Patent Publication Number: US-2011054487-A1

Title: Coaxial transseptal guide-wire and needle assembly

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority of U.S. Provisional Patent Application Ser. No. 61/239,151, filed on Sep. 2, 2009 (pending), the disclosure of which is incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     The present invention generally relates to devices and methods of crossing a tissue and, more particularly, devices and methods of percutaneously piercing through an internal tissue of the heart. 
     BACKGROUND 
     The circulatory system of the human body transports blood containing chemicals, such as metabolites and hormones, and cellular waste products to and from the cells. This organ system includes the heart, blood, and a vascular network. Veins are vessels that carry blood toward the heart while arteries carry blood away from the heart. A septum separates the left and right sides of the heart where each side includes an atrial chamber and a ventricular chamber. The atrial chambers receive blood from the veins and the ventricular chambers, which include larger muscular walls, pump blood from the heart. Movement of the blood is as follows: blood enters the right atrium from either the superior or inferior vena cava and moves into the right ventricle. From the right ventricle, blood is pumped to the lungs via pulmonary arteries to become oxygenated. Once the blood has been oxygenated, the blood returns to the heart by entering the left atrium, via the pulmonary veins, and flows into the left ventricle. Finally, the blood is pumped from the left ventricle into the aorta and the vascular network. 
     A number of surgical procedures are performed on the internal tissues of the heart, such as the implanting of a cardiac assist devices for treating congenital heart disease or valve procedures for repairing a prolapsing valve. Conventionally these procedures involved a thoracotomy, i.e., the opening of the thoracic cavity between successive ribs to expose the internal organs. More typical is cardiac surgery, generally known as open-heart surgery, where the sternum is cut and split to expose the internal organs. Once the thoracic cavity is accessed, the physician must enter the pleural space and puncture both the pericardium and the myocardial wall. There are great risks and an extensive recovery time associated with the invasive nature of the implantation surgery. As such, some patients with severe symptoms are not healthy enough for surgery to receive a circulatory assist system. 
     There have been some catheter-based procedures developed for accessing the chambers of the heart. Conventionally these procedures are performed from a vascular access site near the right femoral vein in order to accommodate the angle between the vena cava and the septum. Yet, there continues to be a need for improvements in crossing the septum and treating defects associated with the atrial septum (e.g., ASDs, PFOs). 
     SUMMARY OF THE INVENTION 
     In one illustrative embodiment of the present invention, a coaxial transseptal device for piercing a tissue within the heart is described. The coaxial transseptal device includes a piercing device with a shaft and a distal needle portion. The coaxial transseptal device also includes a coaxial guide-wire configured to receive the piercing device and move relative thereto and has a flexibility that increases distally. 
     In another illustrative embodiment a guide-wire is described. The guide-wire comprises a tube with proximal and distal ends and a lumen extending between. The flexibility of the tube increases distally. A coil surrounds at least the distal end of the tube and a hub is attached to the proximal end of the tube. 
     Another illustrative embodiment describes a piercing device that includes a shaft having a needle portion on the distal end. The flexibility of the needle portion increases distally. 
     In yet another illustrative embodiment of the present invention, a method of piercing a tissue within the heart of a patient with the coaxial transseptal device is provided. The method includes introducing the distal end of the coaxial guide-wire into a superficial blood vessel. The distal end of the coaxial guide-wire is then directed through the superficial blood vessel and to the tissue within a first chamber of the heart. The needle portion of the piercing device is advanced beyond the distal end of the coaxial guide-wire, across the tissue, and into a second chamber of the heart. The distal end of the coaxial guide-wire is then advanced over the piercing device, across the tissue, and into the second chamber, which dilates the puncture in the tissue. 
     The guide-wire can include a removable adapter on the proximal end that can couple to a pressure monitor. The removable adapter and pressure monitor are configured to determine a pressure within a chamber of the heart. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIGS. 1A and 1B  are diagrammatic views of an exemplary method of accessing the septum of the human heart with a coaxial transseptal guide-wire and needle assembly, shown in cross-section. 
         FIG. 2A  is a disassembled, side-elevational view of the coaxial transseptal guide-wire and needle assembly. 
