Abstract:
A novel catheter is described. The catheter comprises a handle, an inner sheath providing an inner sheath lumen extending along a first length from a proximal inner sheath portion supported by the handle to a distal inner sheath portion connected to a cage gripper, and an outer sheath having a second length extending from a proximal outer sheath portion supported by the handle to a distal outer sheath portion connected to a cage housing. The inner sheath rotatably resides inside the outer sheath with the cage gripper rotatably housed inside cage housing. During a surgical procedure, a distal bridge portion of the inner sheath is connected to an opening in the lead sidewall with the lead received inside the cage housing. A gear knob is manipulated to cause the inner sheath to rotate with respect to the outer sheath so that the cage gripper is moved from an un-deployed position housed inside the cage gripper to a deployed position completely surrounding the lead connected to the distal bride. The catheter connected to the lead is moved into and to a desired location in a vasculature. Then, a screw driver is inserted through the housing and inner sheath lumens and into the lead and manipulated to screw the distal electrode into body tissue. Manipulating the gear knob causes the inner sheath to rotate the cage gripper from the deployed to the un-deployed position and then the catheter is separated from the lead and removed from the vasculature, leaving the lead behind.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority from U.S. Provisional Application Ser. Nos. 61/365,012, filed Jul. 16, 2010 and 61/505,575, filed Jul. 8, 2011. 
     BACKGROUND OF THE INVENTION 
     The present invention is related generally to catheters for accessing the human or animal vasculature. More particularly, the invention describes a catheter that is adapted to position a lead in a vasculature, for example, to anchor a lead electrode in the apex of the right ventricle. 
     SUMMARY OF THE INVENTION 
     Sudden cardiac death remains a major threat despite advances in medication and other treatments for preventing recurrent heart attacks and heart failure. Each year, it claims the lives of more than 400,000 Americans alone, and the overwhelming majority of those deaths are caused by ventricular fibrillation, or rapid, uncoordinated contractions. 
     Randomized trials have shown that implantable defibrillators dramatically reduce mortality in patients with a history of arrhythmias, or abnormal heart rhythms caused by ventricular fibrillation, or in patients at risk for sudden cardiac death. Today, the patient population of defibrillator candidates is significantly underserved. Without a defibrillator, a victim of sudden cardiac arrest has only a five-percent chance of survival. Implantable defibrillators currently on the market, however, are similar in form and function: titanium boxes implanted in the pectoral region. In most patients, this device creates a “cardiac bump” that is visible when not covered by loose-fitting clothes. The implant procedure typically requires hospitalization, followed by frequent device adjustments of complex features that few have the time or requisite skills to fully interpret or optimize. 
     As a solution, InnerPulse, Inc. has developed a percutaneous implantable cardioverter defibrillator. The PICD™ device is implanted within the patient&#39;s vascular system using the present catheter. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a catheter comprising a handle; an inner sheath providing an inner sheath lumen extending along a first length from a proximal inner sheath portion supported by the handle to a distal inner sheath portion connected to a cage gripper; and an outer sheath having a second length extending from a proximal outer sheath portion supported by the handle to a distal outer sheath portion connected to a cage housing, wherein at least a portion of the inner sheath rotatably resides inside the outer sheath with the cage gripper rotatably housed inside cage housing. The handle provides a handle lumen in open communication with the inner sheath lumen. The housing supports a first gear means connected to the inner sheath, the first gear means being manipulatable to rotate the inner sheath inside the outer sheath to consequently rotate the cage gripper inside the cage housing between a closed, un-deployed position to an open, deployed position. The first gear means comprises a rotatable gear knob that meshes with a sun gear connected to the proximal inner sheath portion for selectively rotating the inner sheath inside the outer sheath. Further, the sun gear supports spaced apart first and second magnets that are selectively attractable to a third magnet supported by the handle to thereby maintain the cage gripper connected to the inner sheath in either the un-deployed or the deployed position. That way, the gear knob and the sun gear provide a gear ratio such that angular manipulation of the gear knob produces a greater angular movement of the sun gear. 
