Abstract:
A percutaneous trans-luminal catheter delivery system for an implant. The system includes a catheter shaft with a distal end to carry the implant and an elongate housing at a proximal end that an operator can grasp when deploying the implant. The shaft has an inner push component which can push on the implant in a distal direction and an outer sheath component which radially surrounds the implant until deployment of the implant into the bodily lumen. The outer sheath component is capable of being pulled proximally, from the housing, to deploy the implant, the housing being mounted on a proximal end portion of the push component and defining a channel. The housing may contain a sheath slitter that is fixedly mounted relative to the length of the channel that can slit the outer sheath as the outer sheath is caused to move proximally in the channel relative to the slitter.

Description:
PRIORITY 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/720,252, filed Oct. 30, 2012, and of NL Application No. N2009726, filed Oct. 30, 2012, each of which is incorporated by reference in its entirety into this application. 
     
    
     TECHNICAL FIELD 
       [0002]    This invention relates to a percutaneous trans-luminal catheter delivery system for an implant, the system comprising a catheter shaft with a distal end to carry the implant and a proximal end, and an elongate housing at the proximal end that an operator can grasp when deploying the implant, the shaft having an inner push component which can push on the implant in a distal direction and an outer sheath component which radially surrounds the implant until said deployment of the implant into the bodily lumen, the outer sheath component being capable of being pulled proximally, from the housing, to deploy the implant, the housing being mounted on a proximal end portion of the push component and defining a channel, the housing containing a sheath slitter that is fixedly mounted relative to the length of the channel and that can slit the outer sheath as the outer sheath is caused to move proximally in the channel relative to the slitter. 
       BACKGROUND 
       [0003]    Catheter delivery systems for trans-luminal delivery of implants, particularly self-expanding stents, have a rich history in the patent literature. Early proposals were for a simple sheath radially surrounding the radially-compressed stent at the distal end of the catheter system, the sheath being pulled back proximally, to release the stent from its bed, progressively, starting at its distal end of the bed, within the stenting site or stenosis of the bodily lumen in which the catheter delivery system had been advanced. Readers will appreciate that, because the stent is self-expanding, it is pressing on the luminal surface of the surrounding sheath, up to the moment of its release from the sheath. Thus, friction forces between the stent and the surrounding sheath must be taken into account when devising a delivery system that will allow the sheath to slide proximally over the full length of the outwardly-pushing, self-expanding stent. 
         [0004]    The problems of friction will increase with the length of the stent, and the pressure on delivery system designers is to deliver ever-longer stents. Furthermore, there is steady pressure on stent delivery system designers to come up with systems that have ever-smaller passing diameters at the distal end of the catheter. The conventional unit of dimensions for diameters of systems to advance along a bodily lumen is the “French” which is one third of a millimeter. Thus, one millimeter is “3 French”. To be able to reduce the passing diameter of a delivery system, for example from 7 French to 6 French, is a notable achievement. 
         [0005]    One way to respond to the challenge of friction forces between a proximally withdrawing sheath and a self-expanding stent confined within it is to adopt a “rolling membrane” sheath system, in which the sheath is at least double the length of the stent that it surrounds, being doubled back on itself at a point distally beyond the distal end of the stent. Then, proximal withdrawal of the radially outer doubled back portion of the sheath length will cause the “rolling edge” between the outer and inner sheath portions to retreat proximally, rolling proximally down the length of the stent, to release the stent progressively, as with a single layer surrounding sheath. 
         [0006]    Regardless of whether a conventional or rolling membrane sheath system is employed at the distal end of a stent delivery system, the delivery system requires some form of deployment mechanism provided at the proximal end of the stent delivery system to enable an operator to control at the proximal end the deployment of the distally located stent inside a patient. Typically, the stent is provided on the distal end of a push rod that extends from the proximal end to the distal end of the system. With this push rod held stationary, the user operates such a mechanism at the proximal end, resulting in the sheath system being pulled back, thereby deploying the stent, as described above. 