         FIG. 2B  is an assembled, side-elevational view of the distal end of the coaxial transseptal guide-wire and needle assembly. 
         FIG. 2C  is an assembled, side-elevational view of the proximal end of the coaxial transseptal guide-wire and needle assembly with a pressure adaptor. 
         FIG. 3A  is an assembled, side-elevational view of the distal end of the coaxial transseptal guide-wire and needle assembly, shown in partial cross-section. 
         FIG. 3B  is an assembled, side-elevational view of an alternate embodiment of the distal end of the coaxial transseptal guide-wire and needle assembly, shown in partial cross-section. 
         FIGS. 4A-4B  are side-elevational views of alternate embodiments of the distal end of a piercing device. 
         FIG. 4C  is a cross-sectional view illustrating an alternate embodiment of the piercing device. 
         FIG. 5  is an assembled, side-elevational view of the coaxial transseptal guide-wire and needle assembly with a safety clip secured to the piercing device. 
         FIG. 6  is an assembled, side-elevational view of the coaxial transseptal guide-wire and needle assembly with the safety clip removed. 
         FIGS. 7A-7D  are side-elevational views in partial cross section illustrating successive steps of one exemplary procedure for crossing the intra-atrial septum with the coaxial transseptal guide-wire and needle assembly. 
         FIG. 8  is a diagrammatic view of an alternate method of accessing the septum of the human heart with a coaxial transseptal guide-wire and needle assembly, shown in cross-section. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1A and 1B  illustrate an exemplary method of transseptal crossing according to one embodiment of the present invention. Accordingly, the physician can direct a guide catheter  10  into a vascular access site  12  of the patient  13 . The guide catheter  10  can be any steerable or preformed catheter that can be directed through the vascular system to aid in the delivery of subsequent surgical devices to the surgical site. The vascular access site can be near a suitable superficial blood vessel, such as the right subclavian vein  14 ; however, other superficial vessels could also be used, such as the left subclavian vein  16  or the left or right jugular veins  18 ,  20 , or in some instances a superficial artery could also be used. 
     The guide catheter  10  can include a hub  21  having a hemostasis valve that prevents the loss of blood while maintaining access for passage of the subsequent devices. 
     The guide catheter  10  is directed to the intra-atrial septum  22  of the heart  24  via the superior vena cava  26  and the right atrium  28 . For illustrative purposes additional anatomy is shown, including the inferior vena cava  30 , the right ventricle  32 , the left ventricle  34 , the aortic arch  36 , the brachiocephalic trunk  38 , the left common carotid artery  40 , and the left subclavian artery  42 . 
     In  FIG. 1B  the distal end of the coaxial transseptal device  43  is directed into the guide catheter  10  at the vascular access site  12  and advanced through the lumen of the guide catheter  10  to the right atrium  28 . Typically, the coaxial transseptal device  43  is advanced to an area of the right atrium  28  that is near the fossa ovalis  45 . 
       FIGS. 2A and 2B  illustrate the details of the coaxial transseptal device  43 , which includes a piercing device  44  and a coaxial guide-wire  46 . The coaxial guide-wire  46  receives, and moves relative to, the piercing device  44 . 
     As shown in  FIG. 2A , the piercing device  44  includes a shaft  48  having distal and proximal ends, where the proximal end includes a hub  50  and the distal end includes a sharpened portion, i.e., a needle portion  52 . The hub  50  can be secured to the flexible shaft  48  by either an insert injection molding process or by bonding a previously molded hub  50  to the shaft  48  using a biocompatible adhesive or epoxy. The hub  50  can include grooves  54  for providing additional grip between the physician&#39;s glove and the hub  50 . 
     Referring still to  FIG. 2A , the distal end of the shaft  48  can further include a radiopaque tip  56  constructed from any radiopaque material, such as platinum-iridium (Ptlr), stainless steel, tungsten (W), or tantalum (Ta). Radiopaque materials allow the physician to remotely visualize the structure, in vivo, by X-ray or real-time fluoroscopy. The distal end of the radiopaque tip  56  can be ground to an optimal shape for the needle portion  52 , which facilitates the puncture and passage through a vascular tissue, such as the intra-atrial septum  22  ( FIG. 1 ). 
