Expandable oral suction type blood clot collection catheter

Abstract

To provide a system for retrieving an obstruction in a blood vessel.SOLUTION: A system has an outer catheter and an inner aspirating clot retrieval catheter. The inner aspirating clot retrieval catheter has an expansile distal tip for flow restriction and improved aspiration efficiency, and a large mouth into which a clot or other obstructions can be retrieved. The clot retrieval catheter can have a support tube proximal to the tip. The expansile tip can be a strut framework, and a flexible low-modulus cover is disposed around at least a portion of the tip strut framework and the proximal support tube. The distal end of the tip can be encapsulated by a low-friction elastomeric lip for atraumatic contact with walls of a blood vessel. The tip has a collapsed delivery configuration and expands radially into a deployed configuration. The tip strut framework, support tube and cover can all have characteristics which enhance the deliverability of the clot retrieval catheter to a target.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention generally relates to devices and methods for removing acute occlusions from blood vessels during endovascular medical procedures. More specifically, the present disclosure relates to aspiration retrieval catheters.

Background Art

[0002] Thrombus retrieval catheters and devices are often used for mechanical thrombus removal during endovascular interventions when a patient is suffering from conditions such as acute ischemic stroke (AIS), myocardial infarction (MI), and pulmonary embolism (PE). Accessing remote regions such as the neurovascular bed is difficult with conventional techniques when the target vessel is small in diameter, distant from the insertion site, and highly tortuous.

[0003] The thrombus itself can complicate the procedure by assuming a number of complex forms and consistencies, ranging from a simple tubular structure that conforms to the shape of the blood vessel to a long, strand-like configuration that can span multiple blood vessels at once. The age of a clot can also affect its extensibility, with older clots tending to be less compressible than fresh clots. Clots rich in fibrin also present challenges in that they do not adhere effectively and can have an adhesive property that allows the clot to rotate along the outer surface of a mechanical thrombus removal device. Combinations of soft and firm thrombus regions can also separate during aspiration, with fragmentation leading to distal embolization, which can occur within blood vessels that are inaccessible with currently available devices. Additionally, disrupting the junctions that adhere the thrombus to the blood vessel wall without damaging the delicate blood vessels is a significantly difficult task.

[0004] Conventional blood clot retrieval catheters, particularly those designed to operate within the neurovascular system, can suffer from a number of drawbacks. First, the diameter of the catheter itself must be small enough to avoid causing significant discomfort to the patient. The catheter must also be sufficiently flexible to navigate the vasculature and withstand high strains while providing smooth advancement along the path, yet have axial stiffness. Once at the target site, the typical objects to be retrieved from the body can be substantially larger in size than the catheter tip, making it more difficult to retrieve the object at the tip. For example, fibrin-rich blood clots can often become lodged within the tip of conventional fixed-orifice catheters, making extraction difficult. This blockage can sometimes shear off softer portions of the clot from the firm area, resulting in distal embolization.

[0005] The small diameter and fixed tip size can also be less efficient in inducing the suction necessary to remove blood and thrombus material during the procedure. The suction must be strong enough to hold at least any fragmentation that occurs by using a mechanical thrombectomy device or other method, stationary, such that the fragments cannot move and occlude the distal vessel. However, when suctioning with a conventional fixed-orifice catheter, a significant portion of the suction flow will come from the vascular fluid proximal to the tip of the catheter where there is no blood clot. This significantly reduces the suction efficiency and the success rate of blood clot removal. SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0006] The disclosed design aims to provide an improved suction retrieval catheter that addresses the above deficiencies. MEANS FOR SOLVING THE PROBLEMS

[0007] The object of the present invention is to be designed to provide a system, apparatus, and method that meet the above-mentioned needs. The design features a suction blood clot retrieval catheter that has an expandable mouth facing the blood clot for flow restriction of the blood clot, suction efficiency, and easy retrieval, while also having a collapsed state that is low-profile and flexible enough for delivery with a standard sheath or outer catheter. The catheter can also have an adjusted variable stiffness body section that incorporates enhanced deliverability compared to existing designs and is capable of navigating the tortuous areas of the vasculature to reach occlusive blood clots.

[0008] According to the present invention, there is provided a system that can have an outer catheter that facilitates the introduction of a microcatheter, guidewire, or any of several commercially available products to a target site within a vasculature. The outer catheter may be, for example, a guiding catheter or an intermediate catheter. A suction blood clot retrieval catheter having an expandable distal tip may be within the outer catheter. In one embodiment, the blood clot retrieval catheter is a rapid-exchange (RX) type catheter having an expandable distal tip. The RX device can provide advantages over many over-the-wire type products that can be time-consuming to exchange, have components that extend beyond the sterile field, and can add a risk of contamination.

[0009] The blood clot retrieval catheter can have a proximal end, a distal end located at the mouth of the tip, a proximal port, and an internal lumen that extends proximally from the distal end and terminates at the port. The catheter lumen can be defined by a tubular support structure and configured to pass therethrough a guidewire, a microcatheter, a mechanical thrombectomy device such as a stent retrieval device, and other such devices. The lumen can also direct suction from the proximal end of the outer catheter to the expandable distal tip of the blood clot retrieval catheter. The blood clot retrieval catheter can also have a shaft that extends proximally from the port.

[0010] The blood clot retrieval catheter may have a self-expanding tip disposed at the distal end of the catheter. The tip can have a collapsed delivery configuration and a radially expanded deployed configuration in which the tip is substantially conical or funnel-shaped. In the collapsed state, the tip can be folded during delivery and share a common radial dimension with the outer catheter when constrained, and the radial dimension is smaller than the maximum radial dimension of the tip when in the expanded deployed state. The tip can have an open distal port, and at least a portion of the tip can have a maximum radial dimension in the expanded deployed configuration that is larger than the inner diameter of the outer catheter.

[0011] The expandable tip can be connected at its proximal end to a support tube configured around the longitudinal axis of the blood clot retrieval catheter that defines the inner lumen of the catheter. The support tube can have one or more longitudinally extending longitudinal spines and a series of loop ribs extending laterally at various lengths and at various lengths. The ribs and spines can be formed monolithically through laser machining of a single hypo tube or can be a structure of metal braided wire or coiled wire. The spines can be fixedly connected to or integrally formed with the support arms or connecting struts of the expandable tip.

[0012] In one embodiment, the support tube shares a common radial dimension with the length of the expandable tip when the tip is in the collapsed delivery configuration. When deployed, the tip can expand radially outward of the support tube. A section of the support tube near the proximal end can be flared or sized to a larger diameter to block the flow within the lumen between the outer catheter and the blood clot retrieval catheter.

[0013] The expandable tip can have a support structure having a plurality of struts formed within a porous framework that can include closed cells, loops, or undulations. A plurality of distal crowns can form the outer periphery of the tip opening. The struts of the support arms can connect adjacent crowns that intersect at the proximal crown trough, and the support arms can extend proximally from the crown trough to connect the expandable tip and the support tube.

[0014] The support arms can be axisymmetric with the longitudinal axis of the catheter, or can be wound or placed spirally around the axis. The individual support arms can be attached independently, or can extend from or be aligned with one of one or more axial spines of the support tube. The struts of the crown and support arms can contain features such as narrow segments, curves, and / or undulations to enhance the flexibility of the structure. When in a collapsed delivery configuration, the proximal crown trough may serve as a hinge around which the strut framework folds. When folded in the delivery configuration, at least a portion of the expandable tip shares a common radial dimension with the support tube.

[0015] The strut framework can be a cut pattern of sheet or tube of stainless steel or a superelastic shape memory alloy such as nitinol. The shape of the framework can be such that the profile of the tip in the deployed configuration is radially outwardly flared to have a portion that is in substantially contact with the vessel wall. Upon expansion, at least a portion of the tip assumes the maximum radial size of the expandable tip. The funnel shape formed by the tip can improve suction efficiency, reduce friction, and reduce the risk of vascular trauma due to snagging at the vessel opening. The funnel shape also means that in the deployed state, the expandable tip is tapered such that the proximal end of the tip has a first radial dimension and a more distal portion of the tip has a second radial dimension that is greater than the first radial dimension. The second radial dimension may be greater than the diameter of the target vessel.

[0016] In another embodiment, the crown of the tip framework can form a more atraumatic profile by curving radially inwardly at the distal opening. In this situation, the distal crown apex can have a radial dimension between the first radial dimension and the maximum radial size of the expandable tip.

[0017] One or more support arms or struts of the band may connect the tip framework and the support tube either directly or indirectly through a snap or another loose mechanical joint. The support arms may be connected via a single axial connecting strut or may extend individually and independently from the base strut or the most distal rib of the support tube. The support arms can have a pattern that increases flexibility, such as undulating or expandable cells. In one embodiment, the tip and the support tube can be formed monolithically together. In the case of rigidity, the support arm can fix the longitudinal position of the expandable tip relative to the distal end of the support tube. In an alternative embodiment, the support arm can adopt a waveform shape or have a narrow section to improve the overall flexibility of the framework.

[0018] The flexible cover may be disposed to form a sleeve around at least a portion of the support tube and at least a portion of the strut framework of the expandable tip. The cover can be formed from a ductile elastomer, which has the advantage of being soft and flexible and having resistance to tearing and perforation due to high fracture strain. The cover can envelop the tip framework and the support tube so as to constitute both the inner and outer surfaces of the catheter. Alternatively, the cover may be one or more polymer jackets that are fused together and adhered, reflowed, or stitched to the strut framework. The cover can further be coated with or made from an elastomer or similar material to provide a low friction surface that facilitates navigation within blood vessels and other catheters. When coated, the support tube can be coated both internally and externally with a lubricious film. The coating can be delivered via spray, plasma, or any other commonly used technique. Alternatively, the cover or jacket can be impregnated with particles having low friction properties. These methods can offer the advantage of delivering the reduction of both the static and dynamic coefficients of friction and the reduction of frictional interference between the outer catheter and the blood vessel wall. If desired, the properties of the cover can be adjusted to be semi-permeable or fully permeable.

[0019] In another embodiment, the support tube may also have a tubular liner disposed within the lumen of the support tube and lining the lumen of the support tube. Similar to the cover, the liner may be of PTFE, facilitating the smooth delivery of other devices through the blood clot retrieval catheter and having low friction characteristics or being impregnated with particles to help draw blood clots proximally through the catheter using suction and / or mechanical thrombus removal. In the absence of such a liner, the inner surface of the support tube structure may still be coated for the same delivery advantage.

[0020] In one aspect of the present design, the maximum diameter of the expandable tip during expansion is greater than the diameter of the associated outer catheter of the system. The radial dimension near the distal end of the expandable tip can be sized to non-invasively contact the circumference of the inner wall of the target vessel. The length of the distal end of the expandable tip can be dip-coated to the length of the tip defining the dip zone, thereby forming an elastomeric lip that non-invasively overhangs around the crown and support arms. Dip coating often involves immersing the part in a liquid coating material such as a hydrogel or flexible fluoropolymer and then heating the part in an oven or heating chamber to permanently bond the surface by a fusion process. The original Shore durometer, flexibility, and other tribo properties of the part typically remain unaffected by the dip coating procedure. The dip coating can be adjusted to increase the wall thickness of the cover at the tip, and the elastomeric lip forms a soft protective rim extending around the circumference of the crown at the distal end of the tip. This process effectively encapsulates at least a portion of the strut framework of the tip.

