Abstract:
An instrument shaft for use in small openings where enhanced longitudinal dimensional stability and compressive loading characteristics are desirable. Various embodiments may be shafts of catheters used to treat peripheral vasculatures or coronary vasculatures. Embodiments of the catheter shaft provide enhanced longitudinal dimensional stability and compressive loading characteristics, while maintaining flexibility under loading conditions. In one embodiment, a catheter shaft includes an outer catheter shaft with a lumen therethrough, and an annular compression spring inside the outer catheter shaft. Also included is an actuation member inside the annular compression spring, wherein the actuation member actuates a working element at a distal end of the catheter.

Description:
FIELD OF THE INVENTION  
         [0001]    The invention is in the field of medical instruments and devices, and more particularly in the field of catheters.  
         BACKGROUND OF THE INVENTION  
         [0002]    Medical instruments must often be introduced into small body openings and lumens. In many instances, a small lumen must be navigated by an instrument to a site to be operated on. In such instances, it is necessary for the shaft attached to the working element to be steerable and to have the appropriate flexibility and strength. An example of a procedure in which characteristics of the instrument shaft are important is treatment of a vascular occlusion using a catheter device with some working element at its distal end.  
           [0003]    Prior catheters used to treat near total or total occlusions have several disadvantages. For example, some catheters are not sufficiently steerable, creating a risk that the lumen will be punctured in attempting to reach or traverse the occlusion. The path through the lumen is often complex and tortuous. The occlusion itself often is irregularly shaped. Thus, a steerable catheter is required. Another disadvantage of prior catheters is that they do not have appropriate mechanical characteristics to navigate through a near total or total occlusion, particularly if the occlusion is a hard material. The catheter should have sufficient torque and compression characteristics to allow it to be twisted and pushed as necessary, for steering and to overcome resistance, without deforming undesirably.  
         SUMMARY OF THE DISCLOSURE  
         [0004]    An instrument shaft for use in various types of medical instruments is described. Various embodiments may be shafts of catheters used to treat peripheral vasculatures or coronary vasculatures. Catheter shaft embodiments provide enhanced longitudinal dimensional stability and compressive loading characteristics, while maintaining flexibility under loading conditions. In one embodiment, a catheter shaft includes an outer catheter shaft with a lumen therethrough, and an annular compression spring inside the outer catheter shaft. Also included is an actuation member inside the annular compression spring, wherein the actuation member actuates a working element at a distal end of the catheter.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]    [0005]FIG. 1 is a cross section view of an embodiment of a catheter shaft.  
         [0006]    [0006]FIG. 2A is a cross section view of an embodiment of a compression spring.  
         [0007]    [0007]FIG. 2B is a cross section view of an embodiment of a compression spring.  
         [0008]    [0008]FIG. 2C is a cross section view of an embodiment of a compression spring.  
         [0009]    [0009]FIG. 3 is a cross section view of an embodiment of a catheter shaft.  
         [0010]    [0010]FIG. 4 is a cross section view of an embodiment of a catheter shaft.  
     
    
     DETAILED DESCRIPTION  
       [0011]    An instrument shaft is described. The instrument shaft is for any use in small openings where enhanced longitudinal dimensional stability and compressive loading characteristics are desirable. In one embodiment, the shaft is used as a catheter shaft. FIG. 1 is a cross section view of an embodiment of a catheter shaft  100  with various coaxial elements. The catheter shaft  100  may be used in catheters of any kind, but is particularly useful in situations in which enhanced longitudinal dimensional stability and compressive loading characteristics, as well as flexibility under loading are required. For example, the catheter shaft  100  is useful in situations in which the catheter must navigate a long and tortuous vasculature. The catheter shaft  100  may constitute the entire shaft of a catheter, or some portion of the shaft of the catheter.  