     The shaft  48  can be constructed from metallic materials, such as MP35N, nickel titanium (NiTi), or stainless steel, or from a rigid polymer such as polyamide or polyaryletheretherketone (PEEK). To ensure visual contrast, the shaft material should not be as radiopaque as the material comprising the radiopaque tip  56 . The joint  58  between the shaft  48  and the radiopaque tip  56  can be made by common welding techniques or by using a biocompatible adhesive or epoxy. The shaft  48  can also be coated with a lubricious polymer material to minimize friction between the flexible shaft  48  and the coaxial guide-wire  46 . The shaft  48  is constructed with an outer diameter that is sized such that there is sufficient clearance between the outer diameter of the shaft  48  and the diameter of a lumen  60  extending through the coaxial guide-wire  46  to allow the shaft  48  to move relative to the coaxial guide-wire  46 . 
       FIGS. 2A and 2B  further illustrate the details of the coaxial guide-wire  46 . The coaxial guide-wire  46  includes a proximal portion  62  that is separated by a transition joint  64  from a distal portion  66 . The proximal portion  62  can include a proximal sleeve  68  constructed from a polymeric thermoset material, such as polytetrafluoroethylene (PTFE) or polyimide, or a thermoplastic polymer, such as fluorinated ethylene propylene (FEP), polyurethane, or polyamide. Generally, the material should have a low coefficient of friction or be a material that will accept a lubricious polymer material. While the thickness of the proximal sleeve  68  can vary and depend on a desired final outer diameter of the coaxial guide-wire  46 , the wall thickness of the proximal sleeve  68  can vary from about 0.0127 mm (0.0005 inches) to about 3.81 mm (0.15 inches). Typical outer diameters for the guide-wire can range from about 0.012 inches to about 0.038 inches. 
     The coaxial guide-wire  46  can vary in length to accommodate various surgical procedures, but generally range from about 50 cm to about 400 cm. 
     The distal portion  66  of the coaxial guide-wire  46  can include a coil  70  extending between a distal tip  72  and the proximal sleeve  68 . The coil  70  can be constructed from a metallic material, such as stainless steel or Ptlr, and is typically round in cross-section, though rectangular or flat wire cross-sections are possible. The round cross-section coils can range in diameter from about 0.0254 mm (0.001 inches) to about 0.254 mm (0.010 inches); flat wire coils can have a thickness-to-width ratio ranging from about 1:2 to about 1:4 with thickness ranging from about 0.0127 mm (0.0005 inches) to about 0.127 mm (0.005 inches). The coil  70  can be coated with a lubricious material, such as PTFE. In some embodiments, though not shown here, the coil  70  can extend the full length of the coaxial guide-wire. The proximal sleeve  68  and coil  70  have similar outer diameters to ensure a smooth transition between components and are joined at the transition joint  64  by common welding techniques or by using a biocompatible adhesive or epoxy. 
     The distal tip  72  can be constructed from a dense metal to enhance its radiopacity and has an outer diameter that is substantially similar to the outer diameter of the coil  70  to ensure a smooth transition between the components. 
       FIG. 2C  illustrates a removable adapter  94  that can be attached to the proximal end of the coaxial guide-wire  46 . The removable adapter  94  includes a body  96  and a distal collet  98  with an adjustment mechanism  100  for tightening the collet  98  against the coaxial guide-wire  46 . The collet  98  can include an internal ring (not shown) for creating a fluid tight seal against the coaxial guide-wire  46 . The proximal end of the body  96  can include a hemostasis valve hub  102  to prevent the loss of blood while maintaining a fluidic access to the lumen  60  ( FIG. 2A ) of the coaxial guide-wire  46 . The body  96  further includes a side port  104  with tubing  106  and a stopcock  108 , which can then be attached to a pressure monitor  110 . The pressure monitor  110  can allow the physician to monitor the pressure within the left atrium  92  ( FIG. 1A ) during the surgical procedure, particularly when puncturing the intra-atrial septum  22  ( FIG. 1A ). By monitoring the pressure within the left atrium  92  ( FIG. 1A ) the physician can ensure that the transseptal crossing has occurred in the appropriate location. A luer fitting  112  can be used for attaching the tubing  106  to the pressure monitor  110  or other device within the operating room. 