[0021] The ribs of the support tube may be of several shapes and thicknesses and may or may not extend around the full circumference of the longitudinal axis of the blood clot retrieval catheter. The number of ribs along the length of the axial spine(s) can be made sufficiently large such that the density of the rib spacing is sufficient to support the ductility and conformability cover. The density of the ribs can also vary at different axial lengths of the support tube.

[0022] In some scenarios, such as when retrieving hard blood clots with a high fibrin content, the suction catheter may not be able to successfully remove all of the blood clot. In this case, the suction blood clot retrieval catheter can be used in conjunction with a separate mechanical thrombus removal device. The thrombus removal device can be any of several commercially available blood clot retrieval products. The thrombus removal device can be housed within a microcatheter that is movable relative to the suction blood clot retrieval catheter, and the microcatheter can be used to deploy a blood clot grasping device from the lumen of the microcatheter. The microcatheter can be disposed within the lumen of the suction blood clot retrieval catheter. The proximal port of the suction catheter can facilitate the advancement of the microcatheter to the target site. The suction blood clot retrieval catheter, the microcatheter, and the grasping device can be simultaneously delivered to the target site through an outer catheter. Upon reaching the target site, the distal end of the suction blood clot retrieval catheter can be expanded to a deployed state. The blood clot grasping device can then be deployed from the microcatheter and engaged with the occlusive blood clot while suctioning through the expanded distal end of the suction blood clot retrieval catheter to capture the occlusive blood clot.

[0023] The system may have one or more suction sources for the catheter. The suction source can be utilized to prevent backflow of blood, remove thrombus substances from within the vascular structure, and assist in the removal. The suction source often provides a vacuum to one or more of the catheters while leaving a central lumen that typically does not require advancement / retreat of an auxiliary device, and is connected to a side port of a Luer or rotary hemostatic valve assembly to regulate the vacuum. For example, by the simultaneous use of a stent retrieval device and a microcatheter within the lumen of a suction catheter, suction can be applied through the side port of a hemostatic valve connected to the suction catheter to increase the possibility of evaluating a first-pass TICI 3. The source can be directly attached to the proximal end of the outer catheter such that double suction is applied, where one suction source can suction from the distal end of the outer catheter to the proximal end of the outer catheter and a second suction source can suction from the distal end of the expandable tip to the proximal end of the suction-type blood clot retrieval catheter. The suction source can include one or more syringes, or a vacuum pump interfaced and connected to the distal tip of the catheter(s) through the lumen(s) of the catheter(s) to suction when a blood clot is retrieved.

[0024] In another embodiment, the suction blood clot retrieval catheter may be an RX catheter that transitions from a distal expandable tip to an intermediate tubular section and ultimately to a proximal wire section. The catheter may be able to provide a seal against either or both the vessel wall and the inner lumen of the outer catheter. The seal with the outer catheter can be a catheter segment having a diameter that is enlarged or flared to impede flow, or can be formed from a shaped ring similar to an O-ring. In another example, the seal can be achieved by inflating an inflatable balloon type mechanism. In yet another case, the expandable tip can seal against the vessel wall proximal to the blood clot when deployed in the expanded configuration. The transition from the intermediate tube to the proximal wire maximizes the available cross-sectional area along the length of the catheter and allows for an increase in suction flow rate by taking advantage of the large proximal lumen provided by the outer catheter. The seal between the RX catheter and the outer catheter directs full suction from the proximal end of the outer catheter to the distal end of the expandable tip, eliminating the suction losses in between that would otherwise occur through the lumen formed between the inner diameter of the outer catheter and the outer diameter of the catheter. The seal at the vessel wall provided by the expandable tip allows for more effective suction while directing full suction distal to the expandable tip, providing an inlet profiled such that the blood clot becomes progressively elongated and is drawn into the lumen of the catheter, preventing shearing and fragmentation of the blood clot. When a separate thrombus removal device is used, the expandable tip also provides a larger opening through which the retrieval device and the captured blood clot can be withdrawn, reducing the risk that the tip will shear or remove a blood clot or fragment of a blood clot from the retrieval device. Fragmentation can occur with a catheter having a distal opening with a cross-section smaller than the cross-section of the blood clot itself.

[0025] If a complete seal is not desired, a flow restrictor can be used between the outer catheter and the blood clot retrieval catheter. The flow restrictor can have a dense framework of uprights, or some other form that can impede flow. The flow restrictor can be located on the inner surface of the outer catheter. Alternatively, the flow restrictor can be located on the outer surface of the blood clot retrieval catheter distal to the transition from wire to tube.

[0026] In one example, the system can have an outer catheter and an inner suction-type blood clot retrieval catheter. The blood clot retrieval catheter can have a support tube that defines the lumen of the blood clot retrieval catheter and a radially expandable tip connected to the distal end of the support tube. The expandable tip can be formed monolithically with the support tube, and the proximal end of the tip can be longitudinally fixed to the distal end of the support tube. The tip can also have an internal lumen that communicates with the lumen of the support tube and is configured to aspirate blood clots.

[0027] The expandable tip can have a collapsed state and an expanded state. When collapsed, the tip can have a radial dimension or diameter that is less than the maximum radial dimension or diameter of the expandable tip, and at least a portion of the tip can share a radial dimension with the support tube. When expanded, the expandable tip extends radially outward from the support tube, and at least a portion of the tip assumes a diameter that is greater than the diameter of the outer catheter. The tip can further have an open distal end and a lumen for receiving blood clots that communicates with the lumen of the support tube. In the expanded state, the distal end can contact the inner wall of the blood vessel and form a seal with the inner wall.

[0028] In one embodiment, the distal end may have a framework with a network of strut members. When the outer catheter is retracted and the distal end is actuated to an expanded state, the strut framework assumes a tapered funnel-like shape, having a first radial size at the proximal end of the distal end framework and a second radial size that is larger than the first proximal distal end of the distal end framework. Similar to other embodiments, the network of members can be formed monolithically with the support tube from a laser cut sheet or drawn wire. Some members can connect the expandable distal end to the support tube. Additionally, the width of the struts of the strut framework can be varied to increase the flexibility of the distal end in the meandering area of the vasculature structure.

[0029] The system may further include a flexible elastomeric cover disposed radially around the support tube and an expandable distal end of the aspiration type blood clot retrieval catheter. The cover can be homogeneous or can have multiple layers. The cover can be coated with a low friction coating on both the inside and outside, and similarly, the network members at the distal end of the expandable distal end can be dip coated with the same or different coatings to improve the deliverability quality of the catheter and create a soft distal bulge to reduce the risk of vascular trauma.

[0030] The aspiration blood clot retrieval catheter may have RX features and may have a port with a control member or shaft extending proximally from the port. The port can be configured to transmit aspiration from the proximal lumen of the outer catheter to the distal tip of the aspiration blood clot retrieval catheter. The shaft of the RX catheter can provide excellent advantages in terms of speed, deliverability, ease of use, and optimal aspiration flow rate.

[0031] A method for removing an occlusive thrombus from a blood vessel is also provided. The method can have some or all of the following steps and variations thereof, and the steps are listed in no particular order. The method can involve accessing the patient's arterial blood vessel using conventional means and advancing an outer catheter into the vasculature. An inner thrombus retrieval catheter can be advanced through the outer catheter, and the thrombus retrieval catheter includes a self-expanding tip, a support tube having a hollow structure disposed around the longitudinal axis of the thrombus retrieval catheter, an expandable tip, and a polymer cover disposed around at least a portion of the support tube, and a distal port. The self-expanding tip can be sized to contact the wall of the target blood vessel and seal the wall upon deployment. A further step can involve covering the outer periphery of the port with a soft lip or rib so as to minimize the risk of vascular trauma.

[0032] The outer catheter can be configured to induce suction applied to the proximal end of the outer catheter through the distal lumen of the thrombus retrieval catheter to draw thrombus into the mouth of the thrombus retrieval catheter. In one embodiment, the method can include restricting flow between the outer surface of the thrombus retrieval catheter and the inner surface of the outer catheter. Flow can also be restricted between the inner wall of the blood vessel and the outer wall of either the outer catheter or the thrombus retrieval catheter. If desired, a balloon guide catheter can be used for this purpose.

[0033] The cover can be a flexible elastomer or one or more polymer jackets. In a further step, a low friction liner or coating can be applied to at least a portion of the inner surface and / or outer surface of the support tube and the expandable tip. The liner can be adhered to the struts and ribs using heat or other suitable means. Providing low friction properties to the catheter surface can facilitate the transition of the thrombus retrieval catheter through the outer catheter while also facilitating the passage of auxiliary devices during the procedure.

[0034] This method can continue the step of advancing the inner blood clot retrieval catheter through the outer catheter until the expandable distal tip is aligned with the distal end of the outer catheter. Subsequently, the outer catheter can be retracted relative to the blood clot retrieval catheter, whereby the self-expanding tip expands radially so as to be deployed adjacent to the occlusive thrombus without being covered. The profile of the tip can seal against the vessel wall proximal to the blood clot. This seals the vascular fluid proximal to the mouth and provides a large opening for readily receiving the blood clot.

[0035] Another step can involve suctioning through one or both of the outer catheter and the blood clot retrieval catheter to agitate the thrombus into the mouth of the blood clot retrieval catheter. The captured thrombus can be suctioned through the lumen of the blood clot retrieval catheter and into the suction source and / or the blood clot retrieval catheter, and the captured thrombus can be retrieved from the patient through the vasculature.

[0036] In another embodiment, the method can further include delivering a microcatheter across the target thrombus while suctioning through the expanded tip of the suction-type blood clot retrieval catheter and deploying a mechanical thrombus removal device from the microcatheter. Once the thrombus removal device is deployed, the microcatheter can be withdrawn back along the delivery path to facilitate more efficient blood clot retrieval. The method can include further steps of retracting the thrombus removal device with the captured thrombus into the mouth of the suction-type blood clot retrieval catheter and removing the blood clot retrieval catheter from the patient through the outer catheter.

[0037] Often, after recovering some or all of the occlusive blood clot, contrast agent can be injected through the outer catheter to enable assessment of more complete vascular patency. If an occlusion remains within the vessel, additional channels can be created using the suction-type blood clot retrieval catheter and the thrombus removal device. Subsequently, once it is confirmed that the target vessel has been appropriately recanalized, all remaining devices can be removed from the patient.

[0038] Another advantage of using the clot retrieval catheter of the access port together with the outer catheter is that when the captured clot enters the distal end of the clot retrieval catheter, the clot retrieval catheter can be retracted through the outer catheter so that the outer catheter remains in place to maintain access at the target treatment location. It is understood that there may be cases where a particular clot requires retracting the outer catheter along with the inner clot retrieval catheter and the clot, but most of the clot is likely to be removed through the inner clot retrieval catheter.

[0039] Furthermore, when using a standard intermediate catheter, the lumen of the outer catheter cannot extract debris, leading to the risk that any remaining potential thrombus may not be removed during contrast agent injection. To counter this, users of conventional intermediate catheters may sacrifice access to the target treatment location and remove the catheter to flush any remaining thrombus outside the body before injecting the contrast agent. In comparison, the present disclosure provides means to minimize the number of catheter advancements required to treat a patient, thereby reducing the potential for vascular injury and the associated risk of vascular dissociation when multiple accesses are needed.

