Abstract:
An apparatus for cutting a suture. In one embodiment the suture cutting apparatus includes a distal cutting end and a proximal control end. The apparatus also includes a first tube defining a lumen, and a second tube located and movable within the lumen of the first tube. The second tube defines a lumen and includes a lever arm pivotably attached at the distal cutting end of the apparatus. The lever arm has a cutting edge that is held away from the longitudinal axis of the second tube when the lever arm is located within the first tube, and is biased toward the longitudinal axis of second tube when the lever arm is outside of the first tube.

Description:
REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims priority to and benefit of U.S. Provisional Patent Application No. 60/501,949, filed Sep. 11, 2003, the entire disclosure of which is incorporated by reference herein. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The invention relates to medical instruments for cutting sutures in general and more particularly to devices for cutting sutures remotely such as sutures secured to an intracardiac septal occluder implanted in a patient by a percutaneous route.  
       BACKGROUND  
       [0003]     Sutures, as components of a percutaneous delivery system, can provide the system with a method to remotely control an implant, such as an intracardiac septal occluder, during implantation. Since it is not uncommon for a delivery system to be four feet long or more in order to traverse a vessel, any suture that might extend through the delivery system would be at least as long. In a case where this suture needs to be released from the implant to which it is tethered following remote placement of the implant, it would be undesirable and possibly disruptive to the implant&#39;s integrity and position, to disengage the suture by unthreading an entire four feet of suture through the implant. A more desirable, and less disruptive approach, might be to remotely sever the suture, adjacent to the implant, to allow for efficient unthreading of a shorter section of the suture from the implant.  
       SUMMARY OF THE INVENTION  
       [0004]     The invention generally relates to an apparatus for cutting a suture. More particularly, an apparatus for cutting sutures remotely such as sutures secured to an intracardiac septal occluder implanted in a patient by a percutaneous route.  
         [0005]     In one aspect, the invention relates to a suture cutting apparatus including a distal cutting end and a proximal control end. The distal cutting end further includes a first tube defining a lumen, and a second tube, located and slideably movable within the lumen of the first tube, the second tube defining a lumen and further including a cutting edge.  
         [0006]     In a particular embodiment, the apparatus includes a lever arm having a proximal end and a distal end, and a second tube with a slot for receiving the lever arm. In a further embodiment of the apparatus, the lever arm contains a pivot positioned on the lever arm. In one embodiment, the lever arm is pivotably attached to the distal cutting end of the second tube. Alternatively, the lever arm is flexibly attached to the distal cutting end of the second tube. In one embodiment of the apparatus including a lever arm, the cross section of the lever arm is generally U-shaped.  
         [0007]     In a further embodiment of the apparatus including a lever arm, the cutting edge may be positioned on the distal end of the lever arm. In still another embodiment, the lever arm is parallel to the longitudinal axis of the second tube while the lever arm is located within the lumen of the first tube, and forms an angle relative to the longitudinal axis of the second tube while the lever arm is outside the lumen of the first tube. The angle is in the range of 0-90°. In one embodiment, while the lever arm is outside the lumen of the first tube, the cutting edge is angled towards the longitudinal axis of the second tube. Alternatively, the cutting edge is substantially perpendicular to the longitudinal axis of the second tube. In yet another embodiment of the apparatus, the cutting edge may be replaceable.  
         [0008]     In still another embodiment, the apparatus includes a return guide. The return guide may be positioned on the lever arm and slideably movable within the first tube.  
         [0009]     In a further embodiment, the apparatus includes a catheter.  
         [0010]     In another aspect, the invention provides a method for cutting a suture. The method includes providing an apparatus with a distal cutting end and a proximal control end, the distal cutting end including a first tube defining a lumen and, and a second tube. The second tube is located and slideably movable within the lumen of the first tube. The second tube defines a lumen and includes a cutting edge. The second tube is moved to engage the cutting edge with the suture. In one embodiment of the invention, engaging the cutting edge with the suture sections the suture into two segments.  
         [0011]     In still another embodiment, the apparatus is advanced through a catheter positioned in a patient&#39;s body. In a further embodiment, the suture is joined to an intracardiac septal occluder. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     The aspects of the invention presented above and many of the accompanying advantages of the present invention will become better understood by referring to the included drawings, which show a system according to the invention and in which:  
         [0013]      FIG. 1  is a schematic of the apparatus with a cutaway schematic of the first tube according to an illustrative embodiment of the invention.  
