Fibrin-rich / soft clot mechanical thrombectomy device

Abstract

To provide an improved clot retrieval device.SOLUTION: Designs are disclosed for devices capable of removing both firm and soft clots from body vessels that can have dual layers where an inner expandable body of cells runs within an outer expandable cage of the cells. The designs can be characterized by a constrained delivery configuration and an expanded deployed configuration. An outer cage can have wide opening struts to allow clot integration into the device. Both the inner body and outer cage can be configured with shapes to pinch a clot in addition to embedding it therein. The devices can also be capable of having a portion of the outer cage fold and invert proximally after engaging with a target clot to internalize it. These factors can increase the device's ability to capture clots of all compositions, allowing safer and more efficient flow restoration.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE The present disclosure relates generally to devices and methods for removing acute blockages from body vessels during intravascular medical procedures. More particularly, the present disclosure relates to clot retrieval devices for removing blood clots from blood vessels. [Background technology]

[0002] Mechanical devices and methods can be used to remove acute obstructions from blood vessels. Acute obstructions can include blood clots, misplaced devices, dislodged devices, large emboli, etc. Thromboembolism occurs when part or all of a blood clot detaches from the vessel wall. This clot (referred to herein as an embolus) is then transported in the direction of blood flow, which can cause many complications. Ischemic stroke can result when a blood clot lodges in the cerebral vasculature. Pulmonary embolism can result when a blood clot originates in the venous system or the right side of the heart and lodges in the pulmonary artery or its tributaries. Blood clots can also develop in the form of emboli without being released, locally blocking a blood vessel; this mechanism is common in the formation of coronary artery blockages. The devices and methods herein are particularly suited to removing blood clots from cerebral arteries in patients suffering from acute ischemic stroke (AIS), from pulmonary arteries in patients suffering from pulmonary embolism (PE), from native or transplanted coronary vessels in patients suffering from myocardial infarction (MI), and from other peripheral arteries and veins where a blood clot is causing an obstruction.

[0003] Many access challenges exist that can make it difficult to deliver a device to a target site. When access involves navigating the aortic arch (such as in cases of coronary or cerebral occlusion), the shape of the aortic arch in some patients makes it difficult to position a guide catheter. The problem of tortuosity is even more severe in arteries approaching the brain. At the distal end of the internal carotid artery, it is not uncommon for a device to have to navigate a vessel segment with several dangerous bends in rapid succession over a journey of just a few centimeters. In the case of pulmonary embolism, access can be gained through the venous system and then through the right atrium and right ventricle of the heart. The right ventricular outflow tract and pulmonary artery are delicate vessels that can be easily damaged by inflexible or high-profile devices. For these reasons, it is desirable for a clot retrieval device to be compatible with access catheters that are as low-profile and flexible as possible.

[0004] Stent-like clot retriever devices are increasingly being used to remove blood clots from cerebral vessels in acute stroke patients. These devices often rely on a pinning mechanism to grasp the clot by trapping it between a self-expanding stent-like body and the vessel wall. This approach has many drawbacks.

[0005] A stent-like clot retriever relies on its outward radial force to maintain its grip on the clot during retraction. This compressive force tends to dehydrate the clot, which in turn increases its coefficient of friction and can make it more difficult to expel and remove the clot from the vessel. If the radial force is too small, the stent-like clot retriever may lose its grip on the clot, but if the radial force is too large, the stent-like clot retriever may injure the vessel wall and require excessive force to extract. Thus, a stent-like clot retriever with sufficient radial force to address all clot types may cause vascular trauma and serious patient injury, and a stent-like clot retriever with adequate radial force to remain atraumatic may not be able to effectively handle all clot types in various thrombectomy situations. Trapping the clot between the stent-like clot retriever and the vessel wall also creates high shear forces against the sides of the clot as it is removed, potentially releasing clot fragments that, if not retained by the device, can migrate and cause further blockage in the distal vasculature.

