Patent Publication Number: US-2010121424-A1

Title: Stent compression tool

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to medical devices and equipment, and more particularly to a stent compression tool for diametrically compressing a stent and placing the stent within a stent delivery catheter. A method of stent compression using the tool is also disclosed. 
     2. Description of the Related Art 
     The surgical installation of stents, i.e., tubular devices used to repair or maintain an open passage through a bodily vessel, has been known and practiced for a considerable time. Stents are almost universally delivered and installed in the desired location by means of a stent delivery catheter, i.e., a hollow flexible tube or sheath carrying the stent therein. The smallest practicable diameter is most desirable for the delivery catheter, in order to avoid undue trauma to the patient. Yet, the stent itself must be of sufficient diameter to completely fill the diameter of the vessel in which it is installed. 
     Obviously, some means of placing the stent within the sheath is required. In the case of self-expanding stents, the stent must be compressed diametrically for insertion within the relatively smaller diameter of the delivery catheter sheath. This can be a tedious operation, depending upon the configuration of the stent and delivery catheter. As a result, many stents are pre-installed within the delivery catheter at the time of manufacture of the stent and catheter, thus precluding need for the medical practitioner (e.g., surgeon or nurse) to take the time to install the stent at the time of the stent implant operation. 
     Stents having various characteristics have been developed over the years, e.g., self-expanding and balloon expandable, biodegradable, woven, braided, or mesh construction using natural or synthetic materials, etc. Some of the more desirable materials for stent manufacture are biodegradable, allowing the stent to be absorbed or to dissolve within the body over a period of time to preclude requirement for subsequent additional surgery for stent removal in the case of a temporary implant. 
     However, a problem with many stents, and particularly those formed of biodegradable material, is that such material tends to take a “set,” i.e., to retain the physical shape and configuration to which it has been subjected, if held in that shape and configuration for long. This characteristic does not allow such stents to be installed within the delivery catheter long before the operation. In the case of stents formed of materials that tend to take a set, the stent is generally installed within the delivery catheter immediately before the operation. This can be a tedious procedure, as noted above, and in any case it takes further time to carry out the stent-to-catheter installation process, with time often being critical in the performance of medical procedures. 
     The present inventors are aware of a number of different devices that have been developed in the past for the installation of stents within bodily vessels. An example of such is Czech Republic Patent Document No. 14,595, filed on May 24, 2004. The first named inventor in the &#39;595 Czech Republic reference is also the first named inventor of the present stent compression tool. The &#39;595 Czech reference describes a series of flexible concentric tubes, with the self-expanding stent being placed within the outermost or largest diameter tube. The assembly is used to implant the stent at the desired location by sliding the outermost tube axially from its position over the stent and intermediate tube when the stent has been properly located, and withdrawing the remainder of the delivery assembly. No stent compression tool for loading the stent into a delivery catheter is described in this document. 
     None of the above-described inventions and patents, taken either singly or in combination, is seen to describe the stent compression tool as claimed. Thus, a stent compression tool solving the aforementioned problems is desired. 
     SUMMARY OF THE INVENTION 
     The stent compression tool includes a generally tubular device having a funnel-shaped mouth at one end and a relatively narrower opening at the opposite end. The narrower end portion or sleeve includes a series of longitudinal slots to allow the sleeve to expand over the atraumatic tip of the delivery catheter assembly during the stent installation process. A sleeve retaining collar slides axially along the sleeve to preclude spreading of the sleeve segments or to allow them to spread, depending upon the collar position along the sleeve. A collar stop extends axially from the collar to prevent inadvertent separation of the collar from the tube. 
     The stent compression tool is used with a conventional stent delivery catheter to install the stent within the end of the catheter. The tool is initially installed over the extended atraumatic tip, i.e., a relatively large diameter and blunt tip configured to minimize puncture or other trauma to the bodily passage into which the delivery catheter is inserted, and stent carrying member of the catheter assembly, and the stent is inserted through the larger diameter funnel mouth or opening of the tool. The stent is pushed through the tool, whereupon it is compressed diametrically as it passes through the narrower sleeve portion of the tool. When a portion of the stent has extended from the narrow end or opening of the tool, the stent carrying member with its stent grip is inserted farther through the tool for the grip to engage the inner diameter of the stent and pull it back into the narrow portion of the tool. 