       FIG. 3A  illustrates the cross-sectional features of the distal ends of the coaxial guide-wire  46  and the piercing device  44 . The coaxial guide-wire  46  includes a tube  74  extending proximally from the distal tip  72 . Construction of the tube  74  can include metallic materials, such as MP35N, NiTi, or stainless steel. The tube  74  is formed by a wire drawing process and electro-polished to remove sharp edges. While the wall thickness of the tube  74  can vary, typical thicknesses can range from about 0.0254 mm (0.001 inches) to about 0.254 mm (0.010 inches). 
     The distal portion of the tube  74  can be processed by laser into a spiral cut section  76  to provide a flexibility that increases distally. That is, the distal portions of the spiral cut section  76  are more flexible than the proximal portions of the spiral cut section  76 . As shown in  FIG. 3A , the spiral cut section  76  can have a uniform pitch at the distal end of the tube  74 . Alternatively, as shown in  FIG. 3B , the spiral cut section  76  can have a variable pitch such that the flexibility of the spiral cut section is further increased distally, i.e., the proximal section of the spiral cut section  76  has a larger pitch than the more flexible, distal section. The spiral cut section  76  allows the distal end of the coaxial guide-wire  46  to be flexible enough to pass through the vascular system while still limiting the radius of curvature. The spiral cut section  76  should be constructed with a direction that opposes the direction of the pitch of the coil  70  to prevent the coil  70  from penetrating into the spiral cut section  76  as the coaxial guide-wire  46  is passed through a bend in the vascular system. 
     The distal tip  72  includes a tip shoulder  78  and a radial tip  80 . The tip shoulder  78  provides a surface for adjoining the distal tip  72 , the coil  70 , and the tube  74  by common welding techniques or by using a biocompatible adhesive or epoxy. The radial tip  80  minimizes unintentional trauma to vascular tissue as the coaxial guide-wire  46  is advanced through the vascular network. While a rounded shaped radial tip  80  is shown, it is possible for the radial tip  80  to alternatively include a bullet shape, a bevel, or an elliptical shape. 
     Turning now to  FIG. 4A , one embodiment of the piercing device  44  is illustrated. As shown, the flexible shaft  48  can include a distally-positioned spiral cut section  82 , which can be made by laser machining. The spiral cut section  82  is typically helical and can penetrate into the material of the shaft  48  by no more than ½ of the original outer diameter of the shaft  48 . This would allow at least ½ of the original outer diameter to remain as a core  84 . The core  84  provides structural stability to aid in advancing the piercing device  44  through the coaxial guide-wire  46 . The spiral cut section  82  provides flexibility to the distal end of the piercing device  44  as it advances through the coaxial guide-wire  46  within the vascular network. 
       FIGS. 4B and 4C  illustrate alternate embodiments of the piercing device  44 . In  FIG. 4B , the spiral cut section  82  is cut with a variable pitch, as compared to the constant pitch of  FIG. 4A . Accordingly, the variable pitch is such that the proximal portion of the spiral cut section  82  of the piercing device  44  has a greater pitch and is less flexible than the distal portion of the spiral cut section  82 .  FIG. 4C  illustrates an embodiment where the spiral cut section  82  is cut with a variable depth such that the distal portion of the spiral cut section  82  is cut deeper and is therefore more flexible than the proximal portion. At the most distal portion of the spiral cut section  82 , the helical cut should not penetrate into the material of the shaft  48  by more than ½ of the original outer diameter. 
