Patent Publication Number: US-2015066010-A1

Title: Expandable mesh platform for cardiac ablation

Description:
RELATED APPLICATIONS 
     The present patent document claims the benefit of the filing date under 35 U.S.C. §119(e) of Provisional U.S. Patent Application Ser. No. 61/827,380 filed May 24, 2013, which is hereby incorporated by reference. 
    
    
     FIELD 
     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 around an ostium of a blood vessel. 
     BACKGROUND 
     Atrial fibrillation is a common form of cardiac arrhythmia that can lead to a multitude of health problems including chronic heart failure and stroke. During atrial fibrillation (AF) the electrical impulses originating in the pulmonary veins become disorganized and generate irregular impulses of the ventricles. One of the current treatments of AF is atrial ablation via an intracardiac catheter. This ablation disrupts the irregular electrical impulses stemming from the pulmonary veins. To ensure adequate ablation, the physician will ablate circumferentially around where the pulmonary veins enter the left atrium. To do this, the physician has to ablate multiple places with each ablation partially overlapping adjacent ablations to form a continuous ablation line. Ensuring that the ablation line is continuous can be difficult as there is no direct visual feedback and the ablation sites themselves do not show up under either fluoroscopy or ultrasound. If the ablation line is not continuous, the ablation procedure can potentially be ineffective. Additionally, as the atrium is continuously moving, ensuring adequate contact between the tissue and the electrode can be difficult. 
     It would be beneficial to have a system capable of ablating around the ostium in a single session. 
     SUMMARY 
     Embodiments of the invention include a medical device for ablating tissue around an ostium. The medical device comprises a first longitudinal member having a first longitudinal member distal end, a second longitudinal member having a second longitudinal member distal end, a mesh, and a conductive coating. The second longitudinal member is axially movable from a proximal position to a distal position. The mesh has a distal end attached to the second longitudinal member and a mesh proximal end attached to the first longitudinal member. The mesh comprised of a plurality of flexible non-conductive filaments woven together, the mesh being expandable from an unexpanded configuration to an expanded configuration by axially moving the first longitudinal member and the second longitudinal member relative to each other. 
     In another embodiment, a medical device for ablating tissue around an ostial vessel comprises a sheath, a shaft, a mesh, and a conductive coating. The sheath has a longitudinal lumen with an inside diameter. The shaft is disposed within the longitudinal lumen of the sheath and is moveable relative to the lumen from a proximal position to a distal position. The mesh is attached to a distal end of the shaft and is mesh biased to a shape having a mesh outside diameter greater than the inside diameter of the sheath and comprises a plurality of flexible non-conductive filaments. The conductive coating is disposed on an outer surface of the mesh. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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: 
         FIG. 1  illustrates a cross section of a heart with an ablation device disposed in the right atrium. 
         FIG. 2  illustrates a cross section of the heart with the ablation device disposed in the left atrium. 
         FIG. 3  illustrates a cross section of the heart with the ablation device in an expanded configuration. 
         FIG. 4  illustrates a cross section of an ablation device. 
         FIG. 5  illustrates the ablation device of  FIG. 4  in an expanded configuration. 
         FIG. 5   a  illustrates the ablation device of  FIG. 5  in a head on view. 
         FIG. 6  illustrates the ablation device of  FIG. 5  further expanded. 
         FIG. 6   a  illustrates the ablation device of  FIG. 6  in a head on view. 
         FIG. 7  illustrates an ablation device having a conical expanded mesh. 
         FIG. 8  illustrates another embodiment of an ablation device. 
         FIG. 9  illustrates an embodiment of a bipolar ablation device. 
         FIG. 9   a  illustrates the ablation device of  FIG. 9  in a head on view. 
         FIG. 10  illustrates an embodiment of an ablation device in a vessel. 
         FIG. 11  illustrates an embodiment of an ablation device having a conical mesh. 
         FIG. 12  illustrates a proximal end of an ablation device having an energy source. 
     
    
    
     The drawings are not necessarily to scale. 
     DETAILED DESCRIPTION 
     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. 
     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. 
     Additional advantages of the present invention will become readily apparent from the following discussion, particularly when taken together with the accompanying drawings. 
