Abstract:
A flexible mesh ablation device for ablating tissue in a body lumen. The flexible mesh ablation device includes a flexible mesh with at least one conductor on an exterior surface of the flexible mesh. When the flexible mesh is compressed axially it expands radially to contact the inner surface of the body lumen and conform to the shape of the body lumen. Power is applied to the conductor ablating tissue proximate the conductor.

Description:
FIELD 
       [0001]    This invention relates generally to medical devices for ablating tissue in a body lumen. More particularly, this invention relates to a system for ablating tissue in a wall of a blood vessel. 
       BACKGROUND 
       [0002]    Hypertension, commonly referred to as high blood pressure is typically treated using antihypertensive medication. However, there is a patient population that is unresponsive to this pharmacological approach and other approaches have been developed to treat hypertension. 
         [0003]    Blood pressure has been shown to be partially controlled by the kidneys and renal sympathetic nerve hyperactivity has been linked to hypertension. Recently, intravenous catheter based technologies have been developed to disrupt the sympathetic nervous system surrounding the renal arteries. These intravenous catheter technologies use an energy source to ablate the tissue around the renal artery. Two energy sources being used to ablate the tissue and disrupt these nerves are radiofrequency (RF) and ultrasound. 
         [0004]    The sympathetic nervous system fully encapsulates the renal artery so to be fully effective, a full 360 degree ablation is necessary. However, with the RF systems, a circumferential ablation at one location can damage the lining of the renal artery such that the lumen strictures, or narrows, thus reducing blood flow to the kidneys. To avoid stricturing, the currently available RF systems ablate a helical section of tissue such that 360 degrees of tissue is treated over a much longer section of a vessel. 
         [0005]    One current system uses a balloon platform where a flexible electrode forms a helix on the surface of the balloon. The user guides the balloon to the treatment site and inflates the balloon such that the electrode contacts the target tissue. With this system, the entire ablation can take place with a single application. However, since the system is balloon based, blood flow is blocked for the duration of the ablation procedure. Additionally, as it is balloon based, the size of the balloon will have to closely match the size of the target vessel to ensure adequate tissue/electrode contact without over extension of the vessel. 
         [0006]    In another current system, an electrode is mounted on the distal end of a deflecting catheter. The user deflects the tip of the catheter with the electrode and ablates a section of the vessel. The tip is then moved axially and the catheter rotated to ablate another section of the vessel. This is repeated at 3-4 locations working from distal to proximal while continuing to rotate the catheter approximately ¼ turn at each new site. Energy is dispersed at each independent site for approximately 2 minutes to ablate the tissue, for a total treatment time of 8 minutes for the ablation. 
         [0007]    The balloon system described previously is faster than the deflecting catheter system described since it only needs to disperse energy a single time to ablate a 360 section of the vessel. However, the deflecting catheter system is preferable since it does not stop the flow of blood through the body lumen. It would be beneficial to have a system that combines the speed of the balloon based system while still allowing blood to flow through the vessel like the deflecting catheter system. 
       SUMMARY 
       [0008]    One embodiment is directed to a medical device comprised of a first longitudinal member, a mesh, a conductive coating, and a compression mechanism. The first longitudinal member has a distal end and a proximal end and the mesh has a distal mesh end and a proximal mesh end secured to the distal end of the first longitudinal member. The mesh is comprised of a non-conductive flexible filament woven to form a hollow cylindrical mesh with a longitudinal bore The conductive coating is disposed on an outer surface of the cylindrical mesh. The compression mechanism is adapted to move the distal mesh end between a first position in which the mesh is unexpanded and a second position in which the distal mesh end and the proximal mesh end are near one another thereby expanding the mesh into an expanded state. 
