Abstract:
Provided is a method for the treatment of blood vessel occlusions, comprising the localized anchoring of a catheter during the procedure by temporarily adhering its tip to the occlusion treatment site using a vacuum. Also provided is a catheter with a vacuum anchoring tip controlled by an externally generated vacuum, a catheter with a vacuum anchoring tip controlled by a self-generated vacuum, and a catheter with a vacuum anchoring tip in which the vacuum is controlled by an electronic signal. The localized anchoring method utilizes a vacuum to secure the tip of the catheter in place while allowing a free passage for the wire or dedicated occlusion penetrating device, and thereby frees the operator from constantly monitoring the tip position and pushing the catheter to support the advancement of the wire.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates in general to angioplasty, and in particular to methods and apparatus for use in the treatment of blood vessel occlusion, including chronic total occlusion. 
       BACKGROUND 
       [0002]    The treatment of blood vessel occlusions generally involves the use of percutaneous angioplastic techniques to advance a micro guiding catheter to the location of the occlusion, and to penetrate the occlusion with a wire or dedicated occlusion penetrating device in order to create a micro channel into which the operator can later introduce other percutaneous devices such as angioplasty balloons, and to fully restore blood flow. The mechanism behind occlusion crossing is based on a constant advancement of the wire or dedicated occlusion penetrating device, which allows it to be diverted into the natural micro-channels located within the occlusion until full crossing is achieved. 
         [0003]    Blood vessel occlusions may be acute or chronic, and chronic occlusions, often referred to as Chronic Total Occlusion (“CTO”), are typically fibrotic and often also calcified. CTOs may also be longer than acute occlusions. Accordingly, relatively high axial forces may be required in order to penetrate and advance a wire or dedicated penetrating device through a CTO. 
         [0004]    There is an obvious mechanical limitation to the amount of forward axial force that can be transmitted through a wire because a wire will easily buckle without radial support. Micro guiding catheters (which typically comprise a tight tube having an inner diameter that is only marginally greater than the diameter of the wire, and which are stiff but flexible enough to allow the operator to push them trough the vasculature of the patient to the CTO site) are accordingly commonly used in known CTO treatment techniques. 
         [0005]    However, although the use of a micro guiding catheter improves the amount of available axial force, it does not provide the operator with the full potential of force delivery. This derives from the action-reaction physical law, as pushing a wire constrained within a tube against an obstacle will result in a force acting at the opposite direction from the obstacle back to the wire and to the constraining tube. If the constraining tube is dislodged from the treatment site, the wire in the vicinity of the dislodgement may be exposed, and thereby the wire may lose its ability to deliver axial force or buckle. 
         [0006]    In order to keep the wire fully protected throughout the procedure, the operator must accordingly pay constant attention to the catheter&#39;s tip position, keeping it as close as possible to the occlusion. This is not, however, always feasible because the tortuous path the catheter may be required to follow to arrive at the treatment site can cause a loss of force and/or control at each of the bends the catheter makes. Additionally, in using a typical micro guiding catheter, the operator needs to be careful not to exceed the maximum allowed axial force that could result in buckling of the catheter itself. 
         [0007]    Current state of the art micro guiding catheters thus provide a partial solution for wire buckling and thereby increase slightly the amount of force the operator can apply, but they do not contemplate catheter tip securement, and therefore do not provide the operator with the full potential of force transmutation through the wire. Other state of the art techniques have accordingly been developed to facilitate securement of the micro catheter at the occlusion treatment site. 
         [0008]    These methods involve the use of an angioplasty balloon that, upon inflation, pushes the distal end of the micro guiding catheter shaft against the blood vessel wall. The shaft is therefore pressed between the inflated balloon and the vessel wall, and this keeps the distal end of the catheter relatively secured. However, the use of an angioplasty balloon to secure the distal end of a micro catheter has several disadvantages as well. Most important among these is the safety issue of pushing the shaft into a vessel wall, which could potentially cause serious injury. A further drawback is the resulting inability for the operator to reposition the catheter tip during the procedure since the catheter is virtually locked against the vessel wall. A variant of this method involves a coaxial set up that allows free movement of the wire; however, the risk of vessel injury due to balloon force applied is still present. 
       SUMMARY 
       [0009]    This summary is not an extensive overview intended to delineate the scope of the subject matter that is described and claimed herein. The summary presents aspects of the subject matter in a simplified form to provide a basic understanding thereof, as a prelude to the detailed description that is presented below. 