         [0012]    The outer catheter shaft  102  forms an outer surface of the catheter shaft  100  and has a lumen through its entire length. The outer catheter shaft  102  may be manufactured using braided 0.0007 inch×0.003 inch stainless steel wire. In other embodiments, the outer catheter shaft  102  may be manufactured using 0.0015 inch round wire. In any case, the stainless steel wire may be wound using a known commercial braiding machine and technique. The outer catheter shaft  102  may be impregnated with a polymer material such as nylon, Pebax, Tecoflex, polyamide, or Grilamid. The durometer of the polymer with which the outer catheter shaft  102  is impregnated may be graduated in decreasing hardness toward the distal end of the catheter shaft to enhance catheter tracking characteristics through the vasculature. As used herein, “distal” refers to the direction or portion of a catheter away from an operator of the catheter and toward a working element of the catheter. As used herein “proximal” refers to the direction or portion of the catheter toward an operator of the catheter and away from the working element of the catheter.  
         [0013]    An outer compression spring liner  104  is inside the lumen of the outer catheter shaft  102 . The outer compression spring liner  104  also has a lumen through it. The outer compression spring liner  104  may be manufactured of high density polyethylene, low density polyethylene, polyamide, PTFE, or materials with similar characteristics. The outer compression spring liner  104  provides lateral support to the outer diameter of the annular compression spring  106 . The support provided by the outer compression spring liner  104  reduces “walking” of filers in the annular compression spring  106  relative to each other. This helps maintain a continuous and uniform outer diameter and inner diameter of the annular compression spring  106 , so that it can withstand the required compressive loading.  
         [0014]    The annular compression spring  106  is inside the lumen of the outer compression spring liner  104 . FIGS. 2A, 2B, and  2 C show representative examples of springs that may be used as annular compression spring  106 .  
         [0015]    [0015]FIG. 2A shows two views of a flat wound spring  202 .  202   a  is a cross section taken along the longitudinal axis of the spring  202 .  202   b  is a cross section corresponding to a plane perpendicular to the longitudinal axis of the spring  202 . Spring  202  is made of relatively flat wire, wound so as to lie flat along the outer and inner circumferences of adjoining coaxial elements of the catheter shaft  100 . The support shaft  202  provides improved column loading characteristics and flexibility.  
         [0016]    [0016]FIG. 2B shows two views of an enhanced flexibility spring  204  with a high aspect ratio winding.  204   a  is a cross section taken along the longitudinal axis of the spring  204 .  204   b  is a cross section corresponding to a plane perpendicular to the longitudinal axis of the spring  204 . Spring  204  is wound so that, as shown in cross section, the flat section of the wire lays against successive filers. This type of configuration provides a higher degree of column loading, in part because of the larger contacting surface areas of adjacent filers, which are normal to the column force.  
         [0017]    [0017]FIG. 2C shows two views of an enhanced flexibility spring  206 .  206   a  is a cross section taken along the longitudinal axis of the spring  206 .  206   b  is a cross section corresponding to a plane perpendicular to the longitudinal axis of the spring  206 . Spring  206  is manufactured using round wire, which provides a greater degree of overall flexibility.  
         [0018]    Referring again to FIG. 1, inner compression spring liner  108  inside the annular compression spring  106 . The inner compression spring liner  108  has a lumen therethrough, and may be manufactured using a variety of materials, such as polymers to provide a smooth, continuous surface for the movement of an actuation element  110 . The inner compression spring liner  108  may be manufactured of high density polyethylene, low density polyethylene, polyamide, PTFE, or materials with similar characteristics. The actuation element  110  may be an actuation wire connected to a working element at a distal end of the catheter. The actuation element  110  may be also be a cable or other mechanism that generally operates by sliding proximally and distally in the lumen of the inner compression spring liner  108 .  