         [0009]    In another embodiment a medical device is comprised of a catheter, a mesh, a conductive coating, and a sleeve. The catheter has a distal end and a first outer diameter at the distal end. The mesh has a distal mesh end and a proximal mesh end secured to the distal end of the catheter and the mesh is biased to have a second outside diameter greater than the first outside diameter. The mesh is comprised of a non-conductive flexible filament woven to form a hollow mesh with a longitudinal bore. The conductive coating is disposed on an outer surface of the mesh and the sleeve is disposed about the distal end of the catheter. The sleeve has an inside surface having an inside diameter greater than the first outside diameter and less than the second outside diameter and the sleeve is slidable from a first position in which the inside surface constrains the mesh to have a third outer diameter less than the second outer diameter and a second position in which the inside surface does not constrain the mesh. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    To further clarify the above and other advantages and features of the one or more present inventions, reference to specific embodiments thereof are illustrated in the appended drawings. The drawings depict only typical embodiments and are therefore not to be considered limiting. One or more embodiments will be described and explained with additional specificity and detail through the use of the accompanying drawings in which: 
           [0011]      FIG. 1  illustrates a longitudinal cross section of an embodiment of a flexible mesh ablation device. 
           [0012]      FIG. 2  illustrates a longitudinal cross section of the embodiment of the flexible mesh ablation device of  FIG. 1  with the device in an expanded configuration. 
           [0013]      FIG. 3  illustrates an endview of an embodiment of a flexible mesh. 
           [0014]      FIG. 4  illustrates a longitudinal view of the flexible mesh of  FIG. 3 . 
           [0015]      FIG. 5  illustrates a longitudinal view of an embodiment of a flexible mesh showing the placement of a conductor. 
           [0016]      FIG. 6  illustrates the flexible mesh of  FIG. 5  in an expanded configuration. 
           [0017]      FIG. 7  illustrates a longitudinal view of an embodiment of a flexible mesh showing the placement of a pair of conductors. 
           [0018]      FIG. 8  illustrates the flexible mesh of  FIG. 7  in an expanded configuration. 
           [0019]      FIG. 9  illustrates a longitudinal view of an embodiment of a flexible mesh showing the placement of a pair of conductors. 
           [0020]      FIG. 10  illustrates the flexible mesh of  FIG. 9  in an expanded configuration. 
           [0021]      FIG. 11  illustrates a proximal end of a flexible mesh ablation device. 
           [0022]      FIG. 12  illustrates a longitudinal cross-section of another embodiment of a flexible mesh ablation device. 
           [0023]      FIG. 13  illustrates a longitudinal cross-section of the embodiment of  FIG. 12  with the flexible mesh in a radially constrained state. 
       
    
    
       [0024]    The drawings are not necessarily to scale. 
       DETAILED DESCRIPTION 
       [0025]    As used herein, “at least one,” “one or more,” and “and/or” are open-ended expressions that are both conjunctive and disjunctive in operation. For example, each of the expressions “at least one of A, B and C,” “at least one of A, B, or C,” “one or more of A, B, and C,” “one or more of A, B, or C” and “A, B, and/or C” means A alone, B alone, C alone, A and B together, A and C together, B and C together, or A, B and C together. 
         [0026]    Various embodiments of the present inventions are set forth in the attached figures and in the Detailed Description as provided herein and as embodied by the claims. It should be understood, however, that this Detailed Description does not contain all of the aspects and embodiments of the one or more present inventions, is not meant to be limiting or restrictive in any manner, and that the invention(s) as disclosed herein is/are and will be understood by those of ordinary skill in the art to encompass obvious improvements and modifications thereto. 
         [0027]    Additional advantages of the present invention will become readily apparent from the following discussion, particularly when taken together with the accompanying drawings. 
         [0028]    In the following discussion, the terms “proximal” and “distal” will be used to describe the opposing axial ends of the inventive ablation device, as well as the axial ends of various component features. The term “proximal” is used in its conventional sense to refer to the end of the ablation device (or component thereof) that is closest to the operator during use of the ablation device. The term “distal” is used in its conventional sense to refer to the end of the ablation device (or component thereof) that is initially inserted into the patient, or that is closest to the patient during use. For example, an ablation device may have a proximal end and a distal end, with the proximal end designating the end closest to the operator, such as a handle, and the distal end designating an opposite end of the ablation device. Similarly, the term “proximally” refers to a direction that is generally towards the operator along the path of the ablation device and the term “distally” refers to a direction that is generally away from the operator along the ablation device. 