[0006] Certain conventional clot removal device designs also do not retain their expanded shape well when placed under tension within a bend in a vessel due to the way their strut elements are connected to one another, resulting in the struts remaining under tension during retraction. This tension is due to friction between the device and the vessel and increases when additional loads are applied, such as resistance provided by a clot. This can result in a loss of grip on the clot when the stent-like clot retriever is withdrawn proximally around a bend in a tortuous vessel, potentially resulting in the capture of the clot being dislodged. At the bend, struts on the exterior of the bend are placed under higher tension than struts on the interior. To achieve the lowest possible energy state, the exterior surface of the clot retrieval device moves toward the interior surface of the bend, thereby reducing the tension in the struts but also reducing the expanded diameter of the device.

[0007] In seeking procedural efficiency in this environment, clot retrieval devices with multiple bodies are often preferred. Such devices may have an outer body that can be scaffolded into the target vessel and an inner body for embedding and capturing the clot. While these devices may function well in engaging and expelling the clot, having a larger and often stiffer network of struts can potentially make it more difficult to retract the device and partially or fully collapse and resheath the device within the outer catheter. Additionally, because these devices are designed such that the clot is typically required to migrate radially inward through the outer member, the devices may not have a very firm grip on the area surrounding the clot.

[0008] Additionally, conventional clot removal devices typically aim to remove either fibrin-rich or soft clots. Currently, there is no way to identify whether a clot is fibrin-rich or soft and friable (or some combination of the two) prior to deployment of a clot removal device, preventing users from knowing which device will improve the probability of first-pass success and reduce risk to the patient. Furthermore, clot heterogeneity can mean that a clot can contain a fibrin-rich core in the proximal, central, or distal portions of the overall clot anatomy, making uniform and reliable grasping more difficult. Summary of the Invention [Problem to be solved by the invention]

[0009] Any device must overcome the challenges discussed above to provide a high level of success in removing any type of clot, restoring flow, and facilitating good patient outcomes. The present design aims to provide an improved clot retrieval device that addresses the above deficiencies. [Means for solving the problem]

[0010] The disclosed design solves these problems by providing a flexible, dual-layer clot retrieval device in which inner and outer members work in concert to capture and remove clots. The design can be intended for use as a first-pass device, with the characteristic that it is as effective at capturing fibrin-rich, sticky clots as it is at capturing soft, friable clots.

[0011] The design can feature a constrained delivery configuration and an expanded, deployed configuration. The outer member can have wide-opening struts to allow for clot incorporation into the device. Both the inner and outer members can be configured and shaped to clamp the clot in addition to embedding it. In some embodiments, at least some portions of the device can collapse proximally and invert after engaging, internalizing, and protecting the target clot. These actions can increase the security of the device's grip on the clot during all stages of retrieval, allowing for safer and more efficient blood flow restoration.

[0012] The device can have a proximal tubular shaft for manipulation with a lumen extending therethrough. The shaft can be a variety of sizes depending on the application. In one example, the shaft is a hypotube having an outer diameter of 0.021 inches or less. In another example, the shaft can have an outer diameter of approximately 0.026 inches. Distal to the shaft can be a framework of struts having a constrained delivery configuration, an expanded clot-engaging deployed configuration when deployed at the target site, and an at least partially constrained clot-clamping configuration.

[0013] In some embodiments, the strut framework can form an elongated inner body and outer cage. In one case, the inner body and outer cage can be laser cut from a single continuous hypotube. In another case, the proximal shaft, inner body, and outer cage can all be cut from the same continuous hypotube. The inner body can have a distal end, a longitudinal axis, and one or more clot clamping cells configured to clamp a clot when the device transitions from the deployed configuration to the clot clamping configuration. The outer cage can be disposed around the inner body, can extend from the distal end of the inner body, or some combination thereof. The outer cage can be expandable to a greater radial extent than the expanded inner body, or can have the same or similar radial dimensions.

[0014] The clot clamping structure can take a variety of forms. The clamping structure can have a series of clot-receiving cells. The cells can consist of one or more flexible struts extending between crowns. The cells can have horseshoe-shaped saddle points at the proximal and distal ends of the cells, allowing the cells to constrict portions of the clot within the cells when the struts are in radial compression. These patterns allow a microcatheter or outer catheter to be advanced over the proximal ends of the clamping structure cells to compress and grasp the clot between the tip of the catheter and at least a portion of the struts of the cells as the device transitions from an expanded, deployed configuration to a partially constrained, clot-clamping configuration. In another example, the clot clamping structure can be a flat pattern of struts arranged in a wave or spiral pattern.

