Patent Publication Number: US-2021178123-A1

Title: Articulating Shaft For A Steerable Catheter System And Fabrication Method

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of the filing date under 35 U.S.C. § 119(a)-(d) of European Patent Application No. 19216804, filed on Dec. 17, 2019. 
     FIELD OF THE INVENTION 
     The present invention relates to a steerable catheter system and, more particularly, to an articulating shaft for a steerable catheter system. 
     BACKGROUND 
     Intravascular medical procedures allow the performance of therapeutic treatments in a variety of locations within a patient&#39;s body while requiring only relatively small access incisions. An intravascular procedure may, for example, eliminate the need for open-heart surgery, reducing risks, costs, and time associated with an open-heart procedure. The intravascular procedure also enables faster recovery times with lower associated costs and risks of complication. 
     An example of an intravascular procedure that significantly reduces procedure and recovery time and cost over conventional open surgery is a heart valve replacement or repair procedure in which an artificial valve or valve repair device is guided to the heart through the patient&#39;s vasculature. For example, a catheter is inserted into the patient&#39;s vasculature and directed to the inferior vena cava. The catheter is then urged through the inferior vena cava toward the heart by applying force longitudinally to the catheter. Upon entering the heart from the inferior vena cava, the catheter enters the right atrium. The distal end of the catheter may be deflected by one or more deflecting mechanisms, which can be achieved by a tension cable, or other mechanisms positioned inside the catheter. Precise control of the distal end of the catheter allows for more reliable and faster positioning of a medical device and/or implant and other improvements in the procedures. Apart from structural heart applications, the catheters are also used for minimally invasive procedures such as neurovascular, coronary, peripheral vascular or endoscopic type procedures for gastrointestinal applications or other. 
     An intravascular delivered device needs to be placed precisely to ensure a correct positioning of the medical device, which is essential for its functionality, as the device may be difficult to reposition after the device is fully deployed from the delivery system. Additionally, catheters are required to have the ability to turn or rotate the distal end of the catheter with like-for-like movement of the proximal section or catheter handle. It is achieved through torque transfer along the length of the shaft. For example, single steer to traverse an anatomical challenge. At the same time, catheters are required to achieve movement of parts of the catheter independent of the rest of the catheter. The design of the catheter shaft is a significant factor in determining the formation of curves, angles of deflection and levels of steerability. The choice of material determines the level of pushability, torque, and flexibility and it can be manipulated along the length of the catheter through a variety of means to achieve the desired results. 
     A catheter shaft needs to be placed precisely to ensure a correct positioning of the medical device. Multiple lumens may be created within catheters for the passage of guidewires, catheters, fluids, and gases. The number of lumens depends on the material and cross-sectional area. Lumens can be shaped to meet user requirements. Reinforcement bars (or wires) and pull wires may be inserted in the lumens. A core lumen is usually provided for receiving the catheter with the medial device. Such a core lumen needs to be sealed hermetically in order to protect the medical device. 
     It is known to use single or multilumen shafts and braided, coiled or other layers arranged thereon for enhanced torqueability and deflection. Reinforcement bars and pull wires may be placed in situ during the braiding process. Lack of symmetry in the braid reinforcement layers due to the presence of varying thickness of wire height lead to suboptimal and often poor torque performance through the length of the catheter shaft. Additionally, problems may occur during fabrication related to the integration of reinforcement or pull wires in the lumens, moreover, a complex braider setup has to be provided for assembling the additional braided layers, thus increasing the fabrication costs. There is still a need for an articulating shaft that has improved mechanical properties and allows the hermetic sealing of the core lumen, at the same time improving the fabrication process and reducing the costs of production. 
