Patent Publication Number: US-2019175210-A1

Title: Thrombectomy catheter and a device comprising the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation application of U.S. non-provisional application having the Ser. No. 12/999,104, filed Jun. 19, 2008, which claims priority to and filed under 35 U.S.C. 371 as a U.S. national phase application of PCT/NL2008/050399, having international filing date of Jun. 19, 2008. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to a thrombectomy catheter comprising a distal end for at least partially removing thrombus from a blood vessel, said distal end being conceived to undergo displacement along the blood vessel. The invention further relates to a thrombectomy device. 
     BACKGROUND OF THE INVENTION 
     Venous thrombosis, in particular, deep venous thrombosis is a disease with significant incidence in the Western world, affecting 1-2 per 1000 individual annually. When untreated, severe complications may occur, ranging from redness, swelling and pain, due to venous obstruction, to fatal pulmonary embolism. 
     Concurrently, preferable treatment of the venous thrombosis and/or deep venous thrombosis relates to minimally invasive endovascular interventions. For example, a thrombectomy catheter may be introduced in the affected vein to cause mechanical destruction of the thrombotic tissue and removal thereof from the vein. 
     An embodiment of a thrombectomy catheter is known from U.S. 2003/0055445. The known thrombectomy catheter is arranged to at least partially remove obstructive material from vasculature and comprises an elongated body having a lumen propagating from a proximal end of the catheter to a sub-distal end of the catheter for receiving pieces of obstructive material destroyed by a morcellator arranged at a distal end of the catheter. The morcellator of the known thrombectomy catheter comprises a rotatable body arranged inside a static cage. The morcellator is provided as a suitable bundle of cooperating wires, which may together with the static cage be alternated from a substantially collapsed state to a substantially expanded state. The substantially collapsed state is practical for introducing the distal portion of the known thrombectomy catheter intravascularly. For purposes of collecting and destroying thrombotic tissue, the morcellator is expanded in use. 
     It is a disadvantage of the known thrombectomy catheter that substantially low efficiency of thrombosis removal is achievable. First, due to the fact that the rotating morcellator is arranged inside the outer static cage a substantially small volume is left between the morcellator and the surface of the cage for receiving thrombus. This may have an effect that the known thrombectomy catheter has to be substantially slowly displaced inside a blood vessel thereby increasing time necessary to complete the intervention. Secondly, due to the fact that the outer static cage is implemented as a wire-frame having openings throughout substantially the whole surface of the cage, it is possible that thrombus may exit the cage through such openings before it comes into contact with the morcellator. This may lead to a mere perforation of thrombus instead of removal thereof and, therefore, may further decrease efficacy of the known thrombectomy catheter necessitating the intervention to be repeated to pick up leftovers of thrombus. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide a thrombectomy catheter having an increased efficiency for removal of thrombus. 
     To this end a thrombectomy catheter according to the invention comprises a lumen being arranged for collecting thrombus and having a cross-section which is alterable from a collapsed state to an expanded state, wherein during displacement of the distal end the cross-section of the lumen is self-adjustable for substantially matching local cross-sectional dimensions of the blood vessel. 
     The technical measure of the invention is based on the insight that by providing a lumen with a controllable cross-section substantially at the distal end of the catheter, efficacy of removal of thrombus from the blood vessel is increased. In particular, the lumen may be arranged to be in a collapsed state for enabling due introduction of the catheter into the blood vessel. When it is established that the distal end of the thrombectomy catheter is positioned substantially nearby a thrombotic tissue, the lumen may be expanded to increase its cross-section and to cause an outer surface of the lumen to come into contact with the blood vessel. Under displacement of the catheter with the thus expanded lumen along the blood vessel the lumen may act as a scoop thereby removing the thrombotic tissue from a surface of the blood vessel. After completion of this procedure the lumen of the thrombectomy catheter may be again collapsed for simplifying its removal from the vasculature. 
     Preferably, the thrombectomy catheter according to the invention is formed by a tubular structure running from a proximal end of the catheter to the distal end of the catheter, the lumen forming integral part of said tubular structure. Thus, the expandable lumen acting as a scoop is integrated with the overall lumen of the catheter. Therefore, no extra manufacturing steps are required for providing such lumen. Preferably, the lumen is manufactured from a smooth material, like latex, or the like to ease its displacement along inner periphery of the blood vessel. 
     It has been found that a substantial decrease of time required for intervention is achieved with the thrombectomy catheter according to the invention. For example, it may be possible to successfully accomplish thrombectomy of at least axillary, brachial, iliac, femoral, tibial, popliteal, great saphenous, small saphenous, jugual and basilic veins within about half an hour. 
