Abstract:
A mitral annuloplasty ring with an inner core and an outer band located therearound is disclosed. The ring has an anterior region, a posterior region opposite the anterior region, and two side regions therebetween. A cross-sectional width dimension of the outer band is greater in the posterior region of the ring than in the anterior region. A cross-sectional width dimension of a semi-flexible core is thinner in the anterior and posterior regions than in the side regions so that the mitral ring is more rigid in the anterior-posterior direction. A tricuspid annuloplasty ring of the invention has an inner core and an outer band located therearound. The inner core has an anterior region separated across a gap from a septal region, and a posterior region. A cross-sectional width dimension of the outer band is greater in the septal region than either the anterior or posterior regions.

Description:
RELATED APPLICATION(S) 
       [0001]    The present application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Application No. 60/828,458, filed Oct. 6, 2006. 
     
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to prosthetic annuloplasty rings for effecting and maintaining a mitral or tricuspid repair. 
       BACKGROUND OF THE INVENTION 
       [0003]    Repair of the mitral and tricuspid valves is a steadily growing and vital part of cardiac surgery. Experience has shown that effecting and maintaining a mitral or tricuspid repair requires a prosthetic annuloplasty ring. A major goal of a ring is to restore the shape of the annulus to its normal geometry. In mitral regurgitation, the annulus often becomes circular. The ring should restore the normal “D” shape. Fully flexible rings or bands do nothing to correct the shape of the pathologic mitral annulus. Only rigid or semi-flexible rings mold the shape of the mitral annulus. 
         [0004]    One of the most common causes of a failed valve repair is dehiscence of the ring from the annulus. For the mitral annulus, dehiscence almost invariably occurs along the posterior portion of the ring, since this is the area of the annulus where size reduction and increased stress occurs. 
       SUMMARY OF THE INVENTION 
       [0005]    Briefly, and in accordance with the foregoing, embodiments of the present invention provide prosthetic annuloplasty rings which are configured to minimize the likelihood of dehiscence while maintaining the shape of a healthy valve annulus. 
         [0006]    In one embodiment, the present invention provides a saddle-shaped annuloplasty ring with a 4:3 ratio between the transverse dimension and vertical dimension for repairing the mitral valve. The ring is shaped and configured such that it closely mimics the geometry of a healthy mitral annulus. Preferably, the ring includes trigone markings to aid the surgeon with regard to correct positioning. The ring includes a core, an outer band and a cover. The core may be formed of titanium which provides that the ring is rigid. Alternatively, the core may be formed of a more flexible metal, such as Elgiloy or Nitinol, which would provide that the ring is semi-flexible, in which case preferably the ring is provided as being 20% more rigid in the vertical compared to the transverse dimension. 
         [0007]    Preferably, the outer band comprises silicon rubber, and the cover comprises polyester cloth. Additionally, the width of the outer band is desirably greater in the posterior region of the ring than at the anterior region. This facilitates the placement of overlapping sutures of the posterior annulus to provide extra security against ring dehiscence. 
         [0008]    Also disclosed is a tricuspid ring which is configured to minimize the likelihood of dehiscence while maintaining the shape of a healthy valve annulus. The ring is not complete in the 10% of the circumference around the anteroseptal commissure. This prevents suture injury to the conduction system. The ring may have a somewhat spiral shape that mimics the shape of the healthy tricuspid annulus, and the posterior half of the posterior annulus as well as the septal annulus slope down, preferably by about 4 mm. The ring includes a core which is formed of a semi-flexible material, such as Elgiloy or Nitinol, thereby providing that the ring is semi-flexible rather than rigid, which should decrease the odds of dehiscence. The width of an outer band of the ring is greatest in the septal region, thereby allowing overlapping sutures at the septal annulus to allow better anchoring of the ring. 