     SUMMARY 
     An articulating shaft for a steerable catheter system includes a tubular body and a plurality of wire support elements integrally formed from a single piece with the tubular body. The tubular body has a longitudinal central axis and a sealed lumen with a distal opening and a proximal opening. The wire support elements support an actuating wire. Each of the wire support elements has a feed-through opening receiving the actuating wire. A pair of adjacent wire support elements are separated from each other in an axial direction by a slot. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described by way of example with reference to the accompanying Figures, of which: 
         FIG. 1  is a perspective view of a shaft according to an embodiment; 
         FIG. 2  is a detail perspective view of the shaft of  FIG. 1 ; 
         FIG. 3  is a front view of the shaft of  FIG. 1 ; 
         FIG. 4  is a side view of the shaft of  FIG. 1 ; 
         FIG. 5  is another side view of the shaft of  FIG. 1 ; 
         FIG. 6  is a sectional end view of the shaft, taken along line VI-VI of  FIG. 5 ; 
         FIG. 7  is a sectional end view of the shaft, taken along line VII-VII of  FIG. 5 ; 
         FIG. 8  is a sectional side view of the shaft, taken along line VIII-VIII of  FIG. 5 ; and 
         FIG. 9  is a perspective view of a shaft according to another embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENT(S) 
     The accompanying drawings are incorporated into the specification and form a part of the specification to illustrate several embodiments of the present invention. These drawings, together with the description, serve to explain the principles of the invention. The drawings are merely for the purpose of illustrating examples of how the invention can be made and used, and are not to be construed as limiting the invention to only the illustrated and described embodiments. Furthermore, several aspects of the embodiments may form—individually or in different combinations—solutions according to the present invention. The following described embodiments thus can be considered either alone or in an arbitrary combination thereof. Further features and advantages will become apparent from the following more particular description of the various embodiments of the invention, as illustrated in the accompanying drawings, in which like references refer to like elements. 
     An articulating shaft  100  according to an embodiment is shown in  FIGS. 1 and 2 . The shaft  100  has a distal end  102  with a distal opening and a proximal end  104  with a proximal opening. As used herein, the terms “proximal” and “distal” are to be taken as relative to a user using the disclosed delivery devices. “Proximal” is to be understood as relatively closer to the user and “distal” is to be understood as relatively farther away from the user. 
     The shaft  100  has a tubular body with a longitudinal central axis  130 , the tubular body having at least one sealed, i. e. radially closed lumen with a distal opening and a proximal opening. A main lumen  106  extends along the complete length of the shaft  100 , as shown in  FIGS. 1 and 2 . According to the present invention, the main lumen  106  is delimited by an inner wall, which is closed along the length of the shaft  100 . Thus, the main lumen  106  can be sealed hermetically by connecting the distal and proximal ends  102 ,  104  to respective sealed fittings or connectors. The articulating shaft  100  for a steerable catheter is formed as one single piece, so that the main lumen  106  for inserting the catheter is completely sealed along the entire length of the shaft  100 ,  200 . The main lumen  106 ,  206  may also be referred to as the “central lumen” or “core lumen”. 
     According to the example shown in  FIG. 1 , the articulating shaft  100  has a plurality of wire support elements  110  each having at least one feed-through opening  112 . The feed-through openings  112  are linearly arranged in the longitudinal direction of the shaft  100 , so that a segmented lumen for a steering wire that can steer the shaft  100  is formed. It should be noted that, in the drawings, the steering wires and other elements that are inserted into the various lumens are not shown. Each of the wire support elements  110  is formed as a bracket which is separated from a tubular body  114  of the shaft  100  by a void  116 . In an embodiment, the bracket is shaped symmetric with respect to a mirror plane orthogonally intersecting the cross-section and the central longitudinal axis  130  of the shaft  100 . In particular, the feed-through opening  112  may be arranged in the middle of the bracket. In the shown embodiment, the body of the shaft  100  and the wire support elements  110  are integrally formed in a single piece. 
     Slots  118  separate each of the brackets  110  from the adjacent one in the axial direction, as shown in  FIGS. 1 and 2 . These slots  118  facilitate the bending of the articulating shaft  100  if a pull wire is inserted into the row of feed-through openings  112  and exerts bending forces on the shaft  100 . The presence of the voids  116  further enhances the flexibility and pliability of the shaft  100 . The slots  118  may also be referred to as notches. 