[0040] Other aspects and features of the present disclosure will be apparent to those skilled in the art by considering the following detailed description in conjunction with the accompanying drawings.

Brief Description of the Drawings

[0041] The above and further aspects of the present invention will be further considered in conjunction with the following description of the accompanying drawings, in which like numerals in the various drawings indicate like structural elements and features. The drawings are not necessarily to scale, and instead, emphasis is placed on illustrating the principles of the present invention. The figures depict one or more implementations of the apparatus of the present invention by way of example and not limitation. Those skilled in the art are expected to be able to envision and combine elements from multiple figures to better suit the desires of the user.

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DETAILED DESCRIPTION OF THE INVENTION

[0042] The disclosed design aims to create a clot retrieval catheter capable of providing both local flow restriction / deterrence with a large distally-facing opening and a tailored, highly flexible body section capable of navigating tortuous areas of the vasculature to reach occlusive clots. The flow restriction and large-tipped design provide substantially greater suction efficiency. Such advantages can also be particularly beneficial in the case of stroke intervention procedures, where the blood vessels within the neurovascular bed are particularly small and circuitous, and as a result, the tailored axial and bending stiffness profiles can prevent entanglement and binding. The catheter can also be compatible with relatively low-profile access sheaths and outer catheters, thus enabling easy and reliable closure of the puncture wound at the patient's groin (in the case of femoral access). The catheter can also feature internal and / or external low-friction liners, as well as an outer polymer jacket or membrane disposed around the support structure.

[0043] These improvements can lead to safe and more rapid access to complex areas of the catheter and other devices in order to remove obstructions and shorten treatment times. These descriptions are often related to mechanical thrombus removal treatments, but the systems and methods can be similarly adapted for other procedures and other body passages.

[0044] Accessing various blood vessels within the vascular system involves well-known procedures and the use of numerous conventional commercially available accessory products, regardless of whether they are coronary arteries, lungs, or the brain. These products, such as angiographic materials, rotary hemostatic valves, and guidewires, are widely used in laboratories and medical procedures. When these products are used in conjunction with the systems and methods of the present invention in the following description, their functions and exact configurations are not described in detail.

[0045] Referring to the figures, FIGS. 1-3 illustrate a system 100 for removing an occlusive blood clot 40 from a patient's blood vessel 20. The system 100 can include an outer catheter 30 and an inner suction-type blood clot retrieval catheter 110. The blood clot retrieval catheter 110 can have an elongate proximal catheter shaft 115 for manipulating and delivering the retrieval catheter and an expandable tip 200 at the most distal end of the retrieval catheter. The expandable tip 200 can be self-expanding to non-invasively contact the inner blood vessel 20 wall upon deployment at the target site and be sized and configured to provide the largest possible opening for aspirating or receiving the blood clot 40. The expanded tip can also inhibit flow and prevent unnecessary aspiration of blood proximal to the tip.

[0046] With the system 100, a physician can use a standard sheath, guide, or outer catheter 30 to quickly create a path to near the occlusion, gain access, and then use the suction catheter 110 to aspirate the target blood clot 40. The suction catheter can be of a conventional construction or can have rapid-exchange (RX) type characteristics, many of which can significantly increase the speed and efficiency of the blood clot retrieval procedure.

[0047] In one embodiment, the system can use a suction source 80 with one or more flow restrictions or seals 50, 116. In many cases, the expanded catheter tip can be sealed against the wall of the blood vessel or the seal(s) can be selectively activated to provide suction into the distal lumen of the suction type blood clot retrieval catheter 110. The expandable tip provides a large opening for efficient suction. The suction source 80 is first applied to the proximal lumen of the outer catheter 30 and then directed to the expandable tip 200 of the blood clot retrieval catheter 110. FIG. 3 shows one possible configuration for the retrieval process in which the outer catheter 30, the blood clot retrieval catheter 110, and the captured blood clot 40 are withdrawn from the target site. The seal 50 can inhibit blood flow within the blood vessel and prevent any free blood clot fragments 42 from migrating distally. Alternatively, instead of the seal 116, a portion of the tubular catheter body can have a flared diameter to block the lumen between the two catheters. During retrieval, when the expandable tip 200 is retracted proximally and contacts the outer catheter 30, the tip seals the space that exists between the blood clot retrieval catheter 110 and the outer catheter. As the expandable tip 200 of the blood clot retrieval catheter 110 continues to retract proximally through the outer catheter 30, the tip can act as a piston that applies additional suction distally of the tip within the outer catheter until the tip exits the proximal end of the outer catheter 30.

[0048] The distal section of the suction blood clot retrieval catheter 110 has good thrust, trackability, and torsional resistance characteristics that assist in advancing to the target location. Thus, it can have multiple designs or be made from multiple materials such that it is given a stiffness profile that decreases along its length to minimize the forces of insertion and withdrawal. It can also incorporate features that bias bending or encourage coiling about a particular plane to reduce a given strain. In this way, the catheter maintains excellent lateral flexibility but has no tendency to expand or coil during compression.

[0049] As seen in FIG. 4A, the distal expandable tip 200 of the aspiration blood clot retrieval catheter 110 is intended to open when it exits the outer or intermediate catheter 30 into which it is delivered. The tip provides a large distal opening 114 for aspirating blood clots that is sized to have an expanded size 125 that is approximately the same or slightly larger in diameter than the expected upper end of the diameter of the target blood vessel when unrestrained. Thus, upon deployment, the tip seals the blood vessel or creates sufficient flow restriction such that, when suction is applied, blood and blood clots distal to the opening, rather than blood proximal to the tip, are drawn into the catheter. If the expanded tip 200 does not seal or forms only a partial seal, the suction force applied to the blood clot may be directed to an area where flow is less likely to be restricted proximal to the tip, resulting in reduced effectiveness. However, an expandable tip 200 that partially seals can still outperform many current aspiration catheters that may leave a larger cross-sectional area open to the blood vessel proximal to the tip. The proximal segment 250 of the enlarged catheter body or the seal 116 can also be used to occupy the lumen between the catheters.

[0050] In another embodiment, the expandable tip 200 of the blood clot retrieval catheter 110 is designed to expand to the diameter of a wide range of target blood vessels such as the carotid terminus (3.2 - 5.2 mm), the horizontal M1 segment of the middle cerebral artery (1.6 - 3.5 mm), and / or the internal carotid artery (ICA, 2.7 - 7.5 mm). Then, when the catheter is retracted from the M1 segment to the ICA (or another path having an increasing inner diameter of the blood vessel proximally), the radial force of the self-expanding tip 200 continues to seal the blood vessel over a range of blood vessel sizes. Further, the tip that can accommodate the diameters of various target blood vessels can also seal at a blood vessel bifurcation, and this tip can have a larger cross-sectional area than the blood vessels proximal and distal to the bifurcation.

[0051] The blood clot retrieval catheter 110 can have a proximal elongated catheter shaft 115 connected to a proximal port 117 at its distal end. The blood clot retrieval catheter 110 can be delivered to a target site within the inner lumen 32 of an associated outer catheter 30. The blood clot retrieval catheter 110 can be manipulated by the shaft 115. The blood clot retrieval catheter 110 may be manipulated independently of the outer catheter 30 by a physician, and the blood clot retrieval catheter can be retracted separately from the patient. If the retrieval catheter is blocked by a blood clot, the outer catheter can be left in place to maintain access to the treatment location. Distal to the shaft 115, the catheter body can be a support tube 124 structure disposed around the longitudinal axis 114 of the blood clot retrieval catheter 110. The support tube 124 can be distally fixedly connected to the strut framework 112 of the expandable tip 200.

[0052] At least a portion of the framework 112 of the expandable tip 200 and the support tube 124 can be covered by a flexible cover 118. The expandable tip 200 can adopt an expanded configuration by self-extending radially outward from the longitudinal axis 114 of the blood clot retrieval catheter 110 when it exits the distal end 72 of the outer catheter 30. In one embodiment, the highly elastic cover 118 can stretch as the tip expands and follow the contour of the underlying strut framework. In another embodiment, the cover can be a mating-type non-conforming material that folds properly when the tip 200 is collapsed back into the outer catheter 30. The cover may extend the full length of the support tube or may terminate distal to or at some distance from the proximal port 117.

[0053] The distal support tube 124 section of the blood clot retrieval catheter 110 may define an inner lumen 113 that starts from the proximal port 117 and ends within the distal opening 114 where blood clots can be retrieved. The lumen may be concentric with the longitudinal axis 111 of the catheter. An enlarged proximal segment 250, or a separate flow restrictor or seal 116, can be disposed around the outer circumference of the blood clot retrieval catheter to assist in moving the suction towards the target distal to the opening. The preferred length 123 of the distal section of the catheter may depend somewhat on the location of the target blood clot. Preferably, the length 123 of the tubular section can be made relatively short by expanding the tip 200 at the treatment position so as to avoid the need to advance the expanded tip through the vasculature. In the case of a blood clot located within the anterior cerebral artery or posterior cerebral artery, the length 123 can be greater than 5 cm such that it can extend to the right from the outer catheter to the proximal surface of the blood clot, but can be less than 40 cm so as to leave a minimum length inside the distal end of the outer catheter while maximizing the given volume of the combined outer / retrieval catheter for suction. The shortened length 123 of the distal section also improves the trackability and flexibility of the system for accessing the target. The material of the shaft 115 can have high tensile and compressive strength, and the low profile of the shaft improves the friction and extrusion performance. The shaft 115 can be solid or can be a composition of multilayer materials such as a solid core and an outer tubular portion (e.g., a nitinol core with an outer polymer jacket).

[0054] The large distal port 114 of the expandable tip framework 112 shown from the front in FIG. 4B can provide improved performance over conventional fixed port designs. Conventional fixed port catheters can be impeded by a firm fibrin-rich clot clogging the tip and / or by a softer portion of the clot being sheared off. The progressive compression of the clot as it enters the reducing funnel shape of the tip 200 makes it less likely that the clot will clog within the tubular section of the clot retrieval catheter 110 having the disclosed expandable tip. Further, if a portion of the clot remains distal to the tubular section, the expandable tip 200 collapses over the clogged clot, securing the clot and preventing it from becoming an embolism. The shape can be further collapsed when the tip is retracted into the outer catheter 30 during or after the procedure to reduce or eliminate any flow restriction and allow blood and / or contrast agent to reach the distal vascular structure.

[0055] Additionally, when suctioning through a conventional fixed port catheter, a significant portion of the suction force is directed to the fluid proximal to the tip, reducing the suction force directed to remove the clot and the success rate of clot removal. If the diameter of the catheter with an expandable port can be made close to the diameter of the blood vessel, shear of the clot at the catheter port can be reduced and the volume of fluid and clot distal to the port can be secured. By tapering the diameter of the expandable tip 200 and / or the support tube 124 downward, the clot can be progressively compressed during retrieval, allowing the clot to be completely aspirated through the catheter.

[0056] FIG. 4C shows a cross-sectional view illustrating the various lumens of the system. The clot retrieval catheter 110 can be delivered through the lumen 32 of the outer catheter or sheath 30. The cover 118 can be disposed around the ribs 122 of the support tube 124. One or more spines 120 may extend along the length of the support tube 124 and into the large internal volume provided in the lumen 32 for the passage of auxiliary devices.

