Patent Publication Number: US-2021161665-A1

Title: Semi-flexible annuloplasty ring

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Divisional application of Ser. No. 13/576,982, filed Jan. 29, 2013, entitled, “SEMI-FLEXIBLE ANNULOPLASTY RING,” now allowed, which claims priority under 35 U.S.C. § 371 to International Application No. PCT/US2011/023386, filed Feb. 1, 2011, which claims the benefit of U.S. Provisional Application Ser. No. 61/301,158, filed Feb. 3, 2010 and U.S. Provisional Application Ser. No. 61/301,532 filed Feb. 4, 2010, the entire teachings of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     Annuloplasty rings for heart valve repair, and more particularly, a semi-flexible annuloplasty ring to treat functional tricuspid regurgitation. 
     BACKGROUND 
     The anatomy and physiology of the human heart is well known. Of the four one-way valves in the heart, the two inlet valves are the mitral valve of the left side of the heart, and the tricuspid valve on the right side of the heart. The tricuspid valve is located between the right atrium and the right ventricle. The three leaflets of the tricuspid valve laterally terminate at the tricuspid annulus. Blood flows from the superior and inferior vena cava into the right atrium, then through the tricuspid valve during diastole to fill the right ventricle. During ventricular systole, the tricuspid valve is closed and blood is ejected through the pulmonary valve into the pulmonary artery and hence through the lungs. At the end of ventricular systole the pulmonary valve closes. Leaving the lungs, the now oxygenated blood flows into the left atrium and hence through the mitral valve into the left ventricle during ventricular diastole. Finally, at ventricular systole the mitral valve closes and blood is ejected through the aortic valve into the aorta. However, should the mitral valve become regurgitant due to disease then some percentage of the left ventricular stroke volume will flow backwards through the mitral valve into the left atrium. This regurgitation causes the left atrial pressure to rise, in turn causing pulmonary artery pressure to rise, that is reflected back to the right ventricular pressure. This mechanism was more fully described by Shiran and Sagie (Shiran and Sagie (2009) J. Am. Coll. Cardiology 53:401-408, “Tricuspid Regurgitation in Mitral Valve Disease: Incidence, Prognostic Implications, Mechanism, and Management”) the contents of which, along with contents of all references cited herein, are incorporated herein in their entirety. 
     The right ventricle is a thin walled muscular “pocket” wrapped around the main muscularity of the left ventricle. Without being bound by theory, as a result of the above-described ventricular pressure, the thin-walled right ventricle and a portion of the tricuspid annulus may dilate. Initially, tricuspid leaflet coaptation is reduced, but the valve remains competent. Later, when the tricuspid annulus is further dilated leaflet coaptation is lost and tricuspid valve regurgitation results. This is known as functional tricuspid regurgitation because the tricuspid valve leaflets remain normal. The problem lies with the dilated annulus in the anterior and posterior segments. This was first described by Bex and LeCompte (Bex and LeCompte (1986) J. Cardiac Surgery 1:151-159, “Tricuspid Valve Repair Using a Flexible Linear Reducer”) and later by Dreyfus (Dreyfus, et al. (2005) Ann Thoracic Surgery 79:127-32, “Secondary Tricuspid Regurgitation or Dilation: Which Should Be the Criteria for Surgical Repair?”).  FIG. 1 , which is adapted from Dreyfus, illustrates dilation of the tricuspid annulus  2 , the relative position of the posterior leaflet  60 , anterior leaflet  62  and septal leaflet  64  as well as the anterior/posterior (A/P) commissure  3 , posterior/septal (P/S) commissure  4  and septal/anterior (S/A) commissure  5 . 
     Deformation of the tricuspid annulus by other means than that described above might also lead to functional tricuspid valve regurgitation. 
