Abstract:
A device is described for crossing the atrial septum to properly size a valve annulus for treatment or replacement, having a catheter with an expandable braided tubular structure attached at its distal end. The proximal and distal end regions of the braided tube have an open structure to allow blood flow to pass freely through the gaps or spaces between the braided fibers. The lumen within the tube includes a temporary, artificial valve that acts similar to a native valve, allowing blood to flow in one direction and preventing blood flow in the opposite direction.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Application Ser. No. 62/162,394 filed May 15, 2015 entitled Mitral Annular Measurement and LVOT Obstruction Tool which is hereby incorporated herein by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present patent application makes reference to and fully incorporates all information found in U.S. Pat. No. 8,998,827 issued Feb. 13, 2013 entitled Ellipticity Measuring Device, and U.S. patent application Ser. No. 14,683,055 filed Apr. 9, 2015 entitled Post Dilation Balloon With Marker Bands For Use With Stented Valves. 
         [0003]    Mitral regurgitation (MR) can occur due to a dysfunction of the mitral valve leaflets or due to enlargement of the left ventricle (LV) and mitral annulus causing mitral leaflets to no longer coapt properly. To correct MR, a surgical procedure can be performed to support the mitral annulus from further enlargement or to repair or replace the mitral valve leaflets. 
         [0004]    An alternate procedure that is less invasive can be performed via a catheter that is introduced either across the atrial septum or through the apex of the heart. This mitral transvascular valve replacement (MTVR) procedure is intended to place a synthetic, tissue, or composite stented valve within the native mitral valve. Determining an accurate diameter for the MTVR device within the noncircular mitral annulus can be difficult and failure to make an accurate diameter determination can result in a paravalvular leakage of blood around the stented MTVR. In addition, the MTVR can impose an outward force onto the anterior native mitral valve leaflet causing it to obstruct the flow of blood from the LV out of the left ventricular outflow tract (LVOT). 
         [0005]    What is needed is a device that can be easily inserted across the mitral valve annulus prior to implantation of an MTVR to determine an accurate diameter for the mitral annulus and can further be used to identify if the MTVR will impact onto the native anterior mitral valve leaflet resulting in obstruction to the LVOT. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention is generally directed to a tool that can be introduced across the atrial septum or through the apex of the heart and across the mitral valve. 
         [0007]    In one embodiment that can be used for crossing the atrial septum, a catheter has a braided tubular structure attached at its distal end to a pull tube that passes through a catheter shaft; the proximal end of the tubular braid is attached to the outer shaft of the catheter. The proximal and distal end regions of the braided tube have an open structure to allow blood flow to pass freely through the gaps or spaces between the braided fibers. The central or middle region of the braided tube located in the central third of the braided structure has an elastomeric film that connects the braided fibers with their neighboring fibers to form a fluid-tight region. Located within the central region is a temporary valve that unidirectionally prevents blood flow through the lumen of the central region, similar to a native valve. The temporary valve is attached to the braided tubular structure along the perimeter of the braided tube in a manner similar to the attachment of an aortic valve leaflet to the aortic sinus or a venous valve leaflet to the tubular structure of a vein wall of the body. The temporary valve leaflets form a seal with other leaflets and also against the outer surface of the pull tube. 
         [0008]    The tool can be advanced across a patient&#39;s mitral valve with the pull tube pushed distally with respect to the outer shaft to hold the braided tubular structure into a small diameter state having a long length. After crossing the mitral valve, the pull tube can be pulled with respect to the outer shaft to cause the braided structure to enlarge in diameter and shorten in length and thereby push the native mitral leaflets outwards and make contact with the mitral annulus. With the braided structure expanded in diameter, the temporary valve will function to ensure that blood is not able to pass freely from the LV back into the left atrium (LA). Blood is able to pass freely from the LA through the proximal end region of the braided structure, across the temporary valve leaflets, and out of the distal end region of the braided structure into the LV. Examination of the braided structure under fluoroscopy will enable the operator to determine the diameter of the mitral annulus; further examination of the LVOT will allow the operator to determine if the anterior native leaflet is impinging upon the LVOT. 
         [0009]    The tool can be altered to allow its introduction from an apical approach; in this embodiment the temporary valve leaflets are directed to provide flow from the distal end of the braided structure toward the proximal end of the braided structure toward the direction of the catheter shaft. 
         [0010]    In an alternate embodiment for the tool, the braided tubular structure can have a bulbous shape such that a waist exists within the tubular structure having a smaller diameter by about 3-10 mm than the bulbous portions of the braided structure that are located on each side of the waist. The waist can be held into a smaller diameter configuration during the expansion of the braid by a restraining fiber that extends around the perimeter of the braided tube. The restraining fiber can be, for example, an elastic fiber that can stretch as the waist grows in diameter but serves to hold the waist into a smaller diameter than the bulb regions; alternately a geometric shape that is able to expand in length can be used as the restraining fiber; such structures include the zig zag structure commonly used in vascular stents, or can be a cable that is easily bent but having tensile strength that will prevent diameter enlargement of the waist. 