[0057] The expanded distal end 200 can take a maximum radial dimension 125 that is greater than the diameter 119 of the outer catheter 30, and the mouth 114 of the distal end can take the maximum radial size of the expandable distal end 200 upon deployment. In this way, the distal end can be sealed against the wall of the blood vessel 20 proximal to the blood clot 40. To maintain the seal, the radial force of the expanded distal end must be high enough such that the applied suction does not collapse the distal end. The vacuum delivered through the outer catheter 30 to the blood clot retrieval catheter 110 is of sufficient suction force to draw the distal blood clot into the mouth 114 of the distal end, while preventing unnecessary suction of the blood proximal to the distal end 200. This ensures that the maximum suction force is transmitted and that detachment of the blood clot from the vessel wall and retrieval through the catheter lumen 113 is induced. If the size of the blood clot 40 is too large to pass through the lumen 113 of the blood clot retrieval catheter 110, the expandable distal end 200 can always be withdrawn into the distal end 72 of the outer catheter 30 due to the smooth tapered shape of the distal end under expansion conditions.

[0058] A further detailed view of an example of the distal portion of the suction-type blood clot retrieval catheter of FIG. 4A is illustrated in FIG. 5. The expandable distal end 200 can be designed such that the distal end framework 112 is approximately equal to or slightly larger than the inner diameter of the blood vessel 20 in which the blood clot is located under expansion conditions. Comparing the illustration seen in FIG. 3, the deployed expandable distal end can be shaped such that the distal end framework 112 expands to contact the vessel wall with a large and gentle radius. The flexible cover 118 can be a polymer membrane disposed around the support tube 124 and is expanded to take the profile of the distal end framework 112 in the expanded state. The cover 118 can be trimmed to follow the contour of the mouth 114 of the distal end, folded over the distal end framework 112, or left untrimmed.

[0059] In many embodiments, the expanded deployment configuration of the expandable distal tip framework 112 at the distal end of the blood clot retrieval catheter 110 can take on a flared or funnel shape. This shape allows the blood clot to be gradually compressed to a smaller diameter during retrieval so that it can be completely suctioned through the catheter into a suction syringe or cannister. If the blood clot becomes lodged in the tip opening 114, the expanded opening protects the blood clot and prevents it from being removed when the suction force of the suction is maintained, the catheter 110 is retracted into the sheath or outer catheter 30, and at that point the opening collapses over the blood clot, grasping or pinching the blood clot and pulling it into the outer catheter.

[0060] The struts of the expandable distal tip framework 112 can be formed from nitinol or another shape memory material that has sufficient elastic strain capacity such that when delivered in a configuration where the tip is constrained to collapse within the outer catheter, it does not exceed its elastic limit. This elastic strain capacity can effectively spring bias the tip so that it can self-expand when deployed from the distal end of the outer catheter. In another case, the framework can be constructed from wires since the wires will be free to move independently of each other, and it is possible to use a non-superelastic material such as a stainless steel alloy. It is also possible to envision a framework 112 constructed of wires using a superelastic or shape memory material, and such devices are understood to provide improved torque and durability characteristics. In another case, the framework 112 can be laser cut from a non-superelastic material that accommodates strain by including cells or bends, and the degree of strain required to move from the collapsed state for delivery to the expanded state for blood clot retrieval is low. For example, the framework can include additional cells, longer cell struts, and / or a lower cell angle to reduce the strain requirements.

[0061] As seen in FIG. 6, the proximal port 117 may serve as a tapered transition between the shaft 115 and the main catheter body and can also form an entrance to the lumen 113 of the catheter 110 for other devices used during the procedure, such as a guide wire, a microcatheter, a thrombectomy device, or an angioplasty balloon. To facilitate the introduction of other devices, the port 117 has an axially tapered profile over the length 129 of the transition from the shaft to the body to prevent other devices from snagging on the transition. The shaft 115 may overlap with a portion of the spine 120 of the catheter support tube 124 and can be locked together by mechanical features or with a reinforcing polymer jacket placed thereon.

[0062] The catheter support tube 124 can also be laser cut from a hypotube or alternatively can be of a similar construction including a braid having overlapping or woven spines, enabling good pushability and torque characteristics, a small bend radius, torsional resistance, and solid resistance to tensile elongation. Commonly used materials include nitinol and well-known medical grade stainless steel alloys such as 304 and 316. When using a cut hypotube, the support framework 112 of the flared mouth can be integrally formed with the hypotube so that the stiffness profile of the catheter is smoother and weak transitions can be eliminated. The hypotube can be further coated with a low friction sleeve or jacket such as PTFE, high density polyethylene, or a similar fluoropolymer. It is also possible to join by using hypotubes of different materials such as stainless steel in the proximal section and nitinol in the distal section of the tubular support tube and holding the interlock features in place using welding, bonding, or inner and / or outer polymer jacket materials.

[0063] The support tube 124 of the blood clot retrieval catheter 110 can have a structure similar to the structure illustrated in FIG. 7. The framework can have one or more axial spines 120 that extend distally from the proximal end 128 to the distal end 126. The spines can be of a tubular or wire structure such that they have good axial rigidity for advancing and retracting the catheter while having excellent lateral flexibility for navigating within the bends in the vasculature. The use of multiple spines encourages reducing the likelihood that the support tube 124 elongates under tensile loads, such as when withdrawing the expandable tip into the mouth of the outer catheter while bending along a defined plane. Extending along the length of the axial spine(s), there can be multiple loop ribs 122 that can be axially symmetric with the longitudinal axis 111 of the blood clot retrieval catheter 110. The loop ribs 122 can be of a simple circular configuration as shown or can take on a more complex shape as needed.

[0064] In one instance, the axial spine 120 and the loop ribs 122 can be cut from a single hypo tube, and the individual ribs can be formed by cutting slots using laser machining or electrochemical means. In another case, the loop ribs can include an interlocking spiral, helical, or continuous hinge-like configuration. By utilizing the configuration of the spines 120 and ribs 122, the size and shape of the spines can be customized along with the density and size of the rib struts, resulting in higher flexibility for a particular portion of the catheter. This is important in situations where the system needs to be advanced from the patient's internal femoral, over the aortic arch, and into the intracranial vessels inside the patient's skull, and thus the distance and tortuosity can be quite substantial.

[0065] The interior of the loop rib can define the inner lumen 113 of the blood clot retrieval catheter 110. The cover 118 can be disposed around the support rib and can be fused or extended in place. The axial spacing of the ribs is of sufficient density to maintain column strength and is sufficient to support and prevent the cover from collapsing and to provide good deliverability characteristics to the distal section of the catheter. In situations where the blood clot retrieval catheter has an inflatable seal 116, an internal lumen 121 can be provided within the axial spine 120 for independent actuation of the seal. In another embodiment, a polymeric low friction liner is applied to the inner surface of the blood clot retrieval catheter 110, and the loop rib 122 and spine 120 are sandwiched between the liner and the outer cover. The outer cover can be provided in longitudinally series and / or in radially layered different materials at different points along the length of the catheter to further adjust the stiffness.

[0066] The tubular body of the suction-type blood clot retrieval catheter 110 can also be made only from a polymeric tube that may or may not have multiple layers. The surface of the polymeric tube can be profiled with a series of ridges and valleys that provide enhanced torque, pressure, and trackability characteristics. In one embodiment, the ridges and valleys are applied by passing the polymeric tube section through a heated profiling die that melts and cools the tube as it passes in various directions.

[0067] The ideal nominal diameter of the catheter 110 depends on the location of the target clot and the diameter of other catheters 30 through which the catheter system is delivered. For the retrieval of clots in the intracranial vessels of the cerebrovascular bed where the vessel diameter at the location of M1 is generally about 3 mm, an applicable system may have an outer catheter with an inner diameter of 0.065” - 0.080” and an RX clot retrieval catheter with an inner diameter of 0.055” - 0.070”. When deployed from the outer catheter, the maximum diameter 125 of the expandable tip may be at least 3 mm (but in some cases up to 6 - 7 mm), thereby sealing the tip against the vessel wall and providing a distal port the same size as the vessel itself. In some cases, the tip 200 can also provide an opening large enough to counter the location of the bifurcation and / or proximal vessel. This seal, in combination with the maximized proximal lumen of the disclosed RX system, provides the advantage of increasing flow rate with a design that utilizes the suction force at the clot surface and the larger inner diameter of the outer catheter compared to conventional catheters. The outer catheter 30 constrains the funnel in a collapsed configuration to facilitate advancement to the intended deployment site. If the funnel is designed in such a way that it can advance distally an expanded opening within the vessel, for example, from a balloon or long sheath guide catheter located within the ICA to a target treatment location such as the M1 or M2 vessel, the balloon guide can serve as a larger proximal lumen providing an inner diameter in the range of 0.085” - 0.100”, thereby significantly increasing the flow rate induced to the treatment location. In conventional systems, suction catheters always have a diameter significantly smaller than that of the balloon or long guide sheath catheter positioned within, and it is necessary to limit the effectiveness of the applied vacuum by not using the larger lumen of the outer catheter.

[0068] However, it can be expected that the challenges of the procedure may dictate the practical size of the expandable tip 200. For example, for deliverability, the diameter 125 upon expansion of the expandable tip may be slightly smaller than the diameter of the target vessel in situations where the priority of the low-profile catheter is higher than a sound seal between the tip and the vessel wall.

[0069] It can be envisioned that the pattern of the struts of the framework 112 of the expandable tip 200 can take many forms. In one embodiment, the layout of the pattern of the tip is laser cut from a Nitinol sheet or tube and has a series of interconnected struts as illustrated by the flat plan view of FIG. 8, and at the proximal end 213 of the tip framework, the base 216 of the framework 112 can be connected to the spine 120 (s) of the support tube 124 by one or more struts forming an axial band 218. The axial band 218 can also be connected to points (s) on the circumference of the most distal loop rib. The axial band may be parallel to the longitudinal central axis 111 of the aspiration-type thrombus retrieval catheter 110. In another embodiment, the support tube 124 can be formed monolithically with the expandable tip framework 112 such that the axial band 218 transitions to the support arms of the tip as a distal continuation of the axial spine 120.

[0070] One or more link members 214 may project distally from the base 216 of the distal end portion. Each link member 214 can terminate at the convergence of two or more proximal support arms 212 to form a closed cell. In one embodiment, the link member 214 can have a wide and curved form, providing additional flexibility to the framework and allowing the member to be lengthened to reduce the likelihood that rib 122 of support tube 124 pulls proximally on the mouth of the expanded distal end portion framework 112 during retraction of a blood clot under suction when the link member 214 is not in line with the spine(s) 120 of the support tube. By keeping the spine 120 of support tube 124 in line with the link member 214 and / or support arm 212, direct transmission of pushing / pulling forces between the members is enabled, providing the most efficient resistance to elongation while the device is advancing or retracting within a blood vessel or external sheath. In another embodiment, there are no link members and the support arms themselves are directly connected to the base of the distal end portion or the most distal loop rib. The support arms 212 can be distally connected at the proximal crown trough 215 by a curved crown or undulating distal end segment 210 that forms the outer perimeter of the mouth 114 of the expandable distal end framework 112. The crown 210 can have a distal convex curvature extending from where the distal end segment faces an adjacent segment at the proximal crown trough 215. Together, the crown struts 210 and adjacent support arms 212 can form a closed cell that can provide a petal-like appearance with a rounded edge at the distal portion of the expandable distal end 200. These cells are spaced around the circumference of the distal end portion and the cells form a tapered end portion with a large non-traumatic flare radius of curvature to navigate and interface with the vasculature and ensure good contact with a blood clot.