         [0029]      FIG. 1  illustrates an embodiment of a flexible mesh ablation device  100  in accordance with the present invention. The flexible mesh ablation device  100  includes a flexible woven mesh  102  at a distal portion  104 . The flexible woven mesh  102  is operably connected to an inner shaft  106  and an outer shaft  108 . The flexible woven mesh  102  may be secured at a proximal end  120  to a distal end  122  of the outer shaft  108  and at a distal end  124  to a distal end  126  of the inner shaft  106 . In some embodiments, the inner shaft  106  is coaxially positioned within the outer shaft  108  as shown in  FIG. 1 . The flexible woven mesh  102  expands and collapses by longitudinal movement of the inner shaft  106  relative to the outer shaft  108  as explained in more detail below. A control handle  110  is provided at a proximal portion  112  of the flexible mesh ablation device  100 . The control handle  110  is operable to control the movement of the inner shaft  106  and the outer shaft  108  relative to one another. The control handle  110  may be any type of handle that is operable to control the movement of the inner shaft  106  relative to the outer shaft  108  and need not have the structure illustrated in  FIG. 1 . 
         [0030]    As shown in  FIG. 1 , a distal portion  112  of the flexible woven mesh  102  is operably connected to the inner shaft  106 . A proximal portion  114  of the flexible woven mesh  102  is operably connected to the outer shaft  108 . Relative movement between the inner shaft  106  and the outer shaft  108  causes the flexible woven mesh  102  to change between a collapsed configuration shown in  FIG. 1 , and an expanded configuration shown in  FIG. 2 . The flexible woven mesh  102  in the unexpanded configuration has a first outside diameter  116  and the flexible woven mesh  102  in the expanded configuration extends beyond the first outside diameter  116  at a middle segment  118 . The unexpanded configuration may be used to deliver the flexible mesh ablation device  100  to a treatment site within a patient and for repositioning the flexible mesh ablation device  100  within a patient&#39;s lumen to provide treatment to additional sites if needed. 
         [0031]      FIG. 2  illustrates the flexible mesh ablation device of  FIG. 1  in an expanded configuration. The outer shaft  108  has been moved distally relative to the inner shaft  106  decreasing the distance between the distal end  122  of the outer shaft  108  and the distal end  126  of the inner shaft  106 . The decrease in distance causes the flexible woven mesh  102  to expand radially as shown in  FIG. 2 . Because the mesh is flexible, it will conform to the surface of the lumen in which it is deployed, including many surface irregularities. 
         [0032]    A cross-sectional view of an embodiment of the flexible woven mesh  102  is shown in  FIG. 3  and a side view of the flexible woven mesh  102  is shown in  FIG. 4 . The flexible woven mesh  102  is comprised of a plurality of nonconductive filaments  202  that are woven together to form a cylindrical sleeve  200  having a cylindrical inner surface  204  and a cylindrical outer surface  206 . In some embodiments, the nonconductive filaments  202  may be formed from a polymeric material such as a polyolefin, a fluoropolymer, a polyester, for example, polypropylene, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene terephthalate (PET), and combinations thereof. Other materials known to one skilled in the art may also be used to form the nonconductive filaments  202 , provided that they enable the flexible woven mesh  102  to be changeable from the expanded state and the unexpanded state in response to the inner shaft  106  moving relative to the outer shaft  108 . 
         [0033]      FIG. 5  through  FIG. 9  illustrates various embodiments of a flexible woven mesh  102  suitable for use in the flexible mesh ablation device shown in  FIG. 1 . The inner shaft  106  and outer shaft  108  are not illustrated for clarity. Each embodiment of the flexible woven mesh  102  will be illustrated in an unexpanded state and an expanded state. It will be generally understood that the flexible woven mesh  102  may enter the expanded state when the proximal end  120  and the distal end  124  of the flexible woven mesh  102  are brought closer together. 
         [0034]      FIG. 5  illustrates an exemplary flexible woven mesh  500  illustrating the placement of a conductive coating  502  on at least one nonconductive filament  504 . In some embodiments, the conductive coating  502  is placed on a single filament  504 , while in other embodiments the conductive coating  502  is placed on a plurality of intermeshed filaments, as shown in  FIG. 5 .  FIG. 6  illustrates the same flexible woven mesh  500  as  FIG. 5 , but with the flexible woven mesh  500  being expanded. In this embodiment the conductive coating  502  is applied to the outer cylindrical surface of the flexible woven mesh  500  along a helical pattern of intermeshed filaments  504  to form a helical conductor. Other configurations of conductive coatings are possible. For example, in embodiments in which a different ablation pattern is necessary, the conductive coating  502  could be applied in a complementary pattern, such as run parallel to the axis of the flexible woven mesh  500  or perpendicular to the axis of the flexible woven mesh  500 . The conductive coating  502  may partially circumscribe the cylindrical surface of the flexible woven mesh  500 , extend one full revolution about the axis of the flexible woven mesh  500 , or may extend more than one revolution about the axis. 