[0015] The properties of the inner body and outer cage can be adjusted independently of one another. The outer cage can be coaxial with the inner body or radially offset. The inner body can be disposed substantially within the lumen of the outer cage.

[0016] In some embodiments, the pull wire can extend through the lumen of the proximal tubular shaft and be fixedly connected to the outer cage at a connection point. The connection point can be at least one of a crimp clamp, a weld, or a braid. A user manipulating the pull wire at the proximal end of the shaft can transition the outer cage from an expanded, deployed configuration to an inverted, clot-accommodating configuration. During this transition, the pull wire can invert the outer cage, causing at least a portion of it to fold at the transition point and return proximally over the inner body. Thus, the struts of the outer cage can surround the clot and the inner body in the clot-accommodating configuration. This inversion can internalize and contain both soft and hard portions of the clot for subsequent retraction and removal. In some cases, the remaining distal portion of the outer cage can also expand radially outward upon actuation of the pull wire to serve as a fragment protection element during clot retrieval.

[0017] In some embodiments, the radial sizes of the inner body and outer cage can be heat treated and varied depending on the application and location of the potential target occlusion within the vasculature. For neurovascular targets, the elongate inner body can have an outer diameter of approximately 2.25 mm in the expanded, deployed configuration. Similarly, the outer cage can have an outer diameter of approximately 5 mm in the expanded, deployed configuration and inverted, clot-containing configuration.

[0018] Another design of the clot retrieval device can have a longitudinal axis, a proximal shaft, an inner body, an outer cage, and a tapered strut mesh connected to the distal end of the outer cage. The inner body, outer cage, and strut mesh can have a constrained delivery configuration, an expanded deployed configuration, and an at least partially constrained clot clamping configuration. After being deployed over the clot, the clot clamping configuration can be achieved by advancing a catheter over the proximal ends of the inner body and outer cage until at least a portion of the clot is compressed between the tip of the catheter and at least a portion of the struts of the inner body, outer cage, or a combination of the inner body and outer cage.

[0019] In some embodiments, the inner body can have struts that form a series of clot-receiving cells. The cells can be heat treated so that they extend in a generally sinusoidal pattern along the longitudinal axis in the expanded, deployed configuration. In another embodiment, the cells form a helical pattern around the axis. In one case, the cells of the inner body are configured to embed with and stabilize the clot when expanded. In another case, the cells of the inner body can have at least one bend configured to embed with and stabilize at least a portion of the clot. The inner body can range in radial size. In some embodiments, the inner body can have an outer diameter in the expanded, deployed configuration ranging from 1.25 mm to 1.5 mm.

[0020] The outer cage can have a series of segments extending axially along the length of the device. Each segment can have one or more cells. In some embodiments, each segment can have two cells. Each cell of the outer cage can have horseshoe-shaped saddle points at its proximal and distal ends configured to compress and clamp at least a portion of the clot when the device is moved into the clot clamping configuration. The clot clamping configuration can be achieved by advancing a catheter over the proximal ends of the inner body and outer cage until at least a portion of the clot is compressed between the tip of the catheter and at least a portion of the struts of the outer cage as the struts are radially compressed. Adjacent axial segments can be hinged by flexible connector struts, which can be the only points of contact between the respective segments. Thus, the segments can bend independently as the device is advanced or retracted through bends in the vasculature.

[0021] The outer cage can be a variety of sizes depending on the target location within the vasculature. In one example, the outer cage can have an outer diameter of approximately 3 mm in the expanded, deployed configuration. In another example, the outer cage can have an outer diameter of approximately 5 mm in the expanded, deployed configuration.

[0022] The inner and outer bodies can share the same shaft and be coaxial about the longitudinal axis. At the proximal interface joint with the shaft, the outer cage can have a fully circumferential tubular outer collar that circumscribes the shaft. The inner body can be laser cut from a tube having an outer diameter smaller than the inner diameter of the outer collar of the outer cage. Thus, the inner body can have a collar at the proximal interface that can slide within the outer collar.

