Abstract:
The over-the-wire interlock attachment/detachment mechanism includes a cylindrical lock receiving section of a small diameter attached to an implantable medical device such as a blood clot filter, a stent, or a septal occluder. This cylindrical lock receiving section has a plurality of spaced, curved cutouts to receive both the guide fingers and contoured locking fingers formed on a cylindrical locking section. The locking fingers are angled outwardly from the cylindrical body of the cylindrical locking section, and are moved inwardly into engagement with the curved cutouts of the cylindrical lock receiving section by a sheath which slides over the cylindrical locking section or other suitable operator.

Description:
[0001]     This application is a divisional of U.S. patent application Ser. No. 09/977,971, filed Oct. 17, 2001, now U.S. Pat. No. 6,936,058, issued Aug. 30, 2005, and claims the benefit of provisional patent application Ser. No. 60/241,005, filed Oct. 18, 2000, the disclosures of which are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     In recent years, a number of medical devices have been designed which are adapted for compression into a small size to facilitate introduction into the heart or a vascular passageway and which are subsequently expandable. These devices, among others, include septal occluders, stents and free standing filters which expand and are held in position by engagement with the wall of an organ or vessel. It has been found to be advantageous to form such devices of a shape memory material having a first, relatively pliable low temperature condition and a second, relatively rigid high-temperature condition. By forming such devices of temperature responsive material, the device in a flexible and reduced stress state may be compressed to fit within the bore of a delivery catheter when exposed to a temperature below a predetermined transition temperature, but at temperatures at or above the transition temperature, the device expands and becomes relatively rigid.  
         [0003]     Originally, these implantable medical devices were intended to permanently remain in place, but recently it has become advantageous to retrieve the previously implanted device.  
         [0004]     The development of removable implantable medical devices such as septal occluders, stents and filters which expand and are held in position by engagement with the wall of an organ or vessel has led to the development of intra vascular snares to retrieve these foreign bodies, usually from the peripheral vessels of the cardiovascular system. Single loop snares, such as those shown by U.S. Pat. No. 3,828,790 to Curtiss et al. and U.S. Pat. No. 5,171,233 to Amplatz et al. are commonly used snares. The Amplatz snare consists of a super-elastic loop can be introduced through small lumen catheters without risk of deformation. The loop is formed at approximately 90° to a cable, and this allows for the user to advance the loop over a foreign body and ensnare it by closing the loop with a small catheter. The foreign body is removed from the vasculature by withdrawing the device into a guiding catheter or vascular sheath.  
         [0005]     In an attempt to provide a snare with improved cross sectional vessel coverage, multi-loop snares such as those shown by U.S. Pat. No. 5,098,440 to Hillstead and U.S. Pat. No. 6,099,534 to Bates have been developed. These snares include loops which are joined only at their proximal ends to a shaft, and otherwise are not joined at any point between the shaft and the distal ends of the loops. This provides the advantage over single loop snares of enhanced cross sectional vessel coverage, and the free distal ends of the loops can be brought together to engage multiple surfaces of an intravascular medical device to be removed.  
         [0006]     The problem with known snare recovery devices is that they are difficult to advance over a medical implant device and require skilled manipulation to retrieve an implanted device. Once the medical implant device is engaged by a recovery snare, there is no assurance that the device will not slip out of the snare during the recovery process.  
         [0007]     It is particularly difficult to remove medical implants from the heart, such as septal occluders, with known snare recovery devices. Such snare recovery devices normally require appropriate sizing to the vasculature in order to facilitate successful ensnarement, and the geometry of multi loop snares is difficult to maintain during delivery. The relative position of the loops can change, both within a catheter or delivery tube and within a vessel, and the loops can actually become displaced or entangled during delivery.  
       SUMMARY OF THE INVENTION  
       [0008]     A primary object of the present invention is to provide a novel and improved over-the-wire interlock attachment/detachment mechanism adapted to engage and positively lock on to an implanted medical device.  
         [0009]     Another object of the present invention is to provide a novel and improved over-the-wire interlock attachment/detachment mechanism which automatically aligns to form an interlock attachment with an implanted medical device.  
         [0010]     A further object to the present invention is to provide a novel and improved over-the-wire interlock attachment/detachment mechanism well adapted for use with over-the-wire implanted medical devices.  
         [0011]     Yet another object of the present invention is to provide a novel and improved over-the-wire interlock attachment/detachment mechanism which includes a cylindrical locking section for engagement with a cylindrical lock receiving section connected to the medical implant.  
         [0012]     A further object of the present invention is to provide a novel and improved over-the-wire interlock attachment/detachment mechanism which includes no overlapping components and which maintains a low profile configuration during passage through a vessel and/or catheter.  