         [0011]    As a further alternate embodiment, the waist can be formed via thermal processing that places a bulbous shape into the braided tubular structure. The waist will tend to orient adjacent the annulus of the mitral valve. Located adjacent the restraining fiber is a marker band or alternately the restraining fiber is the marker band. The marker band can be formed from a radiopaque (RO) material that is visualized under fluoroscopy or from a material observable under echogenic signals. The marker band can be formed by embedding RO material into an elastic carrier polymer and applying the polymer or the band onto the waist region or other region of the braided tubular structure. Additional marker bands can be located on one or more of the bulbs. 
         [0012]    After placing this tool across the mitral valve, the braided structure is expanded. The waist of the braided structure centers adjacent the mitral annulus. The waist marker band can be visualized to determine the diameter of the mitral annulus and also to assess the roundedness, ovality, or “D” shape of the mitral annulus. One or more of the bulb marker bands can be visualized to assess a circular shape that can be used as a reference to establish the true shape of the mitral annulus. The tool can also be used to identify if impingement is being generated by the anterior mitral leaflet onto the LVOT. 
         [0013]    In yet another embodiment a tubular balloon can be formed into a spiral shape to cross the native mitral valve and determine if impingement of the anterior mitral leaflet onto the LVOT is anticipated. The spiral balloon is formed such that a central lumen is open to blood flow from the left atrium (LA) to the left ventricle (LV). A temporary valve located in the central lumen ensures that blood flow from the LV cannot pass retrograde from the LV to the LA. The edges of the balloon spiral are attached to neighboring spirals to prevent leakage of blood from the central lumen across the spiral balloon. 
         [0014]    The spiral balloon can be formed such that it contains a waist region that forms a smaller diameter spiral than one or more bulbous regions located adjacent or on each side of the waist. Marker bands can be placed onto the outer surface of the spiral balloon that can be visualized under either fluoroscopy or via echogenic signals. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    These and other aspects, features and advantages of which embodiments of the invention are capable of will be apparent and elucidated from the following description of embodiments of the present invention, reference being made to the accompanying drawings, in which 
           [0016]      FIG. 1A  is a sectional view of the tool in a non-expanded configuration. 
           [0017]      FIG. 1B  is a sectional view of the tool in an expanded configuration within the mitral annulus from the left atrium. 
           [0018]      FIG. 1C  is a sectional view of the tool in an expanded configuration if the tool is entered from the apex of the heart. 
           [0019]      FIG. 2  is a sectional view of the tool in an expanded configuration having a smaller diameter waist and larger diameter bulbs. 
           [0020]      FIG. 3A  is a perspective view of the tool formed from a spiral wound tubing. 
           [0021]      FIG. 3B  is a perspective view of the tool formed from a spiral wound tubing and having a smaller diameter waist and larger diameter 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0022]    Specific embodiments of the invention will now be described with reference to the accompanying drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. The terminology used in the detailed description of the embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, like numbers refer to like elements. 
         [0023]      FIGS. 1A-1B  illustrate a tool  100  that is placed or positioned across the mitral annulus  14  prior to placing a transcatheter mitral valve replacement (TMVR) device. The tool  100  can be visualized under fluoroscopy to determine the diameter of the mitral annulus. Further, the tool  100  interfaces with the native mitral valve leaflets causing them to be pushed outwards such that any obstruction of the left ventricular outflow tract (LVOT)  16  by the native anterior mitral leaflet can be visualized under fluoroscopy and adjustment can be made in the diameter and length of the TMVR that is implanted across the mitral annulus. 
         [0024]      FIG. 1A  illustrates the tool  100  in an unexpanded configuration having a relatively smaller, unexpanded diameter to allow entry and passage through a sheath  12 . The sheath  12  is advanced within the femoral vein so as to allow delivery of the tool  100  through the atrial septum and across the mitral annulus  14 . 
         [0025]    Generally, tool  100  has an expandable portion  106 , having open mesh portions, such as proximal mesh portions  106 A and distal mesh portion  106 B, which allow blood to flow within the expandable portion  106 . An artificial valve  108  composed of valve leaflets are located within the expandable portion  106  and allow passage of blood through the expandable portion  106  in a single direction, similar to a native valve (e.g., in a distal direction in the current example). 