[0023] A method for removing both hard and soft clots from a blood vessel using the disclosed embodiments as a first-pass device can include a device having an inner body, an outer cage, and a proximal shaft. The inner body can be monolithically formed by laser cutting a tube and have struts forming cells configured to embed with at least a portion of the clot. In some cases, the outer cage can also be cut from the same continuous tube and extend distally of the inner body. In other cases, the outer cage can extend around the inner body along the longitudinal axis and be expandable to a greater radial extent than the inner body. The outer cage can also have struts forming cells configured to embed with at least a portion of the clot but allow some of the clot to migrate radially inward. The device can have a constrained delivery configuration, an expanded deployed configuration, and an at least partially constrained clot clamping configuration.

[0024] The method can include delivering a device to a blood vessel adjacent to a target clot site. The clot composition can be hard, soft, or a mixture of both hard and soft portions. The device can be released to embed at least one of the cells of the outer cage and at least one of the cells of the inner body within the clot by expanding the device from a constrained delivery configuration to an expanded, deployed configuration.

[0025] Another step can include advancing the outer catheter distally so that it engages and impacts the proximal ends of the inner body and outer cage, compressing and clamping at least a solid portion of the clot together with the inner body and outer cage. The outer catheter can be a microcatheter, an access catheter, or another suitable outer sheath. The clamping can be maintained and the grip on the clot is not lost while the device is withdrawn.

[0026] In some embodiments, the cells of the inner body and / or outer cage can have struts that form bends or horseshoe-shaped saddle points shaped to be compressed by distal advancement of the outer catheter. The method can then further include clamping at least a portion of the clot at the horseshoe-shaped saddle point of at least one of the inner body cells upon engagement with the outer catheter. Alternatively, or in addition, the method can further include clamping at least a portion of the clot at the horseshoe-shaped saddle point of at least one of the outer cage cells upon engagement with the outer catheter.

[0027] If the clot is friable and not rigid enough to achieve clamping, the user may feel a lack of tactile resistance when the device shaft is retracted or the outer catheter is advanced distally. In this scenario, the outer catheter can be withdrawn and the device can be redeployed to an expanded configuration to embed the clot. In some embodiments, the struts of the outer cage can be everted over the device, and the method can include everting the struts proximally to internalize the clot and inner body. The inner body can be held in place while the outer cage struts are everted, so that the clot is not pushed proximally.

[0028] When a hard and / or soft clot is captured by the device, the method can include removing the clot retrieval device and the captured clot from the patient. This can be done, for example, by using suction to proximally retrieve the device into the guide catheter. If a hard portion of the clot can be clamped, the clamping can be maintained during this step so that the grip on the clot is not lost. Additionally, if the struts of the outer cage are everted proximally (using a tensioned pull wire or other method) to help internalize and secure the clot, this configuration can also be maintained.

[0029] After retrieving some or all of the occlusive clot, an assessment can be made to the extent to which the vessel remains patent. If obstruction remains within the vessel, additional passages can be created by the clot retrieval device. Once proper recanalization of the target vessel has been confirmed, all remaining devices can then be removed from the patient. However, the disclosed devices provide a means for minimizing the number of catheter advancements required to treat a patient, thereby reducing the potential for vessel injury and the associated risk of vessel dissection, even when multiple passages are required.

[0030] Other aspects and features of the present disclosure will become apparent to those skilled in the art from the following detailed description considered in conjunction with the accompanying figures. [Brief explanation of the drawings]

