Abstract:
An active bodily ring having a housing adapted to be sutured to a bodily component and a loop disposed in the housing, the loop capable of actively expanding and compressing during the bodily components normal function. The housing defines a first chamber and a second chamber, the first chamber containing the loop and the second chamber providing a region capable of being sutured to the bodily component. In one embodiment, the housing can be a crimped-fabric housing. In another embodiment, the housing can be a woven-fabric housing having elastic properties. The housing can be made from polyester.

Description:
RELATED APPLICATIONS  
       [0001]     This application claims the benefit of U.S. Provisional Application No. 60/599,923, filed on Aug. 9, 2004 and U.S. Provisional Application No. 60/591,728, filed on Jul. 27, 2004. The entire teachings of each application are herein incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     Congestive heart failure is a leading cause of hospitalization and death in the United States, and its incidence is increasing. Secondary mitral regurgitation, a complication of end-stage cardiomyopathy, refers to the backflow of blood from the left ventricle to the left atrium resulting from imperfections in the mitral valve. When the mitral valve allows blood to flow backward into the left atrium, the left ventricle must pump progressively harder to circulate blood throughout the body, which in turn promotes congestive heart failure. While heart transplantation is considered a standard treatment for select patients with severe congestive heart failure and end-stage heart disease, it is only applicable to a small percentage of patients because of the small number of available donor hearts and surgical risks for weaker patients. Accordingly, alternative medical and surgical strategies are evolving to treat such conditions.  
         [0003]     Mitral valve annuloplasty is a well known approach for treating mitral insufficiency, although other treatments are used which include replacing the mitral valve, repairing the mitral valve leaflets, and shortening or replacing the chordae tendinae. Mitral valve annuloplasty is the reparation of the mitral valve annulus which effects full closure of the leaflets by reestablishing the size and shape of the normal mitral valve annulus. Such an annuloplasty most commonly incorporates the use of a mitral annuloplasty ring wherein the ring is implanted on the mitral valve annulus.  
         [0004]     There are three basic types of mitral annuloplasty rings used in annuloplasty procedures. They include a rigid ring, a flexible ring and a combined ring that has both a flexible component and a rigid component.  
         [0005]     Due to their inflexibility, the rigid rings dictate the shape and contour of the mitral valve. The native mitral valve annulus flexes in response to the movement of the heart. However, with a rigid ring the annulus is not able to flex normally or move freely with the pumping action of the heart. As a result of the rigidity, the physiologic factors that normally shape the mitral valve annulus are not allowed to take precedence in shaping the valve.  
         [0006]     Another drawback with rigid rings is that they can induce a heart condition known as systolic anterior motion in patients having a mitral valve posterior leaflet that is too “tall”. During ventricular contraction, the posterior leaflet pushes the anterior leaflet in a direction opposite to the anterior leaflet&#39;s normal movement, resulting in the obstruction of the left ventricle&#39;s outflow tract.  
         [0007]     Overall, rigid annuloplasty rings do not allow the mitral valve annulus to reestablish its normal shape and form as dictated by the action of the heart pumping. The shape and contour of the annulus are established by the inflexible shape and form of the ring itself.  
         [0008]     Flexible rings made of polyester cloth, unlike the rigid rings, can allow the mitral valve annulus to move and flex as the heart contracts and relaxes. However, several drawbacks still exist. Proper shape and contour of the annulus is necessary in order for the mitral valve leaflets to close effectively. One shortcoming of the flexible ring is its predisposition to crimp during implantation. Crimping can be detrimental to the valve annulus, sometimes resulting in a mitral orifice that is too small. This can lead to stenosis of the valve. Furthermore, neither the flexible rings nor the combined rings can remain flexible indefinitely after annuloplasty. Since the rings are secured in place by a line of sutures attached directly to the annulus, scarring and resultant stiffening of the annulus inevitably develops. This loss of flexibility impedes the normal flexing and movement of the heart, particularly the left ventricle and, therefore, the heart cannot function optimally.  
       SUMMARY OF THE INVENTION  
       [0009]     The present invention is directed toward a new active bodily ring that can be used to preserve the natural mitral valve sphincteric contraction. The active bodily ring allows the two leaflets&#39; coaptation to remain intact and the incidence of left ventricular dysfunction will thus decrease. Also, the active bodily ring can distribute and transmit the stress evenly over the entire valve apparatus, instead of only over the anterior leaflet.  
