Abstract:
A method of removing vascular blockage includes providing a catheter system. comprising an outer catheter, a cutting catheter having a serrated distal end, a bypass catheter, and a guidewire. In the catheter system, the bypass catheter is slidably disposed within the cutting catheter and the outer catheter. The method includes positioning a distal end of the catheter system at a proximal end of an occlusion located within a vessel and moving the bypass catheter through the occlusion so that a medicated treatment solution may be delivered through the bypass catheter to an area of the brain or other tissue served by the vessel blocked by the occlusion. Both during and after the delivery of medicated treatment solution to the blocked part of the vessel with the bypass catheter, the physician may engage the occlusion with the cutting catheter by moving the cutting catheter in a clockwise/counterclockwise or forward/backward direction within the outer catheter, cutting and then removing at least a portion of the occlusion from the vessel.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Patent Application No. 61/361,185, filed on Jul. 2, 2010, entitled Catheter for Use in Revascularization Procedures. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This application relates in general to a revascularization catheter system and method for treating blockage or clots in cerebral blood vessels. Specifically, this application relates to a coaxial catheter system that combines a rotational cutting mechanism over a guidewire with an aspiration mechanism for retrieving clot debris and method to bypass the clot in order to prolong the patency of the patient&#39;s vessel. 
       BACKGROUND OF THE INVENTION 
       [0003]    Immediately following an acute stroke, it may be necessary to reopen an occluded cerebral blood vessel, preferably within eight hours from the initial occlusion. Manipulation of the endothelium of a cerebral blood vessel is attended by adherence of platelets, which stick to the site of injury, and subsequently release clotting factors that act as chemoattractants, both binding platelets together and provoking more clotting proteins from the blood. The result of this mechanism (platelet aggregation and activation) is the accumulation of platelets and their binding together at the site as a “white thrombus.” i.e. fibrin/platelet thrombus, which rapidly re-occludes the blood vessel. In this situation, a thrombolytic agent such as tPA will no longer be effective, as it has no activity against this different type of thrombus. Thus, conventional methods of removing occlusions in a blood vessel may not be adequate in all situations. 
       BRIEF SUMMARY 
       [0004]    A method of removing vascular blockage includes providing a catheter system, comprising an outer catheter, a cutting catheter having a serrated distal end, a bypass catheter, and a guidewire. In the catheter system, the bypass catheter is slidably disposed within the cutting catheter and the outer catheter. The method further includes positioning a distal end of the catheter system at a proximal end of an occlusion located within a vessel and moving the bypass catheter distally through the occlusion so that a medicated treatment solution may be delivered through the bypass catheter to an area of the brain or other tissue served by the vessel, which has been blocked by the occlusion. 
         [0005]    Both during and after the delivery of medicated treatment solution to the blocked part of the vessel, the physician may engage the occlusion with the cutting catheter by moving the cutting catheter in a clockwise/counterclockwise and/or forward/backward direction within the outer catheter, cutting and then removing at least a portion of the occlusion from the vessel. As the occlusion is removed from the vessel, the cutting catheter and the outer catheter may be advanced distally within the vessel. 
         [0006]    The peripherally-disposed outer catheter may include a distal end having perforations. As the occlusion is removed, the distal end of the outer catheter may be delivered to the area of occlusion, remaining within the occlusion to a varying degree, or entirely, enabling the physician to deliver medication through the perforations to a greater surface area of the occlusion. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0007]    The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate various example systems, methods, and so on, that illustrate various example embodiments of aspects of the invention. It will be appreciated that the illustrated element boundaries (e.g., boxes, groups of boxes, or other shapes) in the figures represent one example of the boundaries. One of ordinary skill in the art will appreciate that one element may be designed as multiple elements or that multiple elements may be designed as one element. An element shown as an internal component of another element may be implemented as an external component and vice versa. Furthermore, elements may not be drawn to scale. 
           [0008]      FIG. 1  is a side view of a coaxial revascularization catheter. 
           [0009]      FIG. 2  is a side view of the proximal portion of the coaxial revascularization catheter of  FIG. 1 . 
           [0010]      FIG. 3  is a side view of the coaxial revascularization catheter of  FIG. 1  disposed at an obstruction site. 
