Abstract:
An apparatus and method for anchoring an elongated object, for example a wire, in tubular body vessel, such as arteries, veins, the colon, bile ducts, etc. are disclosed. The wire may be a catheter, a guide wire, a tube or an electrical lead. In one embodiment, a fixation device is advanced over the wire and, upon external actuation, either deforms the wire or deploys an anchoring mechanism so as to secure the wire against the vessel wall. The anchoring mechanism can be easily removed from the vessel even in the presence of vessel occlusion. In another embodiment, a wire tensioned between two locations on a distal section of the wire deforms the wire and urges the wire into wall apposition.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to an apparatus and method for anchoring an elongated object in tubular body passages, such as arteries, veins, the colon, bile ducts, etc. The wire may be a catheter, a guide wire, a tube or an electrical lead. 
       BACKGROUND OF THE INVENTION 
       [0002]    Wires, more particularly guidewires, are used in medical procedures to guide medical instruments and treatment devices, such as catheters, stents, embolic protection devices (EPD), etc., into and through small body lumens. For example, an EPD filter is typically inserted over or together with a guidewire using a delivery catheter. Following the treatment procedure, the filter is collapsed and removed from the body over the guidewire or together with the guidewire. Additional treatment devices, such as balloons and stents, can be inserted and removed via the same guidewire. 
         [0003]    The distal end of the guidewire is in most situations unsupported in the lumen, so that insertion of the medical instruments and treatment devices may cause unwanted movement of the guidewire and even dislodgement of the guidewire. This problem may be exacerbated when heavier devices are advanced over the guidewire. 
         [0004]    Other types of wires used in medical procedures are electrical leads for electrical stimulation therapy to treat a variety of symptoms or conditions such as cardiac arrhythmias, chronic pain, tremor, Parkinson&#39;s disease, multiple sclerosis, spinal cord injury, cerebral palsy, amyotrophic lateral sclerosis, dystonia, torticollis, epilepsy, pelvic floor disorders, or gastroparesis. One or more stimulation leads are typically percutaneously or surgically implanted in a patient on a temporary or permanent basis, with at least one stimulation electrode being positioned proximate to a target stimulation site. The target stimulation site may be, for example, a spinal cord, pelvic nerve, pudendal nerve, stomach, muscle, or within a brain, the heart or another organ of a patient. For example, the electrodes may deliver stimuli for cardiac resynchronization therapy (CRT). 
         [0005]    In most cases, the electric leads are attached to the target organ, such as a cardiac vein or artery, by an anchoring a component located at the tip of the lead in form of, for example, a threaded fixation structure or extendable fixation devices located near the tip, an inflatable balloon, etc. While fixation of pacemaker leads in the right ventricle is successful in most cases, stable fixation within certain vasculature in the human body, such as the coronary sinus for CRT applications, have proven more difficult. Improper lead implantation can sometimes occur during deployment, due to tortuous venous anatomy. Occasionally, lead implantation results in complications, such as coronary sinus dissection or phrenic nerve stimulation. 
         [0006]    Lead migration sometimes occurs subsequent to implantation, due to inadequate anchoring mechanisms. With the introduction of biventricular pacing, leads also had to be permanently placed in the cardiac veins, so that fixating electrodes within the vein has become an important clinical problem. The thin wall of the vein does not support the use of screws for fixation, and the smooth vascular wall does not readily support the use of mechanical friction fixating devices. Currently, several methods have been reported to fixate electrical leads in a cardiac vein; however, lead migration still remains a significant clinical problem. 
         [0007]    With current technologies, the fixation structure or fixation devices are permanently attached to or incorporated in the electrical lead and in most cases form the tip of the lead. This arrangement makes it impossible to later move the tip of the lead relative to the fixation structure, for example, to improve coupling between the lead tip and the treatment site. 
         [0008]    Accordingly, there is a need for improved lead fixation in a body lumen, wherein positioning of the electrical lead or the guidewire is independent of placement of the fixation structure, and wherein possibilities exist for later repositioning the tip of the wire or guidewire relative to the fixation structure, without moving the fixation structure inside the body lumen. 