     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. 
       FIG. 1  is a simplified cut-away view of a heart  100  showing the various chambers and vessels of the heart  100 . Blood (depicted by arrows) flows to the heart  100  from the body through the inferior vena cava  102  and the superior vena cava  104  into the right atrium  106 . From the right atrium  106  blood flows through the tricuspid valve  108  into the right ventricle  110 . From the right ventricle  110  blood is pumped into the pulmonary artery  112  through the pulmonary valve  114 . The blood flows into the lungs from the pulmonary artery  112  and returns via the pulmonary vein  116 . From the pulmonary vein  116 , blood collects in the left atrium  118  and flows into the left ventricle  120  through the mitral valve  122 . The right ventricle  110  and the left ventricle  120  are separated by a septum  128 . Blood flows from the left ventricle  120  through the aortic valve  124  to the aorta  126  where it is delivered to the body. 
     A distal end of an ablation device  200  having an expandable mesh  202  is disposed in the right atrium  106 . In this example the ablation device  200  has been delivered through the lower vena cava  102  and the distal end of the ablation device  200  extends from the lower vena cava  102  into the right atrium  106 . The proximal end of the ablation device  200  extends from the lower vena cava  102  to a location outside the patient&#39;s body. For example a patient may have a small incision made in a vein of the lower extremities which is then used to access the vascular system and guide a guidewire (not shown) to the right atrium  106 . With the guidewire in place, the ablation device  200  may be advanced over the guidewire to the right atrium  106 . In some embodiments the ablation device  200  may be delivered through the superior vena cava  104 . 
       FIG. 2  illustrates the heart  100  of  FIG. 1  with the distal end of the ablation device  200  being advanced into the left atrium  118 . Because there is septum separating the right atrium  106  from the left atrium  118 , the septum must be punctured to allow the distal end of the ablation device  200  to pass into the left atrium  118 . The septum may be punctured using commonly available techniques known to those of ordinary skill in the art. Once the distal end of the ablation device  200  is within the left atrium  118  the expandable mesh  202  is expanded as shown in  FIG. 3 . The expandable mesh  202  may be expanded into a pancake structure, a disk structure, an umbrella structure, or other structures as will be described hereafter. Because the expandable mesh  202  is flexible, it conforms to the wall of the left atrium  202 . Additionally, the mesh is porous, allowing blood to continue to flow through the mesh during use. Flexible electrodes (not illustrated) placed on a distal end of the expandable mesh also conform to the wall of the left atrium  202  such that energy may be efficiently delivered from the electrode to the wall of the left atrium  202  to ablate tissue. 
       FIG. 4  illustrates a distal end of an embodiment of an ablation device  400  having an expandable mesh  402  in accordance with the present invention. The expandable mesh  402  may be comprised of a plurality of nonconductive filaments woven together in a cylindrical shape. The expandable mesh  402  is operably connected to an inner shaft  406  and an outer shaft  408 . The inner shaft  406  may have at least one inner lumen sized to receive a guidewire. The at least one inner lumen may extend the entire length of the inner shaft. In use, the guidewire may be advanced to the ablation site and the ablation device  400  the advanced over the guidewire. The expandable mesh  402  may be secured at a proximal end  420  to a distal end  422  of the outer shaft  408  and at a distal end  424  to a distal end  426  of the inner shaft  406 . The expandable mesh  402  may be secured to the shafts  406 ,  408  using common techniques such as bands, adhesives, thermal bonding, or other techniques as known in the art. 
     In some embodiments, the inner shaft  406  is coaxially positioned within the outer shaft  408  as shown in  FIG. 4 . The expandable mesh  402  expands and collapses by longitudinal movement of the inner shaft  406  relative to the outer shaft  408  as explained in more detail below. A control handle  410  is provided at a proximal portion  412  of the ablation device  400 . The control handle  410  is operable to control the movement of the inner shaft  406  and the outer shaft  408  relative to one another. The control handle  410  may be any type of handle that is operable to control the movement of the inner shaft  406  relative to the outer shaft  408  and need not have the structure illustrated in  FIG. 4 . 