           [0011]      FIG. 4  is a side view of the coaxial revascularization catheter of  FIG. 1  disposed at an obstruction site. 
           [0012]      FIG. 5  is a side view of the coaxial revascularization catheter of  FIG. 1  disposed at an obstruction site. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    A revascularization catheter system  10  may be introduced into a patient suffering from an ischemic stroke in order to quickly and efficiently restore blood flow to an occluded area in a cerebral blood vessel, for example. Generally, the revascularization catheter system  10 , as shown in  FIG. 1 , consists of a coaxial arrangement of tubular members over a guidewire. In one embodiment. the revascularization catheter system  10  includes an outer catheter  12 , a cutting catheter  14 , a bypass catheter  16 , and a guidewire  18 . The outer catheter  12  includes a generally tubular body including a proximal end  20 , a transition portion (not shown), and a distal end  22 . 
         [0014]    Similarly, the cutting catheter  14  and the bypass catheter  16  are comprised of generally tubular bodies including proximal ends  24  and  26 , respectively, transition portions (not shown), and distal ends  28  and  30 , respectively. Each catheter has at least one lumen therein extending from the distal ends  22 ,  28 , and  30  of the tubular bodies to the proximal ends  20 ,  24 , and  26  of the tubular bodies. 
         [0015]    The bypass catheter  16  is disposed within the cutting catheter  14  and is movable, rotatable, or slidable within the cutting catheter  14 . Similarly, the cutting catheter  14  is disposed within the outer catheter  12  and is rotatable in a clockwise/counterclockwise direction and slidable in a forward/backward direction within the outer catheter  12  along a horizontal axis A. 
         [0016]    As shown in  FIG. 1 , the distal end  28  of the cutting catheter  14  may include serrated teeth  32  that can engage and break up a clot or occlusion when rotated in a clockwise/counterclockwise manner or in a forward/backward motion with regard to the cross-section of the vessel and the outer catheter  12 . The teeth  32  may be formed integrally with the distal end  28  of the cutting catheter  14  or may be formed of a different material, such as stainless steel or titanium, and attached to the distal end  28  of the cutting catheter  14  by suitable methods of attachment, such as adhesives. The rotational or forward/backward motions are generally imparted manually by the fingers of the operating surgeon under fluoroscopic visualization, or by an electrical motor outside the patient&#39;s body (not shown). 
         [0017]    The teeth  32  of the cutting catheter  14  are generally no more than about 4.0 mm in length. Moreover, the outer catheter  12  is generally no more than about 1.0 to about 4.0 mm shorter in length than the corresponding cutting catheter  14 , to prevent the teeth  32  of the cutting catheter  14  from extending too far into the vessel, unprotected by the outer catheter. This embodiment provides protection against imparting damage to the vessel wall. 
         [0018]    For intracranial applications (such as an acute stroke), the bypass catheter  16  may have a length from 150 cm to about 300 cm and may have an external diameter from 0.62 mm to 0.95 mm. The cutting catheter  14  may have an external diameter from about 0.60 mm to about 1.40 mm and the outer catheter  12  may have an external diameter from about from 0.75 mm to 1.75 mm. In general, the internal diameter of outer catheter  12  is proximate to the external diameter of cutting catheter  14 , without an intermediate catheter, and will ideally have an internal diameter from about 0.10 mm to about 0.50 mm larger than the external diameter of the cutting catheter  14 . 
         [0019]    In one embodiment, the cutting catheter  14  may have an internal diameter from about 0.40 mm to about 1.17 mm, and the outer catheter  12  may have an internal diameter from about 0.75 mm to about 1.50 mm. Moreover, the cutting catheter  14  may have a length from about 130 cm to about 150 cm. However, it should be appreciated that catheters of any suitable dimensions may be used. 
         [0020]    Cutting catheter  14 , the bypass catheter  16 , and at least one outer catheter  12 , may be color-coded or numerically coded to form a matching system. All catheters that can he used together should be similarly coded to avoid any mismatch. It is contemplated that this feature would minimize potential complications of damage to the blood vessel wall that may occur if the cutting catheter  14  is significantly longer (more than 1-4 mm) than the outer catheter  12 . 