     A significant surgical problem that exists today is the operative recognition of the severity of the tricuspid valve regurgitation problem Immediately prior to mitral valve surgery the patient is anaesthetized and an esophageal ultrasonic probe is introduced and mitral and tricuspid regurgitation assessed. One difficulty is that one effect of the anesthesia may be to significantly suppress tricuspid regurgitation. The ultra-sonic probe display may lead a surgeon incorrectly to believe that the tricuspid regurgitation is absent or minimal. Unfortunately, later, post-operatively when the drugs have worn off, the true level of tricuspid regurgitation typically becomes much more severe than that indicated intra-operatively or pre-operatively. Regrettably, reoperation mortality on patients with tricuspid regurgitation is about 30%, but worse, if severe tricuspid regurgitation is left untreated, 5 year patient survival is only about 50%. This suggests that many more patients undergoing mitral valve repair should also have concomitant tricuspid annulus reduction than is currently the case. The current rate of tricuspid annuloplasty reduction associated with mitral valve repair varies between about 5% and 60%. At the high end of the range are surgeons at centers of excellence who operate early on patients with mitral valve disease before right ventricular and tricuspid dilatation becomes significant. But, many other surgeons fail to appreciate that the minor tricuspid regurgitation diagnosed pre-operatively or intra-operatively may later become severe, even as early as in the recovery room after the effects of the anesthetics have worn off. 
     Early repairs of the tricuspid valve annulus were described by De Vega (De Vega (1972) Rev Esp. Cardiol. 6:555-557, “La anuloplastia selective, regulable y permanente”) who used a double continuous 2/0 or 3/0 polypropylene suture which ran along the anterior and posterior annulus, corresponding to the right ventricular free walls. A drawback of the technique was and remains a tendency for the sutures to tear out of the tissue. However, a modified De Vega technique described by Antunes (Antunes (2003) Operative Techniques in Thoracic and Cardiovascular Surgery De Vega 8:169-76, “De Vega annuloplasty of the tricuspid valve”) using 11-13 pledgets, although adding complexity and time to the operation, appears to mitigate the dehiscence problem. 
     Other methods and devices have been used to treat functional tricuspid regurgitation including the use of flexible or, alternatively, rigid annuloplasty rings, each of which has demonstrated at least one problem. When implanting, tricuspid annuloplasty rings several precautions are needed, in particular the atrioventricular (AV) node must be avoided by the implantation suture, and in this regard the gap of known C-shaped annuloplasty rings may be too small and allow implantation suture to penetrate the AV node and cause heart block. Another issue when implanting a flexible ring on the tricuspid annulus is correct placement of the implant on the annulus. Yet another issue is that the tricuspid annulus is in a roughly concave plane rather than a flat plane. As functional tricuspid regurgitation advances the annulus becomes less concave and more flat. Thus, an entirely rigid tricuspid ring may not conform well to the annulus. 
     The present invention is directed toward overcoming one or more of the problems discussed above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic plan view of a tricuspid valve illustrating a normal tricuspid valve annulus and its progressive asymmetrical enlargement causing functional tricuspid regurgitation as depicted by Dreyfus; 
         FIG. 2  is a plan view of an embodiment of a semi-flexible annuloplasty ring to treat functional tricuspid regurgitation; 
         FIG. 3  is a partial sectional plan view of the annuloplasty ring of  FIG. 2 ; 
         FIG. 4  is a cross-sectional view of the annuloplasty ring of  FIG. 2  taken along line AA of  FIG. 3 ; 
         FIG. 5  is a cross-sectional view of the annuloplasty ring of  FIG. 2  taken along line BB of  FIG. 3 ; 
         FIG. 6  is a plan view of the annuloplasty ring of  FIG. 2  illustrating an outside diameter OD, inside diameter ID, nominal size NS and gap G between the anterior end and the septal end of the ring; 
         FIG. 7  is a side elevation of the annuloplasty ring of  FIG. 2  taken in the direction of the arrow C of  FIG. 6  showing the annuloplasty ring mounted on its holder (not shown); 
         FIG. 8  is a side elevation of the annuloplasty ring of  FIG. 2  taken in the direction of the arrow C of  FIG. 6  showing the annuloplasty ring removed from a holder and axial displacement of the ring ends; 
         FIG. 9  is a schematic perspective view of the annuloplasty ring of  FIG. 2  implanted on a corrected tricuspid valve annulus; and 
         FIG. 10  is a plan view of a semi-flexible annuloplasty ring of  FIG. 2  attached to a ring holder. 
     
    
    
     DETAILED DESCRIPTION 
     Unless otherwise indicated, all numbers expressing quantities of ingredients, dimensions reaction conditions and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about”. 