         [0014]      FIG. 2  is a perspective schematic of the second tube at the distal cutting end of the apparatus shown in  FIG. 1  including a slot and a lever arm according to an illustrative embodiment of the invention.  
         [0015]      FIG. 3  is an illustrative schematic of the apparatus including a cutaway of the first tube at the distal cutting end to illustrate the lever arm with a cutting edge shown in  FIG. 1  according to one illustrative embodiment of the invention.  
         [0016]      FIG. 4  is an illustrative schematic of the apparatus including a cutaway of the first tube at the distal cutting end to illustrate the lever arm with a cutting edge shown in  FIG. 1  according to another illustrative embodiment of the invention.  
         [0017]      FIG. 5  is an illustrative schematic of the lever arm including a pivot according to another illustrative embodiment of the invention.  
         [0018]      FIG. 6  is an illustrative cutaway schematic of the first tube at the distal cutting end of the apparatus shown in  FIG. 1  including a second tube advanced distally from the first lumen of the first tube according to an illustrative embodiment of the invention.  
         [0019]      FIG. 7  is a cutaway schematic of the first tube at the distal cutting end of the apparatus shown in  FIG. 1  including the lever arm in a cutting position and a severed suture according to an illustrative embodiment of the invention.  
         [0020]      FIG. 8  is a cutaway schematic of the first tube at the distal cutting end of the apparatus shown in  FIG. 1  including a return guide in an open position according to an illustrative embodiment of the invention.  
         [0021]      FIG. 9  is a cutaway schematic of the first tube at the distal cutting end of the apparatus shown in  FIG. 1  including a return guide in a collapsed position according to an illustrative embodiment of the invention.  
         [0022]      FIG. 10  is a perspective schematic of the apparatus of  FIG. 1  including a septal occluder with the distal cutting end of the apparatus positioned in the right atrium of the heart according to an illustrative embodiment of the invention. 
     
    
     DESCRIPTION  
       [0023]     The present invention pertains to an apparatus for cutting a suture. The apparatus may be used to deliver implants, e.g., intracardiac occluders, for example, intracardiac septal occluders manufactured by NMT Medical Inc., Boston, Mass. Intracardiac occluders are used to repair congenital or acquired defects in the heart or the major blood vessels, thereof, including interatrial septal shunts, such as a patent foramen ovale, interventricular septal shunts, patent ductus arteriosus and aortic-pulmonary window.  
         [0024]      FIG. 1  is an illustrative schematic of the apparatus  100  with a cutaway schematic of the first tube according to an illustrative embodiment of the invention. In one aspect, the invention relates to an apparatus for remotely severing a suture. The exemplary apparatus  100  for cutting a suture includes a proximal control end  1  and a distal cutting end  2 . The proximal control end  1  is the end proximal to the operator and used to control the distal cutting end  2 . The apparatus  100  also includes a first tube  3 , a second tube  5 , a lever arm  8 , a cutting edge  13 , and a pivot  10 . In some embodiments, according to the invention, the distal cutting end further includes a return guide (not shown) and/or a spring mechanism (not shown).  
         [0025]     The distal cutting end  2  of the apparatus  100  for remotely cutting a suture includes a portion of the first tube  3  including a first lumen  4 . A second tube  5  is longitudinally disposed within the first lumen  4  of the first tube  3 . The second tube  5  includes a longitudinally disposed lumen  6  extending from the proximal control end  1  of the apparatus  100  to the distal cutting end  2  of the apparatus  100 . The second tube  5  is slidably moveable within the first lumen  4  of the first tube  3 . The first tube  3  is generally elongated and has an external diameter sufficiently sized, e.g., a diameter 0.03 mm and a length approximately 150 cm, to allow the first tube  3  to be delivered percutaneously via a vessel to an anatomical site, for example, the atrial septum, in a patient. The first lumen  4  is hollow, typically cylindrically shaped, and has an internal diameter slightly larger than the external diameter of the second tube  5  to allow the second tube  5  to slide within the first lumen  4 . The second tube  5  is elongated and has an internal diameter sized to allow the hollow and cylindrical second lumen  6  to pass a suture, for example, single  0  catgut, polyethylene or nylon suture. The second tube  5  also contains a slot  7  sized and shaped to receive the lever arm  8  pivotably attached to the second tube  5 . In one embodiment, the first tube  3  is longitudinally and slidably disposed within a catheter  18 . In another embodiment, the first tube  3  serves as the catheter  18 . Materials for construction of the apparatus include but are not limited to polyethylene block copolymer (Pebax®), polytetrafluoroethylene (PTFE), metals such as stainless steel, a ceramic, or a composite material.  