         [0007]    One stent deployment mechanism is disclosed in US 2007/0244540 A1 (here “D1”), which is incorporated by reference in its entirety into this application. This mechanism involves the use of a thumb slider that is repeatedly translated distally and proximally, with each progressive proximal movement effecting progressive retraction of the sheath. A disadvantage of this deployment mechanism is the inability to deploy the stent in only one, or at least only a few, translations of the deployment mechanism. For lengthy stents, deploying the stent using this mechanism would prove a laborious task, requiring many translations. However, once the distal end of the implant is in place on the wall of the lumen in the body that is receiving the implant, a swift retraction of the sheath, to deploy the remaining length of the implant in one smooth stroke, is not available from this device. 
         [0008]    D1 teaches the attractiveness of a hand unit that is physically small. The sheath of D1 is not a roll back membrane. Were it to be a roll back membrane, the distance it would have to be pulled back proximally would be doubled. The present invention aims to provide a simple and easy to manufacture hand unit that is small in size but yet is capable of deploying a lengthy implant covered by a roll back membrane. 
         [0009]    US-A1-2010/0268243 Cook (here “D2”), which is incorporated by reference in its entirety into this application, discloses a system to deploy a stent in which a tube is split with a cutting instrument as the tube is withdrawn proximally to deploy the stent. The split tube can be wound up on a spool or simply pulled out of the handle. 
         [0010]    US-B2-7837725 Abbott (here “D3”), which is incorporated by reference in its entirety into this application, also discloses a catheter device for delivering a stent in which an outer tubular member of the catheter is withdrawn proximally to release the stent, and the tubular member is split apart by blades, from its proximal end, whereby the length of the catheter can be reduced down to a length that is no longer than is necessary for the procedure for which it is destined to be used. For the deployment of the stent, a slider in a hand unit is used. Thus, an over-long hand unit would be needed, for deployment of a lengthy stent confined within a roll-back membrane. 
         [0011]    U.S. Pat. No. 5,687,727 Danforth (here “D4”), which is incorporated by reference in its entirety into this application, discloses a proximal adaptor for an over-the-wire angioplasty catheter. The adaptor facilitates exchange of catheters over a guidewire. It grips the guidewire and slits the catheter as the catheter is withdrawn proximally through the adaptor whereby the catheter can be removed completely by slitting it all the way to its distal end. Thereafter, a new catheter can be introduced and advanced along the in situ guidewire. 
         [0012]    The present invention aims to provide a system for deploying implants of any length, with a high degree of tactile feed-back to the operator during deployment, and with optimal management of the forces of static and dynamic friction that occur during such deployment. 
       SUMMARY 
       [0013]    According to the present invention, a catheter delivery system of the general form identified above is characterized in that the housing is slidable on the push component, the housing includes a clamp that can be actuated to clamp the housing to the push component to fix the housing lengthwise on the push component at any desired location along the push component and the housing defines an off-axis side channel for the slitted outer sheath proximal of the slitter, the side channel terminating at a pull aperture where the slitted sheath can be grasped and pulled whereby, with the housing clamped to the push element, the sheath can be pulled proximally, relative to the push component, thereby to deploy the implant. 
         [0014]    With the present invention, the operator can hold the housing to keep the implant at the desired location in the body of the patient. The housing can be placed snug up against the percutaneous introducer through which the catheter enters the patient&#39;s body. Thus, the housing is separated from the distal end of the catheter by the minimum possible distance. The operator does not need to know in advance what this distance is. Simply, the catheter brings the implant to the implant site and then the operator brings the housing up to the introducer by advancing it distally along the shaft of the catheter, slitting the sheath as the housing advances. 
         [0015]    With the housing so placed, the operator is well set to deploy the implant by pulling on the sheath. The line of tension from the operator&#39;s hand to the implant is straight except for any curvature in the bodily lumen in which the catheter shaft lies, and except for the angle in the housing that separates the housing axis and its side channel through which the slit sheath is pulled. 