[0031] These and further aspects of the present invention will be further discussed with reference to the following description taken in conjunction with the accompanying drawings, in which like reference numbers indicate functionally similar or identical elements. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. The figures depict one or more implementations of devices of the present invention, by way of example only, and not by way of limitation. [Figure 1] 1 is a perspective view of a clot retrieval device according to an embodiment of the present invention. [Figure 2] 10 shows the clot retrieval device of FIG. 1 with the struts of the outer cage proximally inverted using pull wires, according to an embodiment of the present invention. [Figure 3A] 1 illustrates a method of using a clot retrieval device to capture a clot having both soft and hard components, according to an aspect of the present invention. [Figure 3B] 1 illustrates a method of using a clot retrieval device to capture a clot having both soft and hard components, according to an aspect of the present invention. [Figure 3C] 1 illustrates a method of using a clot retrieval device to capture a clot having both soft and hard components, according to an aspect of the present invention. [Figure 4A] 10A-10C demonstrate a method of using a clot retrieval device to capture a soft clot, according to an embodiment of the present invention. [Figure 4B] 10A-10C demonstrate a method of using a clot retrieval device to capture a soft clot, according to an embodiment of the present invention. [Figure 5A] 4A-4B depict a continuation of the method steps according to an embodiment of the present invention. [Figure 5B] 4A-4B depict a continuation of the method steps according to an embodiment of the present invention. [Figure 6] FIG. 10 is a plan view of another example of a clot retrieval device, according to an aspect of the present invention. [Figure 7] 7 is an elevational view of the clot retrieval device of FIG. 6, in accordance with an embodiment of the present invention. [Figure 8]7 shows a perspective view of the inner body of the clot retrieval device of FIG. 6, according to an embodiment of the present invention. [Figure 9a] 7 illustrates a top view of the inner body of FIG. 6 according to an embodiment of the present invention. [Figure 9b] 7 depicts an elevational view of the inner body of FIG. 6 according to an embodiment of the present invention. [Figure 10] 7 is a perspective view of an exemplary proximal joint of the clot retrieval device of FIG. 6, in accordance with an embodiment of the present invention. [Figure 11] 1 is a flow diagram outlining a method of use of a clot retrieval device, according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0032] The goal of the disclosed design is to create a clot retrieval device that can more effectively and efficiently remove clots of various compositions within the vasculature while maintaining a high level of deliverability and flexibility during the procedure. The design can be made into a first-pass clot retrieval device that can be used to remove any clot type, whether the clot is hard and sticky, soft and friable, or a combination of the two.

[0033] The design can have an outer expandable cage with an inner expandable body extending therethrough. The inner body and outer cage can have large openings, allowing radial forces to migrate portions of the clot into the openings. One or both cells of the inner body and outer cage can have features configured to clamp at least a portion of the clot as the outer catheter advances distally over the device. These clamping designs increase the retention security of the clot retrieval device. The device can also be configured to allow at least a portion of the device to evertate proximally to internalize and protect the clot during retrieval.

[0034] Both the inner and outer expandable members are desirably made from materials that can automatically recover their shape when released from a significantly distorted delivery configuration. A suitable manufacturing process may be to laser cut a nitinol tube, then heat treat and electropolish the resulting structure to create a framework of struts and connecting elements. As described, a range of designs is contemplated for each of these elements, and it is intended that any of these elements may be used with any other element, although to avoid repetition, these elements are not shown in all possible combinations.

[0035] Accessing the various vessels within the vascular system to reach the clot, whether coronary, pulmonary, or cerebral, involves well-known procedural steps and the use of many conventional, commercially available accessory products that are well understood and widely used in laboratory and medical procedures. When these or similar products are used in conjunction with the present disclosure herein below, their function and exact construction will not be described in detail.

[0036] Specific embodiments of the present invention will now be described in detail with reference to the figures. While the description will be directed in large part to mechanical thrombectomy therapy, the design can be adapted to other procedures and other body passageways as well.

[0037] Referring to FIG. 1 , a clot retrieval device 100 can have an elongate shaft 6 from which extends distally a strut framework 102 with an inner body 110 and an outer cage 210 that is expandable from a collapsed or constrained delivery configuration to an expanded, deployed configuration at the target site of a vascular occlusion or clot. The delivery method can be, for example, through a microcatheter 13 or other outer catheter or sheath, depending on the access requirements of the target location. Once exposed beyond the distal end of the microcatheter 13, the device 100 can self-expand to the deployed configuration depicted in FIG. 1 . An occlusion is typically a thrombus (blood clot) that obstructs blood flow within a blood vessel. Having a configuration with both the inner body 110 and the outer cage 210 allows the clot to be retained within the device, minimizing the risk of vascular injury during removal.

[0038] The inner body 110 can be a network of struts forming an axial series of cells 116. The struts of the cells 116 can have high radial strength when expanded to aid in interpenetrating and embedding the cells within the clot. The proximal and distal ends of each cell can taper to a substantially "U" or horseshoe-shaped saddle point 118. This shape of the saddle point 118 allows the cells 116 to radially contract when the microcatheter 13 or another outer catheter is advanced beyond the proximal end of the device. This contraction can pinch a hard portion of the clot embedded within the cell or cells.

