Abstract:
There is disclosed a device for removing chronic total occlusions (CTO) from blood vessels or other body lumens. In one embodiment the device has a loop at a distal end connected by a shaft to a proximal end. The shaft is provided inside a catheter that has an opening at the distal end and a handle at the proximal end. By manipulating the position of the loop relative to the opening, the effective stiffness of the loop may be changed. This allows a physician to vary the loop stiffness so as to be appropriate with regard to the toughness of a CTO (some CTOs have a relatively tough exterior but a relatively soft interior). The loop may have a single turn or may comprise two or more turns.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to occlusion removal devices and methods for removing deposits and/or blockages from blood vessels or other body lumens. In particular, but not exclusively, the present invention relates to the removal of Chronic Total Occlusions (CTOs). 
       BACKGROUND OF THE INVENTION 
       [0002]    Body lumens, such as blood vessels or the ureter, can be obstructed by blockages such as CTOs or kidney stones, for example. Other types of blockages include polyps or cysts. Such blockages can be either total or partial and can be painful or life threatening to a human patient or to an animal. 
         [0003]    In blood vessels, CTOs are blockages that completely obstruct the flow of blood through the blood vessel. CTOs often have a fibrous cap that makes removal of CTOs difficult as the cap prevents entry of a removal device into the softer underlying plaque material. 
         [0004]    U.S. Pat. No.  5 , 792 , 157  discloses an intravascular occlusion material removal device for removing vascular occlusion material in a vascular lumen. It comprises a prime mover and an expandable material removal element insertable intravascularly into the vascular lumen. A hollow drive shaft operatively connects the prime mover to the expandable material removal element for rotating the expandable material removal element intravascularly. A guidewire is insertable through the distal end of the expandable material removal element and the hollow drive shaft, and is shiftable within the drive shaft and the expandable material removal element. The expandable material removal element is expandable responsive to shifting of the guidewire. A material removal element movement control mechanism is operatively connected to the guidewire for positively incrementally shifting the guidewire, and a guidewire lock mechanism is operatively connected between the guidewire and the material removal element movement control mechanism for fixing the guidewire with respect to the material removal element movement control mechanism. A number of methods for removing vascular occlusion material are also disclosed. One such method comprises the steps of: providing a vascular occlusion material removal device having an expandable occlusion material removal element, the material removal element comprising a braid having a hollow interior; providing a guidewire; intravascularly navigating the guidewire to the occlusion material; inserting the guidewire into the hollow interior; intravascularly navigating the braid to the occlusion material over the guidewire; shifting the guidewire with respect to the braid to expand the braid; expanding the braid such that the braid bites into occlusion material thereby allowing occlusion material to pass into the hollow interior; and shifting the guidewire with respect to the braid to contract the braid and to capture occlusion material within the hollow interior. The expanded braid can also be rotated intravascularly to remove occlusion material. 
         [0005]    EP 0820729 discloses a medical device, in particular a surgical device usually delivered through an intravascular catheter. It may be used in several ways. It may, for instance, be used to open a clear passageway adjacent thrombus to allow both blood and medication to bypass the clot. It may be used to pierce and to remove thrombus. These thrombi are often found in tortuous vasculature. The device includes several sections. The device has a core element, typically a core wire. Placed around the distal end of the core element is a collapsible but preferably self expanding cage assembly. The cage assembly is preferably radio-opaque. The proximal end of the cage is typically is affixed to an actuator in such a way as to allow expansion of the cage after deployment. The cage assembly may have a generally conical distal or “trailing” portion when expanded and also a proximal section. The cage assembly may be used for collecting emboli or for displacing them to allow blood flow to resume. The proximal section may have various uses, e.g., for centering the collector assembly in the vascular lumen or for gathering larger amounts of the targeted clot or to act as a passageway for fluid flow. The assembly further may have an actuator which permits or causes the collector assembly to expand after deployment. 