     At this point, the outer sheath of the delivery catheter is inserted into the narrow end of the tool until it engages a slightly smaller diameter sheath stop. The inner diameter of the sleeve portion of the tool beyond the sheath stop and the inner diameter of the sheath are essentially equal. The sheath carrying member with its stent grip is then withdrawn back into the catheter sheath, pulling the compressed stent into the sheath as well. The carrying member with its atraumatic tip is then pulled back through the lumen or passage of the tool to remove the tool from the catheter assembly, and the carrying member is drawn back through the catheter sheath to position the atraumatic tip at the distal or working end of the catheter sheath to complete the process. 
     These and other features of the present invention will become readily apparent upon further review of the following specification and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a stent compression tool according to the present invention, shown with the sleeve retaining collar secured over the split sleeve of-the device and the collar limit stop retracted. 
         FIG. 2  is a perspective view of the stent compression tool of  FIG. 1 , shown with the sleeve retaining collar retracted to allow the split sleeve to open and with the limit stop extended. 
         FIG. 3  is an environmental side elevation view of the stent compression tool in the configuration of  FIG. 2 , showing the tool ready for installation over the atraumatic tip and carrying member of a stent delivery catheter. 
         FIG. 4  is a detailed environmental side elevation view in section of the stent compression tool of  FIGS. 1-2  being passed over the atraumatic tip of the carrying member. 
         FIG. 5  is a detailed environmental side elevation view in section, showing the stent compression tool of  FIGS. 1-2  being passed beyond the atraumatic tip of the carrying member and the sleeve retaining collar moved to secure the split sleeve in its closed position. 
         FIG. 6  is a detailed environmental side elevation view in section showing the stent partially inserted through the stent compression tool of  FIGS. 1-2 , the stent being partially compressed and disposed over the atraumatic tip and end of the carrying member within the tool. 
         FIG. 7  is a detailed environmental side elevation view in section similar to  FIG. 6 , but showing the diametrically compressed portion of the stent within the stent compression tool of  FIGS. 1-2  and over the carrying member. 
         FIG. 8  is a detailed environmental side elevation view in section, showing the advance of the stent compression tool of  FIGS. 1-2  and the stent toward the stent grip and core situated along the carrying member of the stent delivery catheter assembly. 
         FIG. 9  is a detailed environmental side elevation view in section, showing the stent grip drawing the compressed end of the stent into the stent compression tool of  FIGS. 1-2 , with the core following and the end of the delivery catheter sheath approaching the tool. 
         FIG. 10  is a detailed environmental side elevation view in section, showing the end of the delivery catheter sheath fully inserted into the stent compression tool of  FIGS. 1-2 , with the carrying member and the core and stent grip carried thereon drawing the compressed portion of the stent into the delivery catheter sheath. 
         FIG. 11  is a detailed environmental side elevation view in section, showing the compressed portion of the stent being drawn further into the delivery catheter sheath by the stent grip as it is drawn into the sheath. 
         FIG. 12  is a detailed environmental side elevation view in section, showing the carrying member being withdrawn through the lumen of the stent compression tool of  FIGS. 1-2 , with the stent grip having drawn the compressed stent completely into the sheath. 
         FIG. 13  is a detailed environmental side elevation view in section, showing the stent compression tool of  FIGS. 1-2  being withdrawn over the atraumatic tip of the carrying member, with the fully compressed stent installed within the sheath of the delivery catheter. 
         FIG. 14  is a detailed environmental side elevation view in section showing the completion of the stent compression process, with the atraumatic tip of the delivery catheter assembly retracted to the end of the sheath. 
     
    
    
     Similar reference characters denote corresponding features consistently throughout the attached drawings. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The stent compression tool works in concert with a diametrically compressible stent and conventional stent delivery catheter to compress and install the stent within the delivery catheter.  FIGS. 1 and 2  provide perspective views of the stent compression tool  10  with its second portion retaining collar positioned at the second end of the device, and with the retaining collar moved axially toward the opposite first end, respectively. The tool  10  generally comprises a tube  12  having a relatively large diameter first portion  14  and end  16  with a large funnel opening  18  therein, and an opposite smaller diameter second portion  20  with a relatively smaller diameter opening  22  therein, the smaller diameter opening  22  being concentric with the larger diameter funnel opening  18 . These features are shown clearly in  FIGS. 4 through 13  of the drawings, which illustrate the sequential steps in the compression of the stent and insertion of the stent into the delivery catheter. The funnel opening  18  will be seen to taper smoothly and diametrically to a constant first internal diameter  24 , with the second portion  20  of the tube  12  having a constant internal diameter  26  equal to the first internal diameter  24 . 