     Moreover, the handle supports a valve that is in communication with the handle lumen and the inner sheath lumen. 
     The handle also supports an actuator button connected to a flexible tubing portion of the lumen. The actuator button is movable longitudinally along the handle from a first position in which the flexible tubing is relatively straight for unobstructed communication from the valve and the handle lumen and into the inner sheath lumen to a second position in which the flexible tubing is kinked to thereby block unobstructed communication through the handle lumen. The actuator button supports spaced apart fourth and fifth magnets that are selectively attractable to a sixth magnet supported by the handle to thereby maintain the flexible tubing connected to the actuator button in either the straight or the kinked configuration. 
     A method for implanting the electrode of a lead into body tissue using the present catheter is also described. The lead has a sidewall of a length extending from a distal electrode to a proximal portion connectable to a medical device. A distal bridge portion of the inner sheath is connected to an opening in the lead sidewall with the lead received inside the cage housing. A gear knob is manipulated to cause the inner sheath to rotate with respect to the outer sheath so that the cage gripper is moved from an un-deployed position housed inside the cage gripper to a deployed position surrounding the lead connected to the distal bride. The catheter connected to the lead is moved into and to a desired location in a vasculature. Then, a screw driver is inserted through the housing and inner sheath lumens and into the lead and manipulated to screw the distal electrode into body tissue. Manipulating the gear knob causes the inner sheath to rotate the cage gripper from the deployed to the un-deployed position and then the catheter is separated from the lead and removed from the vasculature, leaving the lead behind. 
     The foregoing and additional advances and characterizing features of the present invention will become clearly apparent upon reading the ensuing description together with the included drawings wherein: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of the catheter  10  of the present invention. 
         FIG. 2  is a perspective view of cage gripper  30  separated from a cage housing  32 , together comprising a cage assembly  20  of the present catheter  10 . 
         FIG. 3  is a perspective view showing the cage assembly  20  with the cage gripper  30  in an un-deployed position, completely housing inside the case housing  32 . 
         FIG. 4  is a perspective view of the cage assembly  20  shown in  FIG. 2  with the cage gripper  30  partially rotated inside the cage housing  32  supported at the distal end of an outer sheath  24  with an inner sheath (not shown) supporting a lead bridge  28  disposed inside the cage housing. 
         FIG. 5  is a perspective view showing the lead bridge  28  housed inside the cage assembly  20  shown in  FIG. 3  with the cage gripper  30  having been rotated inside the cage housing  32  to a fully deployed position. 
         FIG. 6  is a perspective view of the handle assembly  16 . 
         FIG. 7  is a perspective view of the handle assembly  16  shown in  FIG. 6  partly broken away to illustrate the actuator button  48  in relation to the proximal and distal magnets  54 A,  54 B supported by a land  52  inside the handle assembly  16 . 
         FIG. 8  is a plan view of a land  52  supporting the proximal and distal magnets  54 A,  54 B inside the handle assembly  16 . 
         FIG. 9  is a perspective view of the actuator button  48 . 
         FIG. 10  is a partially exploded, perspective view of the handle assembly  16 . 
         FIG. 11  is a side cross-sectional view of the handle assembly  16  having the actuator button  48  in its proximal position with the flexible tubing  56  being unkinked. 
         FIG. 12  is a side cross-sectional view of the handle assembly  16  shown in  FIG. 11  having the actuator button  48  in its proximal position with the flexible tubing  56  kinked. 
         FIG. 13  is a perspective view showing how the gear teeth  60 B of the rotatable knob  60  mesh with a sun gear  62  supporting the inner sheath  22 . 
         FIG. 14  is a perspective view showing the gear teeth  60 B of the rotatable knob  60  meshed with a sun gear  62  and a nose cone  68  supporting the outer sheath  24 . 
         FIG. 15  is a cross-sectional view in perspective of the sun gear  62  supporting magnets  78 A,  78 B. 