         [0006]    US 2002/0016564 discloses apparatus and methods for effective removal of emboli or harmful fluids during vascular procedures, such as angiography, balloon angioplasty, stent deployment, laser angioplasty, atherectomy, intravascular ultrasonography and other therapeutic and diagnostic procedures. A catheter with an occluder mounted at its distal end creates an occlusion proximal to the lesion. The catheter provides a pathway for introducing a treatment catheter. Prior to, during or subsequent to the procedure, suction is activated to establish retrograde flow to remove emboli from the site. Additionally, a thin catheter with a distal fluid ejection nozzle maybe introduced distal to the treatment site to rinse emboli from the treatment site. The suction flow and/or ejected fluid flow may be varied in a pulsatile manner to simulate regular blood flow and/or perturb settled emboli into being captured that may otherwise not be collected. The method establishes a protective environment before any devices enter the site to be treated. 
         [0007]    The above mentioned devices can suffer some disadvantages. CTOs and other occlusions, whether partial or total, are often non-uniform. For example, some CTOs have a relatively tough cap with a relatively soft interior. A problem with some prior art devices is that if the device is suitable for cutting through the tough cap then the device will too easily cut through the softer inner, and there is the risk of a surgeon inadvertently damaging the interior lining of the blood vessel. On the other hand, if a prior art device is suitable for cutting thought the soft inner of a CTO then the device will often be unsuitable for cutting through the tough cap. 
       SUMMARY OF THE INVENTION 
       [0008]    According to an aspect of the invention, there is provided an occlusion treatment device comprising: a catheter provided with a proximal end and a distal end, the distal end being provided with an opening; and a longitudinal inner component provided with a proximal end and a distal end, the distal end including a looped element; wherein the inner component is dimensioned to be received inside the catheter and is slidable relative to the catheter between a retracted position and an extended position in which the looped element extends out of the catheter through the opening; wherein the effective stiffness of the device is changeable by movement of the looped or element between the retracted and extended positions. 
         [0009]    Preferably, the effective stiffness of the device may be increased by reducing the extent of at least a portion of the loop that protrudes from the distal opening, and wherein the effective stiffness of the device may be decreased by increasing the extent of at least a portion of the loop that protrudes from the distal opening. 
         [0010]    Some embodiments of the present invention allow the effective stiffness of the loop to be varied by changing the relative positions of the catheter and the inner component. A physician can thereby adjust the device in situ so as to be suitable for different regions of a total occlusion. The device may also be advantageously be used to treat partial occlusions. 
         [0011]    The occlusion removal device may be used for treatment of humans or animals during surgery. Some embodiments of the device are particularly suitable for the treatment of Chronic Total Occlusions (CTOs) in blood vessels. 
         [0012]    Advantageously, the distal opening is angularly arranged, spatially located or pre-curved to urge the loop to adopt a desired configuration as the loop exits the distal opening. In some embodiments, the loop can be arranged to exit straight ahead out of the distal opening, or towards one side, by suitable angular orientation of the inner component relative to the catheter. This feature enables the loop to be pointed or steered in the vessel being treated in a direction desired by the surgeon. Prior art devices do not provide such a feature. 
         [0013]    Advantageously, the catheter is provided with a port to allow aspiration of debris from an occlusion being removed, or to allow a fluid to be effused to the occlusion. 
         [0014]    Advantageously, the distal opening of the catheter is provided with one or more keys to constrain the loop. Such keys can be used to urge the loop to adopt a particular shape as the loop emerges from the distal opening. Such keys are particularly advantageous when the loop is arranged to comprise two or more turns, for example as a double loop. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0015]    Embodiments of the present invention are described below, by way of example only, with reference to the accompanying drawings, in which: 
           [0016]      FIG. 1  shows a cross-sectional view of a distal end of a first embodiment of device, comprising a catheter and an inner component within the catheter; 
           [0017]      FIG. 2A  shows a view similar to  FIG. 1 , in which a loop of the device protrudes from a distal opening of the catheter and extends at an angle to a longitudinal axis of the catheter; 
           [0018]      FIG. 2B  shows an end-on view of the catheter of  FIG. 2A , and shows the loop extending beyond the radial perimeter of the catheter; 
           [0019]      FIG. 3  shows a view similar to  FIG. 2A , in which the loop extends straight out, substantially parallel to the longitudinal axis of the catheter; 
           [0020]      FIG. 4  shows the loop after it has completely emerged from the distal opening of the catheter; 
           [0021]      FIG. 5  is a schematic view of an embodiment of occlusion removal device incorporating a catheter and loop as taught herein; 
           [0022]      FIG. 6  shows the distal end being used to remove an occlusion from a blood vessel; 
           [0023]      FIG. 7A  shows the distal end of another embodiment of occlusion removal device having a double helical loop; 
           [0024]      FIG. 7B  shows an end-on view of  FIG. 7A ; 
           [0025]      FIG. 8A  shows a view similar to  FIG. 7A  but in which the loop is rotated relative to the catheter and partially extends beyond the opening of the catheter; 
           [0026]      FIG. 8B  shows an end-on view of  FIG. 8A ; and 
           [0027]      FIG. 9  shows a view similar to  FIG. 8A  but in which the loop has completely emerged from the catheter and is unrestrained. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]      FIGS. 1 to 6  show a distal end  100  of an occlusion removal device  10  comprising a catheter  20  and an inner component  30 . The catheter  20  comprises a metallic, radiopaque, distal opening  12  and a polymeric catheter sheath  14 . More generally, the distal opening  12  and the catheter sheath  14  may be formed from other materials (as opposed to a metallic distal opening  12  and a polymeric catheter sheath  14 ). In alternative embodiments, the distal opening is non-metallic and is provided with one or more radiopaque markers (not shown but of a type common in the art). 