     A catheter sheath stop  28  (shown in  FIGS. 4 through 13 ) is disposed internally between the first and second internal diameter sections  24  and  26 . The sheath stop  28  limits the insertion of the end of the catheter delivery sheath into the tool  10  during the process of stent compression and insertion into the sheath, as discussed further below. The sheath stop  28  comprises a third internal diameter  30  smaller than the first and second internal diameters  24  and  26 , with the first end  32  of the stop  28  (i.e., the end toward the funnel opening  18 ) having a smooth conical taper from the first internal diameter  24  to the smaller internal diameter  30  of the stop. This assures a smooth transition for the stent as it is pushed through the tool  10  from the funnel opening  18 , through the sheath stop  28 , and toward the smaller diameter end opening  22 , as explained further below. The opposite second end  34  of the sheath stop comprises an abrupt diametric planar face or flange  34  having an outer diameter equal to the first and second internal diameters  24  and  26  of the device, and an inner diameter equal to the smaller third diameter  30  of the sheath stop  28 . This abrupt planar flange  34  serves as a stop to prevent the insertion of the end of the delivery catheter sheath beyond the stop flange  34 , as explained further below. 
     The tool  10  is formed of a flexible material, e.g., nylon or other durable but flexible plastic. The second portion  20  of the device is divided into a series of longitudinal segments  36  by a corresponding series of longitudinal slots  38  (e.g., four slots forming four segments), with the slots extending along the second portion  20  and into the medial portion  40  of the device. This allows the segments  36  to be spread or expanded radially to allow the passage of an object having an external diameter larger than the internal diameter  30  of the sheath stop  28 , for purposes explained further below. 
     An external circumferential retaining collar  42  is installed about the longitudinal segments  36 , and serves to hold the segments closed when the collar  42  is positioned at the opening end of the second portion  20  of the device, as shown e.g. in  FIG. 1  of the drawings. The collar  42  is adjustably positionable and may be slid axially toward the first portion  14  of the tool as desired. When the collar  42  is thus adjusted, the segments  36  are free to expand radially to allow an object (e.g., the atraumatic tip of a stent delivery catheter) having a larger diameter than the third internal diameter  30  of the sheath stop  28  to pass therethrough. Once the larger diameter object has cleared the smaller internal diameter  30 , the collar may be moved back to its position surrounding the second portion  20  of the tool  10  to hold the segments  36  closed. 
     The retaining collar  42  includes a collar limit bar  44  extending axially therefrom, outside the tube  12 . The limit bar  44  passes through a passage  46  in the larger diameter first portion  14  and an intermediate diameter stop  48  of the tool, and includes a limit stop  50  at the distal end of the limit bar, i.e. the end opposite the collar  42 . The limit stop  50  has a larger dimension than the passage  46 , and thus precludes separation of the retaining collar  42  from the second end portion  20  and beyond the second end opening  22  of the tool. As the passage  46  extends through the funnel opening  18 , the limit stop  50  includes a funnel surface  52  disposed flush with the internal surface of the funnel opening  18  when the collar  42  is positioned at its extreme travel adjacent to the second end opening  22  of the tool. 
     This allows an object, e.g., a stent, to be inserted into the large diameter funnel opening  18  of the tool without risk of catching or snagging on the limit stop  50 . Circumferential first and second collar retaining ridges  54  and  56  are provided around the second portion  20  and the extreme second end opening  22 , and have a separation from one another slightly greater than the width of the collar  42 . These ridges  54  and  56  serve to hold the collar  42  in position about the second portion  20  of the tool and to hold the second portion segments  36  closed as desired. When it is necessary to pass the tool  10  over a relatively large diameter object, the user merely pushes the collar  42  past the first collar retaining ridge  54  to a position around the medial portion  40  and against the intermediate diameter collar stop  48  of the device, allowing the segments  36  to flex radially outwardly as required. 