         [0016]    This is to be contrasted with the situation in devices in which the housing is not snug up against the introducer but, rather, separated from it by a bowed portion of the length of the catheter outside the body of the patient. Any such bowed portion increases the friction forces, defying the operator&#39;s efforts to pull back the sheath to deploy the implant. They can also be detrimental to the one-to-one relationship between a pull-back distance increment at the proximal end of the sheath and the resultant pull-back distance increment at the distal end of the sheath. In other words, with the invention, the operator is provided with as much tactile feedback as is possible, about how the implant deployment process is proceeding up at the distal end of the system. 
         [0017]    Conveniently, the slitter is a single blade that makes a single longitudinal cut through the wall of the sheath. Nevertheless, it may be useful to make more than one cut in the sheath, notably, two cuts on opposite sides of the sheath, that is, one at each end of a diametral section through the axis of the sheath, to leave the slitted sheath in the form of two distinct ribbons. 
         [0018]    The pull aperture of the housing is preferably closed by a cap. Prior to implant deployment, the system will need to be flushed of gas bubbles, using a flushing liquid (as is conventional). Of course, the housing will therefore require flushing components. In this regard, Luer connectors are ubiquitous. The cap might therefore incorporate a Luer connector element, and so might the proximal end of the axial channel. The cap can be used as a pulling knob if the proximal end of the slitted sheath is fixed to the cap that closes the pulling aperture. 
         [0019]    The clamp which is needed to fix the housing to the push element where desired along the length of the push element can conveniently be provided at the proximal end of the channel, conveniently adjacent a flushing port at the proximal end of the channel. A rotatable collet is a convenient device for an operator to use, to lock the housing to the push component. 
         [0020]    The housing preferably comprises a proximal portion and a distal strain relief portion, the distal strain relief portion being formed from a less rigid material and serving to reduce stress concentrations along the length of the catheter shaft distal of the more rigid proximal portion of the housing. This can prevent damage being induced in the catheter shaft during advancement into a patient and prior to deployment, which might otherwise result from undue bowing of the shaft. 
         [0021]    In general, the architecture of the housing can be that of a so-called “Y-Adaptor”, which is an element that, as such, is well-known to those skilled in the catheterization arts. 
         [0022]    The invention aims to provide operators with a system with which deployment skills can readily be practised and improved. The system is intuitive to use, has a minimum of moving parts, and can be manufactured in simple steps (thereby enhancing the probability of unimpeached sterility). 
         [0023]    If “quality” implies “predictability” then the systems of the invention can provide operators with an enhanced level of quality, at the same time being straightforward systems to graduate to, and to operate intuitively (and therefore reliably). 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    For a better understanding of the present invention, and to show more clearly how the same may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, in which: 
           [0025]      FIG. 1  is the proximal end of a catheter delivery system in accordance with a first embodiment of the present invention with the catheter shaft extending through an introducer and terminating at the distal end as shown in either one of  FIG. 2A  or  2 B; 
           [0026]      FIG. 2A  is the distal end of a catheter shaft carrying an implant and incorporating a pullback sheath; 
           [0027]      FIG. 2B  is the distal end of a catheter shaft carrying an implant and incorporating a rolling membrane; 
           [0028]      FIG. 3  is the proximal end of a catheter delivery system in accordance with a second embodiment of the present invention with the catheter shaft terminating at the distal end as shown in  FIG. 4 ; 
           [0029]      FIG. 4  is the distal end of a catheter shaft carrying an implant and incorporating a rolling membrane; and 
           [0030]      FIG. 5  shows the sliding of the housing along the push component of the catheter shaft of a catheter delivery system in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0031]      FIG. 1  shows the proximal end of a first embodiment of a catheter delivery system  10  with a catheter shaft  12  extending distally through an introducer  14  and terminating at the distal end in either one of the distal end catheter shaft configurations  12   a  or  12   b,  depicted in  FIGS. 2A and 2B  respectively. The shaft  12  has an inner shaft  16  which is the push component of the catheter shaft and an outer sheath  30  which is the sheath component of the catheter shaft. The inner shaft  16  runs along a guidewire  17 . As can be seen in  FIGS. 2A and 2B , a stent  18  is carried on the distal end of the inner shaft  16  and is positioned proximal of a tip  24  of the catheter and distal of a stent stop  19 . 