     The nonconductive filaments may be formed from a nonconductive 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 filaments, provided that they enable the expandable mesh to be changeable from the collapsed configuration of  FIG. 4  and the expanded configuration of  FIG. 5  in response to the inner shaft  406  moving relative to the outer shaft  408 . 
     Relative movement between the inner shaft  406  and the outer shaft  408  causes the expandable mesh  402  to change between a collapsed configuration shown in  FIG. 4 , and an expanded configuration shown in  FIG. 5 . The shape of the expanded configuration will vary depending on the amount of movement of the inner shaft  406  and the outer shaft  408  and the configuration of the expandable mesh  402 . The expandable mesh  402  in the unexpanded configuration has a first outside diameter  416  and the expandable mesh  402  in the expanded configuration extends beyond the first outside diameter  416  at a middle segment  418 . The unexpanded configuration may be used to deliver the distal end of the ablation device  400  to a treatment site within a patient and for repositioning the ablation device  400  within a patient to provide treatment to additional sites if needed. 
       FIG. 5  illustrates a distal end of an embodiment of an ablation device  400  having the expandable mesh  402  in an expanded configuration. In this embodiment the outer shaft  404  has been advanced distally relative to the inner shaft  406  decreasing the distance between the distal end  422  of the outer shaft  404  and the distal end  424  of the inner shaft  406 . The resulting longitudinal compression of the expandable mesh  402  causes the expandable mesh  402  to expand radially into the shape shown in  FIG. 5 . Also shown is a flexible conductive coating  500  applied to a distal side of the expandable mesh  402  in a circumferential ring  508 . In some embodiments the flexible conductive coating  500  may not extend along the entire circumference of the expandable mesh  402  and may be a circumferential segment of conductive coating  500 . In other embodiments the flexible conductive coating  500  may extend from near an end of the mesh to an area near a mid-point of the expandable mesh to cover a circumferential portion of the expandable mesh. The flexible conductive coating  500  may comprise a conductive ink. The flexible conductive coating  500  is operably coupled to a conductor that extends to an energy source. The energy source provides a source of energy for ablating tissue proximate the flexible conductive coating  500 . 
     The flexible conductive coating  500  may be arranged in other patterns for ablating different shapes. For example, the flexible conductive coating  500  may be arranged in a zig-zag pattern or have longitudinally extending components to ensure contact with the wall. The flexible conductive coating  500  may be applied only to individual filaments, leaving the mesh porous where the flexible conductive coating  500  is applied. In other embodiments, the flexible conductive coating  500  may cover a gap between adjacent filaments increasing the surface area of the flexible conductive coating  500 . A base layer may be provided between the conductive coating  500  and the expandable mesh  402 . The base layer may be used to span the space between adjacent filaments or to increase the adhesion of the flexible conductive coating  500  to the expandable mesh  402 . By way of non-limiting example, the base layer may comprise silicone, silanes, chlorinated polyolefins, thiolated polymers, organosilanes, organotitanates, zirconates, and zircoaluminates. 
       FIG. 5   a  illustrates a front view of the ablation device  400  of  FIG. 5  showing the flexible conductive coating  500  wrapping around the circumference of the expandable mesh  402  in a circumferential ring  508 . The circumferential ring  508  of flexible conductive coating  500  has a diameter  510  that is dependent on a diameter  512  of the expandable mesh  402 . As the diameter  512  of the expandable mesh  402  increases, the diameter  510  of the circumferential ring of flexible conductive coating  500  increases as well. 
     The expandable mesh of  FIG. 5  may be further expanded by advancing the outer shaft  404  relative to the inner shaft  406 .  FIG. 6  illustrates the expandable mesh  402  being expanded further. Outer shaft  404  has been advanced relative to the inner shaft  406  causing the expandable mesh  402  to form a pancake shape. As shown in  FIG. 6   a  the diameter  510  of the circumferential ring  508  of flexible conductive coating  500  is greater than it was in  FIG. 5 . This allows the expandable mesh  402  to have an adjustable size for varying geometries. If a larger ostium is being ablated the expandable mesh  402  may be expanded larger. For a smaller ostium it may be beneficial to keep the diameter  510  of the circumferential ring  508  of conductive coating  500  smaller. 