         [0010]     The active bodily ring includes a housing adapted to be sutured to a bodily component and a loop disposed in the housing, the loop capable of actively expanding and compressing during the bodily components normal function. The housing defines a first chamber and a second chamber, the first chamber containing the loop and the second chamber providing a region capable of being sutured to the bodily component. In one embodiment, the housing can be a crimped-fabric housing. In another embodiment, the housing can be a woven-fabric housing having elastic properties. The housing can be made from polyester.  
         [0011]     In one embodiment, the loop can be an open-ended flat coil loop, each end adapted to substantially allow free movement of the loop within the housing. One end of the loop can include a plurality of protrusions and the other end of the loop can include a plurality of notches for engaging the protrusions thereby enabling the loop to be adjusted. The loop can provide a retraction force between about 3 and 4 Newtons when maximally stretched. The loop can be made from a material selected from a group consisting of a metal, metal alloy and polymer resin. In another embodiment, the loop can be a distensible coiled spring including a plurality loops.  
         [0012]     A bodily component can be selected from a group consisting of a heart, a larynx, an esophagus, a trachea, a pharynx, an eyelid, a nostril, a mouth, an anus, a rectocele, a pupil, a rectum, a bladder, and a vagina. In one embodiment, the ring can be sutured to a mitral value annulus of the heart. Further, the ring can be used for a medical treatment selected from a group comprising ischemic mitral valve regurgitation, prolapse mitral valve regurgitation; mitral valve regurgitation associated with left ventricular aneurysms; mitral valve regurgitation associated dilated cardiomyopathy; and Barlow&#39;s disease. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.  
         [0014]      FIG. 1A  is a cross-sectional view along an anterior-posterior plane through the left side of a heart illustrating healthy aortic and mitral valves and annuluses;  
         [0015]      FIG. 1B  is a plan view of a healthy mitral valve and annulus;  
         [0016]      FIG. 2A  is a cross-sectional view along an anterior-posterior plane through the left side of a heart illustrating a condition in the mitral valve that leads to mitral valve regurgitation;  
         [0017]      FIG. 2B  is a plan view of the mitral valve of  FIG. 2A ;  
         [0018]      FIG. 3  is a plan view of a flat coil ring of the present invention;  
         [0019]      FIG. 4  is a plan view of an adjustable ring of the flat coil ring of  FIG. 3 ; and  
         [0020]      FIG. 5  is a plan view of a distensible ring of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]     A description of preferred embodiments of the invention follows.  
         [0022]     As seen in  FIGS. 1A and 1B , the mitral annulus  20  represents the junction of the fibrous and muscular tissue that joins the left atrium and left ventricle. The average human mitral annular cross-sectional area is about 5-11 cm 2 . The mitral valve is a bicuspid valve having a large posterior leaflet  22  that coapts or meets with a smaller anterior leaflet  24 . The anterior aspect  26  of the annulus, which is in continuity with the fibrous skeleton of the heart, has limited flexibility, whereas the posterior aspect  28  of the annulus, which is not attached to any rigid surrounding structures, has more flexibility. For the purpose of discussion, the mitral annulus  20  ( FIG. 1B ) lies generally in a datum plane  30  ( FIG. 1A ) at an angle with respect to a second datum plane  32  in which the aortic valve  34  is generally oriented. These datum planes  30 ,  32  can be defined as being perpendicular to the average blood flow through the respective valves. During systole the mitral annulus  20  assumes a generally elliptical shape as shown in  FIG. 1B , and is able to contract and decrease in diameter, whereas, in diastole, it assumes a more circular shape and opens to permit blood to fill the left ventricle. Annular flexibility allows for increased leaflet coaptation during systole and increased annular orifice area during diastole.  
         [0023]     In mitral regurgitation, dilation typically occurs along the more flexible posterior aspect  28  of the annulus, as seen in  FIGS. 2A and 2B . Some patients experiencing a drop in height (h) of the posterior aspect  28  of the mitral valve annulus, as seen in  FIG. 2A , and consequent relaxation of the posterior muscle wall  36  of the left ventricle left ventricle.  FIG. 2B  illustrates the lengthening of the anterior-posterior dimension  38  and subsequent loss of coaptation between the posterior and anterior leaflets  22 ,  24 .  
