lack of stress risers. In a preferred embodiment, the cross-section of the ring body 70 is constant around its periphery, although a varying cross-section to vary the flexibility around the ring body is also contemplated. In one exemplary embodiment, the radial dimension x is between about 60% to 70% of the axial dimension y. Additionally, the top and bottom rounded ends of the cross-section are desirably complete semi-circles having a diameter that equals the radial dimension x. For example, x=0.049 inches (1.24 mm) and y=0.079 inches (2.00 mm).
As mentioned above, the illustrated ring body 70 may be constructed of a single, homogenous length of a relatively rigid material such as titanium. As such, the ring body 70 will substantially resist distortion when subjected to the stress imparted thereon by the mitral valve annulus of an operating human heart. It should be understood that less rigid materials may provide some radial bending flexibility for the ring to accommodate in and out movement of the annulus during systolic-diastolic cycles. For instance, a polymer ring formed with the cross-section shown in
The reader should also note the particular contours of the ring body periphery as seen in the plan view of
Small convex segments having a radius G (centered on the minor axis 86 a distance N from the posterior apex) that have a lesser curvature than the upper corners lead to the relatively straight side segments 94a, 94b (see
Finally, the outermost posterior apex straddling the minor axis 86 has a radius of J that is desirably about the same as the radius F of the anterior corners 95a, 95b. It should be noted that the centers of curvature of the two sides of the outermost posterior apex are slightly offset from the minor axis 86, as indicated, which slightly widens or flattens the posterior point of the ring body relative to a constant curvature. This outermost curved portion spans an angular or peripheral extent of between about 80-90° within the total outward divergence (angle λ,
Although not shown, the ring 30 is usually advanced through the body on a holder, ultimately passing through the left atrium. Many holders are available in the art, though the most preferred are disclosed in co-pending U.S. application Ser. No. ______, filed concurrently herewith, and entitled “Apparatus, System, and Method for Delivering an Annuloplasty Ring,” which is incorporated by reference herein.
The annuloplasty ring of the present invention is believed to more effectively correct the pathology seen with some cases of mitral valve prolapse because it accommodates the longer and/or thicker leaflets instead of attempting to perform a sliding annuloplasty, which is sometimes perceived as more surgical art than an exact science. The combination of the outward bulge and the upward bow on the posterior side of the ring is believed to provide rigid support for the posterior leaflet from which it can more effectively coapt with the anterior leaflet. The annuloplasty ring essentially “pulls” the posterior leaflet outward and upward which reduces its slack or floppiness. Also, in some cases the enhanced anterior bow more correctly conforms to the anterior aspect in systole, which helps shape the anterior leaflet for proper coaptation. Furthermore, the ring should pull the coaptation point outward and upward and away from the LVOT. This should reduce the incidence of SAM and LVOT obstruction and mitral regurgitation post-repair.
While the invention has been described in its preferred embodiments, it is to be understood that the words which have been used are words of description and not of limitation. Therefore, changes may be made within the appended claims without departing from the true scope of the invention.