         [0010]    Provided herein is a method for the treatment of blood vessel occlusions, comprising the localized anchoring of a catheter during the procedure by temporarily adhering its tip to the occlusion treatment site using a vacuum. Also provided is a catheter with a vacuum anchoring tip controlled by an externally generated vacuum, a catheter with a vacuum anchoring tip controlled by a self-generated vacuum, and a catheter with a vacuum anchoring tip in which the vacuum s controlled by an electronic signal. The localized anchoring method utilizes a vacuum to secure the tip of the catheter in place while allowing a free passage for the wire or dedicated occlusion penetrating device, and therby frees the operator from constantly monitoring the tip position and pushing the catheter to support the advancement of the wire. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    For a fuller understanding of the nature and advantages of the disclosed subject matter, as well as the preferred mode of use thereof, reference should be made to the following detailed description, read in conjunction with the accompanying drawings. In the drawings, like reference numerals designate like or similar steps or components. 
           [0012]      FIG. 1  is a schematic illustration of the prior art treatment of a blood vessel occlusion using a conventional micro guiding catheter, and showing the diversion of the wire or a dedicated occlusion penetrating device into the natural micro-channels located within the occlusion. 
           [0013]      FIG. 2  is a schematic illustration of the prior art treatment of a blood vessel occlusion using a conventional micro guiding catheter, and showing the effects of the application of a forward axial force on an unsupported wire “without support”, and on a wire that is supported by a micro guiding catheter “with support”. 
           [0014]      FIGS. 3 and 4  are schematic illustrations of the prior art treatment of a blood vessel occlusion using a conventional micro guiding catheter, and showing the dislodgement of the micro guiding catheter from the treatment site by virtue of the law of action-reaction. 
           [0015]      FIG. 5  is a schematic illustration of the prior art treatment of a blood vessel occlusion using a conventional micro guiding catheter, and showing buckling of the wire in the vicinity of the dislodgement. 
           [0016]      FIGS. 6 and 7  are schematic illustrations of a generalized embodiment of a vacuum anchoring tip for temporarily adhering the tip of a catheter to an occlusion site. 
           [0017]      FIGS. 8 and 9  are cross-sectional views of a vacuum anchoring tip in accordance with embodiments of the present subject matter. 
           [0018]      FIGS. 10 and 11  are perspective views of vacuum anchoring tips in accordance with embodiments of the present subject matter. 
           [0019]      FIGS. 12-17  are cross-sectional views of a vacuum anchoring tip in accordance with embodiments of the present subject matter. 
           [0020]      FIG. 18  is a schematic illustration a single chamber suction device. 
           [0021]      FIG. 19  is a schematic illustration comparing a prior art single chamber suction device with a vacuum anchoring tips in accordance with embodiments of the present subject matter. 
           [0022]      FIG. 20  is a cross-sectional view of a vacuum anchoring tip in accordance with embodiments of the present subject matter. 
           [0023]      FIGS. 21-24  are partial perspective views of a catheter in accordance with embodiments of the present subject matter. 
           [0024]      FIG. 25  is a cross-sectional view of a vacuum anchoring tip in accordance with an alternate embodiment of the present subject matter. 
           [0025]      FIG. 26  is an enlarged perspective view of a spring frame of the vacuum anchoring tip of  FIG. 25 . 
           [0026]      FIG. 27  is an exploded perspective view of  5  the vacuum anchoring tip of  FIG. 25 . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0027]      FIGS. 1 through 5  illustrate the prior art treatment of a blood vessel occlusion such as a CTO using a conventional micro guiding catheter, as discussed in the background section above.  FIG. 1  illustrates the diversion of the wire or dedicated occlusion penetrating device into the natural micro-channels located within the occlusion.  FIG. 2  shows the effects of the application of a forward axial force on an unsupported wire “without support”, and on a wire that is supported by a micro guiding catheter “with support”.  FIGS. 3 and 4  show the dislodgement of the micro guiding catheter from the treatment site by virtue of the law of action-reaction, and  FIG. 5  shows the resulting buckling of the wire in the vicinity of the dislodgement. 
         [0028]    With reference to  FIGS. 6 and 7 , there is illustrated a generalized embodiment of a vacuum anchoring tip for temporarily adhering the tip of a catheter to an occlusion site. The vacuum may be externally generated or self generated, and may be controlled mechanically or by way of an electronic signal. 
         [0029]      FIGS. 8 and 9  schematically illustrate in cross-section a vacuum anchoring catheter tip wherein the vacuum is created and controlled by an externally generated vacuum. The catheter is dimensioned to deliver a conventional guidewire, stiff wire or dedicated occlusion penetrating device through a firmly anchored tip to a blood vessel occlusion, and relies on a vacuum to secure the tip at the site of the vessel occlusion while allowing a free passage for the wire. 