         [0021]    The outer catheter  12 , cutting catheter  14 , and the bypass catheter  16  may all be made of a metallic material, such as stainless steel or titanium, a plastic or polymeric material, or a combination of the two. Other suitable materials are also contemplated. 
         [0022]    As referred to above, the revascularization catheter system  10  may also include one or more guidewires. The primary guidewire  18  may be coated with a hydrophilic substance and may be used for initial placement of the revascularization catheter system  10 . The primary guidewire  18  may have a length from about 180 cm to about 190 cm. A second guidewire (not shown) may be used to exchange the coaxial catheters and may be similarly constructed and have a length of about 300 cm. 
         [0023]    As shown in  FIG. 2 , the revascularization catheter system  10  may be introduced to a patient&#39;s body by inserting a bi-lumen sheath (not shown) into the patient&#39;s femoral artery. The revascularization catheter system  10 , including the outer catheter  12 , the cutting catheter  14 , and the bypass catheter  16  may then be, in the case of a stroke patient, navigated through the first lumen of the sheath into the femoral artery, up and around the arch of the aorta, into the carotid or vertebral artery, to the skull base, and deployed at the site of the arterial occlusion in the cerebral arteries. A guidewire  18  may be used to deploy the coaxial catheters  12 ,  14 , and  16 . 
         [0024]    It should be noted that while the bypass catheter  16 , the cutting catheter  14 , and outer catheter  12 , are navigated through the body and positioned at the site of the occlusion, pressurized (at approximately 300 mm Hg) and/or heparinized saline is pumped through all of the lumen of the catheters  12 ,  14 , and  16 . The influx of the heparinized saline prevents blood and other potential debris, such as emboli, from entering and clogging the catheters. In one embodiment, the catheters each have at least one inlet portal, shown in  FIGS. 2  as  34 ,  36 , and  38 , that generally include luer locks. The inlet portals  34 ,  336 , and  38  be connected to a saline or other treatment solution source with rotating hemostatic valves  34   a,    36   a,  and  38   a,  or other such suitable connection devices. 
         [0025]      FIG. 3  and  FIG. 4  show the revascularization catheter system  10  in successive positions in relation to an occlusion  40  in a vessel  42 .  FIG. 3  shows the bypass catheter  16  the cutting catheter  14 , and the outer catheter  12  disposed within the vessel  42  and positioned at proximal end of an occlusion  40 , while a segment of the guidewire  18  extends through the occlusion  40 .  FIG. 4  shows a portion of the bypass catheter  16  extending through the occlusion  40  along the guidewire  18 . 
         [0026]    As shown in  FIG. 4 , the bypass catheter  16  may be advanced distally past the occlusion  40  to deliver arterialized blood beyond the offending obstruction to a blood starved region of the brain. By using the bypass catheter  16  to deliver blood to the brain, the amount of time that the physician has to reestablish blood flow to the patient&#39;s ischemic brain is increased dramatically. 
         [0027]    Once the bypass catheter  16  is moved through the occlusion  40 , the physician may begin to pump blood through the bypass catheter  16  to the portion of the brain that has been deprived due to an ischemic incident. The blood may be delivered to the bypass catheter  16  through second inlet opening  44  (as shown in  FIG. 2 ). In one embodiment, a second (output) portal in the sheath (not shown) may be used to re route blood from the femoral artery into the bypass catheter  16 . 
         [0028]    Alternatively, an injection of arterialized blood with heparinized pressurized saline may be administered through the bypass catheter  16  through the second inlet portal  44  by withdrawing the patient&#39;s own blood from the femoral artery into a syringe (not shown) and mixing the blood with heparinized saline. 
         [0029]    Generally, the bypass catheter  16  may extend considerably (up to 10 cm) farther beyond the cutting catheter  14  and the outer catheter  12  in order to effectuate the bypass method. In addition to the arterialized blood, thrombolytic agents, cold plasma, and saline may be administered past the occlusion in the manner described above. The cold plasma may be used to create regionalized hypothermia, extending the time the surgeon may have to effectively remove the offending obstruction. 
         [0030]    After delivering the arterialized blood through the bypass catheter  16  for approximately five minutes, the bypass catheter may be removed and cutting catheter  14  may be used to remove a core of the occlusion  40 . 