     In addition, the thrombectomy catheter according to the invention is particularly suited for treating veins located in the lower extremities, as during collecting of thrombus the catheter is conceived to be uni-directionally displaced in a direction not compromising the vascular valves, thereby causing no disruption thereof. When the thrombectomy treatment is accomplished, the catheter&#39;s lumen may be collapsed and the thrombectomy catheter may be removed from the vasculature. Preferably, the veins located in the lower extremities are treated via a small incision in a knee cavity. 
     It will be appreciated that an embodiment of a thrombectomy catheter comprising a capture cone is known from U.S. Pat. No. 7,220,269. The known thrombectomy catheter comprises an occluder, i.e., an inflatable balloon arranged at the distal end of the catheter. Proximally to the occluder in a sub-distal region of the catheter the capture cone is positioned, which is arranged to stationary dwell at a selected position in a blood vessel. During use, the known catheter is positioned inside the blood vessel so that thrombus is positioned between the cone and the occluder. For purposes of removing thrombus, the occluder is displaced towards the capture cone thereby pushing thrombus into the capture cone for collecting thereof. 
     The thrombectomy catheter known from U.S. Pat. No. 7,220,269 has the following disadvantages. First, low efficiency regarding removal of thrombus is obtainable, because the occluder is a smooth body which in fact may slip on the surface of thrombus by-passing it. Secondly, the known thrombectomy catheter may be not suited for treating elongated thrombi, because forces exerted by a substantially distantly located occluder may be not sufficient to cause thrombus to separate from inner periphery of the blood vessel and to penetrate the capture cone. Next, the capture cone is conceived to be manufactured separately and to be laminated to the distal end of the capture catheter which forms part of the known thrombectomy catheter. This may limit forces exertable on the capture cone to avoid delamination thereof on one hand, and leads to increase of manufacturing costs, on the other hand. Finally, the known thrombectomy catheter is not suitable for treating thrombi in lower extremities, because the occluder is to be displaced bi-directionally, namely in one direction during introduction thereof and in the opposite direction during pushing thrombus into the capture cone. Such bi-directional displacement may harm valves located in the veins of the lower extremities, leading to unacceptable medical complications. 
     In an embodiment of the thrombectomy catheter according to the invention the cross-section of the lumen in the expanded state is settable to a larger value than local cross-sectional dimensions of the blood vessel for stretching the blood vessel. 
     It is found that when the cross-section of the lumen of the thrombectomy catheter according to the invention is set to about 10% larger value than a local cross-section of the blood vessel a further increase of efficacy of removal of thrombus is obtained. 
     Preferably, the lumen is pre-tensioned for assisting transition between the collapsed state and the expanded state and/or for assisting is said stretching. This feature may be enabled by providing an expandable, substantially rigid body in the lumen. For example, a suitable wire or a wired structure may be used for this purpose. The wire or a wired structure may be integrated in a material of the lumen. Alternatively, the wire or the wired structure may be received by the lumen or may suitably be affixed to an inner surface of the lumen. Such wire or a wired structure may bias the lumen for exerting radial forces causing radial expansion of the lumen. In a collapsed state such forces may be not present, or may suitably be counteracted to prevent the lumen from expanding. Upon actuation causing a radial expansion of the lumen or upon removal of the counteracting forces the lumen undergoes transition to an expanded state. 
     In an embodiment of the thrombectomy catheter according to the invention the lumen comprises folded regions which are arranged to radially unfold for enabling a transition from the collapsed state to the expanded state. 
     This feature is based on the insight that it is preferable to provide a thrombectomy catheter having a substantially maximized cross-section of the distal end. It may be a case that the cross-section of an elastic lumen in it&#39;s expanded state may be limited by the elasticity of the material of the lumen, especially when the lumen forms an integral part of an overall material of the catheter. In order to enable still greater cross-sections of the lumen in comparison with those which may be obtainable by stretching, for example, a 7 F, 8 F, 9 ; F or a 10 F catheter, the lumen at the distal end may comprise a number of folded regions, which are conceived to be unfolded in the expanded state. For example, such regions may be arranged with an actuator, for example a shape memory alloy (SMA) wire, which may be conceived to be bent in use exerting radial forces on the folded regions and causing unfolding thereof. In this way, when the SMA wire is at rest the regions are at least partially folded and the distal end of the thrombectomy catheter is in its collapsed state. In use, when the wire is actuated, for example by means of application of an electric current, the wire undergoes a controllable bend causing the folded regions to radially unfold for enabling the expanded state with an increased cross-section. It will be appreciated that the lumen of the thrombectomy catheter comprising foldable regions may be manufacture from either stretchable or from non-stretchable material. 
     In an embodiment of the thrombectomy catheter according to the invention the lumen is arranged to cooperate with an actuatable unit for undergoing said alteration. 
