Abstract:
A method and device for puncturing the atrial septum to gain access to the left atrium without causing unintended injury to left atrial tissue. Specifically, the device includes a transseptal needle having a compressible shaft and a puncturing tip. As the transseptal needle is advanced through a delivery sheath and into contact with the septum, the compressible shaft is compressed and stores a minimal amount of mechanical energy but allows force transfer along its length. Force continues to be applied to the needle by the user until the puncturing tip punctures the septum. As the puncturing tip advances through the puncture and into the left atrium, any mechanical energy stored in the compressible shaft is immediately released, and the transfer of force is discontinued, by physical deformation of the compressible shaft. Thus, the puncturing tip enters the left atrium without causing injury to left atrial wall tissue.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    n/a 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    n/a 
       TECHNICAL FIELD 
       [0003]    The present invention relates to a method, system, and device for puncturing the atrial septum to gain access to the left atrium without causing unintended injury to left atrial tissue. Specifically, the device may include a transseptal needle having a compressible shaft and a puncturing tip. As the transseptal needle is advanced through a delivery sheath and into contact with the septum, the compressible shaft may be compressed and may store a minimal amount of mechanical energy but allows force transfer along its length. Force may continue to be applied to the needle by the user until the puncturing tip punctures the septum. As the puncturing tip advances through the puncture and into the left atrium, any mechanical energy stored in the compressible shaft may be immediately released, and the transfer of force may be discontinued, by physical deformation of the compressible shaft. Thus, the puncturing tip may enter the left atrium without causing injury to left atrial wall tissue 
       BACKGROUND 
       [0004]    Many cardiac treatment procedures require access to left atrium of the heart. For intravenous access, transseptal puncture is a critical step in gaining access to the left side of the heart. During transseptal puncture, a needle is passed through a delivery sheath  10  from the venous access point to the atrial septum, typically at the fossa ovalis. Force is applied to the needle near the external access point in order to build up pressure at the needle tip in contact with the cardiac tissue. Once the tip pressure is high enough to penetrate the septal wall, the needle passes through the septum and enters the left side of the heart, typically the left atrium. 
         [0005]    The amount of force exerted from the needle tip on the septal wall can be significant. Consequently, a user may have difficulty in controlling the tip momentum as the septal wall is punctured and force continues to be transferred to the needle tip and the dilator. This applied force cannot be instantaneously removed as the tip penetration may result in a sudden “pop” through the tissue. The response time of the user is typically too slow to reduce the applied pressure at the moment the needle tip punctures the septal wall. 
         [0006]    A risk of transseptal puncture is that the needle tip will unintentionally injure tissue at undesired locations in the heart. For example, if the applied force is not quickly reduced or removed at the time of puncture, the needle tip may continue in the direction of the applied force and come into contact with a wall of the left atrium. 
         [0007]    Therefore, it is desired to provide a device, system, and method that reduce the risk of post-puncture cardiac damage when used to perform a transseptal procedure. 
       SUMMARY 
       [0008]    The present invention advantageously provides a device, system, and method for reducing the risk of post-puncture cardiac damage when used to perform a transseptal procedure. In particular, the present invention provides a transseptal device with a compressible shaft that permits force transfer in a sheath to penetrate tissue while rapidly dissipating tip pressure after puncture is achieved. 
         [0009]    A transseptal device may include a needle having a compressible shaft with a proximal portion and a distal portion, the distal portion having a puncturing tip. The compressible shaft may be configured to compress when a force is applied to the proximal portion of the compressible shaft. Further, the needle may be configured to be advanced through a delivery sheath, the compressible coil being configured to be compressed when the needle is within a delivery sheath and uncompressed when the needle is advanced distally out of a delivery sheath. The puncturing tip may have a distalmost surface. For example, the distalmost surface of the puncturing tip may be tapered to a point configured to puncture septal tissue. Further, the puncturing tip may be composed of a low-mass material. The compressible shaft may be a spring or it may be composed of a deformable material having a low spring constant. The compressible shaft may be configured to transfer mechanical energy from the proximal portion to the puncturing tip, such as when the compressible shaft is compressed against an area of tissue, and may be configured to no longer transfer mechanical energy from the proximal portion to the puncturing tip immediately after the puncturing tip punctures the area of tissue. 
         [0010]    A method of creating a transseptal puncture may include: advancing a compressible transseptal puncture needle into contact with an atrial septum such that the compressible transseptal puncture needle is compressed, the compressible transseptal puncture needle including a proximal portion and a distal portion and being configured to transfer mechanical energy from the proximal portion to the distal portion when compressed; puncturing the atrial septum with the compressible transseptal puncture needle; and discontinuing the transfer of mechanical energy by physical deformation of the compressible transseptal puncture needle. The compressible transseptal puncture needle may include a compressible shaft and a puncturing tip coupled to the compressible shaft. The compressible shaft may have a coiled configuration. The compressible shaft may be a helical compression spring. The compressible transseptal puncture needle may define a proximal portion and a distal portion and further includes a non-compressible segment at the proximal portion, and the puncturing tip may be coupled to the distal portion. 