     In this application and the claims, the use of the singular includes the plural unless specifically stated otherwise. In addition, use of “or” means “and/or” unless stated otherwise. Moreover, the use of the term “including”, as well as other forms, such as “includes” and “included”, is not limiting. Also, terms such as “element” or “component” encompass both elements and components comprising one unit and elements and components that comprise more than one unit unless specifically stated otherwise. 
     A semi-flexible annuloplasty ring  10  is shown in a plan view in  FIG. 2 . As seen in  FIG. 2 , the semi-flexible annuloplasty ring  10  comprises an elongate tube of suturable material  12  formed into a C-shaped ring. In one specific embodiment described herein, the suturable material may be a biocompatible ribbon of heat settable material heat set into a tubular configuration as described in Wright, U.S. Pat. No. 5,674,279, the disclosure of which is hereby incorporated in its entirety herein. An example of a suitable heat settable material is Polyethertetraphylate (Polyester). Embodiments could also include other suitable braided, woven or knitted biocompatible materials such as Nylon or other biocompatible materials. The material must be suitable to readily receive a needle carrying a suture, a suture clip or other similar securing means and be capable of maintaining a position on an annulus of a heart valve without fraying once secured in place. 
     Wright &#39;279 describes a process of making a braided ribbon of material that includes starting with a heat-settable, meltable fiber tubing and sliding the tubing over a mandrel and then rolling the tubing back to form a double-walled tube. The double walled tube is cut to a desired length with a heated blade that cuts by melting the fibers infusing the fibers together to form a fused end with inner and outer walls being joined at a fused joint. The double wide tube is then slipped over a V-shaped mandrel which may be made of a more high temperature resistant polymer or metal and clamped between forming tools configured to define a V-shaped opening the size and shape of a desired V-shaped band. The band is then heat set at a temperature sufficient to set the polymer of which the tubing is formed without fusing. For example, if the tube is of polyester, temperatures in a range of 100-110° C. may be suitable and a heating period may be about 10 minutes. The opening of the V can be sewn together using lengthwise sutures thus forming a 4-walled tube as depicted, for example in  FIGS. 3-5 . 
     Various markers may be provided on the suturable material to aid a surgeon during installation of the semi-flexible annuloplasty ring  10  onto a valve annulus. For example, the embodiment illustrated in  FIG. 2  is intended for installation on a tricuspid valve annulus. In this embodiment, the markers include a demarcation marker  14  and an anterior/posterior (“A/P”) commissure marker  16 . The demarcation marker  14  provides a visual indication to a surgeon of where sutures or suture clips can be placed without the needle or clip used for implanting interfering with an interior stiffener or operation of the semi-flexible annuloplasty ring  10 . The A/P commissure marker is configured to align with the A/P commissure of the tricuspid heart valve and aid the surgeon in correctly placing the semi-flexible annuloplasty ring  10  on the tricuspid valve annulus (see  FIG. 9 ). In embodiments configured for use with other heart valves other markers may be provided. In addition, in such embodiments the semi-flexible annuloplasty ring  10  may have a more symmetric C-shaped footprint than the embodiment of a semi-flexible annuloplasty ring  10  depicted in  FIG. 2 . 
     The embodiment of the semi-flexible annuloplasty ring  10  in  FIG. 2  comprises a central segment  18 , a first end segment  20  (also known as an anterior end) and a second end segment  22  (also known as a septal end). The central segment  18  is defined between radial suture seams  24 ,  26 , which are used to secure an arcuate stiffener lengthwise within the central segment  18  as will be discussed in greater detail below. 
       FIG. 3  depicts the semi-flexible annuloplasty ring  10  of  FIG. 2  with various cutaway portions to illustrate the internal structure of the semi-flexible annuloplasty ring  10 . Referring to the cutaway portion  28  in the central segment  18  (see also  FIG. 4 ), the suturable material  12  is seen to comprise a number of layers as described in the Wright &#39;279 patent referenced and described above. The suturable material  12  is formed into a tube by means of circumferential stitching forming a circumferential seam  25 . 