     The shaft  100  according to the first example further comprises reinforcement lumens  120 , shown in  FIGS. 1 and 2 , for receiving reinforcement bars or wires. These reinforcement wires may for instance be made from steel, Nitinol, or other suitable materials having some elastic properties. The reinforcement wires may also be referred to as the neutral axis support wires because they stabilize the segments formed by the slots  118  in their alignment and position. In the shown embodiment, two reinforcement lumens  120  are provided. It is clear for a person skilled in the art, however, that any other number of lumens  120  may also be provided. Further, also additional lumens for electrical cables or fluid channels can be provided. 
     When a tensile load is applied, an actuating wire shortens and causes the slots  118  to close, thereby causing the assembly to bend in the direction of the slots  118 . The neutral axis support wires arranged in the reinforcement lumens  120  also bend in order to allow the assembly to move. The reinforcement wires also carry some articulation axial load and keep tension on the assembly, thereby preventing the segments from separating. In order to facilitate the bending, the reinforcement lumen  120  may be segmented by peripheral regions of the slots  118 . 
     As shown in  FIG. 1 , at the proximal end  104  a fluidic connector  122  may be provided for a sealed connection to, for instance, a rigid part of a catheter or to a handle. Of course, also at the distal end  102  a similar fluidic connector may be provided. Thereby, a complete sealing of the main lumen  106  can be achieved. If the shaft  100  is intended to contain electric cables, the connector  122  may also comprise a device for forming an electrical connection. 
     In the shown example, the shaft  100  has an essentially circular outer contour. However, any other cross-sectional outline may also be chosen, for instance an oval or polygonal contour. As shown here, also all openings forming a lumen have a circular cross-section. This is not necessarily the case; any other suitable cross-section, e. g. oval or polygonal, may also be used. 
     In an embodiment, the articulating shaft  100  is formed as a 3D printed part, additively building up the part along the longitudinal axis  130  of the shaft  100 . In an embodiment, the shaft  100  is 3D printed from a biocompatible material. 3D printing has become an increasingly cost effective and accurate technology for producing medical material. 3D printing is an additive manufacturing (AM) process defined as a process of joining materials to make objects from 3D model data, usually layer upon layer, as opposed to subtractive manufacturing methodologies, such as traditional machining. 3D printing can deliver parts of very sophisticated and complex geometries with no need of post-processing, built from custom-made materials and composites with near-zero material waste, while being applicable to a diversity of materials, including smart materials such as shape memory polymers and other stimulus-responsive materials, or biocompatible materials. Therefore, 3D printing is a technology that allows designers and engineers to create unique products that can be manufactured at low volumes in a cost-effective way. In the field of medical engineering, 3D printing even allows to produce the shafts custom made and adapted to specific patients. 
     A particularly high freedom of design with low cost can be achieved if the shaft  100  is fabricated by the 3D printing process. However, the shaft  100  may also be fabricated by an extrusion process or an injection molding process. These processes are advantageous for high-volume production at low cost. 
     In an embodiment, the shaft  100  is fabricated from a polymer material having a durometer in the range of 30 Shore A to 70 Shore A. In another embodiment, the polymer material may have a durometer in the range of 35 Shore A to 40 Shore A. For instance, polyamide is a possible material. However, the shaft  100  may also be fabricated from any other suitable material. A material with a relatively low hardness is desirable if low pulling forces and a soft surface are sought, a harder material is advantageous, if an enhanced stiffness is needed. 
     Further views of the articulating shaft  100  according to the example shown in  FIGS. 1 and 2  are depicted in  FIGS. 3 to 8 . 
     As may be derived from the frontal view of  FIG. 3 , the main lumen  106  has a center  128  which is offset with respect to a center  126  through which the longitudinal axis  130  of the shaft  100  is passing. Thus, more room can be given to the bracket  110  comprising the feed-through opening  112  and the pliability of the shaft  100  is enhanced. The first and second lumens  120  for the neutral axis support wires are arranged at the tubular body  114  in a way that they are directly opposing each other along a diameter leading through the center  126  of the shaft  100 . 