       SUMMARY OF THE INVENTION 
       [0009]    In general, the invention is directed toward an implantable medical elongated member, such as a guidewire or an electrical lead, which can be inserted into a body lumen and which can be used to guide a fixation device to a location in the body lumen, wherein the fixation device is held in place inside the body lumen, for example, mechanically by friction. In some embodiments, the guidewire or electrical lead wire can then be also affixed to the fixation device, either releasably or permanently. In some embodiments, the fixation device is in form of a coil or can be shaped into a coil or another deformed or tortuous structure, which can be delivered by a catheter. The coiled shape can be made, for example, of a shape memory metal, such as Nitinol. 
         [0010]    Although the examples described in the context of this application are mainly directed to pacing leads, these can apply to any elongated object such as catheter, guide wire, tube, etc. 
         [0011]    In one exemplary embodiment, the fixation device is tubular and when activated is deformed into a spiral, thus forcing the wire, such as the pacing wire or lead into a helical shape at that location. The formed spiral is in apposition to the vein wall and fixes the lead in place. 
         [0012]    In another embodiment, the tubular fixation device may include an activation wire that is pulled distally (outside of the body) to activate the fixation device, thereby allowing the fixation device to deform into the tortuous shape for vessel wall apposition. 
         [0013]    In some embodiments of the current invention, the fixation device may include an expanding member, for example made of a wire, which engages the vein wall once activated. In some embodiments, the fixation device is an expanding member, for example a balloon, that when inflated is large enough to engage opposing walls of the cecum. It will be understood that the fixation device need not be a single element, but that more than one element can be employed, which allow free passage of the guidewire and other equipment through the fixation device. In yet another embodiment, an inducer apparatus and method, similar to a catheter, are provided for lead retrieval. 
         [0014]    These and other features and advantages of the present invention will become more readily appreciated from the detailed description of the invention that follows. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The following figures depict certain illustrative embodiments of the invention in which like reference numerals refer to like elements. These depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way. 
           [0016]      FIG. 1  shows a heart with the coronary sinus with a pacing lead in partial cross-section; 
           [0017]      FIG. 2  shows the pacing lead of  FIG. 1  re-shaped to a two-dimensional deformed pattern; 
           [0018]      FIG. 3  shows the pacing lead of  FIG. 1  re-shaped to a three-dimensional helical pattern; 
           [0019]      FIG. 4  shows a mechanism configured for reshaping the fixation device inside a vessel; 
           [0020]      FIG. 5  shows the two-dimensional pattern (a) and three-dimensional (b) pacing lead of  FIGS. 2 and 3  in more detail; 
           [0021]      FIG. 6  shows another mechanism configured for reshaping the fixation device inside a vessel; 
           [0022]      FIG. 7  shows a different anchoring mechanism for a pacing lead in a vessel; 
           [0023]      FIG. 8  depicts an approach for retrieving the anchoring mechanism of  FIG. 7  in the event of tissue in-growth; and 
           [0024]      FIG. 9  shows exemplary embodiments for retracting the anchoring mechanism according to  FIG. 8 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    The exemplary embodiments of the invention described below are directed to securing a lead, such as a pacing lead in a coronary vessel. This can be attained by forcing the pacing lead, once introduced into the vessel, into vessel wall apposition by external actuation, for example, from the proximal end of an insertion catheter. This can be attained by advancing a fixation device with a locking mechanism over the pacing lead, using the pacing lead essentially as a guidewire, and then actuating the fixation device externally from the proximal end of an insertion catheter. Additionally, a wire lock can be employed to lock the fixation device in place on the pacing lead. 
         [0026]    Turning now to the appended Figures,  FIG. 1  shows a view of the heart  10 , with the coronary sinus  12  shown in partial cross-section. A straight section of a pacing lead  14  can be seen inside the vessel. As can be seen, the pacing lead  14  is not anchored in the vessel and can be easily dislodged. 