         [0011]    A method of creating a transseptal puncture may include: advancing a compressible transseptal puncture needle out a distal end of a delivery sheath and into contact with an atrial septum of a heart such that the compressible transseptal puncture needle is compressed, the compressible transseptal puncture needle being configured to transfer mechanical energy from a proximal portion to a distal portion of the transseptal puncture needle when compressed; puncturing the atrial septum with the compressible transseptal puncture needle; and immediately after puncturing the atrial septum with the compressed transseptal needle, discontinuing the transfer of mechanical energy by physically deforming the transseptal needle. The compressible transseptal puncture needle may include a compressible shaft and a puncturing tip coupled to the compressible shaft. The compressible shaft may have a coiled configuration. Further, the compressible transseptal puncture needle may define a proximal portion and a distal portion and further include a non-compressible segment at the proximal portion. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    A more complete understanding of the present invention, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein: 
           [0013]      FIG. 1  shows an exemplary placement of a medical device within a heart with transseptal access to the left atrium; 
           [0014]      FIGS. 2A and 2B  show a prior art transseptal device being used to puncture the atrial septum; 
           [0015]      FIG. 3  shows an exemplary graphical relationship between tip pressure and applied force when using a prior art transseptal device; 
           [0016]      FIGS. 4A-4D  show a transseptal device with a compressible needle shaft being used to puncture the atrial septum; and 
           [0017]      FIG. 5  shows an exemplary graphical relationship between tip pressure and applied force when using the transseptal device with compressible needle shaft. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    Referring now to  FIG. 1 , an exemplary placement of a medical device within a heart is shown. A delivery sheath  10  may be navigated to a patient&#39;s heart through the patient&#39;s vasculature, such as by femoral, radial, or brachial access. As a non-limiting example, the delivery sheath  10  may be navigated from the femoral artery, through the inferior vena cava, and into the right atrium, and the transseptal device  12  may be advanced through the delivery sheath  10  and into the heart. From the right atrium, the transseptal device  12  may be used to puncture the atrial septum, such as through the area of septal tissue known as the fossa ovalis, to gain access into the left atrium. The transseptal device  12  may include one or more puncture elements, such as a needle or cannula. Once the transseptal device  12  has punctured the atrial septum, the transseptal device  12  may be withdrawn through the delivery sheath  10  and removed from the heart, and a treatment device may be advanced through the delivery sheath  10  into the left atrium. Alternatively, the transseptal device  12  may also function as a treatment device, the transseptal device  12  remaining within the heart to treat cardiac tissue. Although other methods and treatment locations may be used, methods that require accessing left atrial tissue may involve puncturing the atrial septum with a transseptal device  12 . 
         [0019]    Referring now to  FIGS. 2A-3 , a prior art method of creating a transseptal puncture is shown. As is shown in  FIGS. 2A and 2B , the transseptal device  12  may be advanced through a delivery sheath  10  to the atrial septum. For example, the transseptal device  12  may include a needle  16  with a shaft  18  and a puncturing tip  20 . The shaft  18  may include a distal portion  24  and a proximal portion  26 , with the puncturing tip  20  being at the distal portion  24  and the proximal portion  26  extending out of the patient and being mechanically operable by a user. For example, the user may apply force to the shaft  18  to advance the needle  16  in a forward direction. A force F applied  may be exerted along the shaft  18  to contact the atrial septum with the puncturing tip  20 , and the force F applied  may be sufficient for the puncturing tip  20  to break through or puncture the septal tissue. However, the force F applied  required to puncture the septal tissue may be substantial, and therefore that force may continue to be exerted on the shaft  18  even after the septal tissue is punctured. This continued force may result in the puncturing tip  20  coming into contact with, and possibly injuring, the left atrial wall tissue downstream from the puncture site. 
         [0020]    Even though the user may attempt to reduce or eliminate the force F applied  exerted on the shaft  18  immediately after the septal tissue is punctured, the user&#39;s reaction time may not be fast enough to prevent the puncturing tip  20  from contacting the left atrial wall tissue. As is shown graphically in  FIG. 3 , puncturing the atrial septum with currently known transseptal devices may include four stages. In the first stage A, the pressure of the puncturing tip  20  against the septum may increase as the amount of force F applied  applied to the shaft  18  is increased. In the second stage B, the puncturing tip  20  may penetrate the septal tissue. In the third stage C, the puncturing tip  20  may continue in a forward direction due to the continued applied force F applied  on the shaft  18 . In the fourth stage D, the applied force F applied  may continue, even if somewhat reduced, and there is a risk that the puncturing tip  20  may injure left atrial wall tissue (or any other tissue within the heart other than the targeted septal tissue). 