         [0019]    [0019]FIG. 3 is a cross section view of an embodiment of a catheter shaft  300  with various coaxial elements. Catheter shaft  300  includes some of the coaxial elements found in the catheter shaft  100  and some additional coaxial elements. The catheter shaft  300  may be used in catheters of any kind, but is particularly useful in situations in which enhanced longitudinal dimensional stability and compressive loading characteristics, as well as flexibility under loading are required. Additionally, this embodiment affords a higher degree of internal support when the shaft is acutely bent or flexed, in part because of the presence of the outer support shaft or spring  304 . For example, the catheter shaft  300  is useful in situations in which the catheter must navigate a long and tortuous vasculature. The catheter shaft  300  may constitute the entire shaft of a catheter, or some portion of the shaft of the catheter.  
         [0020]    The outer catheter shaft  302  forms the outer diameter of the catheter shaft  300  and includes a lumen therethrough. The outer catheter shaft  302  may be generally described with reference to the description of the outer catheter shaft  102  of FIG. 1. The outer support shaft or spring  304  is positioned inside the lumen of the outer catheter shaft  302  and has a lumen itself The outer support shaft or spring  304  may be manufactured as described with reference to FIGS. 2A, 2B, and  2 C. Alternatively, the outer support shaft or spring  304  may be manufactured using a polymer, such as nylon, high density polyethylene, or any polymer with good mechanical properties.  
         [0021]    The catheter shaft  300  further includes an outer compression spring liner  306 , an annular compression spring  308 , and an inner compression spring liner  310 . The descriptions of the outer compression spring liner  104 , the annular compression spring  106 , and the inner compression spring liner  108  (with reference to the discussion of FIG. 1) are applicable respectively.  
         [0022]    Element  312  is an actuation wire or cable connected to a working element at a distal end of the catheter. The element  312  may be also be a cable or other mechanism that generally operates by sliding proximally and distally in the lumen of the inner compression spring liner  310 .  
         [0023]    [0023]FIG. 4 is a cross section view of an embodiment of a catheter shaft  400  that includes coaxial elements arranged along more than one interior longitudinal axis. The catheter shaft  400  may be used in catheters of any kind, but is particularly useful in situations in which enhanced longitudinal dimensional stability and compressive loading characteristics, as well as flexibility under loading are required. For example, the catheter shaft  400  is useful in situations in which the catheter must navigate a long and tortuous vasculature. The catheter shaft  400  may constitute the entire shaft of a catheter, or some portion of the shaft of the catheter.  
         [0024]    The catheter shaft  400  has an outer catheter shaft  402 . The outer catheter shaft  402  forms an outer diameter of the catheter shaft  400  and has a lumen through it. The outer catheter shaft may be described with reference to the description of the outer catheter shaft  102  of FIG. 1. Inside the lumen of the outer catheter shaft is multi-lumen inner body  404 . Multi-lumen inner body  404  defines two working lumens for the catheter shaft  400 . In other embodiments, the multi-lumen inner body  404  defines various numbers of working lumens other than two. The catheter shaft  400  includes lumen  408  and lumen  410 . Lumen  408  can be used as a guidewire lumen, or to carry fluids, while lumen  410  can be used as an actuation element lumen. The multi-lumen inner body  404  can be made of materials such as nylon or Pebax that are extruded to produce the appropriate form. Materials and durometers may be chosen to provide required attributes such as strength and flexibility for a particular application.  
         [0025]    Lumen  408  is lined at its circumference by the guide wire liner  406 . The guide wire liner  406  may be manufactured using a variety of materials, such as polymers to provide a smooth, continuous surface for the movement of a guide wire (not shown).  
         [0026]    The lumen  410  is lined by an outer compression spring liner  412 , an annular compression spring  414 , an inner compression spring liner  416 , and an actuation element  418 . All of these items in the lumen  410  are similar to the similarly named items described with reference to FIG. 1 (elements  104 ,  106 ,  108 , and  110 ).  
         [0027]    Various embodiments have been described with reference to the figures, but the detailed description is not intended to be limiting. Various combinations of the elements described have not been shown, but are within the scope of the invention as defined by the claims. For example, a catheter shaft including more than two axial lumens and including some or all of the elements shown is within the scope of the claimed invention. Further, an instrument shaft manufactured using materials not specifically listed in the detailed description is within the scope of the claimed invention.