         [0009]    A further understanding of the nature and advantages of the present invention are set forth in the following description and claims, particularly when considered in conjunction with the accompanying drawings in which like parts bear like reference numerals. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The organization and manner of the structure and operation of the invention, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings wherein like reference numerals identify like elements in which: 
           [0011]      FIG. 1  is a top plan view of a mitral annuloplasty ring which is in accordance with an embodiment of the present invention: 
           [0012]      FIG. 2  is a side view of the annuloplasty ring shown in  FIG. 1 ; 
           [0013]      FIGS. 3A ,  3 B and  3 C are cross-sectional views of the annuloplasty ring shown in  FIG. 1 , taken along lines A-A, B-B and C-C, respectively, of  FIG. 1 , where a core of the ring is a formed metal ring; 
           [0014]      FIGS. 4A ,  4 B and  4 C are cross-sectional views of the annuloplasty ring shown in  FIG. 1 , taken along lines A-A, B-B and C-C, respectively, of  FIG. 1 , where a core of the ring is a round wire; 
           [0015]    FIGS.  1 ′,  2 ′,  3 A′,  3 B′,  3 C′,  4 A′,  4 B′ and  4 C′ correspond to  FIGS. 1 ,  2 ,  3 A,  3 B,  3 C,  4 A,  4 B, and  4 C, respectively, but show preferred dimensions, in millimeters; 
           [0016]      FIG. 5  is a top plan view of a tricuspid annuloplasty ring which is in accordance with an embodiment of the present invention; 
           [0017]      FIG. 6  is a side view of the annuloplasty ring shown in  FIG. 5 ; 
           [0018]      FIGS. 7A and 7B  are cross-sectional views of the annuloplasty ring shown in  FIG. 5 , taken along lines A-A and B-B, respectively, of  FIG. 5 , where a core of the ring is a round wire; 
           [0019]      FIGS. 8A and 8B  are cross-sectional views of the annuloplasty ring shown in  FIG. 5 , taken along lines A-A and B-B, respectively, of  FIG. 5 , where a core of the ring is a formed metal ring; and 
           [0020]    FIGS.  7 A′,  7 B′,  8 A′, and  8 B′ correspond to  FIGS. 7A ,  7 B,  8 A and  8 B, respectively, but show preferred dimensions, in millimeters. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0021]    While this invention may be susceptible to embodiments in different forms, there are shown in the drawings and will be described herein in detail, specific embodiments with the understanding that the present disclosure is to be considered an exemplification of the principles of the invention, and is not intended to limit the invention to that as illustrated. 
         [0022]      FIG. 1  is a top plan view of a mitral annuloplasty ring  10  which is in accordance with an embodiment of the present invention, while  FIG. 2  is a side view. The ring  10  is configured to minimize the likelihood of dehiscence while maintaining the shape of a healthy valve annulus. The ring  10  is a saddle-shaped ring (described below) with a 4:3 ratio between a transverse dimension (identified with reference numeral  12  in  FIG. 1 ) and vertical dimension (identified with reference numeral  14  in  FIG. 1 ). The reader will note that the vertical dimension is as viewed in plan view with an anterior side  28  up, though it is not oriented in this way in the drawings. The ring  10  is shaped and configured such that it closely mimics the geometry of a healthy mitral annulus. Preferably, an exterior surface  16  of the ring  10  includes trigone markings  18 ,  20  to aid the surgeon with regard to correct positioning. The trigone markings  18 , are located at the junction of the anterior region  28  and the side regions  32 ,  33 . Preferably, the range of ring sizes varies from a transverse internal diameter of 24-36 mm. The size needed is determined by measuring the area of the anterior leaflet with templates corresponding to the various ring sizes. 
         [0023]      FIGS. 3A ,  3 B and  3 C are cross-sectional views of the ring  10  taken along lines A-A, B-B and C-C, respectively, of  FIG. 1 . As shown, the ring  10  consists of a core  22 , an outer band  24  and a cover  26 . 
         [0024]    In a first embodiment of the present invention, the core  22  is formed of titanium which provides that the ring  10  is rigid. Alternatively, the core  22  may be formed of a more flexible metal which would provide that the ring  10  is semi-flexible rather than rigid. In this sense, the term “semi-flexible” refers to annuloplasty ring materials that are somewhat rigid but do flex due to the natural forces after implant. Semi-flexible means not as rigid as titanium, but more rigid than “fully flexible” rings made of, for example, silicone. Specifically, in a second embodiment of the present invention the core  22  is made of Elgiloy, and in a third embodiment of the present invention the core  22  is made of Nitinol. Regardless of what the core  22  is comprised of, preferably the outer band  24  comprises silicon rubber, and the cover  26  comprises polyester cloth. Although not specifically shown, the ring  10  may also include a barium impregnated string to render the ring radiopaque. 