         [0021]    Referring now to  FIGS. 4A-5 , a method of creating a transseptal puncture with a transseptal device having a compressible needle shaft is shown. The transseptal device  40  may be navigated to a location proximate the atrial septum as shown and described in  FIGS. 1-2B . Unlike the currently known transseptal device  12  of  FIGS. 1-3 , however, the transseptal device  40  of  FIGS. 4A-5  may include a needle  42  with a compressible shaft  44  and a puncturing tip  46 . The puncturing tip  46  may have a distalmost surface  48  that is sharp, pointed, tapered, or otherwise able to puncture tissue. The compressible shaft  44  may include a distal portion  50  and a proximal portion  52 , with the puncturing tip  46  being at the distal portion  50  and the proximal portion  52  extending out of the patient and being mechanically operable by a user. As a non-limiting example, the puncturing tip  46  may be affixed to the distal portion  50  of the compressible shaft  44  by any known means, such as welding, laser welding, chemical or heat bonding, use of adhesives, or the like. Alternatively, the puncturing tip  46  may be integral with (for example, co-extruded with) the compressible shaft  44 . The compressible shaft  44  may be a flexible coil, similar to a spring. In fact, the compressible shaft  44  may be a spring, such as a helical compression spring, that has a low spring constant in order to store a minimal amount of mechanical energy created by the force F applied  applied on the shaft  44 . Although the compressible shaft  44  may be configured to store a minimal amount of mechanical energy, it may also be configured to facilitate transfer of the applied force F applied  from the rigid proximal portion  52  of the shaft  44  to the puncturing tip  46  when it is constrained within the delivery sheath  54 . The coil design may be able to undergo compression while constrained within the delivery sheath  54  without directly applying a high level of pressure from the puncturing tip  46  to the septal tissue. Alternatively the compressible shaft  44  may not have a coiled configuration, but instead may be composed of a material that is physically deformable with a low spring constant such that only a small amount of energy is stored when it is physically compressed along the direction of the applied force. 
         [0022]    As the user applies force F applied  on the proximal portion  52 , the compressible shaft  44  may become compressed and pressure slowly builds up at the puncturing tip  46 . Once the compressible shaft  44  becomes fully compressed within the delivery sheath  54 , tip pressure may build between the puncturing tip  46  and the septal tissue as long as the compressible shaft  44  is constrained within the delivery sheath  54 . Further, the proximal portion  52  of the compressible shaft  44  may include a rigid segment  56  at the proximalmost end of the shaft  44  that is not compressible and is able to transmit force F applied  along the shaft to the compressible segment  58 . 
         [0023]    When sufficient pressure at the puncturing tip  46  is reached, the puncturing tip  46  may break through or puncture the atrial septum. As the puncturing tip  46  and the compressible shaft  44  continue forward (i.e. in a proximal-to-distal direction) out of the distal end  60  of the delivery sheath  54  and through the puncture in the atrial septum, the compression of the compressible shaft  44  is immediately dissipated and the puncturing tip  46  “flops” forward into the left atrium without reaching the left atrial wall tissue (or other non-target tissue). That is, the compressible shaft  44  may be configured to release the stored mechanical energy and absorb the pressure from the proximal portion  52  via physical deformation immediately after the puncturing tip  46  punctures the area of tissue. As the compressible shaft  44  is no longer constrained within the delivery sheath  54 , the transfer of applied force F applied  to the puncturing tip  46  is greatly diminished as shown in  FIG. 4D . For example, a helical compression spring compressible shaft  44  may be fully compressed against the atrial septum and may expand to its non-compressed configuration immediately upon puncturing the septal tissue and entering the left atrium. To enhance the rapid dissipation of pressure, the puncturing tip  46  may be composed of a material having a low mass. Further, the compressible shaft  44  may be constructed from a variety of materials, including but not limited to stainless steel, and/or nitinol. 
         [0024]    As is shown graphically in  FIG. 5 , puncturing the atrial septum with the transseptal device  40  with the compressible shaft  44  may include four stages. In the first stage A, the pressure at the puncturing tip  46  against the septum may increase gradually as the amount of force F applied  applied to the compressible shaft  44  is increased. The slope of the line shown in  FIG. 5  may be less steep than the slope of the line in the first stage A shown in  FIG. 3 . That is, the pressure at the puncturing tip  46  of the transseptal device  40  shown in  FIGS. 4A-4D  may increase less rapidly than the pressure at the puncturing tip  20  of the transseptal device  12  shown in  FIGS. 2A and 2B . In the second stage B, the puncturing tip  46  may penetrate the septal tissue. In the third stage C, the compression of the compressible shaft  44  may be immediately reduced, and force transfer discontinued, as the compressible shaft  44  relaxes and physically deforms (for example, the spring decompresses), and the puncturing tip  46  continues harmlessly into the left atrium. In the fourth stage D, the low-mass puncturing tip  46  does not transfer force F applied  to cardiac tissue within the left atrium. 
         [0025]    It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described herein above. In addition, unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. A variety of modifications and variations are possible in light of the above teachings without departing from the scope and spirit of the invention, which is limited only by the following claims.