     Within the central portion of the semi-flexible annuloplasty ring  10  resides an arcuate stiffener  30 . The arcuate stiffener  30  in the illustrated embodiment comprises a close-coiled spring  32  of a biocompatible metal such as a Carpentier MP35N alloy. The spring may be wound using 0.009-0.012 inch diameter wire, although other wire diameters in the range of 0.005-0.020 inches are suitable. In the particular embodiment described herein, the spring has an inside diameter of about 0.029 inches and an outside diameter of about 0.055 inches. Other inside and outside diameters are within the scope of the invention. The helical coils of the spring define a spring cavity within the inside diameter. The stiffener  30  is configured to prevent lengthwise compression and to resist axial and radial deformation of the first circumferential segment. As used herein, “axial” and “radial” are relative to an axis of a valve annulus that extends in the direction of blood flow. Thus, “axial” deformation means in a direction along this axis and “radial” deformation means in a direction toward or away from the axis. “Axial and radial” deformation is intended to encompass only axial deformation, only radial deformation or deformation that is concurrently axial and radial. A stiffener wire  34  is axially received in the spring cavity to provide the resistance to axial and radial deformation. The stiffener wire  34  may be, for example, a biocompatible metal of the same composition as the spring to prevent galvanic corrosion. The stiffener wire should be of a diameter to resist radial deformation, as this phrase is defined above. By way of example, where the semi-flexible annuloplasty ring is to be used for a tricuspid valve to treat functional tricuspid regurgitation, a MP35N alloy, with a diameter of about 0.028 inches provides good results and a range of 0.015-0.050 inches (depending upon the desired stiffness and the ring size) generally being acceptable. 
     The stiffener wire  34  is secured lengthwise within the close coiled spring  32  by end caps  36  on each end of the stiffener. An end cap  36  proximate the second end segment  22  is shown in the cutaway portion  38  of  FIG. 3 . Although not shown, an identical end cap  36  is proximate the first end segment  20  abutting the radial suture seam  24 . Each of the end caps  36  are radiused or chamfered to remove any sharp edge and may be hemispherical. The end caps are configured to prevent the stiffener from protruding through the suturable material  12  when the semi-flexible annuloplasty ring  10  is formed as illustrated in  FIGS. 2 and 3 . In the illustrated embodiment, the end caps have an outer diameter of about 0.046 inches. The stiffener  30  comprises a posterior portion  40  between the A/P commissure marker  16 , and the radial suture seam  26  having a posterior radius  42  selected to conform the posterior portion  40  of the semi-flexible annuloplasty ring  10  to at least a posterior portion of a healthy tricuspid valve annulus prior to dilation (a “pre-dilated annulus”). The stiffener  30  further comprises an anterior portion  44  extending between the A/P commissure marker  16  and the radial suture seam  24 . The anterior portion  44  has an anterior radius  46  that is larger than the posterior radius  42  and is selected so that with the semi-flexible annuloplasty ring  10  operatively attached to the annulus of a tricuspid valve, the anterior radius conforms to at least an anterior portion of the pre-dilated annulus. The close coiled spring  32  is received inside a silicon rubber tube  47 . 
     The first end segment  20  and the second end segment  22  do not include a stiffener and as a result the first and second end segments are axially and radially deformable as will be described below. In the embodiment illustrated herein, an x-ray marker  48  is disposed within the tube and each of the first and second ends  20 ,  22 . The x-ray marker  48  is non-structural in that it does not significantly inhibit radial or axial deformation of the first and second ends. In the illustrated embodiment, the x-ray marker  48  is a 0.020 inch silicone rubber band impregnated with tungsten and barium sulfate. Referring again to  FIG. 3 , the x-ray markers  48  are secured within the first and second end segments  20 ,  22  by feeding the x-ray marker  48  through braids  50  of the suturable material  12  that are teased out of the suturable material  12 . 