         FIG. 16  is a schematic view showing the housing  16  supporting a magnet  80  that is selectively attracted to the magnets  78 A,  78 B of the sun gear  62 . 
         FIG. 17  is a perspective view showing the cage assembly  20  at the distal end of the sheath assembly  18  being moved through a vasculature  14 . 
         FIG. 17A  is an end view of the cage assembly  20  shown in  FIG. 10  in the vasculature  14 . 
         FIG. 18  is a perspective view showing the cage assembly  20  just prior to engagement of the tubing bridge  28  with a lead  12 . 
         FIG. 19  is a perspective view showing the cage assembly  20  engaged with the lead  12  illustrated in  FIG. 18  and with the gripper finger  30 C in an un-deployed position shown in  FIG. 3 . 
         FIG. 20  is a perspective view showing the cage assembly  20  engaged with the lead  12  illustrated in  FIG. 19 , but with the gripper finger  30 C having been rotated to the fully deployed position shown in  FIG. 5 . 
         FIG. 21  is a perspective view, partly in cross-section, showing a rotation stop  32 D of the cage housing  30  to prevent over rotation of the gripper finger  30 C. 
         FIG. 22  is a side cross-sectional view showing a movable nest  82  housed inside the handle  16  and secured to the outer sheath  24 . 
         FIG. 23  is a cross-sectional view showing the relative position of the tubing bridge  28  and the gripper finger  30 C as a result of the positioning of the nest  82  in  FIG. 22 . 
         FIG. 24  is a side cross-sectional view of the movable nest  82  having been moved in a proximal direction with respect to the view shown in  FIG. 23 . 
         FIG. 25  is a cross-sectional view showing the relative position of the tubing bridge  28  and the gripper finger  30 C as a result of the positioning of the nest  82  in  FIG. 24 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Turning now to the drawings,  FIG. 1  illustrates a catheter  10  according to the present invention. The catheter  10  is useful for anchoring a lead  12  ( FIGS. 18 to 20 ) in a desired position in a vasculature  14  ( FIGS. 17 and 17A ) and comprises a handle assembly  16  supporting a flexible sheath assembly  18 . The sheath assembly  18 , in turn, supports a cage assembly  20 . The vasculature  14  can be that of a human or an animal. 
     As shown in  FIGS. 11 and 12 , the sheath assembly  18  comprises an inner sheath  22  disposed inside an outer sheath  24 , both being elongate tubular structures that are flexible yet substantially non-compressible along their lengths. A distal end  18 A ( FIG. 1 ) of the sheath assembly supports the cage assembly  20  while a proximal sheath portion  18 B connects to the handle assembly  16 . 
     An exemplary construction for the sheath assembly  18  comprises the outer tubular sheath  24  formed of a polymeric material, such as PEBAX, encasing a tubular wire (not shown) braided as a mesh. The inner tubular sheath  22  is of a second polymeric material, for example PTFE, and resides inside the PEBAX outer tubular sheath  24 . The inner sheath  22  provides part of a lumen  26  ( FIGS. 11 to 14 ) extending from the handle assembly  16  to a lead bridge  28  ( FIGS. 3 to 5 ,  17 ,  17 A,  18  to  21 ,  23  and  25 ) supported at the distal end thereof. PTFE material provides the inner tubular sheath  22  with sufficient lubricity so that medical instruments, fluids, and the like, can readily slide through its lumen  26  while the inner sheath is selectively rotatable inside the outer sheath  24  using a minimal amount of force. The outer sheath  24  has sufficient lubricity to be relatively easily pushed or moved through the vasculature  14 . Rotational movement of the inner sheath  22  inside the outer sheath  24  will be described in detail hereinafter. 
     As shown in  FIGS. 2 to 5 , the cage assembly  20  supported at the distal ends of the inner and outer sheaths  22 ,  24  comprises a cage gripper  30  rotatably housed inside a cage housing  32 . 