       FIGS. 3 through 13  illustrate the progressive steps for compressing a stent and installing the stent within the sheath of a stent delivery catheter by means of the stent compression tool  10 . In  FIG. 3 , a stent delivery catheter D assembly is shown to the right side of the Fig., opposite the stent compression tool  10 . The retaining collar  42  of the tool  10  has been moved to its alternative position about the medial portion  40  of the tube  12  and against the intermediate diameter collar stop  48 , to allow the longitudinal segments  36  to expand as required. 
     The delivery catheter D assembly includes a flexible tubular catheter sheath T having a first or distal end E, with a small diameter carrying member M disposed concentrically through the sheath T. The sheath T serves as a stent compression member once the stent has been installed therein. The sheath T includes a radiopaque band B disposed concentrically therearound adjacent the end E thereof, to enable the medical practitioner to locate the end E of the tubular sheath T when installed within a bodily vessel or passage. 
     A core C is affixed concentrically about the carrying member M, with the core C assisting in locating the carrying member M concentrically within the sheath T. The core C can also assist in holding the stent in place within the bodily vessel or passage as the sheath T is withdrawn over the carrying member M during the installation operation. A stent grip or retention member G is also affixed concentrically upon the carrying member M, but is spaced apart from the core C. The stent grip G is formed of a relatively soft silicone material, or at least coated with such material or a similar material having a surface with a high coefficient of friction. The stent grip G is of slightly smaller diameter than the internal diameter of the sheath T, in order to fit within the compressed stent and press or grip the stent against the inner surface of the tubular sheath T. Finally, an atraumatic tip A is affixed to the distal end of the carrying member M. The atraumatic tip A has an external diameter equal to that of the tubular sheath T, with a relatively rounded blunt tip-to preclude or minimize damage to the bodily vessel or passage as the stent delivery catheter assembly D is inserted and passed therethrough. The above described delivery catheter assembly D with its components T, B, M, C, G, and A are conventional, with the stent delivery tool  10  being configured to fit and work with a given diameter delivery catheter assembly D and stent as required. 
       FIG. 4  of the drawings illustrates the first step in the stent compression process, with the relatively large diameter atraumatic tip A being inserted into the smaller diameter opening end  22  of the tool  10 . The atraumatic tip A has an external diameter equal to that of the tubular sheath T, with this diameter being about the same as, or perhaps slightly smaller than, the first and second internal diameters  24  and  26  of the tool  10 . However, the diameter of the atraumatic tip A (and sheath T) is somewhat larger than the internal diameter  30  of the sheath stop  28  within the tool, when the longitudinal segments  36  are held closed by the collar  42 . Hence, it is necessary to move the collar  42  to the position shown in  FIGS. 2 through 4  to allow the segments to expand or spread, thus allowing the atraumatic tip A to pass completely through the tool beyond the larger diameter funnel opening  18  to the general position shown in  FIG. 5 . Once the atraumatic tip A is beyond the sheath stop  28 , the collar  42  may be moved back to its position adjacent the second end opening  22  of the tool, as shown in  FIG. 5 . 
     When the atraumatic tip A has been passed through the tool  10  as shown in  FIG. 5 , the stent S may be passed over the atraumatic tip A and compressed into the tool  10  through the large diameter funnel opening  18  thereof, generally as shown in  FIG. 6  of the drawings. The stent S may comprise multiple spirally wound fibers as shown, or other construction as desired. In any case, the stent S has a natural diameter at least equal to that of the vessel or passage into which it is to be installed, with the natural stent diameter also being somewhat greater than the internal diameter of the stent delivery sheath or tube T into which it is being placed. Thus, the stent S must be diametrically compressed to fit into the sheath T, with the stent S later expanding within the bodily vessel or passage in which it is installed, once the sheath T has been removed. In  FIG. 6 , this stent compression process through the tool  10  is shown partially completed, with the right or proximal end portion PE of the stent S located about halfway through the tool  10  within the relatively smaller first diameter portion  24  and the remainder of the stent S extending from the larger diameter funnel mouth end  18  of the tool. 
     This stent compression process continues as shown in  FIG. 7  of the drawings, with the proximal end PE of the stent S having been diametrically compressed through the tool  10  and extending from the small diameter end  22 . The plastic material of which the tool  10  is preferably formed provides a low friction surface against which the stent S may slide as it is pushed through and compressed within the tool. It will be seen that the proximal end PE of the stent S has expanded diametrically in  FIG. 7  after passing beyond the diametric restriction of the tool  10 , as the stent compression process is not yet complete. 