       FIG. 7  illustrates another embodiment of an ablation device  700 . This embodiment is substantially similar to the previously described embodiment of  FIG. 4 , with the exception of the shape of the expandable mesh  702  and the flexible conductive coating  706 . In this embodiment the expandable mesh  702  is formed into an inverted cone like shape  704 . The expandable mesh  702  may be formed into an inverted cone like shape  704  by bringing together a distal end  710  of the expandable mesh  702  and a proximal end  712  of the expandable mesh  702  to form a pancake shape, and then folding the resulting pancake shape distally. The flexible conductive coating  706  is placed on a base  708  of the inverted cone like shape  704 . The diameter  710  of the base  708  of the inverted cone like shape  704  may be adjusted by movement of the inner shaft  406  relative to the outer shaft  404  as described previously. 
     It may be preferable to approach the ostium of a blood vessel from within the vessel itself instead of from the heart as described previously. In such embodiments the ablation device will pass out of the vessel and into the heart, where the expandable mesh is expanded. The ablation device is then retracted until the proximal side of the ablation device contacts the wall near the ostium. 
       FIG. 8  illustrates an embodiment of an ablation device  800  suitable for abating an ostium of a blood vessel from within the blood vessel. This embodiment is substantially similar to the previously described embodiment of  FIG. 4 , with the exception of the placement of the flexible conductive coating  806 . The flexible conductive coating  806  is placed on a proximal side  808  of the expandable mesh  802  in a circumferential strip that forms a ring shape when the expandable mesh is expanded, as shown in  FIG. 8 . The distal end of the ablation device  800  may be advanced into the patients left atrium  118  and the expandable mesh  802  is expanded. The distal end of the ablation device  800  is then retracted until the expandable mesh  802  and the flexible conductive coating  806  contact the wall of the atrium  118 . Energy is then delivered to the flexible conductive coating  806  through a conductor and the wall is ablated. The expandable mesh  802  is then returned to its unexpanded state and may be removed from the atrium  118 . 
       FIG. 9  and  FIG. 9   a  illustrate another embodiment of an ablation device  900 . This embodiment is substantially similar to the previously described embodiment of  FIG. 4 , with the exception of the configuration of the flexible conductive coating. In this embodiment, the ablation device  900  has a first conductive coating  904  and a second conductive coating  906  to form a bipolar configuration. The first conductive coating  904  is in electrical communication with a first pole of a power source and the second conductive coating  906  is in electrical communication with a second pole of a power source. The first conductive coating  904  and the second conductive coating  906  are separated by a nonconductive annular region  908  of the expandable mesh  402 . The ablation device functions in the same manner as the embodiment of  FIG. 4 , changing size and shape as the inner shaft  406  is moved relative to the outer shaft  404 . Because the flexible conductive coating covers a large portion of expandable mesh, the flexible conductive coatings  904 ,  906  typically coat only the filaments leaving space between individual filaments. The spaces allow blood to continue to flow through the expandable mesh while in use. 
     A thermistor  910  may be disposed near the nonconductive annular region  908 . The electrical resistance of the thermistor  910  may vary depending on the temperature of tissue near the thermistor. The electrical resistance of the thermistor  910  may be measured to provide a measurement of the temperature of the tissue near the expandable mesh  406  during ablation. Other types of temperature sensors may be used to measure the temperature such as resistance temperature detector (RTD) or thermocouple. 
     To ablate tissue in the embodiment of  FIG. 9 , the expandable mesh is expanded and pressed against the wall of the heart. Energy is delivered to the first conductive coating  904  and the second conductive coating  906  from the power source. The first conductive coating  904  acts as a first pole and the second conductive coating  906  acts as the second pole of the power source. With the expandable mesh pressed against the wall, ablation will occur in tissue proximate the nonconductive annular region between the poles of the energy source. 