         [0032]    In  FIG. 2A , the stent  18  is radially confined by a pullback sheath  20  that extends distally to the tip  24  of the catheter. In an overlapping zone  32  at the proximal end of the stent  18 , the outer sheath  30  is bonded to the outside of the pullback sheath  20 . Of course, the pullback sheath  20  and the outer sheath  30  could alternatively be formed as one. 
         [0033]    In  FIG. 2B , the stent  18  is radially confined this time by a rollback membrane  22  with one end  26  secured to the inner shaft  16  at a location just proximal of the stent stop  19 , the membrane extending from this end  26  to the tip  24  of the catheter, at which point it reverses direction at a roll back annulus  28  and then advances proximally over the length of the stent  18 . In this figure, no transition between the membrane  22  and the outer sheath  30  is shown, reflective of a unitary construction, but the membrane  22  and the outer sheath  30  could be formed separately and bonded, akin to the bonding between the pullback sheath  20  and the outer sheath  30  shown in  FIG. 2A . 
         [0034]    At the proximal end of the catheter shaft  12  there is provided an elongate housing  40  having a distal end  42  through which the catheter shaft  12  extends proximally. The housing  40  comprises two main portions, a distal strain relief portion  40   a  and a proximal grip portion  40   b.  The inner shaft  16  is slidably retained within a channel running through the length of the housing  40 . The strain relief portion  40   a  is formed from a less rigid material than the grip portion  40   b  and, owing to its relative flexibility, serves to smooth out stress concentrations along the length of the catheter shaft  16  resulting from axial misalignment between the portion of the catheter shaft  16  in the section of channel associated with the relatively rigid grip portion  40   b  and the portion of the catheter shaft  16  distal of the channel of the housing  40 . 
         [0035]    The proximal end of the channel terminates in proximal end cap  50  formed from a female Luer connector element that receives the proximal end of the inner shaft  16  and is connected at the proximal end  52  of the housing  40 . 
         [0036]    At a fixed point along the channel of the housing  40 , proximal of the distal end  42 , a blade  34  is mounted to the housing  40 . The blade  34  is longitudinally aligned to extend parallel with the axis of the catheter shaft  12 , with the cutting surface facing distally, and extends through the outer surface of the outer sheath  30  so that a portion of the blade  34  protrudes radially inwards of the outer sheath  34 . Although not apparent from  FIG. 1 , it is arranged that the radially innermost portion of the blade cannot bind on, or cut, the inner catheter. 
         [0037]    Distal of the blade  34 , the outer sheath  30  and inner shaft  16  are co-axial, with the outer sheath  30  surrounding the inner shaft  16 . Proximal of the blade  34  however, outer sheath  30   a,  having been slitted by the blade  34 , separates from the inner shaft  16 , (which is unaffected by the blade  34 ) and extends proximally through the bore of an off-axis side channel  44 , exiting through an aperture  46  and terminating in a pull knob  48 . In the illustrated embodiment, the bore of the off-axis side channel  44  forms an acute angle of about 30° with the proximal direction of the channel of the housing  40 . In that respect, the housing  40  resembles a well-known “Y-Adaptor”. 
         [0038]    In the embodiment shown in  FIG. 1 , the blade  34  is positioned at the same side on the circumference of the housing  40  as the off-axis side channel  44 . This means that, when viewed along the longitudinal axis, the blade  40  is circumferentially offset from the off-axis side channel  44  if at all then by less than 90 degrees. The angular position of the blade  34  with respect to the bore of the off-axis side channel  44  will influence the cutting dynamics and ease of separation of the outer sheath  30  from the inner shaft  16 . 
         [0039]    On the outside surface of the housing  40  is provided a push button  54  that clamps down on the inner shaft  16  thereby preventing relative axial movement between the housing  40  and the inner shaft  16 . In the illustrated embodiment, the portion of the push button  54  impacting upon the inner shaft  16  is provided with a high coefficient of friction to minimise slip. The push button  54  may be resiliently biased in the unclamped position to prevent unwanted clamping. There may be provided a latching mechanism to maintain the push button  54  in a clamped position upon being pushed radially inwards, which is released upon the push button  54  being pushed once again radially inwards. 