     The next step in the stent compression process is shown in  FIG. 8 , with the tool  10  and the stent S carried therein both moved along the delivery catheter carrying member M toward the stent grip member G and core C affixed to the carrying member. The tool  10  and the stent S are positioned with the proximal end PE of the stent surrounding the stent grip member G. At this point, both the distal end DE of the stent S and the carrying member M are held to preclude movement of the stent relative to the carrying member, and the tool is moved further to the right (as shown in  FIGS. 8 and 9 ) to move the proximal end PE of the stent and the grip member G therein into the smaller diameter second end portion  20  of the tool  10 . 
     The stent grip member G frictionally grips the stent material, with the stent sliding relative to the inner surface of the tool  10 . The grip member G has a diameter only very slightly less than that of the narrower third diameter  30  of the sheath stop portion  28  of the tool, and thus grips the stent S firmly between the grip member G and the inner surface of the sheath stop portion  28 . The retaining collar  42  remains around the second end portion  20  of the tool, thus preventing the longitudinal segments  36  of the tool from spreading and assuring that the stent S remains tightly secured against the grip member G. 
     At this point, the proximal end PE of the stent S has been compressed back into the tool  10  just inside the sheath stop portion  28  of the tool. This is shown in  FIG. 10  of the drawings. As the second end portion  20  of the tool is now open, excepting the carrying member M, the end E of the stent delivery sheath tube T may be installed within the second end  20  of the tool. In  FIG. 10  the insertion of the stent delivery tube T is nearly complete, but has not quite reached the diametric flange or ring  34  forming the abrupt end of the sheath stop portion  28 . 
       FIG. 11  illustrates the next step in the process, with the end E of the stent delivery sheath T having been pushed into the second end portion  20  of the tool  10  essentially as far as possible, with further insertion being stopped by the sheath stop flange  34  forming the second end of the sheath stop  28 . The outer diameter of the sheath tube T is essentially equal to the inner diameter  26  of the second end portion of the tool  10 , while the inner diameter of the sheath T is essentially equal to the inner diameter  30  of the sheath stop  28 . This allows the stent S to continue to move into the delivery catheter sheath tube T as the carrying member M and its stent grip member G are drawn back to the right (in the orientation shown in  FIG. 11 ). 
     The process of inserting the stent S completely into the stent delivery sheath tube T has been completed in  FIG. 12 , with the carrying member M having been drawn further to the right to cause the grip member G to draw the stent S farther into the delivery sheath or tube T. The atraumatic end A is adjacent to, or slightly within, the larger diameter funnel end  18  of the tool  10  at this point, with the stent S being completely compressed and positioned entirely within the delivery sheath tube T. 
       FIG. 13  illustrates the penultimate step in the compression and installation of the stent within its delivery catheter sheath. In  FIG. 13 , the retaining collar  42  has been repositioned over the medial portion  40  of the tool, adjacent to the intermediate retaining collar stop  48 . This allows the longitudinal segments  36  to spread or expand as the atraumatic tip A is pulled back through the tool  10  from the larger diameter first end  16  to the smaller diameter second end opening  22 . Once the atraumatic tip A has been removed from the tool  10  (or the tool removed from the atraumatic tip), the retaining collar  42  is returned to its position surrounding the second end portion  20  of the tool to retain the longitudinal segments, as shown in  FIG. 1 . The carrying member M is drawn further to the right to position the atraumatic tip A at the end E of the stent sheath tube T, as shown in  FIG. 14 , to complete the process of stent compression and stent installation into the delivery sheath. 
     Accordingly, the stent compression tool greatly facilitates the compression and installation of a compressible stent into a delivery sheath prior to use. This procedure has heretofore been a tedious task that requires a fair amount of time and expertise to accomplish properly. The stent compression tool removes much of the exacting labor previously required for this task, reducing the task essentially to drawing and removing various sheath components and the stent into and from the tool. The end result is a properly compressed stent free of kinks or damage, positioned within the delivery catheter, ready for placement within the patient. 
     It is to be understood that the present invention is not limited to the embodiment described above, but encompasses any and all embodiments within the scope of the following claims.