         [0025]      FIG. 3A  provides a cross-sectional view of an anterior region  28  of the ring  10 , while  FIG. 3B  provides a cross-sectional view of a posterior region  30 , and  FIG. 3C  provides a cross-sectional view of side regions  32  and  33 , which are identical in cross-section. In a “saddle-shaped” ring, the ring periphery describes a three-dimensional path that gradually curves up at the anterior and posterior regions  28 ,  30 , and down at the side regions  32  and  33 , as seen in FIGS.  2  and  2 ′. In the illustrated embodiment, the anterior and posterior regions  28 ,  30  rise to about the same height, though they may be at different heights as desired. 
         [0026]    As identified by comparing  FIG. 3A  to  FIG. 3B , the width (dimension  34  in  FIGS. 3A ,  3 B, and  3 C) of the outer band  24  is greater, such as 30% greater, in the posterior region  30  of the ring  10  than at the anterior region  28 . This facilitates the placement of overlapping sutures of the posterior annulus to provide extra security against ring dehiscence. Preferably, the width  34  of the band  24  begins to change at the trigone markings  18 ,  20  on the ring  10 , gradually becoming thicker until a maximum at the mid-point of the posterior region  30 . It should also be noted that the width of the outer band  24  at the posterior region  30  is equal to or greater than the width of the band at both the side regions  32 ,  33 . For example, as seen by comparing FIGS.  4 A′ and  5 A′, and  4 B′ and  5 B′, the width of the outer band  24  at the posterior region  30  ranges between 1.3 mm (with a titanium core  22 ) to 2.2 mm (with a semi-flexible core), while the width of the outer band  24  at the side regions is a maximum of 1.3 mm (same with all core materials). In contrast, depending on the form and material of the inner core  22 , the width of the outer band  24  at the anterior region  28  is less than, equal to, or greater than the width at the side regions  32 ,  33 , as seen by comparing FIGS.  3 A′ and  5 A′, and  3 B′ and  5 B′. 
         [0027]    As discussed above, the core  22  can be provided as being formed of titanium which would tend to make ring  10  rigid. Alternatively, the core  22  may be formed of a more flexible metal, such as Elgiloy or Nitinol, which would make the ring semi-flexible rather than rigid. This semi-flexible alloy allows the ring  10  to flex during the cardiac cycle without losing its shape. Hopefully, the flexibility will minimize local annular stresses likely to produce dehiscence. 
         [0028]    If Elgiloy or Nitinol is used for the core  22 , the core  22  may be shaped somewhat differently than if titanium is used. This change in cross-sectional shape is identified in  FIGS. 3A ,  3 B,  4 A,  4 B,  3 A′,  3 B′,  4 A′ and  4 B′ using a dotted line  36 . The dotted line  36  represents the outer surface of a titanium core  22 , in contrast to the solid cross-section of a semi-flexible (e.g., Nitinol or Elgiloy) core. In the illustrated embodiment, the solid cross-section includes an axially-oriented surface that defines the outer surface of a semi-flexible core  22 , in contrast to the dotted line  36  which represents the outer surface of a titanium core and has a concave outer profile in radial section as shown. 
         [0029]    If Elgiloy or Nitinol is used for the core  22 , the ring  10  is preferably configured such that it is 20% more rigid in the vertical dimension  14  (the anterior-posterior direction) as compared to the transverse dimension  12 . In other words, it is harder to squeeze the ring  10  between the anterior and posterior regions  28 ,  30  in  FIG. 1  than it is to squeeze the ring  10  between the side regions  32 ,  33 . This difference in rigidity/flexibility derives from a particular cross-sectional shape of the core  22  which overcomes the natural inclination for the ring to be more flexible in the vertical dimension. That is, if the ring  10  were the same cross section all the way around its periphery, the longer moment arm in bending when squeezing the anterior and posterior regions  28 ,  30  would naturally permit greater flexing or inward movement than when squeezing the side regions. 
         [0030]    In an exemplary embodiment, the width (dimension  35  in  FIGS. 3A-3C  and  4 A- 4 C) of the core  22  may be thinner in the anterior and posterior regions ( 28  and  30 ) than in side regions  32  and  33 . More specifically, the width dimension  35  is shown measuring the extent of the core  22  as seen in dotted line  36 , but the width for cores of semi-flexible material such as Elgiloy or Nitinol would only extend to the solid line cross-section. There is thus a difference in the width dimension at the anterior and posterior regions for rings made of a semi-flexible material versus a ring made of a rigid material, such as titanium. However, the core width  35  of both semi-flexible and rigid rings remains the same at the side regions  32 ,  33  because it is desirable to maintain in semi-flexible rings the resistance to bending from squeezing the ring  10  in the transverse dimension (vertical in  FIG. 1 ). 