[0039] Having multiple clamping cells 116 can be beneficial for capturing clots with fibrin cores at proximal, central, and / or distal locations within the clot. The cells present a clamping grip that can firmly grasp the clot as the device is retracted into the outer catheter until resistance is felt, and can be further secured with suction.

[0040] This clamping facilitates clot removal by increasing the device's grip on the clot, especially in the case of clots that are substantially fibrin-rich. This clamping can also reduce expulsion forces by elongating the clot, thereby pulling it away from the vessel wall during the expulsion process. Clot retention can be improved during retraction into the microcatheter or outer catheter by controlling the proximal end of the clot and preventing it from catching on side branch vessels.

[0041] The ends of adjacent cells 116 may be connected by flexible connecting struts 117. The connecting struts 117 may act as hinges between the cells and may be the only point of contact between adjacent cells. As a result, individual cells may bend independently as the device advances or retracts through bends in the vasculature and may respond locally to forces exerted on the device by trapped clots.

[0042] The outer cage 210 can be fixedly connected to the distal end 114 of the inner body 110. The gently curved loops of the outer cage 210 can give the device 100 an atraumatic profile near the distal end 114. In some embodiments, the inner body 110 and outer cage 210 can be monolithically formed, whereby the inner body struts transition to become the struts of the outer body and take on the shape of the outer body. This is illustrated in FIG. 1 , where a transition point 115 at the distal end 114 of the inner body 110 transitions to the wider looped structure of the outer body 210. Cutting and heat treating the inner body 110 and outer cage 210 from the same tube can simplify the manufacturing process and eliminate potential kink points from stiffness gradients within the device.

[0043] The struts of the outer cage 210 can be highly flexible with low radial force, allowing the struts to be manipulated by pull wires 218 or other suitable actuation methods to change the shape of the outer cage as desired. The flexibility of the struts also allows the outer cage 210 to collapse onto the outer diameter 122 of the inner body 110 for navigating through narrower vessels.

[0044] The inner body 110 and outer cage 210 may preferably be made from a superelastic or pseudoelastic material, such as nitinol or other such alloys with high recoverable strain and suitably high modulus and tensile strength. An advantage of using self-expanding bodies with these materials is that, due to the volumetric properties and stiffness of the target clot, resistance allows the device 100 to initially expand to only a fraction of its freely expanded diameter as it is deployed throughout the clot. This gives the outer body 210 the ability to further expand to a larger diameter during retraction, thereby enabling it to appose the vessel walls as it is retracted into progressively larger and more proximal vessels.

[0045] In one embodiment, the inner body 110 and outer cage 210 can be laser cut from a single continuous piece of tubing that also functions as the shaft 6. Having the shaft 6 double as a tube can allow the lumen 7 of the shaft tube to be used as a conduit for pull wires 218 or other actuation members or devices, if desired.

[0046] The tubing can be in raw material form, such as, for example, nitinol hypotubing, so that the struts of the inner body 110 and outer cage 210 can be laser cut and heat treated to the desired shape and dimensions. For example, the inner body 110 can be heat treated to have an outer diameter 122 of approximately 2.25 mm when expanded to a deployed configuration. Similarly, in the same deployed configuration, the outer cage 210 can be heat treated to have an outer diameter 222 of approximately 5.00 mm. Thus, the device can be effectively spring-loaded within the microcatheter and expanded to these dimensions when deployed at the target site.

[0047] This radial dimension of outer cage 210 may allow the outer cage to maintain contact with the vessel wall as the device is retracted proximally into vessels of progressively larger diameters, not only apposing the vessel wall but also preventing distal migration of the clot, which may also reduce the axial force required to initially expel the clot from the vessel.

[0048] 2 shows an exemplary configuration of the device 100 of FIG. 1 after capture of a clot (not shown). The cells 116 of the inner body 110 act as ports to stabilize the clot and can allow the device to apply a force to the clot in a direction substantially parallel to the direction in which the clot is pulled from the vessel (i.e., substantially parallel to the longitudinal axis 8) when retracted. This also means that any outward radial force applied to the vasculature by the outer cage 210 can be kept to a minimum.