         [0027]    One approach for anchoring the pacing lead in the coronary sinus  12  is to deform the pacing lead  14  into a deformed shape, either two-dimensionally in a meander shape  3 , as shown in  FIG. 2 , or three-dimensionally in form of a helical shape  5 , as shown in  FIG. 3 . This deformation may be performed with a separate fixation device or fixation attachment. Examples of such fixation devices will be described below in conjunction with  FIGS. 4 ,  6  and  7 . The resulting deformation, illustrated schematically in  FIG. 2 , will bring sections  22  and  24  of the deformed fixation device into apposition with the vessel wall  12 ′, thereby anchoring the pacing lead  14  through friction. 
         [0028]      FIG. 4  illustrates an exemplary embodiment of a fixation device  40  which includes structural attributes and a mechanism for deforming an originally straight fixation device  40  into the meander ( FIG. 2 ) or helical shape ( FIG. 3 ). The fixation device  40  is here formed as a hollow shaft receiving the pacing lead  14  and has a pattern  42  formed in the shaft wall, with an exemplary pattern including, for example, precut grooves or a section with decreased wall thickness to provide weak links or rated break points. The fixation device  40  may be deployed at the implant site by a delivery catheter (not shown) similar to the delivery catheter  75  described below in conjunction with the discussion of  FIG. 7 . A pulling wire  44  is attached at  41  to the distal end  49  of the fixation device  40 . When the wire  44  is pulled downward in the direction of arrow  44 , i.e., towards the proximal end of the pacing lead  14 , the location of the proximal end of the hollow fixation device  40  is fixed by the delivery catheter, so that fixation device  40  will collapse to a predetermined shape defined by the pattern  42  and deform the pacing lead  14 , as shown in more detail in  FIG. 5   a  (corresponding to the two-dimensional meander shape of  FIG. 2 ) and  FIG. 5   b  (corresponding to the three-dimensional meander shape of  FIG. 3 ). It will be understood that the depicted shapes of the deformation are only examples, and that other deformed configurations can be contemplated as long as these configurations securely anchor the pacing lead  14  in a vessel  12 . The wire  44  can be detached from the fixation device  40  by incorporating a rated breakpoint at a location along the wire, for example, near the distal attachment point  41 . The rated breakpoint can be constructed similar to breakpoints described in copending applications WO 2009/050599 and WO 2009/050600, both titled “Guidewire Stop.” The wire  44  can be severed either by pulling or twisting. 
         [0029]    In another exemplary embodiment illustrated in  FIG. 6 , an originally straight section of a pacing lead  14  ( FIG. 6   a ) can be shaped into a deformed pattern adapted for securement in a vessel  12  by securing a pulling wire  64  to the distal portion  67  of the pacing lead  14  at two locations  61  and  62 . The pulling wire  64  is fixedly attached near the distal end  61  of pacing lead  14 ; the pulling wire  14  is guided through an opening  62  of a shaft ring  63  secured to the pacing lead  14  proximal of the distal end  61  for longitudinal movement relative to the shaft ring  63  and hence relative to the pacing lead  14 . A securement device  66 , illustrated as an exemplary wedge  66 , is attached to the pulling wire  64  at a location between the distal end  61  and the shaft ring  63 . It will be understood that the securement device  66  may have other shapes, such as a conical shape or shapes similar to those described in copending applications WO 2009/050599 and WO 2009/050600. When the pulling wire  64  is pulled in the direction of arrow  65 , the distal portion  67  of the pacing lead  14  bends until the securement device or wedge  66  engages with and locks inside the opening  62  of shaft ring  63 . Alternatively, instead of providing a separate opening  62 , the wedge  66  may lock directly between the shaft ring  63  and the distal portion  67  of the pacing lead  14 . As indicated in  FIG. 6   b , the pulling wire  64  may be designed to tear at the rated break point  68  under the pulling force following locking of wedge  66  or by a rotation of the pulling wire  64 . The curved section  64  of the pacing lead  14  is now in apposition with the vessel wall (not shown), securing the pacing lead inside the vessel  12 . 