         [0031]    With rotational and axial movement of the teeth  32  at the distal end  28  of the cutting catheter  14 , the physician begins to sculpt a core section of the occlusion  40  and create small emboli. The torsional/rotational sculpting maneuver, in additional to the axial movement of the cutting catheter  14 , facilitates the distal progress of the cutting catheter  14  into the vessel  42 , continuously breaking up the offending occlusion  40 . After the sculpting maneuver is performed, the cutting catheter  14 , bypass catheter  16 , and the primary guidewire  18  may be removed from the vessel  42 , leaving the outer catheter  12  in place for delivery of medicine, blood, or other fluid to the ischemic portion of the vessel  42 . 
         [0032]    In this embodiment, once the physician begins to cut the occlusion  40 , the pressurized saline within the cutting catheter  14  and the outer catheter  12  should be discontinued, so that the disrupted emboli are not flushed further into the vessel  42 . A negative pressure may be applied to the lumen within the cutting catheter  14 . The pressure may be imparted by a negative-pressure pump or by the operator, using a syringe with a flow-limiting valve. The negative pressure generated will generally be less than the pressure required to collapse the walls of the involved blood vessel. 
         [0033]    In another embodiment, emboli created by the sculpting maneuver may also be treated using repeated doses of thrombolytic or platelet antagonist medication, depending on the nature of the obstruction. The medication may be delivered through the lumen of the cutting catheter  14 . 
         [0034]    The bypass procedure described above may be repeated for as many times as necessary, alternating the use of the cutting catheter  14  for about ten minutes with the use of the bypass catheter  16  to administer an arterialized blood mixture for about 5 minutes. Moreover, because the bypass catheter  16  and the cutting catheter  14  have separate and distinct lumina, the bypass catheter  16  may remain in place while the cutting catheter  14  is used to engage and remove at least a portion of the occlusion  40 . Therefore, in another embodiment, the bypass catheter  16  may be made to function simultaneously with the use of the cutting catheter  14 . 
         [0035]    As shown in FIGS.  1  and  3 - 5 , the distal end  22  of the outer catheter  12  includes a diffusion portion  46  having multiple perforations  48 . The perforations  48  provide fluid communication from the lumen of the outer catheter  12  to the vessel  42  wall. It is also contemplated that the perforations  46  may extend beyond the distal end  22  of the outer catheter  12 . 
         [0036]    The outer catheter  12  is peripherally disposed around the cutting catheter  14  and may be closed at its distal end  22 . The closure of the distal end  22  may be accomplished by tapering the distal end  22  of the outer catheter  12  to meet the outer diameter of the cutting catheter  14 . The cutting catheter  14 , however, will still be rotatable within the outer catheter  12 . 
         [0037]    Referring again to  FIG. 5 , as the cutting catheter  14  is used to remove portions of the occlusion  40 , the cutting catheter  14  and the outer catheter  12  may be moved distally within the vessel  42 . As the cutting catheter  14  and outer catheter  12  are moved through the vessel  42 , the diffusion portion  46  of the outer catheter  12  may be positioned within the occlusion  40  for the duration of the treatment. The diffusion portion  46  may also include radiographic markers  50   a  and  50   b,  as those shown in  FIG. 5 . The radiographic markers may include radiopaque rings or embedded pellets, among other suitable markers. Although it would be helpful to know a priori the length of the actual occlusion, not knowing the length does not limit the use of the revascularization catheter system  10 , as it can become known simultaneously with initialization of thrombolysis. 
         [0038]    Once the diffusion portion  46  of the outer catheter  12  is positioned within the occlusion  40 , the negative pressure being applied to the lumen of the cutting catheter  14  can be discontinued so that a medicated treatment solution can be introduced directly to the remaining occlusion  40  through the diffusion portion  46  of the outer catheter  12 . This system of localized, distributed administration of medication through the distal end  22  of the cutting catheter  14  and the perforations  48  in the diffusion portion  46  exposes a greater surface area of the target occlusion  40  to the medicated treatment solution, such as a thrombolytic agent, antiplatelet agent, or nitrovasodilator (i.e. a nitric oxide-based medication). The localized delivery of thrombolytic agent, antiplatelet agent, or nitrovasodilator through the diffusion portion  46  will remove or reduce the size of the occlusion  40 , thereby increasing the size of the lumen of the occluded vessel  42  to improve blood flow there through. 