         [0026]      FIG. 2  is a perspective schematic of the second tube  5  at the distal cutting end  2  of the apparatus  100  including the slot  7  and the lever arm  8  according to an illustrative embodiment of the invention. In one embodiment, the illustrative second tube  5  is a cylindrical tube including a central longitudinal axis  30 . The second tube  5  includes two planes, plane  31  and plane  32 , perpendicularly intersecting the central longitudinal axis  30  and perpendicular to each other. In one embodiment, the slot  7  is a longitudinal defect in the wall  33  of the second tube  5 . In one embodiment, the slot  7  extends through the entire thickness of the wall  33  to the second lumen  6 . In one embodiment, the slot  7  is substantially symmetrical about the plane  31  which longitudinally bisects the slot  7 . The length  35  of the slot  7  is in the range of about 0.5 mm to 10 mm, or 1 mm to 3 mm, preferably. The maximum width  36  of the slot  7  is generally equivalent to the external diameter of the second tube. The slot  7  is sized and shaped to receive the lever arm  8 .  
         [0027]     The illustrative lever arm  8  is generally an inverted U shape in a traverse section, wedge-shaped when viewed from the side, and substantially symmetrical about plane  31 . The lever arm  8  pivots about a pivot  10 . The axis  34  of the pivot  10  is perpendicular to the axis  30  and parallel to the plane  32 . The top  40  of the wedge-shaped illustrative lever arm  8  in a collapsed position is parallel to the longitudinal axis  30  of the second tube  5  and is flush with the outer wall  33  of the second tube  5 .  
         [0028]      FIG. 3  is an illustrative schematic of the apparatus  100  including a cutaway of the first tube  3  at the distal cutting end  2  to illustrate the lever arm  8  with a cutting edge  13  shown in  FIG. 1  according to one illustrative embodiment of the invention. The lever arm  8  pivots about the pivot  10 . The top  40  of the wedge-shaped illustrative lever arm  8  is positioned parallel to the longitudinal axis  30  of the second tube  5  and is flush with the outer wall  33  of the second tube  5 . The lever arm  8  includes the pivot  10 , a lever arm proximal end  12 , and a lever arm distal end  9 . A cutting edge  13  is positioned on the top  40  of the lever arm  8  at the lever arm distal end  9  of the lever arm  8 . In one embodiment, illustrated in  FIG. 3 , the cutting edge  13  is a straight edge blade. Alternatively, the cutting edge  13  is tooth-like or pointed such that the cutting edge  13  may pierce and/or fracture a suture.  
         [0029]      FIG. 4  is an illustrative schematic of the apparatus  100  including a cutaway of the first tube  3  at the distal cutting end  2  to illustrate the lever arm  8  with a cutting edge  13 ′ shown in  FIG. 1  according to another illustrative embodiment of the invention. The illustrative cutting edge  13 ′ biases downward in the direction of the pivot  10  at an angle  11  of about 0 to 90 degrees, preferably about 45 degrees from a line perpendicular to the longitudinal axis of the second tube  5 .  
         [0030]     With continued reference to  FIG. 4 , the lever arm  8  includes a pivot  10  according to one illustrative embodiment of the invention. The illustrative pivot  10  pivotably connects the lever arm  8  to the second tube  5 . In one embodiment, the pivot  10  with two ends  41 ,  41 ′ is a transverse rod that passes through a solid portion of the second tube  5  connecting the pivot ends  41 , 41 ′ of the lever arm  8  to the second tube  5 . The pivot  10  may be located anywhere along the longitudinal axis of the lever arm  8  between the lever arm proximal end  12  and the lever arm distal end  9 , preferably located approximately halfway between the lever arm proximal end  12  and the lever arm distal end  9 .  
         [0031]      FIG. 5  is an illustrative schematic of the lever arm  8  including a pivot  10 ′ according to another illustrative embodiment of the invention. The illustrative pivot  10 ′ pivotably connects the lever arm  8  to the second tube  5 . In one embodiment, the pivot  10 ′ is a flexible material connecting the pivot ends  41 ,  41 ′ of the lever arm  8  to the second tube  5  allowing the lever arm  8  to pivot by flexing the flexible material of the pivot  10 ′.  