         [0013]     These and other objects of the present invention are achieved by providing a cylindrical lock receiving section of a small diameter attached to an implantable medical device such as a blood clot filter, a stent, or a septal occluder. This cylindrical lock receiving section has a plurality of spaced, curved cutouts to receive both the guide fingers and contoured locking fingers formed on a cylindrical locking section. The locking fingers are angled outwardly from the cylindrical body of the cylindrical locking section, and are moved inwardly into engagement with the curved cutouts of the cylindrical lock receiving section by a sheath which slides over the cylindrical locking section, or by another suitable operator which can be activated to move the fingers inwardly. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1  is a perspective view of the over-the-wire interlock attachment/detachment mechanism of the present invention with the control sheath shown in section;  
         [0015]      FIG. 2  is a perspective view of an over-the-wire free standing filter with the cylindrical lock receiving section for the over-the-wire interlock attachment/detachment mechanism of  FIG. 1 ;  
         [0016]      FIG. 3  is a perspective view of the partially engaged locking and lock receiving sections for the over-the-wire interlock attachment/detachment mechanism of  FIG. 1 ;  
         [0017]      FIG. 4  is a perspective view of the engaged locking and lock receiving sections for the over-the-wire interlock attachment/detachment mechanism of  FIG. 1 ;  
         [0018]      FIG. 5  is a second embodiment of a locking section for the over-the-wire interlock attachment/detachment mechanism of the present invention; and  
         [0019]      FIG. 6  is a third embodiment of a locking section for the over-the-wire interlock attachment/detachment mechanism of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]     Referring to  FIG. 1 , the over-the-wire interlock attachment/detachment mechanism of the present invention indicated generally at  10  is adapted for movement along a conventional guidewire  12  such as a 0.014″ guidewire. The over-the-wire interlock attachment/detachment mechanism includes a male locking section  14 , a female lock receiving section  16 , and a tubular sheath  18  dimensioned to slide over the male and female sections. Preferably, the female section  16  is secured to an implantable medical device  20  such as a septal occluder, a filter or stent to be released in the heart or a blood vessel or other vessel of the human body or to be retrieved or repositioned within the heart or vessel.  
         [0021]     The male locking section  14  includes a tubular body  22  which defines an open ended central chamber  24  through which the guidewire  12  passes. Projecting outwardly from the forward end of the tubular body  22  are one or more elongate guide fingers  26 . These guide fingers are straight, elongate pins with arcutely shaped ends  28 , and two such guide fingers are shown in  FIG. 1  although more than two can be provided. The outer surface of each guide finger is preferably coextensive with the outer surface of the tubular body  22 .  
         [0022]     Also projecting outwardly from the forward end of the tubular body  22  are one or more flexible, elongate locking arms  30  which are substantially equal in width to the width of the guide fingers  26 . Underlying each of the locking arms is a slot  32  formed in the tubular body to receive the locking arm. When unconfined, each locking arm is formed to angle outwardly beyond the outer surface of the tubular body  22 .  
         [0023]     A shaped locking member  34  is formed at the end of each locking arm. Preferably, this locking member, which extends laterally from at least one side of the locking arm, is circular in shape, but other shapes which extend laterally from the locking arm including but not limited to an ellipse, a “T”, a rectangle, a square, a hook, a triangle or an “L” can be used. A circular locking member facilitates engagement with the lock receiving section  16 . The guide fingers and locking arms are equally spaced around the tubular body  22 . They are preferably equal in number, and although two of each are shown, more can be used.  
         [0024]     The female lock receiving section  16  includes a tubular body  36  which defines an open ended central chamber  38  for receiving the guidewire  12 . The tubular body  36  is substantially equal in diameter to the tubular body  22  so that the two are coextensive when the male locking section is engaged with the female lock receiving section.  
         [0025]     The female lock receiving section includes a plurality of shaped locking cutouts  40  which are shaped to conform to and receive the shaped locking members  34 . The number of shaped locking cutouts  40  is equal to the number of guide fingers  26  and locking arms  30 . Extending into each of the shaped locking cutouts  40  is a straight, open ended, cutout entry section  42  which is formed to receive either a guide finger  26  or a locking arm  30 .  
         [0026]     The shaped locking cutouts  40  and open ended entry cutout sections  42  are equally spaced around the tubular body  36  to conform to the spacing of the guide fingers  26  and locking arms  30 . Outwardly projecting spacer sections  44  extend outwardly between adjacent shaped cutouts and open ended entry cutout sections and each terminate in inclined outer end surfaces  46  and  48  which form an apex  50 . Each inclined outer surface angles downwardly toward an open ended entry cutout section  42  and the inclined outer end surface  46  of a spacer section  44  forms with the inclined outer end surface  48  of an adjacent spacer section an enlarged outwardly tapered opening  52  for each open ended cutout section.  