         [0030]    Another exemplary embodiment illustrated in  FIGS. 7   a  to  7   c  employs a different type of anchoring mechanism  70  for improving securement of a pacing lead  14  in a blood vessel  12  (not shown in  FIG. 7 ). The anchoring mechanism  70  is here embodied as a plurality of wires loops  71  protruding from a shaft ring  72 . The anchoring mechanism  70  can be advanced into the vessel over a conventional pacing lead  25 , operating much like a guidewire, for example, by using an insertion catheter  75 . The shaft ring  72  can be locked in place on the pacing lead  14  with a guidewire stop of a type described in copending applications WO 2009/050599 and WO 2009/050600, which may be implemented as a wedge  76 . The wedge  76  is attached to a proximate pulling wire  74 , with the wedge  76  between drawn between the shaft ring  72  and the pacing lead  14  when pulling wire  74  is pulled proximately in the direction of arrow  77 . As indicated in  FIG. 7   b  and similar to the embodiment of  FIG. 6   b  described above, the pulling wire  74  may be designed to tear at a rated break point  78  under the pulling force following locking of wedge  76  or by a rotation of the pulling wire  74 .  FIG. 7   c  shows the wires loops  71  of the anchoring mechanism  70  in apposition with the vessel wall  12 . As indicated schematically in  FIGS. 7   a  and  7   b , the anchoring mechanism  70  may be advanced over the pacing lead  14  inside a delivery catheter  75 , with the wire loops initially collapsed ( FIG. 7   a ). When reaching the implantation site, the delivery catheter  75  is withdrawn proximally, allowing the wire loops  31  to expand ( FIG. 7   b ). 
         [0031]    Turning now to  FIG. 8 , it may occasionally be necessary to retrieve the pacing lead  14  from the blood vessel  12 . If the vessel wall is smooth without tissue growth, this can be accomplished, for example, by using a removal catheter which is pushed over the anchoring mechanism  70  and into which the wire loops  71  are retracted. However, retrieval becomes difficult when occlusion due to tissue growth in the wire loops prevents the use of a traditional retrieval catheter ( FIG. 8   b ). In this situation, an anchoring mechanism  70  may be used where the wire loops  71  are slidingly attached to the shaft ring  72  so that they can be retracted proximally into the shaft ring  72 .  FIG. 8   c  and  FIGS. 9   a  to  9   d  depict arrangements for pacing lead retrieval that can be used in the presence of vessel occlusion. The wire loops  71  detach from the vessel wall when pulled back toward the shaft ring  72 . For example, the open wire configuration  71   b  (see also  FIG. 9   a ) makes it much easier to pull the pacing wire  14  out of the tissue, because the friction resistance will be low and the vessel will not be harmed. Conversely, pulling out a closed loop shown as  71  in  FIG. 8   b  may tear the tissue into which the loop  71  has grown into. 
         [0032]      FIGS. 9   a - d  depict different embodiments of retractable wire loops  71  that can be used with the embodiment of  FIG. 8   a . In  FIG. 9   a , the wire loop  71  has a junction  91  configured to allow separation of the two wire sections  71   a  and  71   b  on either side of the junction  91 . The wire sections  71   a  and  71   b  can then be separately retracted through the openings  93  in the shaft ring  32  by pulling on free ends  71   e  and removed. In  FIG. 9   b , one end  92  of the wire loop  71  is fixedly attached of the shaft ring  32 , whereas the free end  71   c  of wire loop  71  can be pulled through the opening  93  in shaft ring  32  until the wire loop is collapsed.  FIG. 9   c  illustrates an embodiment where the wire loop  71  can be pulled through two openings  93  in the shaft ring  72  by pulling on both free ends  71   e  until the wire loop is collapsed. 
         [0033]    While the invention is receptive to various modifications, and alternative forms, specific examples thereof have been shown in the drawings and are herein described in detail. For example, it should be understood, that while in disclosed embodiments a tubular fixation device is advanced over the pacing lead proximate to the distal end of the pacing lead, the shape of the fixation device may also be changed into the desired deformed shape through external activation (shape memory alloys, fracture or severance of restraining elements by an external stimulus, such an electric current, magnetic forces and the like). 
         [0034]    The implant may include any pacing lead in any vein (e.g., transvenous nerve and muscle stimulation), and may also include any sensing catheter in any vein, such as pressure sensor, flow sensor, etc. The invention is therefore not limited to the particular forms or methods disclosed, but to the contrary, the invention is meant to cover modifications, equivalents, and alternatives.