         [0026]    In one embodiment, the expandable portion  106  is constructed of a braided or expandable metal tube that is bonded at its proximal end to the outer shaft  102 , near the distal end of the outer shaft  104 . The braided or expandable tube portion  106  can be formed from wire composed of Nitinol (NiTi), stainless steel, or other material that allows expansion to a larger diameter as its length becomes shorter. 
         [0027]    The distal end of the braided tubular member  106  is preferably bonded to a distal end of a hollow pull tube  102  that moves relative to the outer shaft  104 . Movement of the pull tube  102  with respect to the outer shaft  104  by application of tension on the pull tube  102  by the physician causes the braided tube  106  to shorten in length as it grows in diameter. 
         [0028]    The central region  106 C of the braided tube  106  has an elastomeric film  105  such as polyurethane or silicone applied to the braided fibers and extending across the gaps or spaces that extend from one fiber of the braid to the neighboring fibers. The film  105  prevents the flow of fluid such as blood through the spaces between the fibers in the central region which extends approximately along the central third of the braided tube  106 . The film  105  prevents blood flow from traveling from the lumen  107  of the braided tubular structure  106  to an outer region that is located outside of the braided tubular structure  106  and adjacent to the valvular tissues and the other tissues of the heart. 
         [0029]    The central region  106 C contains a temporary, artificial valve  108  that directs blood flow downstream from the proximal open mesh  106 A to the distal end  106 B of the braided tube  106  (i.e., it allows blood flow in a distal direction but prevents backflow in a proximal direction). The temporary leaflets  108  can be formed from a tissue material or a synthetic polymer film, such as polyethylene terephthalate (PET) or Nylon, that is formed into a trileaflet or bileaflet valve such as those found within the human body. The leaflets of the valve  108  are attached to the elastomeric film  105  in the central region  106 C forming a crown-shaped attachment to the central region  106 C similar to the attachment of a native tricuspid valve leaflet of the aortic valve or a bicuspid leaflet of a venous valve. 
         [0030]    The proximal end region  106 A has an open spacing between the fibers or wires of the braided tube to allow blood to travel from the left atrial chamber or left atrium (LA) of the heart into the lumen of the braided tubular structure; the distal end region has an open spacing to allow flow from the lumen of the braided tubular structure to the left ventricle (LV). The hollow pull tube  102  provides passage for a guidewire  10  for delivery of the device  100  across the mitral valve  14 . 
         [0031]    As shown in  FIG. 1B  the pull tube  102  has been moved proximally relative to the outer tube  104 , causing the distal end  106 B of the braided tube  106  to move closer to the proximal end  106 A and thereby causing the diameter of the braided to tube  106  to enlarge. This enlargement of the braided tube  106  causes the braided structure  106  to make contact with the native mitral leaflets pushing them outwards, and make contact with the mitral annulus. The braided structure  106  and particularly radiopaque markers  110  can then be observed under fluoroscopy to allow measurement of the diameter of the mitral annulus. The movement of the native anterior mitral leaflet into the LVOT  16  will establish if placement of an MTVR device will result in anterior leaflet obstruction of the LVOT  16 . 
         [0032]      FIG. 1C  illustrates an alternate version  101  of the device  100  used for insertion via an apical approach rather than from the femoral vein. In this respect, the direction of the leaflets of the temporary valve  109  located within the lumen  107  of the braided tubular structure  106  open in an opposite direction than those of device  100 . In other words, the valve  109  allows blood flow to move proximally since it is generally positioned in an “upside-down” position verses the device  100 . However, the mode of action for this tool is similar to that described for the device  100  of  FIG. 1B . 
         [0033]      FIG. 2  illustrates an embodiment  120  for the present invention similar to the devices  100  and  101  described in  FIGS. 1A-1C , having a pull tube  102 , an outer tube  104 , a temporary valve  108 , and a braided tubular structure  122  having a proximal end  122 A and a distal end  1226  through which blood flows. However, the tubular structure  122  expands to a “dog bone” shape or a shape having a proximal bulb  122 D with a diameter  122 F, a waist  122 C with a diameter  122 G, and a distal bulb  122 E with a diameter  122 H. A restraining fiber  123  formed from a polymer or metal material can be used to restrict the waist diameter to a magnitude that is, for example, approximately 3-10 mm smaller than the diameter of the proximal or distal bulbs  122 A,  122 B. The waist can alternately be formed via thermal processing of an elastic metal such as Nitinol, for example. The bulb diameters in a fully expanded configuration can be approximately 3-10 mm larger than an effective diameter of the mitral annulus. The mitral annulus is typically D-shaped with an effective diameter (equal to the diameter of a circle having the same perimeter) of 25-45 mm. 