         [0035]    In some embodiments, the conductive coating  502  may span a gap between adjacent nonconductive filaments  504 . A flexible base material may be wrapped around the mesh as a base layer for the conductive coating  502 . The flexible base material may span the area between filaments  504  which may increase the amount of conductive coating  502  that can be applied. One example of a suitable flexible base material between the conductive coating  502  and the filaments  504  is silicone. 
         [0036]    The conductive coating  502  may be a conductive ink applied to the surface of the mesh. One example a conductive ink is silver ink, although other metallic inks are possible. The conductive coating  502  may comprise a conductive painting, conductive glue, or other conductive materials that form a flexible coating on the non-conductive filaments  504 . 
         [0037]      FIG. 7  illustrates an exemplary flexible woven mesh  700  illustrating a bipolar arrangement of conductive coatings  702 ,  704 .  FIG. 8  illustrates the flexible woven mesh  700  of  FIG. 7  with the flexible woven mesh  700  being expanded. A first conductive coating  702  coats a first pattern of nonconductive filaments  706  and a second conductive coating  704  coats an adjacent pattern of nonconductive filament  706 . An ablation zone  708  is formed between the first conductive  702  coating and the second conductive coating  704 . The first conductive coating  702  and the second conductive coating  704  are electrically isolated from one another such that there is no conductive path from the first conductive coating  702  to the second conductive coating  704 . This bipolar arrangement allows for a precise ablation zone  708  between the conductive coatings  702 ,  704 . 
         [0038]      FIG. 9  illustrates another embodiment of an exemplary flexible mesh  900  illustrating another pattern of conductive coatings to form a bipolar ablation device.  FIG. 10  illustrates the flexible mesh  900  of  FIG. 9  with the flexible mesh  900  expanded. In the embodiment of  FIG. 9  a first conductive coating  902  coats a proximal hemispherical portion of filaments  910 . A second conductive coating  904  coats an opposite, distal hemispherical portion of filaments  910  that are electrically insulated from the first conductive coating such that there is no conductive path from the first conductive coating  902  to the second conductive coating  904 . An ablation zone  906  is formed in a region between the first conductive coating  902  and the second conductive coating  904 . The first conductive coating  902  and the second conductive coating  904  may have a boundary  908  that follows a nonconductive filament  910  as shown in  FIG. 10 . In some embodiments the boundary of the conductive coatings may follow a path other than a nonconductive filament  910 . 
         [0039]      FIG. 11  illustrates the proximal end of a flexible mesh ablation device  1100 . In each of the previously described embodiments, the conductive coating is operably connected to an energy source. As shown in  FIG. 11 , a handle  1102  may include a connector  1104  for operably connecting the conductive coating to an energy source  1106 . As shown, the energy source  1106  may be a radio frequency source. However, other types of energy sources may also be used to provide energy to the conductive coating. By way of non-limiting example, additional possible energy sources may include microwave and electric current. The conductive coating is connected to the power source by an electrical conductor, such as one or more wires  1108  that extend from the conductive coating to the connector  1104  that connects to the energy source  1106 . The one or more wires  1108  may extend through a lumen  1110  of the inner  1112  shaft or may extend through a lumen of the outer shaft  1114  or external to the outer shaft  1114  and may optionally include a sleeve surrounding the outer shaft  1114  and one or more wires  1108 . 