         [0032]      FIG. 6  is an illustrative cutaway schematic of the first tube  3  at the distal cutting end  2  of the apparatus  100  including either a second tube  5  advanced distally from the first lumen  4  of the first tube  3  or alternatively the first tube  3  and first lumen  4  retracted proximally from the second tube  5  according to an illustrative embodiment of the invention. The illustrative slot  7  and the lever arm  8  are extended beyond the distal end  20  of the first tube  3 . The slot  7  is sized and shaped to allow the cutting edge  13  to pivot as indicated by arrow  21  into the second lumen  6  of the second tube  5 . A biasing mechanism, such as spring  56 , urges the lever arm distal end  9  of the lever arm  8  to move from a collapsed position, shown in phantom, to an open position across the longitudinal axis  30  of the second lumen  6 . The desired angle  11  of the lever arm  8  relative to a vertical axis perpendicular to the longitudinal axis  30  of the device  100  is in the range of about 0 degrees to about 90 degrees, preferably 45 degrees. As the lever arm  8  pivots on the pivot  10 , the lever arm proximal end  12  lifts out of the second lumen  6 .  
         [0033]      FIG. 7  is a schematic of the first tube  3  at the distal cutting end  2  of the apparatus  100  including the lever arm  8  in a cutting position extended distally beyond the distal end  20  of the first tube  3 , and a severed suture  14  cut by the cutting edge  13  of the lever arm  8  according to an illustrative embodiment of the invention. The illustrative cutting edge  13  cuts the suture  14  into two separate segments.  
         [0034]      FIG. 8  is a cutaway schematic of the first tube  3  at the distal cutting end  2  of the apparatus  100  including a return guide  15  in an open position with the lever arm  8  in a cutting position extended distally beyond the distal end  20  of the first tube  3  according to an illustrative embodiment of the invention. In one embodiment, the return guide  15  is a wire loop as illustrated in  FIG. 9 . The wire loop  15  includes two ends  50 ,  51  joined to the proximal end  12  of the lever arm  8  and an apex  52  that extends proximally from the two loop ends  50 ,  51 . The wire loop  15  includes a bend  53 . As the second tube  5  is withdrawn into the first tube  3 , or the first tube  3  is advanced distally over the second tube  5 , the apex  52  of the wire loop  15  slides into the lumen  4  of the first tube  3 . As the distal end  20  of the first tube  3  provides the necessary force to compress the wire loop  15  thereby minimizing the bend  53  in the wire loop  15 , the proximal end  12  of the lever arm  8  returns to a collapsed position enclosed within the slot  7 .  
         [0035]      FIG. 9  is a schematic of the first tube  3  at the distal cutting end  2  of the apparatus  100  including a return guide  15  in the collapsed position according to an illustrative embodiment of the invention.  
         [0036]     In another aspect, the invention is a method for introducing an implant, such as a septal defect occluder, to an anatomical site in a patient. For example, the invention is a method for implanting a septal occluder to occlude a patent foramen ovale.  
         [0037]     For example,  FIG. 10  is an illustrative schematic of the apparatus  100  including a septal occluder  17 . The distal cutting end  2  of the apparatus  100  is positioned in the right atrium  54  of the heart according to an illustrative embodiment of the invention. The proximal control end  1  is used by an operator to guide the occluder  17  into position at the patent foramen ovale. Once the occluder  17  is positioned as desired, the operator manipulates the control end  1  to urge the second tube  5  distally, or, alternatively, the first tube  3  proximally until the slot  7  and lever arm  8  are extended beyond the distal end  20  of the first tube  3 . The cutting edge  13  of the lever arm distal end  9  engages the suture  14 . In one embodiment, proximal retraction of the suture  14  draws the suture  14  against the cutting edge  13  thereby severing the suture  14 . In another embodiment, further distal advancement of the second tube  5 , or, alternatively, withdrawal of the first tube  3  proximally advances the cutting edge  13  through the suture  14 , thereby slicing the suture  14  into two segments and releasing the occluder  17 . Alternatively, if the cutting edge  13 ′ illustrated in  FIG. 4  is used, engagement of the cutting edge  13 ′ with the suture  14  fractures the suture  14  such that it may be segmented with minimal tension applied to the suture  14  by the operator.  
         [0038]     Once the occluder  17  is in place as desired and the suture  14  is severed, the short end of the suture  14  is unthreaded from the occluder  17  and drawn through the catheter  18  towards the proximal control end  1 . As such, rather than drawing the entire length of the suture  14  that extends from the proximal control end  1  to the occluder  17 , only the short length of the segmented suture  14  that extends from the distal cutting end  2  to the occluder  17  is drawn through the occluder  17 .  
         [0039]     Although the present invention has been described with reference to the preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail with departing from the spirit and scope of the invention.