         [0027]     The female lock receiving section  16  is secured to one end of a medical implant  20 , which can be an over the wire device such as a septal occluder. For purpose of illustration, the female lock receiving section is shown with the over-the-wire free standing filter  54 . The free standing filter  54  has a filter body with an elongate guidewire receiving member  56  extending centrally therethrough to define an open ended channel configured to receive a plurality of different sized guidewires. An expandable and contractible frame  58  surrounds the elongate guidewire receiving member and is connected at a proximal end to the elongate guidewire receiving member. A porous embolic capturing unit  60  has an open end  62  connected to the frame and a closed end  64  connected to the elongate guidewire receiving member which extends through the porous embolic capturing unit.  
         [0028]      FIGS. 1, 3  and  4  disclose the manner in which the over-the-wire interlock attachment/detachment mechanism  10  is operable to positively engage and remove a medical implant  20  from a body organ or vessel. The male locking section  14  is enclosed within the sheath  18  so that the locking arms  30  are forced into the slots  32  and do not project outwardly beyond the periphery of the male locking section. In this configuration, the male locking section is passed along the wire  12  until it is positioned in close proximity to the female lock receiving section  16 . At this point, the sheath  18  is drawn back to permit the locking arms  30  to angle outwardly from the male locking section  14 . The male locking section is then moved toward the female lock receiving section  16  until the guide fingers  26  engage the outer end surface  46  or  48  of a spacer section  44 . As the male locking section continues to move toward the female lock receiving section, each guide finger will be guided by an inclined outer end surface  46  or  48  into an open ended cutout entry section  42  which then guides the guide finger into the associated shaped cutout  40 . The over-the-wire interlock attachment/detachment mechanism is now in the configuration illustrated in  FIG. 3 . It will be noted that when the guide fingers move into the open ended cutout entry sections  42 , they position the locking arms  30  and the locking members  34  above and in alignment with open ended cutout sections  42  and their associated shaped cutouts  40 . Now, shown in  FIG. 4 , the tubular sheath  18  is moved forwardly over the tubular bodies  22  and  36  to force the locking members  34  into the shaped cutouts  40  and positively engage the male locking section  14  with the female lock receiving section  16 .  
         [0029]     Once a positive engagement has been established between the male locking section and female lock receiving section, the over-the-wire interlock attachment/detachment mechanism can be drawn back over the wire  12  to remove-the medical implant  20 . Because of the positive locking engagement, forces present on the medical implant as it is withdrawn will not result in detachment from the over-the-wire interlock attachment/detachment mechanism. This is very important for medical implants such as the removable filter  54  where hooks  58  must be withdrawn from the wall of the vessel.  
         [0030]     It is often difficult to accurately position a medical implant within a vessel without disconnecting or misaligning the implant relative to the positioning device. This problem is rectified by the over-the-wire interlock attachment/detachment mechanism  10 . The medical implant  20  with an attached female lock receiving section  16  is positively locked to the male locking section  14  in the manner shown by  FIG. 4  before it is moved over the wire  12  into position within a body vessel. The positive locking action between the male locking section and female lock receiving section facilitates accurate positioning of the medical implant within a vessel without misorientation or the likelihood of a disconnect. Once the implant device is positioned, the sheath  18  can be moved back as shown in  FIG. 3  allowing the locking arms  30  to spring outwardly to disengage the locking members  34  from the shaped cutouts  40 . Now the male locking section  14  can be drawn back over the wire  12  away from the female lock receiving section  16 .  
         [0031]     The sheath  18  may be replaced by other operating mechanisms capable of moving the locking arms  30  into the slots  32 . For example, elongate tethers attached to the ends of the locking arms which extend back through the central chamber  24  might perform this function.  
         [0032]     The male locking section  14  can be modified as shown in  FIGS. 5 and 6  to provide a flexible end section  68  adjacent to the elongate guide fingers  26  and elongate locking arms  30 . By providing a flexible section  68  in the body  22  proximal to the guide fingers and locking arms, it becomes easier to align the guide fingers, locking arms and locking members  34  with the cutouts in the female lock receiving section  16 . The flexible section  68  can be formed in a variety of ways. For example, a spring section can be welded or bonded to the body  22  between the main portion of the body and the guide fingers and locking arms to form the flexible section  68 . Ideally, as shown in  FIG. 5 , the body  22  is formed with a unitary spring section  68  by cutting the body in a spiral to create a helical spring  70 . This can be done with a laser which can also be used to shape the guide fingers, locking arms and locking members in the tubular body  
         [0033]     Alternatively, as shown in  FIG. 6 , a flexible, tubular polymer section  72  can be formed between the main portion of the body  22  and the guide fingers and locking arms to provide the flexible section  68 .