[0071] Of course, the distal end portion framework structure 112 and pattern shown in FIG. 8, as well as the other figures discussed herein, are used to illustrate a single aspect of the invention. The invention can have distal end portion frameworks of various shapes and sizes and can be made from a single section or multiple sections.

[0072] When in the expanded state, at least a portion of the distal end 200 can be tapered distally from a larger radial dimension to a smaller radial dimension. In this configuration, the outer axial profile of the distal end body may also be rounded to provide a smooth interface connection with the vessel wall. Combining a rounded crown feature with a rounded outer axial profile that tapers radially inward in the distal direction (from the maximum radial dimension at the intermediate position to a diameter that is larger than the support tube but smaller than the maximum diameter), and including link member 214 and / or support arm 212 that taper from the support tube at a shallow angle, preferably less than 45 degrees, more preferably less than 30 degrees, to the maximum diameter, allows the expanded distal end 200 to be advanced distally within the blood vessel in a non-invasive manner that does not pose a risk of damage to the vessel wall.

[0073] The framework 112 of the expandable distal end 200 can be overlaid by the flexible cover 118 as seen in the previous figure. Various features such as the curved profile of the link segment 214, and the wide petal-shaped cells formed by the crown 210 and support arms 212 of the pattern of FIG. 8 are combined to provide more support surface area to support the cover. When the expandable distal end is fully deployed, the cover surface on the distal end can have a curved funnel-shaped profile that tapers to an increased diameter until it is substantially parallel to the longitudinal axis 114 at some point near the distal end 211 of the distal end.

[0074] An example of a collapsed delivery configuration and an expanded deployment configuration of the expandable tip 200 are shown in FIGS. 9A and 9B, respectively. When in the collapsed state constrained within the outer catheter 30 of FIG. 9A, the petal-shaped cells formed by the crown 210 and the support arms 212 are narrowed about the longitudinal axis 111 buttressed to the proximal crown trough 215, folded in a generally axially symmetric manner, and at least the length of the expandable tip 200 between the proximal end 213 and the distal end 211 may share a first radial dimension common with the outer catheter 30. This first radial dimension is smaller than the maximum second radial dimension of the tip in the expanded state. The expanded second radial dimension 125 may be equal to or greater than the diameter size of the target vessel when unconstrained. Removal of the distal end of the outer catheter allows the expandable tip framework 112 to project radially outward and push the cover 118 into the deployed shape, as shown in FIG. 9B. The petal-shaped cells open a hinge around the proximal crown trough 215 to assume a maximum radius dimension near the distal end 211 of the expandable tip 200.

[0075] The visibility during deployment of the aspiration blood clot retrieval catheter 110, and the position of the catheter and the blood clot 40 during capture and retraction can be assisted by adding alloying elements (such as palladium, platinum, gold, etc.), by applying a radiopaque compound, or by placing a radiopaque marker 68 on one or more of the catheter and the device. Suitable embodiments are frequently used in connection with other devices and implants and are well known in the art. For example, as seen in FIGS. 9A and 9B, a radiopaque compound can be incorporated over the cover 118 around the expandable tip 200, or one or more radiopaque markers 68 can be added near the distal end 211 of the tip. By incorporating multiple markers 68 in a position close to the portion of the tip 200 that reaches its maximum diameter during expansion, the physician can visually confirm that the mouth has fully expanded to the vessel wall. Additional markers can be placed at the base of the expanded mouth and / or at a more proximal location, whereby the physician can visualize the curvature of the device during deployment and during any slight forward or backward movement in order to aspirate the blood clot towards the distal end of the device and adjust the curvature to achieve a more desirable straight axial profile. Further, markers can be placed on other devices such as microcatheters and auxiliary mechanical thrombectomy devices that the physician uses to mark the terminal end of the device during the procedure. Markers can also be used to indicate the working length and the expanded diameter of the stent retrieval device. Such markers would be particularly useful if such a device was not completely withdrawn into the outer catheter 30 during retraction from the target site and for fine-tuning the positioning between the devices with respect to the target blood clot.

[0076] Cover 118 can take on a variety of different forms or configurations, as further described herein. The cover can be formed of a highly elastic material in a substantially tubular profile that has been collapsed, such that upon expansion of the expandable tip, it provides sufficient radial force to stretch the tubular structure to the profile of the expandable tip when unrestrained. Alternatively, cover 118 can be formed in an expanded state of expandable tip 200 such that it can be folded or creased into a collapsed state when within the outer catheter. When tip 124 and tip framework 112 are cut from the hypotube, a space, slot, or pattern can be laser cut into the outer surface of the hypotube, and the cover can be reflowed or injection molded into the space during manufacture. Cover 118 can also be adhered to the struts of support tube 124 and tip framework 112 using heat or an adhesive with a primer.

[0077] Cover 118 may be of a structure having good ductility and a high elastic strain limit such that it can be easily expanded by a minimal radial force from the self-expanding frame 112 below. Or, if cover 118 is formed of an elastomeric or non-conforming material in an expanded configuration, it may be possible to properly enclose cover 118 when collapsed for delivery and re-cover it when expanded for use. The cover of tip framework 112 may also have flow-inducing features such as a plurality of flexible fins or vanes (not shown) disposed around the inner circumference in a configuration with vortices or laminar flow. Such features can be included in a forming or molding mandrel.

[0078] The cover 118 can be trimmed to follow the contour of the support framework 112 along the outer periphery of the mouth 114, or can be finished with a planar surface. In another embodiment, the cover membrane can be folded radially inwardly to a proximal position of the mouth 114 and thermally welded between the inner and outer layers. The thickness of the cover 118 can be maintained between and on the struts of the support framework 112, can be finished with a uniform thickness, or can vary in thickness between the base and the distal tip of the expanded tip portion 200.

[0079] A single or variable stiffness cover 118 can be extruded onto the support tube. Alternatively, the cover can be formed from a series of polymer jackets 238. Different jackets or sets of jackets 238 can be disposed around the loop rib 122 at different lengths along the axis of the support tube to impart separate pushability and flexibility characteristics to different sections of the tubular portion of the catheter, as shown in FIG. 9B. By configuring the jackets in an axial array, it is possible to transition the overall stiffness of the catheter from being stiffer at the proximal end to being extremely flexible at the distal end. The transition between jackets 238 may be tapered or slotted so as to provide a more seamless transition between the flexible profiles of the abutting jackets positioned in series longitudinally. Alternatively, the polymer jackets 238 of the cover can be disposed radially in series around the support tube to adjust the material properties through the thickness, as shown in FIG. 9C.

[0080] A series of polymer jackets 238 can be butted together on the framework of the support tube 124 and reflowed using heat to fuse the jacket sections to each other and to the framework. The expandable tip framework 112 can have the same or separate jacket(s) that can be dip-coated, can abut the jacket(s) of the support tube, can extend to the jacket, or can be placed under or over the jacket. If the jacket of the tip framework 112 is under the jacket of the support tube 124, it can be made of a material capable of withstanding the heat generated when the jacket of the support tube is reflowed. Alternatively, if it is desired to fabricate the jacket of the tip framework from a material with low resistance to the heat generated during reflow, a heat shield and / or a precision laser reflow machine can be used to protect the tip framework cover. The jacket and cover sections can also be made of similar or compatible materials that can bond to each other during reflow. A cover with a single outer jacket can be preformed with various stiffness and elasticity characteristics, for example, by extruding a variable blend of polymers with different stiffness properties, to replace the series of polymer jackets.

[0081] In another embodiment, the tip framework 112 can include an electrospun or other porous cover that can reduce the flow of blood from the proximal side of the tip vascular wall seal. A 50% - 99%, more preferably 60% - 80% reduction in flow still allows a small portion of the recovery flow from the proximal side while directing most of the suction flow towards the blood clot. This flow can help reduce the likelihood of the blood vessel collapsing under excessive suction where the blood vessel is not well supported by the surrounding tissue or where there is no lateral branch between the occluded blood vessel and the expanded tip 200 and a mechanical thrombectomy device or stent retrieval device cannot open a portion of the occluded blood vessel.

[0082] Additional steps can be performed to make the seal with the target vessel more non-invasive. In addition to or instead of the cover 118, the length of the tip portion extending proximally from the distal end 211 can define a dip zone 220 that specifies a portion of the tip that can be further dip-coated with a low-friction elastomer, as shown in FIG. 10. Struts near the distal end 211 of the expandable tip framework 112, such as the crown 210 and support arm 212, serve as a substrate for this process. The dip coating can be a reliable process for coating complex geometries. The dip coating deposits a seamless and circumferential non-invasive elastomeric lip 222 around and overhanging the crown 210. This overhang of the lip can also resist captured blood clots from returning from the blood clot retrieval catheter and potentially migrating distally. The dip zone can also extend further to the proximal length of the connecting arm 212 or even to the entire tip framework 112 defined by the longitudinal span of the dip zone 220.

[0083] To form a lip by dip coating over the expandable mouth of the catheter, a substantially conical mandrel that conforms to the undulations of the tip framework can be placed inside, aligned with the shape of the framework. Multiple dip coating layers can be applied before and / or after removal of the mandrel. After removal of the mandrel, the dip coating can form a portion of the lip both radially inward and outward of the tip framework so as to overhang at the edge. Alternatively, the dip coating mandrel can have machined features, such as circumferential recesses or grooves, that allow material to be formed under the end of the tip. Other features, such as longitudinal, axial, or offset patterns, can be machined into the mandrel such that these features indent the cover during dipping to achieve a cover with additional support and / or flexibility at specific locations.

[0084] The final state of the companion material of the elastomeric lip 222 can be adjusted by regulating the controlled factors of the dip coating process. To impart the desired soft and uniform profile to the lip, all of the factors such as underwater residence time, substrate withdrawal speed, temperature, humidity, and number of dipping cycles can be modified.

[0085] In another embodiment, the lip 222 can be formed by a loose or sagging membrane cover 118 that is placed over the mouth of the distal end framework 112 and folded radially inward. The overlying layer can be heat welded in place such that the membrane extends radially outward and radially inward of the circumference of at least the distal portion of the expanded distal end framework defined by the dip zone 220.

[0086] The elastomeric lip 222 creates a gentle contact surface for sealing against the wall of the blood vessel 20 when the expandable distal end 200 is deployed in the expanded configuration. When formed, the lip can be a soft elastomer, gel, and / or hygroscopic ribs to provide non-traumatic contact with the blood vessel wall. The seal can concentrate the suction force distally and limit the flow of fluid proximal to the tip where there is no blood clot from being drawn into the catheter.