         [0024]     Mitral regurgitation leads to a cycle of continuing volume overload of the already dilated left ventricle left ventricle, progression of annular dilation, increased left ventricle wall tension, increasing degrees of mitral regurgitation and worsening congestive heart failure. In mitral regurgitation, the regurgitant volume ejected into the left atrium is dependent upon mitral orifice size, ventricular/atrial pressure gradient and heart rate. The regurgitant flow into the left atrium increases left atrial pressure, which leads to atrial enlargement and an increase in compliance, and decreases forward systemic flow. Left atrial pressures rise during systole and decline in diastole.  
         [0025]      FIG. 3  shows an active bodily ring  300  according to the principals of the present invention. The active bodily ring  300  includes an outer casing/housing  310  and a flat coiled loop  350 . The casing  310  is divided by a seam  320  that defines an inner chamber  310   a  of the casing  310  and an outer chamber  310   b  of the casing  310 . The inner chamber  310   a  houses the flat coiled loop  350  while the outer chamber  310   b  is adapted to be sutured to a bodily component, such as a mitral valve annulus  20  ( FIG. 1B ).  
         [0026]     Returning to  FIG. 3 , the casing  310  is preferably a crimped-fabric or woven-fabric having elastic properties to allow the flat coiled loop  350  to expand and compress during the bodily component normal function. The casing  310  fabric is preferably made from Dacron® polyester from Dupont Corporation. In one embodiment, each crimp  330  of the outer circumference of the casing  310  is approximately 1.5 mm wide while each crimp  340  of the inner circumference of the casing  310  is approximately 3.0 mm.  
         [0027]     The flat coiled loop  350  is open-ended wherein each end  360  is adapted to allow free movement of the flat coiled loop  350  within the housing while the bodily component functions. As shown, each end  360  is rounded to allow free movement, but any means known in the art can be used. The flat coiled loop  350  can preferably made from steel, a nickel-titanium alloy, also known as Nitinol, a nickel-cobalt-chromium alloy composition, sold by Elgiloy Limited Partnership under the trademark Elgiloy®, an acetal resin, sold by Dupont Corporation under the trademark Delrin®, or any other suitable FDA approved material. The active bodily ring  300  provides an active retraction force during expansion and compression of the bodily component of which it is attached. The retraction force of the flat coiled loop  350  is between about 3 and 4 Newtons when maximally stretched.  
         [0028]      FIG. 4  shows an optional embodiment of the flat coiled loop  350  of  FIG. 3 . The flat coiled loop  350 ′ functions essentially the same as the embodiment of  FIG. 3  with the exception the flat coiled loop  350 ′ is adjustable. As such, the flat coiled loop  350 ′ includes a plurality of protrusions  370  and notches  380  for receiving the protrusions  370  to allow the flat coiled loop  350 ′ to be adjusted to a particular bodily component. The numbers  24 ,  26 ,  28 , and  32  show the adjustable size in millimeters of the flat coiled loop  350 ′.  
         [0029]      FIG. 5  shows another embodiment of the active bodily ring  300  of  FIGS. 2 and 3 . The active bodily ring  400  includes an outer casing/housing  410  and a distensible coiled spring  450 . The casing  410  is divided by a seam  420  that defines an inner chamber  410   a  of the casing  410  and an outer chamber  410   b  of the casing  410 . The inner chamber  410   a  houses the distensible coiled spring  450  while the outer chamber  410   b  is adapted to be sutured to a bodily component, such as a mitral valve annulus  20  ( FIG. 1B ).  
         [0030]     The casing  410  is preferably a crimped-fabric or woven-fabric having elastic properties to allow the distensible coiled spring  450  to expand and compress during the bodily component normal function. The casing  410  fabric is preferably made from Dacron® polyester. In one embodiment, each crimp  430  of the outer circumference of the casing  410  is approximately 1.5 mm while each crimp  440  of the inner circumference of the casing  410  is approximately 3.0 mm.  
         [0031]     The distensible coiled spring  450  is close-ended and includes a plurality of loops  452  to allow expansion and compression during bodily component normal function. For mitral valve treatment, the distensible coiled spring  450  can be soft and pliable when stretched and relaxed, thus it preserves maximum coaptation of the leaflets of a mitral valve. Further, the distensible coiled spring  450  assures effective transfer of the pressure stresses from the left ventricular to the annulus as well as to the left atrium.  