         [0040]    As discussed above, the handle  1102  is operable to move the inner shaft  1112  relative to the outer shaft  1114  so that the flexible woven mesh  1102  moves between the expanded configuration and the collapsed configuration (see  FIGS. 1 and 2 ). By way of non-limiting example, the handle  1102  includes a first portion  1116  and a second portion  1118  that move relative to each other. As shown in  FIG. 11 , the first portion  1116  is operably connected to the inner shaft  1112 . The second portion  1118  is operably connected to the outer shaft  1114 . The first portion  1116  may be moved proximally and/or the second portion  1118  may be moved distally to move the inner shaft  1112  proximally and/or the outer shaft  1114  distally to move the flexible woven mesh  102  to the expanded configuration as shown in  FIG. 2 . As shown in  FIG. 1 , the first portion  1116  may be moved distally and/or the second portion  1118  moved proximally to move the inner shaft  1112  distally and/or the outer shaft  1114  proximally to move the flexible woven mesh  102  to the collapsed configuration. 
         [0041]    The handle  1102  may include a lock  1120  shown in  FIG. 7  to releasably lock the first portion  1116  in position relative to the second portion  1118  and thus lock the flexible woven mesh  102  in position. The lock  1120  may releasably lock the first and second portions  1116 ,  1118  of the handle  1102  together at any proximal/distal positioning of the inner and outer shafts  1112 ,  1114  so that the flexible woven mesh  102  may be locked at any size that is suitable for the treatment site. For example, if the treatment site is in a narrow lumen, the first portion  1116  of the handle  1102  may be moved slightly in the proximal direction to give the flexible woven mesh  102  a smaller diameter than if the first portion  1116  were moved fully distally to give the flexible woven mesh  102  the largest diameter. 
         [0042]      FIG. 12  illustrates another embodiment of a flexible mesh ablation device  1200 . The flexible mesh ablation device  1200  is comprised of a catheter  1202 , a nonconductive flexible mesh  1204 , and a sheath  1206 . The sheath  1206  is mounted about the catheter  1202  such that it may be moved between a first location (shown in  FIG. 13 ) in which the sheath  1206  provides a radial constraint to the nonconductive flexible mesh  1204  and a second position (shown in  FIG. 12 ) in which the sheath  1206  does not provide a radial constraint to the nonconductive flexible mesh  1204 . A conductive coating  1208  is disposed on an exterior of the nonconductive flexible mesh  1204  and is in electrical communication with a power source (not shown) through a conductor  1210 . 
         [0043]    The nonconductive flexible mesh  1204  is woven in an expanded configuration with an outside diameter  1212  greater than an outside diameter  1214  of the catheter  1202 . The nonconductive flexible mesh  1204  is biased to maintain the expanded configuration. A proximal end  1216  is radially compressed to have a reduced diameter complementary to the outside diameter of the catheter  1202 . The reduced diameter is secured to the catheter  1202 , maintaining the reduced diameter despite the bias of the nonconductive flexible mesh  1204 . The nonconductive flexible mesh  1204  tapers from the reduced diameter portion to the expanded diameter. As previously described, the conductive coating is applied to an outer surface of the nonconductive flexible mesh  1204 , preferable in a helical pattern. Because the filaments of the nonconductive flexible mesh  1204  are typically woven in a helical pattern, the conductive coating  1208  may follow at least one filament. In the embodiment of  FIG. 12 , the conductive coating  1208  is applied to adjacent filaments and the filament segments between the adjacent filaments. A flexible base material may be applied between the nonconductive flexible mesh  1204  and the conductive coating  1208 . 
         [0044]    The nonconductive flexible mesh  1208  may be changed from the expanded state of  FIG. 12  to the radially constrained state of  FIG. 13  by advancing the sheath  1206  relative to the catheter  1202 . Advancing the sheath  1206  engages the taper of the nonconductive flexible mesh  1204  providing an inward radial force to collapse the nonconductive flexible mesh  1204 . As the nonconductive flexible mesh  1204  collapses, the sheath  1206  can be advanced further, constraining the nonconductive flexible mesh  1204  and further collapsing it. The sheath  1206  may be advanced until it completely covers the nonconductive flexible mesh  1204 . In this collapsed state, the nonconductive flexible mesh  1204  may be delivered to a treatment site. 
         [0045]    The above Figures and disclosure are intended to be illustrative and not exhaustive. This description will suggest many variations and alternatives to one of ordinary skill in the art. All such variations and alternatives are intended to be encompassed within the scope of the attached claims. Those familiar with the art may recognize other equivalents to the specific embodiments described herein which equivalents are also intended to be encompassed by the attached claims.