[0087] In the foregoing embodiments, a low-friction inner liner 130 applied to the inner circumference of the support tube 124 is shown in FIG. 9C. An inner liner, such as PTFE, can provide the advantage of reducing friction with auxiliary devices that advance through the catheter lumen 113. The liner material can also extend to the outer surface of the support tube, to an intermediate position within the inner and outer diameters of the support tube 124, or can be bonded only to the surface of the inner diameter of the support tube. By having a liner bonded only to the inner diameter of the support tube, the rib struts of the support tube can be bent more freely because a liner that extends more radially outward relative to the wall thickness of the support tube can harden the catheter. It is also possible to provide a gap between the support tube ribs 122 such that a liner fused to the inner diameter surface of the support tube 124 and also having a cover 118 or membrane connected to the outer diameter surface allows the ribs to move freely axially. In another embodiment, the cover and / or liner can be spray or dip coated such that the surface of the cover and / or liner can undulate with the surface of the support tube 124.

[0088] The inner liner can add rigidity to the catheter and has the potential for delamination, while the outer coating or coatings may form air bubbles or peel off at the serpentine bends. Alternatively, the cover 118 may be one or more outer jackets impregnated with or formed from a polymer containing low-friction particles 240 to reduce the coefficient of friction of the outer and / or surface to allow for smooth delivery through the outer catheter. Such materials can eliminate the need for an internal liner and an outer lubricious coating because the particles in the material move to the outer and inner surfaces to provide low-friction properties. By eliminating the inner liner and the outer lubricious coating, the durability and flexibility of the device can be improved. In another embodiment, the inner surface and / or the outer surface can be modified by methods such as ion implantation or plasma to impart low-friction properties.

[0089] In addition to what has already been described, further embodiments of the profile and structure of the extensible tip 200 are illustrated in FIGS. 11-22. Referring to FIGS. 11A-11D, the extensible tip framework 112 can have four crowns 210 joined by a proximal crown trough 215 and four support arms 212 having two sets of opposing arms. Each support arm can be attached proximal to the base, or the most distal rib of the support tube 124. Since the support arms are not connected to each other, they move and bend independently and freely. The support arms can have narrow sections or segments 226 to enhance flexibility for delivery. The narrow segments can be circumferentially aligned or offset circumferentially. For example, the two sets of opposing support arms can have circumferentially aligned narrow segments that allow the framework to have flexibility in two planes that are perpendicular to each other and bend at two longitudinally separated locations. In another embodiment, the support arm 212 can have more than one narrow segment 226. The additional narrow segment 226 can reduce the radial force of the extended tip compared to a support arm having only one narrow segment, as long as the support framework 112 has sufficient hoop strength to withstand the pressure gradient created when suction is applied.

[0090] In another embodiment shown in FIGS. 12A-12D, the tip framework 112 having four crowns 210 and four support arms 212 has narrow segments 226 on both the support arms and the crown struts, allowing the framework to bend more easily during advancement and assisting in easily collapsing the frame when the framework is withdrawn into the mouth of the outer catheter or intermediate catheter. The struts of the crown and support arms can also be widened in some areas to increase the radial force of the extended tip while maintaining a low profile. The support arms can narrow to a narrow segment proximal to the proximal crown trough 215 and then flare out to a wider section near the proximal end of the tip framework.

[0091] Figures 13A - 13D show a distal end framework 112 having six crowns 210 joined to six support arms 212 in a proximal crown trough 215. Each of the support arms may have a constricted segment 226 offset a longitudinal distance from the crown trough 215. The proximal ends of the support arms can be integrally formed with a tubular support tube 124 and can connect to a distal end base 216, an axial spine 120, or a most distal loop rib 122. By having support arms 212 that each connect independently of the support tube 124, flexibility is increased around the circumference, allowing the distal end framework 112 to better conform to the anatomical structure of the blood vessel.

[0092] Figures 14A - 14C illustrate some views of an embodiment in which the distal end framework 112 has eight crowns 210 and eight support arms 212. Compared to embodiments having fewer crowns, the additional crowns and support arms provide additional support to the cover 118 while sacrificing some flexibility of the framework. The cover may either follow the contours of the crowns and support arms or extend over them. As with other embodiments, the support arms and / or crowns may have constricted segments 226 for additional flexibility.

[0093] Another embodiment of the distal end framework 112 is shown in FIGS. 15A-15C, in which eight crowns 210 and eight support arms 212 are connected by a proximal crown trough 215. The support arms extend longitudinally and may have at least two undulations or curves along their lengths. The proximal first curve 227 may be a concave curve facing the adjacent wall of the blood vessel, and the second distal curve 228 may be a convex curve facing the adjacent wall of the blood vessel. The curves of the support arms 212 help the arms to shorten or lengthen on both sides in a collapsed delivery configuration when advancing through a tortuous blood vessel to the target site. The curves also help, in the same way as imposed by the shape of the blood vessel, when a particular arm is bent around a bending surface and is able to apply torque, if it is not aligned with the bending surface of the blood clot retrieval catheter 110. Further, the curves combined with an acute taper angle (<45 degrees) from the support tube 124 to the maximum expansion diameter can also help prevent the framework 112 from extending excessively when the catheter 110 is pushed forward while the distal end is expanded.

[0094] Referring to FIGS. 16A-16D, an expandable distal end framework 112 is shown, in which six crowns 210 and six support arms 212 are disposed around the longitudinal axis 111 of the suction type blood clot retrieval catheter 110. The support arms can have a helical arrangement with respect to the axis, whereby the support arms can apply torque when the arms shorten and lengthen while advancing through the bends and corkscrew portions of the vasculature (in a collapsed configuration). Similar to the previous embodiment, the support arms can also have at least two curves along their lengths. The first proximal curve 227 can have a concave surface facing the adjacent wall of the blood vessel, and the second distal curve 228 can have a convex surface facing the adjacent wall of the blood vessel. By having concave and convex curves, it helps the support arms to shorten or lengthen when navigating the blood vessel path. The curves also help prevent the distal end framework from expanding excessively when the device is pushed forward while the distal end is in an expanded state.

[0095] Figures 17A - 17D show another expandable tip framework 112, which also has six crowns 210 and six support arms 212 that come together at the proximal crown trough 215. The support arms can extend along a substantially conical surface with a smooth periodic vibration of a curve aligned with the longitudinal axis 111 of the blood clot retrieval catheter 110. The undulating curves of the support arms allow them to bend about their own axes and provide additional flexibility to the tip framework when delivered to the target site in a collapsed configuration. The circumferential undulations of the support arms also provide more support area to prevent the cover 118 from collapsing. The undulations can have a constant pitch and amplitude as shown, or the pitch and amplitude can be varied to adjust the stiffness from the proximal end to the distal end of the support arms. Similar to other embodiments, the trackability and flexibility can also be improved by making the support arms thicker or thinner in the region of the struts.

[0096] Figures 18A - 18D illustrate a view of the tip framework 112 having six crowns 210 and six support arms 212 where adjacent crowns come together at the proximal crown trough 215. The support arms can extend proximally from the proximal crown trough and be tapered to form a substantially conical shape. The support arms can have periodic sinusoidal undulations along their lengths, which allows the arms to bend about their own axes and provides additional flexibility to the tip framework for navigating tortuous blood vessels or when the tip needs to be refolded into a collapsed state when withdrawn back into the outer catheter. The undulations also provide an additional structural support surface area to the cover 118. Additional flexibility is obtained by spirally wrapping the support arms around the longitudinal axis 111 of the blood clot retrieval catheter 110. The spiral configuration facilitates and encourages rotation and bending of the tip through the anatomical structure of tortuous blood vessels.

[0097] Figs. 19A - 19E show some views of a variant of the expandable tip framework 112, in which six crowns 210 and two support arms 212 are joined at the proximal crown trough 215. The two support arms can be spaced 180 degrees apart and can extend along a substantially conical surface with smooth periodic vibrations in a direction aligned with the longitudinal central axis 111. The vibrations enable the support arms to bend about their own axes and impart flexibility to the tip framework to facilitate tracking through the outer catheter when in a collapsed delivery configuration.

[0098] The proximal ends of the support arms 212 can be integrally formed with the support tube 124. The support tube can have two or more axial spines 120, along whose length a plurality of circular ribs 122 are disposed. When using two spines, the spines are located on the longitudinal axis 111 and define a common flexure surface of the blood clot retrieval catheter 110 passing through the two spines. The spines can also be aligned with the support arms so that the expandable tip can easily bend along the same plane. The ribs and spines can have a uniform or variable thickness, enabling adjustment of the stiffness profile along the length of the support tube.

[0099] In this embodiment, further support of the cover 118 at the expandable tip 200 can be provided by a string-like member strut 232 that non-rigidly connects the expandable tip framework 112 and the support tube 124. In one embodiment, four string-like members can be disposed about a longitudinal axis 111 that is equally spaced between support arms 212 such that they are approximately 60 degrees apart. Instead of a direct connection, the string-like members can be screwed through a grommet 229 located in the proximal crown trough 215 and attached to the most distal rib of the support tube, as seen in FIGS. 19A-19D. The string-like members can be fixedly positioned in place with enlarged valves 230 at both ends of the string-like member 232, as shown in FIG. 19E. The valve ends can be formed during manufacture after the string-like member has been fed through the associated grommet by any of several methods, such as a method involving forming a knot, applying heat, or mechanical plastic deformation. The string-like members help support the cover and provide a smooth transition during retraction of the expandable tip between the mouth of the outer catheter and the proximal trough 215 of the crown that is not directly connected to the support tube by the support arms 212. By having only two rigid support arms spaced 180 degrees apart, the tip can bend around the flexion surface as it advances through the outer catheter to the target site.

[0100] In another embodiment of the expandable distal end framework 112 shown in FIGS. 20A-20D, the distal end framework is expanded and there may be six crowns 210 and six support arms 212 laser cut in a sine wave pattern from a shape memory alloy before the shape is set to a substantially conical shape during manufacture. During the shape setting process, the support arms can be wound around the axis of the support arm between the proximal connection to the support tube and the distal connection to the proximal crown truss 215 such that the curves undulate radially rather than circumferentially of the cut circumference. The winding angle can be 90 degrees or any other angle as shown in the figure. If desired, additional offset winding can be added for each arm. The radial undulation allows the support arms to be bent more easily when the aspiration type blood clot retrieval catheter 110 is tracked through the outer catheter within the tortuous area of the vasculature. In other embodiments, the bending characteristics of the distal end framework 112 can be adjusted by simply winding a subset of the support arms 212 or by incorporating different winding angles and winding directions.

[0101] Multiple views of the expandable distal end framework 112 with eight crowns 210 and eight support arms 212 joined together at the proximal crown truss 215 are shown in FIGS. 21A-21D. The support arms can extend independently from the proximal crown truss of the distal crown to a single connection strut 234 aligned with the axial spine 120 of the support tube 124. The support tube can have circular, semi-circular, or other shaped ribs 122 for supporting the cover 118 while having a single axial spine for additional flexibility.

[0102] The connecting strut 234 can be configured such that the support arm 212 intersects at different points along the length of the connecting strut, providing additional flexibility to the support arm. This added flexibility allows the support arm to expand radially outward when a blood clot is being retrieved, providing a larger opening for suction and blood clot reception that can result in a higher success rate when extracting a hard blood clot. The expansion of the support arm 212 allows the cover 118 to be further extended while suctioning and removing the blood clot recovery catheter 112 and the blood clot into the distal tip of the outer catheter 30.