         [0032]     Either active bodily ring  300  or active bodily ring  400  can be used for a wide range of bodily components. Some of the bodily components include a heart, a larynx, an esophagus, a trachea, a pharynx, an eyelid, a nostril, a mouth, an anus, a rectocele, a pupil, a rectum, a bladder, and a vagina. Medical treatment associated with the repair of the heart can include ischemic mitral valve regurgitation, prolapse mitral valve regurgitation, mitral valve regurgitation associated with left ventricular aneurysms, mitral valve regurgitation associated dilated cardiomyopathy, and Barlow&#39;s disease.  
         [0033]     Either active bodily ring  300  or active bodily ring  400  can be used to treat mitral valve regurgitation since each design lowers energy expenditure of the ventricle by actively moving the annulus, whereas prior art designs are passively moving the annulus. The 10 to 20 year survival with the standard (prior art), non-coiled, non-springed ring is around 85%. However, the 80-90 percent effectiveness is with the assumption that the surgeon successfully installs the prior art ring. The initial success rate for mitral repair (non-ischemic) approaches no more than 75%. However, the active bodily ring  300  or active bodily ring  400  allows for much easier insertion and therefore the success rate can be higher. Because the active bodily ring  300  or active bodily ring  400  are active in nature, the simulation of the natural movement of the annulus allows easier completion of the repair.  
         [0034]     The active bodily ring  300  has the most clinical impact in ischemic type of mitral regurgitation. In the ischemic patient, the ventricle needs all the assistance it can get, as the five-year survival rate approximate 50%. The loop  350  helps the ventricular contractility to be transmitted harmoniously across with less energy expenditure than the standard prior art rings. Thus, the ventricular strain can be improved.  
         [0035]     The following active bodily ring  300  parameters are for a mitral valve ring: 
        Perimeter=10 cm for a 26-24 mm ring;     Normal mitral valve diameter shortening (commissure to commissure) between systole and diastole=˜10 mm;     Circular perimeter shortening of mitral valve=(2π)=˜3 cm;     Number of sutures=12; wherein each suture comprises two crimps&#39; length (3 mm/crimp);     Length of crimped polyester knit fabric cover/casing  310  for the sutures=7 cm (˜12×6 mm each);     Remaining un-sutured length of crimped fabric cover/casing  310 =11 intervals (1 interval=3 mm) at ˜33 mm total;     Size of each inner crimp  320  on the inner cover=˜3 mm;     Outer edge to inner edge length=˜4 mm;     Outer edge crimps=˜1 mm each;     Height of inner crimp edge=˜3 mm; and     Outer crimps  330 =˜1.5 mm each.        
 
         [0047]     The active bodily ring  400  is well suited for mitral valve regurgitation when restoring left ventricular aneurysms or dilated cardiomyopathy. For treatment of mitral regurgitation associated with left ventricular aneurysms, the dynamic nature of the distensible coiled spring  450  ensures much greater ventricle efficiency than standard prior art non-dynamic rings. This advantage ensures a higher ten-year survival rate in this group of patients (presently at 25%). The number of loops  452  of the distensible coiled spring  450  can be i decreased according to the level of severity of ventricular dysfunction. Therefore, there are two sub-types of the active bodily ring  400 .  
         [0048]     One sub-type is for severe left-ventricular dysfunction (4+ mitral regurgitation). In this situation, a smaller number of loops  452  are needed. The other sub-type is for less severe left-ventricular dysfunction (3+ mitral regurgitation). In this situation, a greater number of loops  452  are needed.  
         [0049]     The active bodily ring  400  provides the following advantages: 1) dynamic reduction of the posterior annulus in systole; 2) effective distribution of left ventricular force during systole; 3) preservation of the physiologic saddle conformation of mitral annulus; 4) avoids late paravalvular leaks because of absence of abnormal retraction between healing tissues and the sewing ring; 5) maintains left ventricular and left atrial geometry and functions; and 6) mimics the corrugation of collagen bundles of the mitral valve because of its dynamic geometry and the orientation of its loops. Further, the active bodily ring  400  improves survival rates because it provides: 1) decreased in subsequent myocardial decompensation and failure; 2) decreased myocardial oxygen demand; and 3) decreased transmural wall tension.  
         [0050]     While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.