         [0034]    Located along the perimeter of the waist  122 C of the braided structure  106  is a marker band  110  such as a radiopaque (RO) marker or an echo-sensitive marker. The echo-sensitive marker can be a marker that absorbs, reflects, generates, or scatters echogenic energy that is delivered via a cardiac echo transducer to visualize the structures of the heart. The RO marker can be formed from materials that absorb x-rays such as tungsten, platinum, platinum-iridium and others. An echo-sensitive marker or RO marker can also be located on one or both of the bulbs. Visualization of the RO or echo-sensitive marker under fluoroscopy or echo will allow the operator to observe the shape and diameter of the mitral annulus. The marker  110  located along one of the bulbs is typically round in shape along its perimeter and can serve as a reference to identify the angle of the fluoro or echo camera and any magnification factor associated with the diameter of the bulb. The marker  110  located along the perimeter of the waist can then be used to identify the diameter and shape of the mitral annulus as described further in the patents that are referenced herein. 
         [0035]    The device  120  of  FIG. 2  also can be used in a manner similar to that described for the devices  100  and  101  of  FIGS. 1A-1C  to identify if a subsequently placed MTVR is likely to obstruct the LVOT. The structure of the braided tube  122 , the temporary valve  108 , the film  105  located in the central region  122 C is similar to that described in  FIGS. 1A-1C . 
         [0036]    The method of use for the embodiments of the tool shown in  FIGS. 1-3  are herein described. The tool is delivered across the mitral annulus from either the left atrium or via the left ventricular apex in a small diameter configuration. The pull tube is placed into tension causing the braided mesh to expand in diameter pushing the native mitral leaflets outward to the side. The temporary leaflets located near the central region of the tool prevent blood flow from retrograde flow from the left ventricle to the left atrium. The elastic film located adjacent the temporary leaflets and attached to the central region of the mesh prevent blood flow from forming a perivalvular leak for blood flow around the temporary leaflets. The braided mesh in the central region is pushed against the mitral annulus; the presence of a marker band allows the operator to measure the diameter of the mitral annulus. The braided mesh located in the left ventricle pushes outward against the anterior native mitral valve leaflet pushing the native leaflet into the left ventricular outflow tract (LVOT). Fluoroscopy is used by the operator to view potential for obstruction of the LVOT from the native leaflet. If obstruction is observed, the subsequent transcatheter mitral valve replacement (TMVR) procedure may require some adjustment in the type of TMVR device to use or else cancel the TMVR procedure. Alternately, if no obstruction is observed, then the TMVR procedure is performed with knowledge apriori that obstruction is not of concern for than patient. Following measurement of mitral annulus diameter and determination of obstruction of the LVOT, the braided mesh is reduced in diameter by the operator to a smaller introduction diameter and the catheter is removed from the body. 
         [0037]      FIGS. 3A and 3B  illustrate another embodiment for a tool  130  of the present invention that can be placed across the mitral annuls in a similar manner as the previously described embodiments. In this embodiment, the device  120  includes an elongated, helical balloon  132  having a diameter of approximately 0.5-1 cm. The balloon  132  is wound into a spiral shape having a diameter for the spiral of approximately 25-45 mm in an inflated configuration. A central through lumen  131  provides a channel for blood flow from the LA to the LV. The spirals of the spiral balloon  132  are preferably bonded to their neighboring spiral along an edge such that blood flow through or between the spirals is prevented. 
         [0038]    A temporary valve  140  is located in the central lumen to allow flow from the LA to the LV and restrict flow from the LV to the LA. The tool can be delivered across the mitral annulus in a small diameter configuration and inflated with contrast or other fluid to form a fully inflated configuration as shown in  FIGS. 3A and 3B . The diameter of the mitral annulus can be view upon fluoroscopic examination. As shown in  FIG. 3B  the spiral loop can be formed such that it contains a waist region  132 B having a smaller diameter than either bulbous regions  132 A,  132 C. A marker band  110  can be located along the perimeter of the waist  132 B to allow improved visualization of the diameter and shape of the mitral annulus. A marker band  110  can also be located around the perimeter of one or both bulbs  132 A,  132 C to serve as a diameter reference and also to identify the angle of fluoroscopy camera or echo camera with respect to the axis of the spiral balloon. A guidewire lumen  138  can also be located along the axis of the spiral balloon  132  to assist in delivery of the device across the mitral annulus. The balloon  132  can be connected to a single inflation tube  136  at its proximal end and/or to a second inflation tube  134  connected to a distal end of the balloon  132 . 
         [0039]    Although the invention has been described in terms of particular embodiments and applications, one of ordinary skill in the art, in light of this teaching, can generate additional embodiments and modifications without departing from the spirit of or exceeding the scope of the claimed invention. Accordingly, it is to be understood that the drawings and descriptions herein are proffered by way of example to facilitate comprehension of the invention and should not be construed to limit the scope thereof.