       FIG. 10  illustrates the ablation device of  FIG. 4  ablating a wall  1000  proximate the pulmonary vein  116 . The distal end of the expandable mesh  402  is fitted within the pulmonary vein  116  centering the ablation device  400 , in some embodiments the distal end of the inner shaft may extend beyond the flexible mesh  402  to form an elongated tip. The elongated tip may be used to center the location device in the vessel. The outer shaft  408  has been advanced relative to the inner shaft  406  expanding the expandable mesh  402 . The expandable mesh  402  conforms to the shape of the ostium of the pulmonary vein  116 . The flexible conductive coating is pressed against the wall and contacts the tissue. The flexible conductive coating  508  is in electrical communication with a first pole of a power source. A second pole of the power source is in electrical communication with the patient&#39;s body. Energy is delivered to the two poles and ablates the tissue proximate the flexible conductive coating  502  as it flows from the first pole to the second pole. 
       FIG. 11  shows another embodiment of an ablation device  1100 . The ablation device comprises a shaft  1102 , a sheath  1104 , and an expandable mesh  1106 . In this embodiment the expandable mesh  1106  is self-biased to the shape of a cone having a base diameter  1108  greater than an inside diameter  1110  of the sheath  1104 . In one embodiment the expandable mesh  1106  is comprised of a material having shape memory. The expandable mesh is formed with the self-biased shape being a low energy state. The expandable mesh  1106  is connected to the shaft  1102  at an apex  1114  of the cone and at an apex  1116  of the interior of the cone. A flexible conductive coating  1112  is applied to the base of the cone and is in electrical communication with an energy source. The ablation device  1100  is illustrated in an expanded state, but may be compacted by moving the inner shaft proximally relative to the sheath so that the sheath covers the expandable mesh. The sheath provides a radial constraint that inhibits the cone from expanding to its self-biased conical shape. 
       FIG. 12  illustrates the proximal end of an ablation device  1200 . In each of the previously described embodiments, the conductive coating is operably connected to an energy source. As shown in  FIG. 12 , a handle  1202  may include a connector  1204  for operably connecting the conductive coating to an energy source  1206 . As shown, the energy source  1206  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 energy source  1206  may incorporate feedback such as temperature and impedance measurements to control the energy delivered to the ablation device  1200  during use. 
     The conductive coating is connected to the energy source  1206  by an electrical conductor, such as one or more wires  1208  that extend from the conductive coating to the connector  1204  that connects to the energy source  1206 . The one or more wires  1208  may extend through a lumen  1210  of the inner shaft  1212  or may extend through a lumen of the outer shaft  1214  or external to the outer shaft  1214  and may optionally include a sleeve surrounding the outer shaft  1214  and one or more wires  1208 . 
     As discussed above, the handle  1202  is operable to move the inner shaft  1212  relative to the outer shaft  1214  so that the expandable mesh  1202  moves between the expanded configuration and the collapsed configuration. By way of non-limiting example, the handle  1202  includes a first portion  1216  and a second portion  1218  that move relative to each other. As shown in  FIG. 12 , the first portion  1216  is operably connected to the inner shaft  1212 . The second portion  1218  is operably connected to the outer shaft  1214 . The first portion  1216  may be moved proximally and/or the second portion  1218  may be moved distally to move the inner shaft  1212  proximally and/or the outer shaft  1214  distally to move the expandable mesh  402  to the expanded configuration. The first portion  1216  may be moved distally and/or the second portion  1218  moved proximally to move the inner shaft  1212  distally and/or the outer shaft  1214  proximally to move the expandable mesh  402  to the collapsed configuration. 
     The handle  1202  may include a lock  1220  shown to releasably lock the first portion  1216  in position relative to the second portion  1218  and thus lock the expandable mesh  402  in position. The lock  1220  may releasably lock the first and second portions  1216 ,  1218  of the handle  1202  together at any proximal/distal positioning of the inner and outer shafts  1212 ,  1214  so that the expandable mesh  402  may be locked at any size that is suitable for the treatment site. 
     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. It is contemplated that the different described embodiments may be combined with one another. For example, the bipolar configuration of  FIG. 9  is suitable for use in the example shown in  FIG. 10  and similarly the bipolar configuration of  FIG. 9  may have alternative expanded mesh configurations such as those shown in  FIGS. 7 ,  10 , and  11 . 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.