     The cage housing  32  comprises a sidewall extending from an outer base  32 A supported at the distal end of the outer sheath  24  in a fluid tight relationship. The outer base  32 A in turn supports a partially cylindrically-shaped portion  32 B having a first length extending to a distal end  32 C thereof. A longitudinal bore  34  is provided in the base  32 A. A lateral opening  36  extends along the length of the partially cylindrical portion  32 B from the outer base  32 A and its bore  34  to and through the distal end  32 C of the cage housing  32 . 
     The cage gripper  30  resides inside the cage housing  32  and comprises an inner base  30 A supported at the distal end of the inner sheath  22  in a fluid tight engagement. The inner base portion  30 A of the cage gripper  30  supports a partially cylindrically-shaped portion having a length extending along an intermediate gripper portion  30 B to a distal annularly-shaped gripper finger  30 C. An inner lateral opening  38  extends along a second length of the intermediate portion  30 B and the distal gripper finger  30 C. However, the intermediate portion  30 B has a lesser annular extent than the gripper finger  30 C. This means that the inner lateral opening  38  has a greater annular extent in the vicinity of the intermediate portion  30 B than at the distal gripper finger  30 C. With the cage gripper  30  residing inside the cage housing  32 , the first and second openings  36 ,  38  align with each other. 
     One embodiment of the handle assembly  16  ( FIG. 1 ) includes a right handle portion (not shown) mated to a left handle portion (not shown). In another embodiment, the handle assembly  16  comprises upper and lower portions that are mated to each other. In any event, the handle halves are mirror images of each other and provide an ergonomically designed curved shape, the extent of which is defined by an annular sidewall  16 A extending longitudinally from a proximal end  16 B to a distal or forward end  16 C ( FIG. 6 ). The proximal end  16 B includes an opening  40  supporting a 3-way valve  42  ( FIGS. 11 and 12 ). 
     A rectangularly-shaped recess  44  leading to a slot  46  of a reduced width is provided part-way into the handle from an upper surface thereof. The recess  44  and slot  46  extend along the length of the handle  16 , aligned with its longitudinal axis. An actuator button  48  ( FIGS. 7 and 9 ) comprises a thumb plate  48 A supported on a vertically aligned post  48 B connected to a base plate  48 C. The thumb plate  48 A is sized to move back and forth along the recess  44  with the vertical post  48 B confined along the slot  46 . The base plate  48 C supports a first magnet  50  disposed inside the handle. 
     As shown in  FIGS. 7 and 8 , an internal land  52  inside the handle  16  supports a proximal magnet  54 A spaced from a longitudinally aligned distal magnet  54 B. The handle post  48 B further supports a relatively short piece of flexible tubing  56 , for example, of TYGON®. The TYGON® tubing  56  provides a robust portion of the lumen  26  that is highly resistant to scuffing, scratching and tearing, but which kinks fairly easily while recovering its inner circular lumen shape upon straightening. Therefore, it is ideal for an application in which one wants the lumen to collapse and open repeatedly and reliably. 
     A tubing bridge  58  supported by the opposed, distal face  48 D of the post  48  ( FIG. 9 ) connects between the inner sheath  22  and the flexible tubing  56 . A suitable material for the tubing bridge  58  is PETROTHENE®. The lead bridge  28  is an extruded tubular portion of the inner sheath. Together, the inner sheath  22  including the flexible tubing  56 , the tubing bridge  58  and the lead bridge  28  are about 35 inches long. It has an inner diameter of about 0.044 inches and an outer diameter of about 0.077 inches. A tip  12 A ( FIG. 5 ) of the lead bridge  28  is thermoformed with a taper angle of about 4° to 6°. 
     As previously described, the inner sheath  22  is part of the sheath assembly  18  and provides part of the lumen  26  extending to the cage assembly  20 . The actuator button  48  provides open communication along the lumen  26  from the 3-way valve  42 , the vertical post  48 B of the actuator button, the flexible tube  56 , the tubing bridge  58  and into the inner sheath  22  including the distal bridge  28 . 