         [0040]      FIG. 3  shows the proximal end of a second embodiment of a catheter delivery system  100  with a catheter shaft  112  extending distally and terminating at a distal end as shown in  FIG. 4 . Only significant points of difference between this embodiment and the previous embodiment shall be discussed below. 
         [0041]    The blade  134  is provided on the opposite side of the off-axis side channel  144 . This means that, when viewed along the longitudinal axis, the blade  140  is circumferentially offset from the off-axis side channel  144  by more than 90 degrees. Preferably, the offset is 180°. In  FIG. 4 , this offset is 180 degrees. Positioning the blade  134  on the opposite side of the off-axis side channel  144  is understood to give a smoother cutting and divergence of the slitted outer sheath  130  from the inner catheter  116 , as the slitted material of the outer sheath  130   a  can simply lift off the inner catheter  116  without there being required any degree of twisting of the outer sheath  130  before it can enter the side channel  144 . 
         [0042]    The proximal end of the slitted portion of the outer sheath  130   a  proximal of the blade  134  terminates in a pull cap  148  formed from a Luer connector that is detachably connected to the aperture  146  of the off-axis side channel  144 . 
         [0043]    Rather than a push button  54 , there is provided a collar, a rotatable collet  154  that may be rotated back and forth to move between a clamped position, in which there is exerted a clamping force on the inner catheter  116 , and an unclamped position, in which the inner catheter  116  is free to slide within the channel of the housing  140 . 
         [0044]    At the distal end of the delivery system  100  shown in  FIG. 4 , there is this time provided an overlap section  132  in the rolling membrane  122 , in which a portion of the membrane proximal of the overlap portion  132  is bonded to the outside of a portion distal of the overlap portion  132 . It can also be seen that the inner catheter  116  is provided with a stent bed  116   a  on which the stent  118  is provided having a reduced circumference. This serves to reduce the lengthwise variation in the catheter thickness associated with the presence of the stent  118 . 
         [0045]    To illustrate the operation of the catheter delivery system, reference will be made to  FIG. 5 . The housing  240  of the delivery catheter system  200  is shown in two positions, an initial position A and a deployment position B. 
         [0046]    In position A, e.g. following advancement of the catheter shaft  212  through an introducer  214  into a patient lumen to the desired stenting site in the lumen, there is a shaft length Y between the housing  240  and the introducer  214 . The pull cap  248  and the proximal end cap  250  are released from the housing  240  and, ensuring that the clamping means  254  is not clamped to the inner shaft  216 , whilst holding the proximal end cap  250  so as to prevent any movement of the distal end of the catheter shaft  212  in the patient lumen and optionally also holding the pull cap  248  so as to avoid bunching of the outer sheath  230  by maintaining tension in the vicinity of the cut, the housing  240  is slid distally along the length of the inner shaft  216  surrounded by the outer sheath  230 . As the blade  234  in the housing  240  advances over the outer sheath  230 , it forms a longitudinal cut in the outer sheath  230 , and the point of separation between the inner shaft  216  and the outer sheath  230  advances with the blade  234 . During this motion, the length of the slit outer sheath  230   a  that is proximal of the off-axis side channel  244  increases. Eventually, the housing  240  will meet with the introducer  214  and snugly fits close to, inside or in abutting contact therewith. The catheter delivery system  200  is then in position B, ready for deployment. At this point the clamping means  254  is activated to prevent relative movement between the housing  240  and the inner catheter  216 , preventing unwanted movement of the stent  218 . 
         [0047]    With the housing  240  snugly against the introducer  214 , either a section of the portion of the outer sheath  230   a  proximal of the off-axis side channel  244 , or the pull cap  248 , is pulled by a release distance X, thereby to deploy the stent  218 . 
         [0048]    At any point during the process, any adjustment of the position of the stent  218  relative to the patient lumen can be effected by pushing or pulling on the proximal end cap  250  with the clamping means  250  deactivated or by pushing or pulling on the housing  240  with the clamping means  250  activated.