         [0031]    Preferably, the width  35  of the core  22  begins to change at the trigone markings  18 ,  20  on the ring  10 , and most preferably reduces gradually from the trigones to the mid-point of the anterior and posterior regions  28 ,  30 . In particular, the cross-section of the core  22  of semi-flexible rings desirably attains a maximum at the side regions  32 ,  33 , as seen in  FIGS. 3C and 4C , and gradually reduces toward the anterior and posterior regions  28 ,  30 , as seen in solid line in  FIGS. 3A-3B  and  4 A- 4 B. Alternatively, an abrupt change in cross-section or one which while not abrupt is sharp or non-linear may be utilized. For instance, from a maximum at the side regions  32 ,  33 , the width  35  may decrease smoothly but rapidly over an arc of, say, 10° to the lesser width of the anterior and posterior regions  28 ,  30 . It is also worth mentioning that the reduced width  35  at the anterior and posterior regions  28 ,  30  may be equal or not as desired. 
         [0032]    If Nitinol is used as the core  22  of the ring  10 , the ring  10  could be used in association with a method which is in accordance with an embodiment of the present invention. Specifically, the design would be uniquely well suited for minimally invasive valve cases with working ports too small to accommodate currently available rigid rings. At present, only fully flexible prostheses, such as the Duran ring or the Cosgrove band, can traverse these 20 mm working ports. These fully flexible prostheses do nothing to decrease the vertical dimension, which has been increasingly recognized as important in maintaining a durable valve repair. By immersing the Nitinol core ring in iced saline, the ring would be readily deformable (martensite phase). This would facilitate passage of the ring through 20 mm working ports used in robotic valve repair. As the ring warmed up in the chest, it would resume its saddle shape (austensite phase). The silicon rubber band would facilitate anchoring the band to the annulus with Coalescent Nitinol clips. Until now, these clips could only be used with fully flexible prostheses. 
         [0033]    Regardless of whether the core  22  is made of titanium, Elgiloy or Nitinol, the core  22  can be formed of a round wire, in which case the cross-sectional views taken along lines A-A, B-B and C-C of  FIG. 1  would appear as shown  FIGS. 3A ,  4 A and  5 A, respectively. Alternatively, the core  22  can be a formed metal ring, in which case the cross-sectional views taken along lines A-A, B-B and C-C of  FIG. 1  would appear as shown  FIGS. 3B ,  4 B and  5 B, respectively. A dotted line  36  is also used in  FIGS. 3B ,  4 B and  5 B to show the situation where the core  22  is an Elgiloy or Nitinol formed metal ring. 
         [0034]    As shown in  FIG. 2 , the ring  10  may be provided as being slightly asymmetric, with the portion at the left trigone  20  one mm deeper than the right trigone  18 . In other words, the side regions  32 ,  33  drop to different heights, with the left side  32  (as viewed from above with the anterior side  28  up) lying on a reference line seen in  FIG. 2  while the right side  33  is slightly spaced therefrom. This more closely reproduces the true natural shape of the healthy mitral annulus. Even if the ring  10  is provided as being slightly asymmetric, the core  22  can be titanium, Elgiloy, or Nitinol, for example. 
         [0035]    FIGS.  1 ′,  2 ′,  3 A′,  4 A′,  3 A′,  3 B′,  4 B′ and  5 B′ correspond to  FIGS. 1 ,  2 ,  3 A,  4 A,  5 A,  3 B,  4 B and  5 B, respectively, but show preferred dimensions, in millimeters. It should be noted that the dimensions shown are only one example, intended to provide the desired properties described herein, and other dimensions may be used while staying fully within the scope of the present invention. For instance, the magnitudes shown may represent dimensionless ratios of the various dimensions. In one example, as seen in FIG.  2 ′, the left side  32  (see  FIG. 2 ) has a height of 5 mm from the summit of the anterior side  28 , while the right side  33  has an equivalent height of 4 mm. The downward drop of the left side  32  may be more or less, but desirably is about 20% more than the downward drop of the right side  33 . 