         [0030]    The tip  100  is preferably formed from a single piece of a flexible material that can be manufactured by injection molding, by two piece mold assembly methods, or by machining. In preferred embodiments, the outer surface geometry of tip  100  has seven distinct areas, as follows: sealing ring  1 , sealing ring recess  2 , contact chamber wall  3 , vacuum chamber wall  4 , chambers divider recess  5 , vacuum chamber recess  6 , and tail wall  7 . The inner surface geometry of tip  100  also has, in preferred embodiments, seven distinct areas, as follows: secondary sealing ring  8 , chambers divider septum  9 , guiding cone  10 , tail  11 , vacuum chamber  12 , chambers divider lumen  14 , and contact chamber  14 . 
         [0031]    The sealing ring  1  serves as the primary contact zone for adhering the tip to the occlusion site to create an initial seal and thus to allow vacuum to be built up in the tip  100 . Associated sealing ring recess  2  facilitates the sealing of the sealing ring  1  by enhancing the flexibility thereof vis-à-vis the occlusion site. 
         [0032]    As vacuum is built up within tip  100 , contact chamber  14  becomes the main interface between the tip  100  and the target surface of the occlusion site. Secondary sealing ring  8  is optional, and in embodiments that include it enhances further sealing ability of the contact chamber  14  by providing additional reinforcement. 
         [0033]    As is best seen in  FIG. 12 , the contact chamber  14  maintains a selected degree of vacuum during use, and is able to stretch to fit the topography of the target surface area whether it has rough, bumpy or smooth areas. To facilitate this, the wall  3  of contact chamber  14  may be thinner compared to other areas of the tip  100  to enhance the ability thereof to stretch, expand and generally accommodate for the target surface topography. The wall  3  of contact chamber  14  may also be manufactured from a lower durometer material to further assist in achieving these attributes. 
         [0034]    With reference now to  FIG. 13 , the vacuum chamber  12  of tip  100  maintains vacuum during use, and provides a reservoir of vacuum for the contact chamber  14 . The wall thickness  4  of vacuum chamber  12  is preferably thicker than the wall  3  of contact chamber  14  to enhance its ability to withstand constant vacuum without collapsing. The wall  4  of vacuum chamber  12  may also be manufactured from a higher durometer material to further assist achieving this attribute. 
         [0035]    The chambers divider lumen  13  connects the vacuum chamber  12  and contact chamber  14 , and is suitably constructed and dimensioned to permit the free passage therethrough of a wire or dedicated occlusion penetrating device during use (see  FIG. 14 ). In some embodiments, an additional lumen  18  may optionally be provided to run through the entire length of the catheter and extend all the way to the level of the distal tip for additional support of the wire or dedicated occlusion penetrating device  19 . 
         [0036]    The chambers divider recess  5  facilitates flexibility between the vacuum chamber  12  and contact chamber  14 , thereby providing contact chamber  14  with additional degrees of freedom to bend and thus to better fit to the topography of the target surface without breaking vacuum, and also to minimize the effect of bending of the catheter shaft  16 . 
         [0037]    The vacuum chamber recess  6  provides a secondary flexibility zone, but also guides the tip  100  into its delivery sleeve prior to the procedure (see  FIG. 21 ). 
         [0038]    The tail  11  provides an interface between the flexible tip  100  and the catheter shaft  16 , and it&#39;s the thickness and shape of the tail wall  7  are optimized for various known bonding or fusing techniques, including lamination, in which case tail wall  7  could be placed in between the layers that comprise a conventional catheter shaft  16 . 
         [0039]    Guiding cone  10  is dimensioned to guide the wire or dedicated occlusion penetrating device through the center of the tip  100 , and reduces the risk of damage to the inner structure of tip  100  in embodiments where a stiff wire or dedicated occlusion penetrating device is being used (see  FIG. 15 ). 
         [0040]    Referring now to  FIG. 16 , the twin-chamber construction of tip  100  enables the more efficient maintenance of a stable level of vacuum as compared to prior known devices. Contact chamber  14  creates a robust sealing area, while the vacuum chamber  12  buffers and delivers a constant under-pressure “delta P” to maintain the adhering force “F”. 
         [0041]    In addition, as best seen in  FIG. 17 , the twin-chamber construction of tip  100  and the hinge-like action of divider recess  5  enhances the ability of tip  100  to maintain contact chamber  14  generally parallel to the target surface despite changes in the inclination of catheter shaft  16 . This further enhances the ability of the tip  100  to maintain a stable level of vacuum despite changes in the inclination of shaft  16 , and isolates the contact chamber  14  from perturbations to the proximal portions of the catheter shaft  16 . 