       FIGS. 4 and 6  illustrate that the slots  118  which separate the plurality of segments formed by the wire support elements  110  from each other lead around the center  126  of the shaft  100  to cover a relatively large angle α of at least 45° and, in the shown embodiment, for instance 270°. Only a wall  132  forming the main lumen  106  remains closed continuously along the complete length of the shaft  100  for providing a sealed inner lumen  106 . When the shaft is bent in a direction toward the feed-through openings  112 , the slots  118  close, but also the brackets  110  formed by the voids  116  can be deformed if necessary, so that the distance between the feed-through openings  112  and the wall  132  is reduced. Thus, a sufficiently large segment of the shaft  100  has enough pliability to facilitate the steering process. 
     In an embodiment, each slot  118  may have a gradually diminishing depth in a radial direction towards the slot  118  peripheral regions around the circumference of the shaft  100 . This design allows for an optimized force distribution when bending the shaft  100 . 
       FIG. 9  illustrates a second embodiment of an articulating shaft  200  according to the present invention. The shaft  200  has a distal end  202  with a distal opening and a proximal end (not visible in this Figure) with a proximal opening. 
     A main lumen  206  extends along the complete length of the shaft  200  in the embodiment of  FIG. 9 . According to the present invention, the main lumen  206  is delimited by an inner wall  208 , which is closed along the length of the shaft  200 . Thus, the main lumen  206  can be sealed hermetically by connecting the distal and proximal ends to respective sealed fittings or connectors. 
     According to the example shown in  FIG. 9 , the articulating shaft  200  has a plurality of first wire support elements  210  each having a first feed-through opening  212  and a plurality of second wire support elements  211  each having a second feed-through opening  213 . The feed-through openings  212 ,  213  are linearly arranged in the longitudinal direction of the shaft  200 , so that two segmented lumens for two steering wires is formed. The rows of wire support elements  210 ,  211  are arranged opposite each other in a radial direction. Thus, a two way steerable catheter can be provided using the shaft  200  shown in  FIG. 9 . Again, it should be noted that in the drawings the steering wires and other elements that are inserted into the various lumens are not shown. Each of the wire support elements  210  is formed as a bracket which is separated from a tubular body  214  of the shaft  200  by a void  216 . 
     Slots  218  separate each of the brackets  210  from the adjacent one, as shown in  FIG. 9 . These slots  218  facilitate the bending of the articulating shaft  200  if a pull wire is inserted into the row of feed-through openings  212 ,  213  and exerts bending forces on the shaft  200 . The presence of the voids  216  further enhances the flexibility and pliability of the shaft  200 . 
     The design of the shaft  200  further differs from the design of the shaft  100  in that the cross-section is symmetrical, in other words, that the center of the main lumen  206  is coaxial with the central axis of the shaft  200 . 
     When the shaft  200  is bent in a direction towards one of the rows of feed-through openings  212 , the notches  218  close, but also the brackets  210  formed by the voids  216  can be deformed if necessary, so that the distance between the feed-through openings  212  and the wall  232  is reduced. 
     In the embodiment shown in  FIG. 9 , each of the slots  218  extends along less than 180° of the outer circumference of the shaft  200 , leaving two spines  234  for stabilizing the shaft  200 . In the shown example, the spines  234  as such stabilize the neutral axis. However, it is clear for a person skilled in the art that one or more additional reinforcement lumens (similar to the ones shown with the first example of the shaft  100 ) can be embedded in the spines  234  for receiving a neutral axis support wire of bar. These reinforcement wires may for instance be made from steel, Nitinol, or other suitable materials having some elastic properties. The reinforcement wires may also be referred to as the neutral axis support wires because they stabilize the segments formed by the slots  218  in their alignment and position. When a tensile load is applied, the actuating wire on the respective side shortens and causes the notches  218  on the side of the actuated wire to close, thereby causing the assembly to bend in the direction of those notches  218 . The neutral axis support wires arranged in the reinforcement lumens would also bend in order to allow the assembly to move. The reinforcement wires also carry some articulation axial load and keep tension on the assembly, thereby preventing the segments from separating. Further, also additional lumens for electrical cables or fluid channels can be provided. These lumens can be attached to the inner surface of the outer unsealed wall or they can be attached to the outer surface of the inner sealed wall. 