         [0039]    In the case of administration of nitric, oxide-based vasodilator, the effect is one of distributing vasodilator medication to a segment of occluded vessel, allowing localized vasodilation and helping to liberate the vessel wall from the occlusive thrombus by allowing it to expand away from the latter. 
         [0040]    The diffusion portion  46  may also be used to deliver intralesional medication, especially thrombolytic medication for dissolving the lesion, and/or vasodilator medication for increasing the width of the vessel  42  at the site of obstruction. The diffusion portion  46  also may be used to deliver medication, such as antiplatelet (2B3A glycoprotein receptor blocker) or vasodilator medication, to a chosen segment of a blood vessel. 
         [0041]    Once the revascularization catheter system  10 , as shown in  FIG. 5 , has been used to remove a portion of the occlusion  40 , the cutting catheter  14  may be used to impart localized fluid-mediated hypothermia by delivering a pressurized cooling solution beyond the occlusion. The solution may generally include a heparinized pressured saline and/or a blood/oxygenated compound that is delivered to produce localized regional hypothermia to the brain via the bloodstream. In this embodiment, the heparinized pressured saline component of the solution is cooled before it is introduced into the revascularization catheter system  10 , either by itself or in combination with the oxygen-carrying compound (usually blood). It is contemplated that any suitable method of cooling the solution may be used, such as by a thermostat-controlled refrigeration device outside of the patient&#39;s body. 
         [0042]    In another embodiment, after the cutting catheter  14  has removed a portion of the occlusion  40 , the cutting catheter  14  may be removed and replaced with a second cutting catheter (not shown) of larger diameter within the outer catheter  12 . In this manner, the core of occlusion  40  created by the cutting catheters may be progressively removed. This concept of removal of the cutting catheter  14  and its replacement with cutting catheters of ever-increasing outer diameter will create a progressive increase in luminal diameter in the blocked artery, while avoiding unnecessary disruption of the vessel  42  wall that is created by stripping portions of the occlusion  40  away in its entirety. 
         [0043]    In yet another embodiment, the revascularization catheter system  10  shown in  FIG. 1  can be constructed with a second outer catheter (not shown). The support provided by the tri-axial arrangement allows the revascularization catheter system  10  to be used for distal penetration into a cerebral vessel. Once the revascularization catheter system  10  engages the offending occlusion  40  with the serrated distal end  28  of the cutting catheter  14 , the revascularization catheter system  10  can be disassembled by removing the second outer catheter, leaving only the first outer catheter  12 , the cutting catheter  14 , the bypass catheter  16 , and the primary guidewire  18  disposed within the larger lumen of the first outer catheter  12 . This embodiment provides a larger lumen through which the obstructing emboli can be aspirated or captured or through which specific medication may be delivered. 
         [0044]    It is also contemplated that the revascularization catheter system  10  may be used without the bypass catheter  16 . In addition, it is contemplated that the revascularization catheter system  10  may be used for both intracranial and peripheral (limb, ischemic bowel, organ ischemia) situations characterized by vascular insufficiency. One such embodiment may be used to treat cardiac ischemia, by insertion into a coronary artery and utilizing endovascular bypass, clot removal and localized medication delivery functions of the system. It may also be used in venous vasculature, for situations of venous obstruction or insufficiency. 
         [0045]    While example methods and compositions have been illustrated by describing examples, and while the examples have been described in considerable detail, it is not the intention of the applicant o restrict or in any way limit the scope of the appended claims to such detail. It is, of course, not possible to describe e every conceivable combination of components or methodologies for purposes of describing the systems, methods, devices, and so on, described herein. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention is not limited to the specific details, the representative evascularization catheter system  10 , and illustrative examples shown and described. Thus, this application is intended to embrace alterations, modifications, and variations that fall within the scope of the appended claims. Furthermore, the preceding description is not meant to limit the scope of the invention. Rather, the scope of the invention is to be determined by the appended claims and their equivalents.