       FIG. 5  illustrates the assembled coaxial transseptal device  43 . The piercing device  44  is back-loaded into the coaxial guide-wire  46  until the hub  50  is positioned near the proximal end of the coaxial guide-wire  46 . To ensure that the needle portion  52  remains sheathed within the coaxial guide-wire  46 , and to prevent inadvertent and premature puncture of the vascular tissue, a safety clip  86  can be positioned on the shaft  48  between the hub  50  and the proximal end of the coaxial guide-wire  46 . The safety clip  86  can be machined or molded from a thermoplastic material, a polymer, or metal and can include grooves  88  to improve the grip between the physician&#39;s glove and the safety clip  86 . In the illustrative embodiment, the safety clip  86  is constructed with an attachment portion  90  that snaps onto the flexible shaft  48 , though additional safety locks and features could also be used. The attachment portion  90  creates a frictional fit against the shaft  48  and prevents the needle portion  52  from prematurely advancing beyond the distal end of the coaxial guide-wire  46 . The length of the attachment portion  90  that contacts the shaft  48  will determine the penetration depth of the piercing device  44  into the left atrium  92  ( FIG. 1A ), in a manner that is described in greater detail below. 
       FIG. 6  illustrates the removal of the safety clip  86 , which then allows the hub  50  of the piercing device  44  to advance distally and contact the proximal end of the coaxial guide-wire  46 . As the hub  50  is advanced, the needle portion  52  extends distally from the radial tip  80  of the distal tip  72 . Though not drawn to scale, from  FIG. 6  is can be seen that the piercing device  44  can only extend distally from the radial tip  80  by an amount that is equal to the length of the attachment portion  90  that contacted the shaft  48  in  FIG. 5 . 
     With the details of the coaxial transseptal device  43  described with some detail, one method of transseptal crossing can be described with reference to  FIGS. 7A-7D . 
       FIG. 7A  illustrates the coaxial transseptal device  43  as it is advanced into the right atrium  28  and such that the radial tip  80  contacts the intra-atrial septum  22 . The needle portion  52  remains sheathed within the coaxial guide-wire  46 . 
     In  FIG. 7B , the physician can remove the safety clip  86  ( FIGS. 5 and 6 ), if used, to release the shaft  48  such that it is distally moveable with respect to the coaxial guide-wire  46 . The physician can then advance the piercing device  44 , as had been shown previously in  FIGS. 5 and 6 , such that the hub  50  is advanced toward the proximal end of the coaxial guide-wire  46 . Coincidentally, the needle portion  52  extends beyond the distal end of the radial tip  80  and punctures the intra-atrial septum  22 . Continued advancement of the piercing device  44  causes the needle portion  52  to pass across the intra-atrial septum  22  and into the volume of the left atrium  92 . During the piercing and crossing of the intra-atrial septum  22 , the physician can constantly monitor the pressure within the left atrium with a pressure monitor via the removable adapter  94  ( FIG. 2C ). 
     In  FIG. 7C , the physician advances the coaxial guide-wire  46  across the intra-atrial septum  22  while maintaining the relative position of the piercing device  44  to the coaxial guide-wire  46  so as to not puncture additional tissues. The radial tip  80  can be used to dilate the puncture created by the piercing device  44  through the intra-atrial septum  22  to a diameter that is similar to the outer diameter of the coaxial guide-wire  46 . 
     With the distal tip  72  of the coaxial guide-wire  46  in the left atrium  92 , the physician can then retract the piercing device  44  from the coaxial guide-wire  46 . The removable adapter  94  ( FIG. 2C ) is removed leaving only the coaxial guide-wire  46  in place and as shown in  FIG. 7D . The coaxial guide-wire  46  is then prepared to receive auxiliary devices. 
       FIG. 8  illustrates an alternate method of accessing a tissue within the heart  24  of a patient  13 . As shown, a vascular access site  114  can be chosen to be from an inferior location, such as the right or left femoral veins  116 ,  118 . The guide catheter  10  and coaxial transseptal device  43  are then directed to the right atrium  28  from the inferior vena cava  30 . The physician can then cross the intra-atrial septum  22  in a manner similar to the procedure described in detail above. 
     While the present invention has been illustrated by a description of various preferred embodiments and while these embodiments have been described in some detail, it is not the intention of the Applicants to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. The various features of the invention may be used alone or in any combination depending on the needs and preferences of the user. This has been a description of the present invention, along with the preferred methods of practicing the present invention as currently known. However, the invention itself should only be defined by the appended claims.