     As shown in  FIG. 12 , when the actuator button  48  is in its proximal position, held there by attraction of the first button magnet  50  with the proximal handle magnet  54 A, the flexible tube  56  has a kink  56 A that prevents movement of a stylet (not shown), and the like, into the lumen  26  including the inner sheath  22 . When the actuator button  48  is moved to its distal position, held there by attraction between the button magnet  50  and the distal magnet  54 B, the flexible tube  56  is un-kinked and relatively straight to permit communication through the 3-way valve  42  and into the lumen  26  through the flexible tube  56 , the vertical post  48 B, the tubing bridge  58  and into the inner sheath  22  and finally the distal bridge  28 . 
     Using magnets  54 A,  54 B for stops imparts a smooth feel for transitioning the actuator button  48  distally and proximally between the forward and backward positions. Moreover, this magnetic actuation does not require the user to depress the button  48  as much as, for example, is typically required of a spring loaded button (not shown). Spring loaded buttons are often standard on catheter handles containing slider buttons. The force induced by the magnets  50  and  54 A,  54 B is also robust and repeatable, and less susceptible to material changes that can be induced by standard accelerated shelf life testing and sterilization. 
     As shown in  FIGS. 6 and 10  to  12 , the forward end  16 C of the handle assembly  16  provides an annular handle ledge  16 D of a reduced diameter that rotatably supports a knob  60 . The knob  60  is provided with a series of raised fins  60 A between which a user can fit his thumb for rotational manipulation thereof. The knob  60  further comprises an annular inner gear  60 B disposed between internal proximal and distal bearing surfaces  60 C and  60 D, respectively. 
     A sun gear  62  ( FIGS. 10 and 15 ) is an elongate member comprising an annular bearing surface  62 A disposed between a proximal enlarged annular portion  62 B and distal gear teeth  62 C. A rectangularly-shaped nest  64  is provided in the distal end of the sun gear  62  surrounded by the annular gear teeth  62 C. 
     As shown in  FIGS. 11 to 14 , the inner sheath  22  supports an overmolded tab  66  at its proximal end that fits snuggly into the nest  64  provided in the sun gear  62 . The sun gear  62  is rotatably supported by a platform  16 E extending outwardly from the proximal end of the handle  16 . The inner gear  60 B of the knob  60  meshes with the gear teeth  62 C of the sun gear  62 . That way, manipulation of the knob  60  causes the knob to rotate on the annular handle ledge  16 D as the meshed sun gear  62  rotates the tab  66  and the inner sheath  22 . 
     A nose cone  68  extends forwardly or distally, supported by the internal distal bearing surface  60 D of the knob  60 . A number of screw openings  70  receive threaded members (not shown) connecting between the nose cone  68 , the intermediate knob  60  and the handle assembly  16 . In a similar manner as the tab  66  received in the nest  64  of the sun gear  62 , a second tab  72  is overmolded onto the proximal end of the outer sheath  24 . As shown in  FIGS. 11 ,  12  and  14 , this tab  72  is snuggly received in a nest  74  in the nose cone  68 . That way, the outer sheath  24  is fixed in relation to the handle assembly  16  as the knob  60  is rotated with respect to the handle to thereby rotate the inner sheath  22  inside the stationary outer sheath. A strain relief cone  76  supported at the distal end of the nose cone  68  provides additional support to the outer sheath  24  at the handle assembly  16 . 
     In that manner, rotational movement of the knob  60  on the handle ledge  16 D rotates the gear teeth  60 B meshed with the sun gear  62  and its nested tab  66  fixedly supported on the proximal end of the inner sheath  22 . In this manner, rotational manipulation of the knob  60  causes the inner sheath  22  to rotate inside the outer sheath  24 . Moreover, rotation of the inner sheath  22  causes rotational movement of the cage gripper  30  inside the cage housing  32 . 