         [0029]    As shown particularly by  FIGS. 1 to 4 , the tip of the distal end  100  of the catheter  30  is pre-curved. By pre-curved, it is meant that the distal end  100  of the catheter  20  is curved at the time of manufacture or final formation and thus before the catheter  20  is inserted into a body lumen. The pre-curved portion may be adjacent to the distal opening  1 , or may include the distal opening  1 . The degree of curvature may be greater or lesser than that shown in the drawings. 
         [0030]    The inner component or tool  30  comprises a shaft  16  and a loop  18 . A bond or weld  22  closes the shaft  16  to form the loop  18 . The loop  18  is arranged to adopt a helical configuration within the catheter  20 , and comprises two helical branches  24  that make up the loop  18 . The loop  18  maybe centered along the axis of the shaft  16  but in some instances could be offset to one side. 
         [0031]    In practice, the inner component or tool  30  may represent a guide wire which has torquability. 
         [0032]    The tool  30  may be provided with identifying feature to distinguish it from a guide wire or other component. 
         [0033]      FIG. 5  shows a proximal end  500  of the removal device  10  which remains external to the patient. The device  10 , at the proximal end  500 , is provided with a handle  510  to allow a surgeon to manipulate the catheter  20  so that the distal end  100  is adjacent the occlusion to be treated. 
         [0034]      FIG. 6  shows the distal end  100  adjacent an occlusion  600  within a blood vessel  610 . The blood vessel  610  comprises a tunica intima  611 , tunica media  612  and tunica externa  613 . The occlusion  600  has a tough cap  601  and a softer inner  602 . 
         [0035]    The handle  510  may be any suitable shape to allow a surgeon to manipulate the catheter by advancing or retreating the catheter  20  along a patient&#39;s blood vessels, and to allow the surgeon to rotate the catheter  20  relative to the patient. 
         [0036]    The inner component or tool  30 , at the proximal end  500 , is provided with a handle  520  to allow a surgeon to manipulate the tool  30 . The handle  520  may be any suitable shape to allow a surgeon to manipulate the tool  30  so that the loop  18  is adjacent an occlusion. The handle  520  allows a surgeon to advance or retreat the tool  30  along the inside of the catheter  30  and also allows a surgeon to rotate the tool  30  relative to the catheter  20 . 
         [0037]    The tool  30  can be moved axially and rotationally relative to the catheter  20 .  FIGS. 2A and 2B  show a configuration where the tool  30  interacts with the catheter  20  so that the loop  18  emerges off the longitudinal axis of the catheter  20 . As shown, the distal opening  12  is angularly offset to facilitate the emergence of the loop  18  off the longitudinal axis. In other embodiments the distal opening  12  may also/instead be spatially offset from the longitudinal axis, i.e. off-centre. 
         [0038]    The relative positioning between the catheter  20  and the inner component  30  allows a physician to steer the device  10  selectively, and to control how compliant/aggressive the loop  18  is when removing deposits or blockages such as a CTO. The Seldinger technique may be used to guide the distal end  100  of the device  10  towards a CTO. 