[0103] Figures 22A - 22D show some views of a variant of the expandable distal tip framework 112 having eight crowns 210 and eight support arms 212. The support arms extend distally from the proximal crown trough 215 and intersect one of two connecting struts 234 that are spaced 180 degrees apart across the diameter of the support tube 124. The support tube can have a plurality of axial spines 120 aligned with the connecting struts, or a single axial spine aligned with the first connecting strut, and an opposite second connecting strut connected to the distal peak of the most distal support rib 122. The connecting strut is divided distally of its connection to the support tube and can rejoin at a further distal distance for connection to at least one support arm 212. The division(s) create(s) closed expansion cell(s) 236 that can be made longitudinally longer such that as the support rib 122 of the support tube 124 pulls proximally on the crown 210 of the expanded distal tip framework while suctioning during retraction of the blood clot, the likelihood of this is reduced.

[0104] The crown struts 210 that form the mouth of the distal end frame 112 may have a curve that extends radially inward at the distal end. Thereby, when the blood clot retrieval catheter 110 advances distally through the blood vessel with the distal end in the expanded deployment configuration, the risk that the distal end will catch on the opening of the capillary or that force will act on the blood vessel wall can be reduced. Thus, the curve can assist in sliding the distal end along the blood vessel wall without the risk of blood vessel injury or perforation. To further enhance the ability of the catheter to advance distally without causing tissue damage while the distal end is expanded, the angle between the edge of the substantially conical or funnel-shaped distal end frame 112 and the longitudinal central axis 111 of the catheter can be less than 45 degrees. An angle less than 45 degrees can bias and slightly compress the distal end during the advancement of the blood clot retrieval catheter. When the angle is greater than 45 degrees, there may be an increased risk of catching on the blood vessel wall or eroding the blood vessel wall if the distal end is otherwise biased and the diameter is expanded while advancing within the blood vessel. Thus, an angle less than 45 degrees, more preferably 5 to 30 degrees, is desirable.

[0105] The radially inward curve of the crown struts 210 may have a first radial dimension at the proximal end, a second radial dimension at an intermediate location, and a third radial dimension at the distal end of the distal end frame 112, and it may mean that the second radial dimension is larger than the first and third radial dimensions. When not expanded and constrained, the diameter of the distal end frame can be in the range of 1 mm to 10 mm, preferably 3 mm to 6 mm, at an intermediate location of a device intended to treat occlusions at the ICA, carotid terminus, M1, and M2 locations. The third radial dimension may be larger than the first radial dimension to provide a non-traumatic distal end, but may be smaller than the second radial dimension.

[0106] In some cases, it may not be possible to remove or completely retrieve a blood clot using suction alone. Referring to FIG. 23, a system 300 is illustrated having a suction blood clot retrieval catheter 110 and a mechanical thrombectomy device 60 or a stent retrieval device. The catheter 110 may be similar to that of FIG. 2 in that it provides an expanded proximal segment 250 or a seal 116 against the inner wall of the outer catheter 30 such that suction by a source 80, such as a syringe or a pump, can be applied to the outer catheter and transmitted through the expandable tip 200 of the blood clot retrieval catheter 110. The thrombectomy device 60 is shown deployed within the blood clot 40 and being delivered through a microcatheter 70 by a proximal device shaft 64 and being operated. The shaft 64 can be fitted to a proximal torque device (not shown) to assist the physician in controlling and gripping the shaft. The thrombectomy device 60 may be any of several commercially available products that may be supplied with or separate from the suction-type blood clot retrieval catheter.

[0107] Using a thrombectomy device in combination with a clot retrieval catheter at the dilation site has several benefits that increase the likelihood of first pass success. The thrombectomy device can support the lumen of the blood vessel during aspiration so that it is less likely to collapse under negative pressure. The thrombectomy device will hold together a clot that consists of a series of rigid and flexible segments that might otherwise fragment. The thrombectomy device can also enable the user to pinch off a clot that would not otherwise fully enter the lumen of the clot retrieval catheter between the catheter tip and the thrombectomy device. Since the clot retrieval catheter, the clot, and the thrombectomy device retract together through the vasculature and the outer catheter, the likelihood that the pinched-off clot will be removed from the clot retrieval catheter is reduced. In this case, the interaction between the outer catheter and the dilation site helps compress the clot, thereby enabling the clot to be pulled through the outer catheter by the clot retrieval catheter and the thrombectomy device. Also, if the clot is too large to enter the outer catheter, the outer catheter, the clot retrieval catheter, the thrombectomy device, and the clot can be retracted proximally through the blood vessel into a larger proximal catheter, such as a balloon guide. If the clot is still too hard to retrieve through the larger proximal catheter, all of the devices can be retracted together as one through the vasculature to the outside of the body.

[0108] In one embodiment, as illustrated in FIG. 24, the thrombectomy device can be advanced to the target site using the microcatheter 70 within the lumen of the blood clot retrieval catheter 110 and deployed distal to the expandable tip 200 by retracting the microcatheter. When a blood clot is captured, the thrombectomy device can be withdrawn into the expandable tip 200 where the funnel shape can compress the structure of the thrombectomy device and enhance the grip on the blood clot during retrieval. The expandable tip can also prevent snagging or shearing of the blood clot on the device and catheter. While the thrombectomy device is being retrieved, if access to the target site can be maintained through the suction-type blood clot retrieval catheter 110 and / or the outer catheter 30, suction can prevent any free blood clot fragments from migrating distally. If additional retrieval attempts are required to remove the blood vessel, the microcatheter 70 and the thrombectomy device 60 can be rapidly redelivered to the target site.

[0109] The thrombectomy device 60, the microcatheter 70, the blood clot retrieval catheter 110, and the blood clot 40 can be fully retrieved into the lumen 32 of the outer catheter 30 beyond the distal end 72. The blood clot retrieval catheter 110 and the expandable tip 200 can be designed to cooperate with an outer catheter 30 such as a guide sheath or balloon guide sheath having a length of 7Fr, 8Fr, 9Fr, or 10Fr. Alternatively, the blood clot retrieval catheter 110 can be designed to cooperate with an outer catheter 30 such as an intermediate catheter of 4Fr, 5Fr, or 6Fr.

[0110] The suction source 80 can be a manual syringe that is directed to the distal tip of the blood clot retrieval catheter 110, or a small displacement vacuum pump, and can perform suction. Effective suction can be achieved by the sealing action between the expandable tip 200 and the blood vessel wall or the inner wall of the outer catheter, and / or by using the enlarged proximal segment 250 of the retrieval catheter or the flow restrictor / seal 116. In order to ensure that the maximum flow rate and pressure drop are transmitted to the proximal port 117 by restricting the flow between the catheters, the lumen 32 of the outer catheter can be combined with the lumen 113 of the blood clot retrieval catheter 110. In addition, there is a possibility that blood is prevented from entering the tip of the outer catheter 30, which can interfere with the efficiency of suction. The enlarged segment 250 or seal 116 does not need to be completely airtight, but it is necessary to significantly restrict the flow so that sufficient suction is available at the target position.

[0111] In one embodiment shown in FIG. 25A, the seal 116 is located on the outer surface of the blood clot retrieval catheter 110 and can be actuated to expand radially outwardly relative to the inner wall of the outer catheter 30. In an alternative configuration shown in FIG. 25B, the seal 116 is located on the inner wall of the outer catheter 30 and can be actuated to expand radially inwardly relative to the outer surface of the blood clot retrieval catheter 110.

[0112] FIGS. 25A and 25B also illustrate a further case where another flow restriction or seal 50 can be configured between the inner wall of the blood vessel 20 and the outer wall of either the outer catheter 30 or the blood clot retrieval catheter 110. This can be useful when the funnel cover or membrane 118 of the expandable tip 200 is porous, such that the seal 50 can be opened or closed to inject a contrast agent through the funnel of the expandable tip 200. The contrast agent can be flowed into the blood clot and then flowed back through the porous funnel and the proximal region of the blood vessel by suction so as not to extrude the blood clot distally. Then, the seal 50 can be closed to block the flow so that the blood clot can be efficiently suctioned.

[0113] In other embodiments, a seal is not required. The catheter can be sized such that the lumen between the inner diameter of the outer catheter and the outer diameter of the aspiration blood clot retrieval catheter is small enough that aspiration losses are negligible. Similarly, a portion of the blood clot retrieval catheter can be flared to a larger diameter to restrict or block flow, or a portion of the body of the blood clot retrieval catheter can be coated with a hydrogel that swells upon hydration to achieve a seal with the inner surface of the outer catheter. Alternatively, the lumen between the outer diameter of the blood clot retrieval catheter and the inner diameter of the outer catheter can be configured such that aspiration is applied at both of two locations, the distal end of the blood clot retrieval catheter and the distal end of the outer catheter.

[0114] As illustrated in FIG. 26, the system can also be used with a balloon guide catheter 35 that serves as an external sheath for the outer catheter 30 and the aspiration blood clot retrieval catheter 110. Similar to other embodiments, a thrombus removal device 60 can be used to remove and grasp the blood clot 40. One or more suction sources 80 can be connected at the proximal end of the system to draw a vacuum through any combination of the balloon guide catheter, the outer catheter, and / or the aspiration blood clot retrieval catheter. When inflated, the balloon can arrest blood flow and secure the balloon guide catheter 35 in place for treatment.

[0115] FIGS. 27 and 28 are flow diagrams each including steps of a method for performing a thrombus removal procedure using such a system. The steps of the method can be performed by any of the exemplary systems, devices, and / or instruments described herein or by means known to those of skill in the art.

[0116] Referring to method 2700 outlined in FIG. 27, step 2710 describes the task of providing and positioning an outer catheter and an inner blood clot retrieval catheter, the blood clot retrieval catheter including a self-expanding tip, a support tube having a hollow structure disposed around the longitudinal axis of the blood clot retrieval catheter, an expandable tip and a cover disposed around the support tube, and a distal port. The outer catheter may be supplied with the blood clot retrieval catheter or may be a suitable product known in the art. The self-expanding tip can be sized to have a diameter equal to or slightly larger than that of the target vessel containing the occlusive blood clot or thrombus when unrestrained, such that the tip forms a seal with the vessel upon deployment and can provide local flow restriction / deterrence. In step 2720, a flow restriction or seal can be provided between the inner wall of the outer catheter and the outer wall of the blood clot retrieval catheter to connect their respective lumens and induce more efficient suction to the blood clot. This step may involve using a flared or enlarged proximal segment or an actuatable seal to restrict / deter the flow or another approach commonly used in the art. In step 2730, low friction and / or lubricity characteristics can be provided to at least a portion of the blood clot retrieval catheter by surface treatment, coating, or similar implementation. The coating can be applied, for example, by spraying, reflow, injection molding, or ion transport / plasma. Those skilled in the art can also understand that the coating step may not be necessary if the tip and / or cover are made of materials that already exhibit low friction characteristics.

[0117] In step 2740, the outer periphery of the distal port of the blood clot retrieval catheter can be covered with a soft elastomeric lip having a large edge radius or can be coated or encapsulated with a compatible material for non-traumatic contact with the vessel wall. In step 2750, access to the patient's arterial blood vessels is obtained using conventional well-known means.