     It is found to be preferable to alternate from the collapsed state to the expanded state of the lumen positioned at the distal end of the thrombectomy catheter using a suitable actuator. SMA materials may be used for this purpose, because they may be arranged to have two stable configurations, a first configuration corresponding to a collapsed state of the lumen and a second configuration corresponding to the expanded state of the lumen. Preferably, the lumen at least partially comprises the actuatable unit. 
     For example, the actuatable unit may relate to a cage or a wire-frame. Preferably, the actuatable unit comprises a cage or a wire-frame at least partially covered by a cover member, the cage or the wire-frame being collapsed when substantially covered by the cover member and being expanded when substantially exposed. 
     For example, the cover member may relate to a retractable catheter sheet. This embodiment has an advantage that no electric current is needed for actuating the cross-section of the lumen, eliminating electric hazard for a patient. 
     In an embodiment of the thrombectomy catheter according to the invention the wire-frame is partially received by the lumen, the wire-frame being cone-shaped at least in a region distally from the lumen. 
     It is found to be advantageous to provide the wire-frame distally to the lumen for assisting in protruding through thrombus. It will be appreciated that such wire frame does not hamper a substantially frontal penetration of the lumen by thrombus and, thus, does not decrease efficacy of the thrombectomy catheter. The extending cone of the wire-frame may be arranged with substantially sharpened wires for cutting through the thrombus, still further improving efficacy of the intervention. 
     In a still further embodiment of the thrombectomy catheter according to the invention at least an outer surface of the lumen conceived to contact the blood vessel comprises an anti-friction agent. 
     It is found to be advantageous to provide, preferably to coat, the outer surface of at least the distal end of the thrombectomy catheter with an anti-friction agent for further decreasing a mechanical resistance of the blood vessel to displacement of the catheter. This may lead to a decrease of damage risk for the inner periphery of the blood vessel, on one hand, and to increase of efficacy of the intervention, on the other hand. It will be appreciated that it lies within an ordinary skill of the artisan to select a suitable material for anti-friction agent. 
     In a still further embodiment of the thrombectomy catheter according to the invention the lumen further comprises a morcellator for at least partially destructing thrombus received by the lumen. 
     It is found to be advantageous to still further increase the efficacy of the thrombectomy intervention by providing the catheter with supplementary means for destroying thrombus. For example, the morcellator may comprise a suitable rotational body for mechanically cutting the tissue received by the lumen. 
     In a still further embodiment of the thrombectomy catheter according to the invention, the catheter is arranged with a drug deposition system conceived to act on thrombus. 
     For example, suitable chemical thrombolysis agents may be injected via a supplementary lumen of the catheter to at least partially dissolve the thrombotic tissue prior to or simultaneously with displacement of the lumen along the blood vessel. 
     A thrombectomy device according to the invention comprises a thrombectomy catheter as described with reference to the foregoing. 
     These and other aspects of the invention will be discussed in more detail with reference to the figures, wherein like reference signs correspond to like elements. It will be appreciated that figures are presented for illustrative purposes and may not be used for limiting the scope of the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  presents a schematic view of an embodiment of the thrombectomy catheter according to the invention. 
         FIG. 2  presents a schematic view of a further embodiment of the thrombectomy catheter according to the invention. 
         FIG. 3  presents a schematic view of a still further embodiment of the thrombectomy catheter according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
       FIG. 1  presents a schematic view of an embodiment of the thrombectomy catheter according to the invention. The thrombectomy catheter  10  may be used during minimally invasive thrombectomy, wherein the catheter is displaced along the inner periphery of a blood vessel  4 , for example a lower extremity vein, to at least partially remove and collect thrombi T. The thrombectomy catheter  10  may be used for at least partially, preferably substantially, removing venous thrombus and/or deep venous thrombus. 
     The thrombectomy catheter  10  comprises a lumen  3  arranged at the distal end D of the catheter, wherein said lumen is alterable between a collapsed state (now shown) and an expanded state S 2 . For this purpose the lumen  3  may cooperate with an actuatable unit  8 , which may be conceived to be collapsed at rest and to expand at use exerting radial forces to the lumen  3  causing radial expansion thereof. The actuatable unit  8  may relate to any suitable wire or a wire-frame configuration, comprising but not limited to a set of longitudinally arranged wire strips, a ring  8 , a cage or any other suitable structure. Preferably, the actuatable unit is preserved at its collapsed condition at rest by the cover sheet  2  having a smaller cross-section S 1 . The actuactable unit  8  together with the lumen  3  may substantially be confined within the smaller cross-section S 1 . Preferably, the cross-section S 1  corresponds to a standard intravascular cross-section corresponding to 7 F-10 F catheters. It will be appreciated that invention may be practiced on catheters having different dimensions. 