     Although not visible in  FIG. 9 , at the proximal end of the shaft  200  a fluidic connector may be provided for a sealed connection to for instance a rigid part of a catheter or to a handle. Of course, also at the distal end  202 , a similar fluidic connector may be provided. Thereby, a complete sealing of the main lumen  206  can be achieved. If the shaft  200  is intended to contain electric cables, the connector may also comprise a device for forming an electrical connection. 
     In the shown example, the shaft  200  has an essentially circular outer contour. However, any other cross-sectional outline may also be chosen, for instance an oval or polygonal contour. As shown here, also all openings forming a lumen have a circular cross-section. This is not necessarily the case; any other suitable cross-section, e. g. oval or polygonal, may also be used. 
     In an embodiment, the articulating shaft  200  is formed as a 3D printed part, additively building up the part along the longitudinal axis of the shaft  200 . However, it is clear that also other techniques of manufacturing the shaft  200  can be used. 3D printing is used to achieve the features required to allow articulation while also maintaining a sealed lumen. 
     In summary, the present invention may provide an articulating shaft  100 ,  200  design based on 3D printed low durometer biocompatible material, containing a sealed main lumen  106 ,  206 . The 3D printed articulating design may contain one or more lumens for wires or cables and the sealed lumen  106 ,  206  may be placed concentric to the outer diameter or offset from the center axis. The outer wall contains notches  118 ,  218  to allow the shaft  100 ,  200  to contract and bend on this side. 
     In case of a two-way steering shaft  200 , as shown in  FIG. 9 , it is advantageous to arrange the closed main lumen  206  concentrically within the outline of the shaft  200 . On the other hand, for an articulating shaft  100  as shown in the embodiment of  FIGS. 1 to 8 , which has to be bent only in one direction, it is advantageous to arrange the main lumen  106  offset from the central axis  130 , so that the closed lumen  106  is arranged within the outline of the shaft  100  with its central axis  128  being distanced from the longitudinal central axis  130  of the shaft  100 . In this case, a larger part of the shaft&#39;s cross-section can be used for the wire support elements  110 . 
     The wire or cable lumens can be attached to the inner surface of the outer unsealed wall or they can be attached to the outer surface of the inner sealed wall. Additional wires may be assembled into these lumens. These can be steel or Nitinol or other suitable materials with some elastic properties. These will be referred to as the neutral axis support wires. When these wires are attached to the distal end  102 ,  202  of the assembly and a tensile load applied then the wire (cable) shortens. This causes the notches  118 ,  218  to close, causing the assembly to bend in the direction of the notches  118 ,  218 . The neutral axis support wires bend to allow the assembly to bend. These wires also carry some articulation axial load. The wires keep the segments  110 ,  210  in alignment and position. The wires also keep tension on the assembly, preventing the segments  110 ,  210  from separating. The notches  118 ,  218  can be configured in a multitude of ways, with single way and two way steering possible. 
     A hermetic sealing of the core lumen  106 ,  206  can be achieved easily without additional covers or sheaths. Moreover, the assembly process is facilitated due to the one-piece design of the shaft  100 ,  200 . 
     The present invention further relates to a method for fabricating a shaft  100 ,  200  for a steerable catheter system, using 3D printing to achieve the features required to allow articulation while also maintaining a sealed lumen  106 ,  206 . The method includes providing a tubular body with a longitudinal central axis, the tubular body having at least one closed lumen  106 ,  206  with a distal opening  102 ,  202  and a proximal opening  104 . The method includes fabricating a plurality of wire support elements  110 ,  210 ,  211  for supporting at least one actuating wire, wherein each of the wire support elements  110 ,  210 ,  211  has at least one feed-through opening  112 ,  212 ,  213  for receiving the actuating wire, wherein two adjacent wire support elements  110 ,  210 ,  211  are separated from each other in an axial direction by a slot  118 ,  218 , and wherein the body  114 ,  214  and the wire support elements  110 ,  210 ,  211  are integrally formed from a single piece.