         [0036]      FIG. 6  is a top plan view of a tricuspid ring  40  which is in accordance with an embodiment of the present invention, while  FIG. 7  is a side view. The ring  40  is configured to minimize the likelihood of dehiscence while maintaining the shape of a healthy valve annulus. Preferably, the ring  40  comes in different sizes with an internal diameter being between 24-36 mm. Regardless of the size, the ring  40  is not complete in 10% of the circumference around the anteroseptal commissure (i.e., area  42  in  FIGS. 6 and 7 ). This prevents suture injury to the conduction system. The ring  40  has a somewhat spiral shape that mimics the shape of the healthy tricuspid annulus. The anterior annulus  44  and anterior half  46  of the posterior annulus  48  are in the same plane (identified with line  50  in  FIG. 7 ). The posterior half  52  of the posterior annulus  48  as well as the septal annulus  54  slope down, preferably 4 mm (identified with dimension  56  in  FIG. 7 ). 
         [0037]      FIGS. 8A and 9A  are cross-sectional views of the ring  40  taken along lines A-A and B-B, respectively, of  FIG. 1 . As shown, like the ring  20  described hereinabove, the ring  40  includes a core  58 , an outer band  60  and a cover  62 . Preferably, the core  58  is formed of a semi-flexible material. Specifically, in one embodiment, the core  58  is provided as being formed of Elgiloy. In another embodiment, the core is provided as being formed of Nitinol. Regardless, using a semi-flexible material for the core  58  provides that the ring  40  is semi-flexible rather than rigid, which should decrease the odds of dehiscence. Currently, only rigid rings have been specifically constructed for tricuspid repair. Regardless of what the core  58  is comprised, preferably the outer band  60  is formed of a silastic material, such as silicone, and the cover  62  is comprised of polyester cloth. 
         [0038]      FIG. 8A  is a cross-sectional view taken along line A-A of  FIG. 6  and provides a cross-sectional view of the anterior region of the ring  40 . This view also applies to the posterior region. In contrast,  FIG. 9A  provides a cross-sectional view taken along line B-B of  FIG. 6  and corresponds to the septal region of the ring. As recognized by comparing  FIG. 8A  to  FIG. 9A , the width (dimension  64  in  FIGS. 8A and 9A ) of the outer band  60  is greater (such as 1.3 times greater) in the septal region  54  than either the anterior region  44  or posterior region  48 . This allows overlapping sutures at the septal annulus  54  to allow better anchoring of the ring  40 . 
         [0039]    As discussed above, an embodiment of the present invention provides that the core  58  of the ring  40  is provided as being formed of Nitinol. This allows further flexibility and further minimizes the likelihood of dehiscence. If Nitinol is used as the core  58  of the ring  40 , the ring  40  could be used in association with a method which is in accordance with an embodiment of the present invention. Specifically, cooling the ring  40  in iced saline will facilitate passage of the ring  40  through small working ports for minimal access valve surgery. Additionally, the diameter  64  of the silicone rubber band  60  will facilitate attachment of the ring  40  to the annulus with Coalescent Nitinol clips. 
         [0040]    Regardless of whether the core  58  is made of Elgiloy or Nitinol, the core  58  can be formed of a round wire, in which case the cross-sectional views taken along lines A-A and B-B of  FIG. 6  would appear as shown  FIGS. 8A and 9A , respectively. Alternatively, the core  58  can be a formed metal ring, in which case the cross-sectional views taken along lines A-A and B-B of  FIG. 6  would appear as shown  FIGS. 8B and 9B , respectively. 
         [0041]    FIGS.  8 A′,  9 A′,  8 B′ and  9 B′ correspond to  FIGS. 8A ,  9 A,  8 B and  9 B, respectively, but show preferred dimensions, in millimeters. It should be noted that the dimensions shown are only one example, intended to provide the desired properties described herein, and other dimensions may be used while staying fully within the scope of the present invention. For instance, the magnitudes shown may represent dimensionless ratios of the various dimensions. 
         [0042]    Disclosed herein are several embodiments of mitral and tricuspid rings, each of which is configured to minimize the likelihood of dehiscence while maintaining the shape of a healthy valve annulus. While preferred embodiments of the invention are shown and described, it is envisioned that those skilled in the art may devise various modifications without departing from the spirit and scope of the foregoing description.