         [0039]    If an occlusion  600  has a tough cap  601  then the distal end  100  of the device  10  may be biased towards a wall  611  of a blood vessel  610  and/or to the interface between the vessel wall  611  and the cap  601 . The distal opening  12  may be positioned so as to cause the loop  18  to impinge-between the tunica media  612  (the elastic and muscular middle layer of an artery or vein) and the tunica adventitia  613  (the collagenous outer layer of an artery or vein), or to create a passageway between the occlusion  600  and the blood vessel  610 . This positioning can be achieved with the aid of fluoroscopy techniques using appropriately positioned radiopaque markers as the catheter and/or tool. 
         [0040]    In situations where the distal end  600  of the device  10  has been positioned between the tunica media  612  and the tunica adventitia  613 , the device  10  (i.e. the catheter  20  and the inner component  30 ) may be advanced along the blood vessel  610  until the distal opening  12  reaches a position where it is desired to re-enter a main lumen  620  of the blood vessel  610 . To re-enter the main lumen  620 , the catheter  20  is oriented to steer the inner component  30  toward the main lumen  620 . The inner component  30  may be extended out of the catheter  20  to allow the loop  18  to “open” and exhibit more compliance-(and thus less potential trauma) or the inner component  30  may be retracted into the catheter  20  to close the loop  18  such that the portion of the loop  18  that remains protruding (out of the distal opening  12 ) and in particular to distal end  100  of the catheter  20  exhibits sufficient stiffness to burrow through the occlusion  600  or the through tunica media  612 . 
         [0041]    The inner component  30  may be caused to “spin” by being rotated relative to the catheter  20  to facilitate “digging” of the loop  18  into an occlusion  600 . In an alternative embodiment, the inner component  30  may comprise a tubular portion instead of the shaft  16 , in order to facilitate the transfer of torque from the proximal end  500  of the inner component  30  to the loop  18 . 
         [0042]    If necessary, the catheter  30  may be aspirated or eluted to remove occlusive material that has been freed from the CTO  600 .  FIG. 5  also shows an aspiration port  530  provided at a region of the handle  510 . The aspiration port  530  is used to suck fluid (e.g. blood), together with pieces of the occlusion  600 , from the vicinity of the distal opening  12 . The fluid passes along the interior of the catheter  30  towards the proximal end  500 . The port  530  may also be used to convey a fluid toward the distal opening  12 . For example, a thrombolytic agent may be directed towards the occlusion material to assist in the destruction and removal of the occlusion  600 . In embodiments where the inner component  30  is tubular, the inner component  30  may be used for aspiration. 
         [0043]      FIGS. 7A to 9  show an embodiment in which the device  10 ′ has a double-loop  28  instead of the single loop  18 . Also shown are two keys  32  that form part of the distal opening  12 ′. Other versions of this embodiment may have a single key  32 . In some versions of this embodiment, the one or more keys  28  may be used to help the loop  28  adopt a double curved configuration within the catheter  20 . In other versions of this embodiment, the one or more keys  32  may be used to control the shape of the loop  28  when the loop  28  is being extended out of the distal opening. In yet other versions of this embodiment, the one or more keys  32  may be used to restrain the loop  28  when the loop is partially extended, thereby allowing the catheter  20  to be rotated in order to place an additional force on the loop  28  (in addition to rotation of the inner component relative to the catheter  20 ). 
         [0044]    In yet other embodiments, the tool  16 ′ may comprise a looped element having three or more loops (instead of the double loop  8  shown at  FIGS. 7A-9 ). 
         [0045]    As those skilled in the art will appreciate, in some embodiments, the catheter  20  and/or the inner component  30  may be coated, for example, with a hydrophilic or hydrophobic substance. Such substance(s) may be used to reduce friction between the catheter  20  and the inner component  30 . Such substances may also be used to reduce friction between the catheter  20  and a body lumen  610  of a patient being treated. 
         [0046]    It will be appreciated that the disclosed devices capitalize on the co-operation between the sheath and tool to be selectively steerable as well as being selectively compliant or aggressive. 
         [0047]    Those skilled in the art will also appreciate that the invention may be supplied as a kit in which the inner component  30  is not inside the  30  catheter  20 ; a physician may insert the inner component  30  into the catheter  20  at a convenient time.