     Since the cage assembly  20  has only the open or deployed ( FIG. 3 ) and closed or un-deployed ( FIG. 5 ) positions, it is necessary to constrain rotation of the inner sheath  22  to 180° by means of a stopping mechanism at both the open and closed positions. Similar to the sliding actuator button  48 , two magnets  78 A,  78 B reside in the proximal face of the enlarged annular portion  62 B of the sun gear  62 . A third magnet  80  is supported at a distal end of the handle assembly  16 . Magnet  80  maintains the sun gear  62  in one of two positions, depending on which one of the magnets  78 A,  78 B it is aligned with. As previously described, since the sun gear  62  rotates the inner sheath  22  connected to the cage gripper  30 , the cage gripper is held in either its closed or open position in that manner. 
     This planetary gear system of the meshing gear knob  60 B and sun gear  66  provides a gear reduction ratio that is designed so that a smaller turn of the knob  60  creates a relatively large turn of the sun gear  62 . That way, a user does not have to turn the knob  60  180° to turn the cage gripper  30  180°. This is an ergonomic advantage—less rotation of the knob  60  means less range of motion, which means the thumb undergoes less stress. Also, the user does not have to adjust his/her hand grip half way through rotation of the knob  60 . Instead, the thumb only needs to move through an arc of about 75° in the transverse plane. 
     Furthermore, utilizing the magnets  78 A,  78 B and  80  for stops imparts a very smooth feel for transitioning the cage gripper  30  from the open or un-deployed to the closed or deployed position. Like the actuator button  48 , it requires the user to do nothing more than rotate the knob  60  to move the cage assembly  20  between the two positions. 
     As previously discussed, the cage housing  32  is connected to the outer sheath  24  while the cage gripper  30  is connected to the inner sheath. The cage assembly  20  has two positions: open and closed. In the open position ( FIG. 3 ), the cage gripper  30  is rotated in such a way that it is completely housed or un-deployed inside the cage housing  32 . This is the position at the beginning of a surgical procedure, before the lead  12  is attached to the bridge  28  and gripped by the cage assembly ( FIG. 20 ). 
       FIGS. 17 and 17A  illustrate that the present catheter  10  has a relatively low profile that makes navigation of the cage assembly  20  through the vasculature, such as the super vena cava, relatively easy and atramatic. In fact, the case assembly  20  provides a low profile without sharp edges or corners that could potentially damage or puncture the endothelial layer of the intima of a vessel. 
     At the beginning of a surgical procedure ( FIG. 18 ), the lead  12  is slid into the cage housing  32  until the bridge  28  engages with an opening  12 A in the lead ( FIG. 19 ). This engagement provides communication through the bridge  28  and into a lumen (not shown) in the lead  12 . Next, as previously discussed, the knob  60  on the housing assembly  16  is manipulated to rotate the cage gripper  30  180° into the closed position ( FIG. 20 ) producing the deployed cage assembly position shown in  FIG. 5 . In that manner, the bridge  28  acts as a portion of the conduit for delivering a stylet (not shown) from the proximal end  16 B of the handle assembly  16  located outside the body during the procedure to the lead lumen. The tip of the stylet has a small hex bit which functions to screw the lead anchoring helix (not shown) into the myocardium. At the end of the procedure, after the lead tip has been anchored, the cage gripper  30  is rotated back to the initial, open position shown in  FIG. 3  and catheter  10  including the bridge  28  is withdrawn from the lead  12 . 
     One potential issue that can arise clinically is that while the cage assembly  20  is in the closed position ( FIGS. 5 and 20 ), the cage housing  32  or outer sheath  24  can become constrained while the cage gripper  39  and inner sheath  22  remain free to rotate. If either the handle  16  or outer sheath  24  is rotated at this point, the cage gripper  30  can unintentionally rotate in relation to the cage housing  32 . If the cage gripper  30  rotates too far (over-rotates) in one direction, the cage gripper finger  30 C can “cut” into the lead body  12 . If the cage gripper  30  rotates too far in the other direction (under-rotates), a small opening is created between the gripper finger  30 C and the partially cylindrically-shaped portion  32 B of the cage housing  32 . In the partially closed configuration, the lead  12  can inadvertently release or dislodge from the cage assembly  20 . 