     It will be appreciated that the thrombectomy catheter according to the invention having the increased cross-section S 2  is conceived to be uni-directionally displaced along the blood vessel  4 . In this case no damage is caused to the valves  6   a ,  6   b  present in the lower extremity veins. When the intervention is completed the cross-section of the lumen  3  is reduced to the original cross-section S 1 , for example by positioning the retractable cover sheet  2  over the distal end D of the catheter  10 . 
     The thrombectomy catheter  10  comprises a tubular structure  1  running from a proximal end P to a distal end D and terminating at the distal end D with a lumen  3 , which may be altered from a substantially collapsed cross-section S 1  to a substantially extended cross-section S 2 . The lumen  3  forms preferably an integral part of the tubular structure  1 . 
     In accordance with an aspect of the invention, the cross-section S 2  of the lumen  3  at the distal portion D is conceived to be self-adjustable at least to substantially match cross-sectional dimensions D 1 , D 2 , D 3 , etc of the inner periphery of the blood vessel  4 . It is found that next to a consistent difference in cross-sectional sizes between a proximal part of a vessel D 1  and a distal part of the vessel D 3 , also local size differences D 2  may occur. By arranging the distal portion  3  of the catheter with a lumen having an increased cross-sectional dimension S 2 , which is self-adjustable to a local cross-section of the blood vessel a substantially continuous contact between the lumen  3  and the inner periphery of the blood vessel  4  is maintained. In this way the lumen  3  may act as an efficient scoop for efficiently collecting thrombi T encountered by the lumen  3  along its displacement through the blood vessel  4 . In order to facilitate said displacement a guide wire  7  may be provided. 
       FIG. 2  presents a schematic view of a further embodiment of the thrombectomy catheter according to the invention. In this particular embodiment the thrombectomy catheter, discussed with reference to  FIG. 1 , the lumen  3  is provided with an actuator unit  5 , which may be partially received by the lumen. The actuator  5  may relate to any suitable wire-frame comprising any shape memory alloy. In this case the actuator unit is arranged to assist the lumen  3  in maintaining the desired expanded cross-section S 2 , even when substantially obstructed blood vessels having substantially elongated thrombi T are to be treated. 
     Preferably, the actuator  5  has a cage form, allowing for a substantially frontal penetration the lumen  3  by thrombus. The cage  5  is collapsible when the cover sheet  2  is positioned substantially over the lumen  3 . Due to the shape memory characteristic, the cage  5  will expand (as shown), when the cover sheet  2  is retracted exposing the cage  5 . When thrombus T 1  is received by the lumen  3  it may be destroyed by a morcellator  9  arranged proximally to the lumen  3 . Any suitable morcellator known in the art may be suitable for this purpose. 
     Optionally, the catheter  10  may further comprise a further lumen (not shown) arranged to deposit a suitable chemical thrombolysis agent for at least partially dissolving thrombus. 
       FIG. 3  presents a schematic view of a still further embodiment of the thrombectomy catheter according to the invention. The thrombectomy catheter, shown in view  30  is arranged in its expanded state, having a substantially enlarged cross-section S 2 ′ with respect to the cross-section S 1 ′ of the proximal part of the catheter. In order to facilitate an increase or a superior increase of the cross-section of the distal portion D, the lumen  3  in the distal portion is provided with foldable regions  36 ,  38 . Although two such regions are shown in view  30 , it will be appreciated that any suitable number of the foldable regions may be provided. The foldable regions  36 ,  38  may be provided with an actuator in the form of a SMA wire  32 ,  34 , each wire being conceived to undergo controlled bending upon actuation by an electric current. In this way the SMA wires  32 ,  34  exert radial force to the folded regions and unfold them yielding expanded regions  36 ,  38 . This results in providing a lumen  3  with a substantially increased cross-section S 2 ′ with respect to the cross-section S 1 ′ at rest. The foldable regions may be manufactured from a stretchable material or from a non-stretchable material. 
     View  35  shows schematically the thrombectomy catheter according to the invention at rest, when the SMA wires  32 ,  34  are not actuated. The foldable regions  36 ′,  38 ′ are accordingly folded and the lumen  3  at the distal end D of the catheter has cross-section S 3 ′ which may be as small as the cross-section of the proximal portion S 1 ′. Alternatively, the foldable regions  36 ′,  38 ′ may be arranged to fold in a button-like way, so that the cross-section S 3 ′ is smaller than the cross-section S 1 ′, which substantially improves catheter intravascular maneuverability. 
     It will be appreciated that although specific embodiments of the thrombectomy catheter according to the invention are discussed separately for clarity purposes, interchangeability of compatible features discussed with reference to isolated figures is envisaged. While specific embodiments have been described above, it will be appreciated that the invention may be practiced otherwise than as described. The descriptions above are intended to be illustrative, not limiting. Thus, it will be apparent to one skilled in the art that modifications may be made to the invention as described in the foregoing without departing from the scope of the claims set out below.