[0049] When the cells 116 of the inner body 110 are embedded within the clot, the pull wire 218 can be tensioned and retracted to proximally invert the flexible struts of the outer cage 210 as shown to internalize the inner body and clot. The pull wire 218 can be retrieved using a handle positioned at the proximal end of the device shaft. The wire 218 can pull the larger diameter outer cage 210 while the inner body 110 is left in place, so that a clamp can be maintained between the saddle points 118 of the inner body cells 116, the microcatheter 13, and at least a hard portion of the clot as described.

[0050] When everted, the outer cage 210 can feature a series of wide loop segments 216 disposed about the longitudinal axis 8 and the inner body 110. At the distal end 114 of the inner body, the inner body / outer cage transition point 115 can form a distal crown 220 to act as a fragment protection element to prevent distal migration of debris during clot removal. The crown 220 can also have a flared diameter similar to the target vessel, which can help securely capture fragments from the friable portion of the clot.

[0051] The shaft 6 may be a stock tubing size selected to be compatible with commonly available delivery sheaths. In one example, the outer diameter 9 of the shaft 6 may be less than approximately 0.021 inches to ensure compatibility with a 0.021 inch inner diameter microcatheter. In another example, the shaft 6 may have a slightly larger outer diameter of approximately 0.026 inches to be compatible with a 0.027 inch inner diameter microcatheter.

[0052] The shaft 6 and other portions of the device 100 may also have indicator bands or markers (not shown) to indicate to the user that the distal end of the device is close to the end of the microcatheter during insertion or to mark the end of the device during a procedure. These indicator bands may be formed by printing, removing, or masking areas of the shaft for coating or radiopaque elements visible under fluoroscopy so that they are visually distinct from the rest of the shaft.

[0053] The shaft 6 can also be coated with a material or have a polymer jacket to reduce friction and thrombus formation. The coating or jacket can be made of a polymer, a low-friction lubricant such as silicone, or a hydrophilic / hydrophobic coating. This coating can also be applied to some or all of the outer cage 210 and inner body 110.

[0054] 3A-3C illustrate a method for using the device 100 within the vasculature 40 to capture a heterogeneous clot 20, 22 having both hard and soft components. In FIG. 3A, the device can be deployed from a microcatheter 13 within a clot where the cells 116 of the inner body 110 section are exposed to the clot. The microcatheter 13 can then be advanced distally to resheath at least a portion of the cells 116 and the pullwires 218 of the inner body 110. Alternatively, a separate outer catheter or sheath can be used. The saddle point 118 forms a natural inflection point for the cells 116, allowing them to fold radially. If a fibrin-rich portion 20 of the clot is present, the cells 116 can achieve a clamping action over this section of the clot between the inner body 110 and the microcatheter, as shown in FIG. 3B.

[0055] Once clamping is achieved and the user feels the resulting resistance, the pull wire 218 can be retracted through the shaft 6. The wire pulls the larger diameter heat-treated portion of the outer cage 210 proximally at the juncture 219, while leaving the inner body 110 in place to maintain the clamping. Withdrawal of the pull wire 218 pulls the loop segment 216 of the outer cage 210 over both the hard portion 20 and the soft portion 22 of the clot to internalize the entire clot within the outer cage, as depicted in FIG. 3C . The entire device, along with the clot, can then be withdrawn into a guide catheter or other outer sheath.

[0056] The bond between the pull wires 218 and the struts of the outer cage 210 at the connection points 219 can be achieved in several ways. In some embodiments, a mechanical connection such as a crimp, braid, or a bulb / eyelet combination can be utilized. In other cases, a thermal process such as welding or brazing can be used.

[0057] 4A-4B and 5A-5B demonstrate a method for using the device when only a soft clot 22 is present. The device can be deployed within the clot 22 so that the cells 116 of the inner body 110 are exposed to the clot and can embed into the clot, as shown in FIG. 4A. In FIG. 4B, the microcatheter 13 can be advanced distally to resheath at least a portion of the cells 116 of the inner body 110 and the pullwire 218 in an attempt to clamp the clot, as seen in FIG. 4B. If the user does not feel any clamping resistance between the inner body 110 and the microcatheter, this suggests that the clot 22 is soft (no fibrin-rich portions or areas). The device can then be redeployed from the microcatheter 13 to embed the inner body 110 and stabilize the clot (FIG. 5A). The user can then pull the pull wires 218, drawing them proximally and inverting the outer cage 210 while leaving the inner body 110 in place to internalize the soft clot 22 (FIG. 5B). The crown 220 can prevent distal migration of clot fragments while the entire device and clot are drawn into the guide catheter.