[0118] Referring to method 2800 outlined in FIG. 28, in step 2810, an inner blood clot retrieval catheter is placed within the lumen of an outer catheter, and the catheter is advanced into and through the vasculature to the location of the occlusive blood clot. In step 2820, the inner blood clot retrieval catheter is deployed from the outer catheter adjacent to the blood clot in order to radially expand the expandable tip. Then, depending on how the user deploys the flow restriction and / or seal, in step 2830, suction can be applied through one or both of the outer catheter and the blood clot retrieval catheter to stimulate the blood clot into the mouth of the blood clot retrieval catheter. In step 2840, if suction alone is insufficient to remove and capture the thrombus, or if further gripping of the blood clot is desired during initial suction and removal, a microcatheter having a mechanical thrombus removal blood clot retrieval device can be advanced to the target. Then, using any method generally known in the art, the mechanical thrombus removal device can be deployed to capture the blood clot. Suction can be continued throughout this process, or at intervals selected by the user, to prevent blood reflux and maintain a tight grip on the blood clot. In step 2850, the captured blood clot and the blood clot retrieval catheter can be removed from the patient, or the blood clot retrieval catheter can be left in place to maintain access when the mechanical thrombus removal blood clot retrieval device is removed from the patient with the blood clot. If the blood clot is observed at the suction source and / or thrombus removal device and the flow is not blocked within the blood clot retrieval catheter, this step may involve carefully injecting a contrast agent into the system under low pressure using known techniques to determine whether the blood vessel is open. The user may further desire to collapse the expanded mouth of the blood clot retrieval catheter prior to injecting the contrast agent by retracting the tip into the outer catheter so that any remaining debris is not inadvertently pushed distally. If the blood vessel is open, the blood clot retrieval catheter can be removed. If an occlusion remains, additional passes of suction, thrombus removal, or a combination thereof may be repeated until the blood vessel opens.

[0119] The present invention is not necessarily limited to the described examples, which may vary in composition and detail. The terms "distal" and "proximal" are used throughout the foregoing description and are meant to refer to the position and direction relative to the treating physician or user. Thus, "distal" or "distally" refers to a position away from or a direction away from the physician. Similarly, "proximal" or "proximally" refers to a position close to or a direction toward the physician. Further, unless the context clearly dictates otherwise, the singular forms "a," "an," and "the" include plural referents.

[0120] As used herein, the term "about" or "approximately" when referring to any numerical value or range of numerical values indicates a suitable dimensional tolerance that allows the component part or collection of components to function in accordance with its intended purpose as described herein. More specifically, "about" or "approximately" may refer to a range of values within ±20% of the recited value; for example, "about 90%" may refer to a range of values from 71% to 99%.

[0121] In describing exemplary embodiments, technical terms are used for clarity. Each term is intended to have the broadest meaning understood by those skilled in the art and is intended to include all technical equivalents that operate in a similar manner to achieve a similar purpose without departing from the scope and spirit of the present disclosure. It should also be understood that reference to one or more steps of a method does not exclude the presence of additional method steps or method steps intervening between those explicitly identified. Some of the steps of the method can be performed in an order different from that described herein without departing from the scope of the disclosed technology. Similarly, it should be understood that some of the method steps may be omitted.

[0122] Reference to one or more components in an apparatus or system does not exclude the presence of additional components or components intervening between those components that are explicitly identified. For the sake of clarity and brevity, not all possible combinations are enumerated, and such modifications are often obvious to those skilled in the art and are intended to be within the scope of the following claims.

[0123] 〔Embodiment〕 (1) A system for retrieving an occlusion within a blood vessel, the system comprising an outer catheter, and an inner blood clot retrieval catheter disposed within the outer catheter, the blood clot retrieval catheter comprising an expandable tip including a porous framework, an open distal port disposed at the distal end of the expandable tip, a folded delivery state, and an expanded deployment state, and a support tube proximal to the expandable tip and having one or more spines, and a cover disposed radially around at least a portion of the support tube and at least a portion of the expandable tip, wherein the expandable tip has a radial dimension in the folded delivery state that is smaller than the maximum radial dimension of the expandable tip in the expanded deployment state, wherein in the expanded deployment state, the expandable tip self-expands from the folded delivery state such that at least a portion of the expandable tip projects radially outward of the support tube in a state having the maximum radial dimension of the expandable tip, and wherein the maximum radial dimension of the expandable tip is greater than the inner diameter of the outer catheter. (2) The system according to embodiment 1, wherein the support tube further comprises a plurality of loop ribs disposed along the length of the one or more spines, the loop ribs defining a lumen of the blood clot retrieval catheter extending therethrough. (3) The system according to Embodiment 1, wherein in the folded delivery state, at least a portion of the expandable tip between the proximal end and the distal end and the outer catheter have a common radial dimension. (4) In the deployed state, the expandable tip is tapered such that the proximal end of the expandable tip has a first radial dimension and a portion of the expandable tip near the distal end has a second radial dimension greater than the first radial dimension, The system according to Embodiment 1, wherein the second radial dimension is sized to be greater than the inner diameter of the blood vessel when the expandable tip is unconstrained. (5) The porous framework of the expandable tip further comprises a plurality of crowns and a plurality of support arms terminating within a proximal crown trough, In the folded state, the framework is folded around the proximal crown trough, The system according to Embodiment 1, wherein the cover is disposed radially around at least a portion of the framework.

[0124] (6) The system according to Embodiment 1, further comprising a dip zone defining a length of the framework encapsulated by a low friction elastomeric lip. (7) The system according to Embodiment 1, wherein the framework is at least partially encapsulated by the cover. (8) The system according to Embodiment 1, wherein the cover is adhered to the framework. (9) The system according to Embodiment 1, wherein the inner blood clot retrieval catheter is disposed within the lumen of the support tube and further comprises a tubular liner lining the lumen of the support tube. (10) The system according to Embodiment 1, wherein the cover further comprises one or more polymer jackets.

[0125] (11) The system according to embodiment 10, wherein at least one of the one or more polymer jackets is impregnated with particles having material properties for reducing the coefficient of friction of the surface. (12) The system according to embodiment 5, wherein the framework further comprises one or more narrow segments. (13) The system according to embodiment 5, wherein the support arm of the porous framework has a radial undulation. (14) The system according to embodiment 1, wherein at least a portion of the support tube is coated with a low-lubricity friction coating. (15) The system according to embodiment 1, wherein at least a portion of the cover is permeable.

[0126] (16) The system according to embodiment 5, wherein at least one of the one or more spines of the support tube is aligned with a respective support arm among the plurality of support arms. (17) A method for retrieving an occlusive thrombus from a patient's blood vessel, providing an outer catheter and an inner blood clot retrieval catheter, the inner blood clot retrieval catheter comprising a self-expandable tip, a support tube including a hollow structure disposed around a longitudinal axis of the blood clot retrieval catheter, a cover disposed around the expandable tip and the support tube, and a distal port; restricting flow within the lumen between at least a portion of the inner wall of the outer catheter and at least a portion of the outer wall of the blood clot retrieval catheter; accessing the patient's arterial blood vessel using conventional means; advancing the outer catheter and the inner blood clot retrieval catheter to a target site; deploying the blood clot retrieval catheter adjacent to the thrombus to radially expand the self-expandable tip; aspirating through one or both of the outer catheter and the blood clot retrieval catheter to agitate the thrombus into the mouth of the blood clot retrieval catheter. A method comprising removing the blood clot retrieval catheter from the patient together with the captured thrombus. The method according to embodiment 17, further comprising coating an outer periphery of the distal port with an elastomeric lip. The method according to embodiment 17, further comprising coating at least a part of the blood clot retrieval catheter with a low friction coating. The method according to embodiment 17, further comprising capturing the occlusive thrombus with a mechanical thrombus removal device and removing the thrombus removal device into the distal port of the blood clot retrieval catheter.

Claims

1. A system for retrieving an occlusion within a blood vessel, the system comprising an outer catheter, and an inner blood clot retrieval catheter disposed within the outer catheter, the inner blood clot retrieval catheter comprising an expandable tip comprising a porous framework and an open distal port disposed at a distal end of the expandable tip, the expandable tip having a folded delivery state and an expanded deployed state; a support tube proximal to the expandable tip, the support tube comprising two or more spines extending in a longitudinal direction, two of the spines being disposed facing each other, and a plurality of loop ribs disposed along a length of each of the two or more spines, the plurality of loop ribs being axially symmetric with a longitudinal axis of the inner blood clot retrieval catheter and defining a lumen of the inner blood clot retrieval catheter extending therethrough, at least one of the two or more spines being connected to the plurality of loop ribs such that the at least one spine extends into the lumen; a cover disposed radially around at least a portion of the support tube and at least a portion of the expandable tip; the expandable tip having a radial dimension in the folded delivery state that is less than a maximum radial dimension of the expandable tip in the expanded deployed state; in the expanded deployed state, the expandable tip self-expands from the folded delivery state such that at least a portion of the expandable tip projects radially outward of the support tube in a state having the maximum radial dimension of the expandable tip; the system, wherein the maximum radial dimension of the expandable tip is greater than an inner diameter of the outer catheter.

2. The system according to claim 1, wherein the spine extending into the lumen has a tubular or wire structure.

3. The system according to claim 1, wherein in the folded delivery state, at least a portion of the expandable tip and the outer catheter have a common radial dimension.

4. In the expanded deployed state, the expandable tip is tapered such that a proximal end of the expandable tip has a first radial dimension and a portion of the expandable tip near the distal end has a second radial dimension greater than the first radial dimension. The system according to claim 1, wherein when the expandable tip is not constrained, the second radial dimension is sized to be greater than the inner diameter of the blood vessel.

5. The porous framework of the expandable tip further comprises a plurality of crowns and a plurality of support arms terminating within a proximal crown trough, in the folded delivery state, the porous framework is folded around the proximal crown trough, The system according to claim 1, wherein the cover is disposed radially around at least a portion of the porous framework.

6. The system according to claim 1, further comprising a dip zone defining a length of the porous framework encapsulated by a low friction elastomeric lip.

7. The system according to claim 1, wherein the porous framework is at least partially encapsulated by the cover.

8. The system according to claim 1, wherein the cover is adhered to the porous framework.

9. The system according to claim 1, wherein the inner blood clot retrieval catheter is disposed within the lumen of the support tube and further comprises a tubular liner lining the lumen of the support tube.

10. The system according to claim 1, wherein the cover further comprises one or more polymer jackets.

11. The system according to claim 10, wherein at least one of the one or more polymer jackets is impregnated with particles having material properties for reducing the coefficient of friction of the surface.

12. The system according to claim 5, wherein the porous framework further comprises one or more constricted segments.

13. The system according to claim 5, wherein the support arms of the porous framework have radial undulations.

14. The system according to claim 1, wherein at least a portion of the support tube is coated with a lubricious low friction coating.

15. The system according to claim 1, wherein at least a portion of the cover is permeable.

16. The system according to claim 5, wherein at least one of the two or more spines of the support tube is aligned with a respective one of the support arms of the plurality of support arms. **Claim 17**: The porous framework of the expandable tip further comprises a plurality of support arms that terminate distally at the proximal crown trough, the support arms are connected distally at the proximal crown trough by a crown and form petal-shaped cells, The system according to claim 1, wherein at least one of the two or more spines of the support tube is aligned with one of the plurality of support arms.

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