         [0042]    By way of comparison,  FIG. 18  illustrates the deleterious effects of bending on vacuum maintenance in a single chamber design. In such a single chamber design, if a bending force “M” is applied to the catheter shaft after vacuum has been built in single vacuum chamber  15 , then the contact area of chamber  15  will experience compression (+T) and tension (−T) forces. Since the compression force assist in adhering to the contact surface, it is the tension force that needs to be minimized to prevent the contact area seal to break. 
         [0043]      FIG. 19  illustrates these effects in greater detail vis-à-vis both a single vacuum chamber design  15  and the dual chamber design of the presently disclosed subject matter. In the dual chamber design, stress isolating point  17  (which, as described above, may comprise the twin-chamber construction of tip  100  and the hinge-like action of divider recess  5  of the present subject matter) results in a lower tension force (t 1 ,t 2 ) to be transmitted to the contact surface (sealing ring  1  and optionally also secondary sealing ring  8  of the present subject matter) as a consequence of shaft bending increments (M 1 , M 2 ). In a single chamber design, such force increment (M 1 , M 2 ) has higher effect on the tension magnitude (T 1 , T 2 ) as compared to a dual chamber design. @M 1 : t 1 &lt;T 1 ; @M 2 : t 2 &lt;&lt;T 2   
         [0044]    The difference in force reaction is converted through the isolating point to different angled force vector (d 1 , d 2 ), that causes internal deformation of the chambers which do not affect the tension force (t 1 , t 2 ). @M 1 : t 1 +d 1 =T 1 ; @M 2 : t 2 +d 2 =T 2   
         [0045]    Referring now to  FIG. 20 , tip  100  permits the maintenance of a stable vacuum while allowing a wire or dedicated occlusion penetrating device to pass freely through lumen. Additionally, tip  100  it will not impose high drag to the wire or device during its passage regardless of the amount of vacuum. This is achieved by cooperation of the chambers divider  9  with vacuum chamber  13 , such that radial deformation is minimized and compensated for by axial deformation upon vacuum actuation. This cooperative action keeps the chambers divider lumen  13  at an almost constant diameter regardless of the surrounding under-pressure, thereby permitting the free passage of the wire or device through to the target area. 
         [0046]      FIGS. 21 through 24  illustrate steps in the method of use of the vacuum anchoring catheter. Since the vacuum anchoring catheter is a percutaneous device, it is normally introduced via a guiding catheter, so its flared tip  100  tip should be compressed to enable loading into the guiding catheter lumen. One design for loading is a sliding sleeve connected to an actuating knob at the hub. The sleeve is pushed forward to capture the flared tip and encapsulate it to fit a smaller diameter to allow the vacuum anchoring catheter to be introduced into the guiding catheter (see  FIG. 23 ). Once the vacuum anchoring catheter has reached the target occlusion, the sleeve using the knob is pulled back to expose the tip  100  to be ready for the occlusion penetrating procedure. Once the tip  100  makes contact with the target area of the occlusion, a vacuum is applied through the catheter by the withdrawal and temporary locking of a piston at the proximal end of the catheter. When the occlusion penetrating procedure is concluded, the vacuum is released and the guiding catheter is withdrawn (see  FIG. 24 ). 
         [0047]      FIGS. 25 through 27  illustrate alternate embodiments in which vacuum is self-generated and continuously built by the bending movement of the catheter. In these embodiments, tip  100  further includes embedded spring frame  20  generally encircling chambers dividing lumen  13  and extending into catheter shaft  16 . Bending of shaft  16  causes the spring frame  20  to convert the bending movement of the shaft  16  into radial expansion/contraction of the vacuum chamber wall  4 , and thereby build vacuum by increasing/decreasing the volume of vacuum chamber  12 . 
         [0048]    In preferred embodiments, the frame  20  comprises radial spring  21  and two or more pairs of asymmetrical connecting struts  22  in communication with embedded actuation wires or struts  23  within the shaft  16 . The embedded actuation wires or struts  23  within the shaft  16  are preferably located in dedicated lumens  24 . In other embodiments, the frame may comprise an uneven number of connecting struts  22  and actuation wires or struts  23 . 
         [0049]    The present description includes the best presently contemplated mode of carrying out the subject matter disclosed and claimed herein. The description is made for the purpose of illustrating the general principles of the subject matter and not be taken in a limiting sense; the subject matter can find utility in a variety of implementations without departing from the scope of the disclosure made, as will be apparent to those of skill in the art from an understanding of the principles that underlie the subject matter.