     The tube of suturable material  12  may be formed in a manner discussed in the Wright &#39;279 patent referenced and described above. With the suturable material  12  formed into a length having a V-cross section, the stiffener  30  is placed at the bottom of the V and is held in place with tack stitches  52  (see  FIG. 3 ) spaced circumferentially around the circumference of the stiffener  30 . The x-ray markers  48  are likewise placed in bottom of the V and, as described above, are secured by feeding the x-ray marker  48  through the teased braids  50  of the suturable material  12 . Thereafter the circumferential seam  25  is provided to form the V-cross section into a tube. The demarcation marker  14  and the A/P commissure marker  16  can be added as sutures. Further, the radial suture seams  24 ,  26  can be added to circumferentially confine the arcuate stiffener within the central segment. The assembled semi-flexible annuloplasty ring  10  is then preferably heat set to maintain the configuration as illustrated in  FIGS. 2, 3 and 6-10 . Referring to  FIG. 6 , the semi-flexible annuloplasty ring  10  is heat set to have a select outer diameter OD and a select inner diameter ID as illustrated. This leaves the semi-flexible annuloplasty ring  10  with a nominal size NS dimension as illustrated in  FIG. 6 . When heat set, the semi-flexible annuloplasty ring  10  further maintains a gap G between the first end segment  20  and second end segment  22 . The gap G has a length greater than about 50% of a nominal size NS of the annuloplasty ring. In one embodiment, the gap G may have a length of about 60% of the nominal size NS. This size is selected to minimize the risk of damaging the atrioventricular (AV) node during implantation of the semi-flexible annuloplasty ring  10 . Referring to  FIG. 7 , when heat set, the semi-flexible annuloplasty ring  10  is substantially planar about a plane  51  defined by the arcuate stiffener  30 . 
     Referring to  FIG. 8 , the central segment  18  of the semi-flexible annuloplasty ring  10  is intended to remain substantially within the plane  51  of the arcuate stiffener  30 . The first and second end segments  20 ,  22  are substantially free to deform axially in either direction as depicted in  FIG. 8 . Although not shown, the first and second end segments  20 ,  22  can also deform radially. 
       FIG. 9  illustrates the semi-flexible annuloplasty ring  10  operatively attached to a tricuspid valve of a heart with the right atrial wall cut and retracted to expose the tricuspid valve. The semi-flexible annuloplasty ring  10  is dimensioned and positioned to conform the tricuspid valve annulus to a pre-dilated or near-normal state. The posterior portion  40  is shown aligned with the tricuspid annulus at the base of the posterior leaflet  60 . The anterior portion  44  of the central segment  18  overlies about one third the circumferential length of the anterior portion of the tricuspid valve annulus at the base of the anterior leaflet  62 . The first end segment  20 , which can also be referred to the anterior end, is secured to the anterior annulus as well. The second end segment  22 , also known as the septal end, is attached to the septal portion of the tricuspid valve annulus at the base of the septal leaflet  64 . As seen in  FIG. 9 , only 8 sutures  66  are required to secure the semi-flexible annuloplasty ring  10  to the tricuspid valve annulus. Depending on patient&#39;s anatomy, one or two or even three fewer or more sutures may be used. In any event, this is fewer than the 12-14 sutures required for implanting prior art annuloplasty rings to a tricuspid valve. Decreasing the number of sutures allows the semi-flexible annuloplasty ring  10  to be implanted more quickly, on the order of about fifteen minutes, which is considerably faster than prior art devices. 
       FIG. 10  is a plan view of a semi-flexible annuloplasty ring  10  of  FIG. 2  attached to a holder  70 .  FIG. 10  further illustrates preferred locations of eight attachment sutures for implanting the annuloplasty ring on a tricuspid valve annulus. 
     The central portion  40  of the semi-flexible annuloplasty ring  10  maintains the attached portion of the tricuspid valve annulus substantially planar to prevent a “hammock” effect in the area of tricuspid annulus dilation. The flexible first and second end portions, on the other hand, can deform axially and radially to the tricuspid valve annulus to substantially eliminate stress on the attachment sutures and annulus tissue, while still controlling dilation of the tricuspid annulus and without substantially interfering with the normal function of the tricuspid valve. In other words, the flexible end portions do not inhibit the normal operative effectiveness of a tricuspid valve having a corrected or non-dilated annulus. 
     Various embodiments of the disclosure could also include permutations of the various elements recited in the claims as if each dependent claim was a multiple dependent claim incorporating the limitations of each of the preceding dependent claims as well as the independent claims. Such permutations are expressly within the scope of this disclosure. 
     While the invention has been particularly shown and described with reference to a number of embodiments, it would be understood by those skilled in the art that changes in the form and details may be made to the various embodiments disclosed herein without departing from the spirit and scope of the invention and that the various embodiments disclosed herein are not intended to act as limitations on the scope of the claims. All references cited herein and the Appendix are incorporated in their entirety by reference.