     As illustrated in  FIG. 21 , one consideration is not to allow the cage gripper  30  to be over-rotated greater than 180° past the fully deployed position shown in  FIG. 5 . Such over deployment is prevented by having the leading edge of the gripper finger  30 C contact a rotation stop  32 D as a ledge provided into the thickness of the wall forming the partially cylindrical portion  32 B of the cage housing  32 . The amount of rotation by the cage gripper  30  does not necessarily have to be 180°. Instead, this angle could be tweaked by adjusting the depth of the rotation stop  32 D in the cage housing  32 . The stop could also be located in the cage housing  32  to prevent the cage gripper  30  from being rotated too much past the un-deployed position shown in  FIG. 3 . 
     A potential solution to under-rotation of the cage gripper  30  is to “over torque” the inner sheath  22  connecting between the knob  60  in the handle  16  and the cage gripper. This requires that the knob  60  be capable of rotating the proximal portion of the inner sheath  22  more than 180°. That is while the cage gripper  30  is kept from over-torquing (stopped at 180°) by the rotation stop  32 D described above with respect to  FIG. 21 . In order to accomplish this, the gear ratio between the knob ring gear  60 C and the sun gear  62  has to be set such that, for example, a 180° turn of the knob  60  in the closing direction ( FIG. 5 ) actually rotates the sun gear  62  and the inner sheath  22  more than 180°. For example, the inner sheath  22  gets rotated 270°. This “over torque” of the inner sheath  22  serves to store up “closing torque” (i.e., potential energy), that keeps the cage gripper  30  in its closed position, even in those scenarios that previously caused under-rotated of the cage gripper  30 . 
     In another embodiment, the knob  60  could directly rotate the inner sheath  22  thereby eliminating the planetary gear configuration of the gear knob  60 B meshed with the sun gear  62 . 
     When assembling the present catheter  10 , it is important to ensure that the tip of the bridge  28  falls within the clasping area in relation to cage gripper  30 . This location is a function of many variables, including the length of the outer sheath  22 , the length of the inner sheath  24  and the length of the distal bridge  28 , among other length considerations. When the tolerance stack up is calculated, it is very difficult to have an assembly in which the tip of the bridge  28  falls in the desired position, especially within a reasonable tolerance window. 
     A solution is to design some adjustability into the handle  16 , such that the tip  28 A of the distal bridge  28  can be set at a specific location during assembly, regardless of the tolerance stack up of all of the other components. One embodiment for accomplishing this is to design a movable nest  82  inside the housing  16  that allows the proximal location of the tab  72  overmolded onto the proximal end of the outer sheath  24  to be adjusted with respect to the position of the inner sheath  22 . Assuming the distal bridge  28  secured to the inner sheath  22  is held constant, its distal tip  28 A position will change in relation to the cage gripper  30  and cage housing  32  by providing the nest  72  as a longitudinally movable member housed inside the handle  16 . 
     As shown in  FIGS. 22 and 24 , the nest  82  supporting the overmolded tab  72  at the proximal end of the outer sheath  24  comprises spaced apart oval-shaped openings  84  supported on stationary pins  86  secured inside the handle  16 . In  FIG. 22 , the nest  82  is at its distal most position with the pins  86  residing at the proximal end of the oval openings  84 . This puts the distal bridge  28  in a position axially aligned with the cage finger  30 C ( FIG. 23 ). In  FIG. 24 , the movable nest  82  has been moved proximally with the pins  86  residing at the distal end of the openings  84 . Now, the distal bridge  28  is in a position spaced proximally from the cage finger  30 C. In that manner, the relative position of the cage housing  32  can be adjusted with respect to the gripper cage  30  and the distal bridge  28  during the manufacturing process. 
     It is appreciated that various modifications to the inventive concepts described herein may be apparent to those of ordinary skill in the art without departing from the spirit and scope of the present invention as defined by the appended claims.