[0058] Another example of a clot retrieval device 300, which can be a first-pass device for capturing both hard and soft clots, is seen in plan view in FIG. 6 . The device 300 can have a constrained delivery configuration for delivery via a microcatheter, an expanded deployment configuration, and an at least partially constrained clot clamping configuration for grasping hard or fibrin-rich clots. The device 300 can have a longitudinal axis 8, a proximal shaft 6, and an expandable structure of struts forming an inner body 310 and an outer cage 410. As with other designs, the inner body 310 and outer cage 410 can be cut from a shape-memory alloy such as Nitinol to allow the struts to be heat-set into a desired shape when expanded. The inner body 310 and outer cage 410 can help retain the clot within the device to prevent the clot from brushing against the vessel wall due to the gripping, reducing the risk of damage to the vessel wall during retrieval.

[0059] The inner body 310 can be configured to stabilize the clot during the removal process, adding support and additional grip, especially for soft clots. The inner body 310 can be a series of low-profile clot-engaging cells designed with an "S-wave" or sinusoidal final heat-treated shape. The low-profile design allows for more clot-receiving space between the inner body 310 and the outer cage 410 to minimize clot shear when the device is retrieved into a midcatheter or other outer catheter. In one embodiment, the inner body 310 can have an expanded outer diameter in the range of approximately 1.25 to 1.5 mm. In other embodiments, the inner body can have an expanded diameter determined by the difference in foreshortening when the inner body and outer cage are crimped together into a microcatheter for delivery to the target site.

[0060] An elevated side view of the device 300 from Figure 6 is depicted in Figure 7. The outer cage 410 can have an axial series of body segments 412 disposed about the inner body 310 and is heat treated with an outer diameter 422 that is substantially larger than the inner diameter 322 of the inner body. In some preferred embodiments, this outer diameter 422 can be approximately 5 mm. Each segment 412 can have one or more cells 416 with horseshoe-shaped saddle points 418 at the proximal and distal ends of each cell.

[0061] 6-7, for example, has two cells 416 per segment 412 about longitudinal axis 8 that are perpendicular to one another. Note that due to the perpendicularity of the cells 416 from the plan and elevation views as shown in FIGS. 6 and 7, respectively, each cell of body segment 412 can have a 180-degree curvature, with flexible connector struts 417 acting as the top / bottom of adjacent cells when device 300 is rotated 90 degrees. Thus, the result can be a cylindrical shape for outer cage 410 about longitudinal axis 8.

[0062] Expansion of the outer cage 410 can cause compression and / or displacement of the clot during expansion, depending on the level of scaffolding support provided by the struts. When the expandable body provides a high level of scaffolding, the clot may be compressed. Alternatively, when the expandable body provides an escape route or opening, the expanding body urges the clot toward the opening. The clot itself can have many degrees of freedom and can move in a variety of different directions. When the device is long enough, many of the degrees of freedom of movement available to the clot are eliminated. This allows the clot to be retrieved without excessive compression. This is advantageous because compression of the clot can dehydrate the clot, but in turn increases frictional properties and stiffness, making it more difficult to disengage and remove the clot from the vessel. This compression can be avoided if the clot can easily move inward through the cells of the outer cage.

[0063] 6 and 7 can have wide-opening struts to allow the clot to move radially through the outer cage 410 when deployed within the clot. As with other examples, distal advancement of a microcatheter or other catheter after deployment can compress the saddle points 418 of each cell 416 to pinch the fibrin-rich portion of the clot for firm grip during removal.

[0064] Adjacent segments 412 of the outer cage 410 can be joined by flexible connector struts 417. As saddle points 418 taper the ends of the cells 416 of each segment 412 to a point, a single connector strut 417 can be the only point of contact between the respective segments. This allows the segments to hinge around the connector struts to improve device flexibility and vessel wall apposition. The connector struts can also allow the cells 416 of individual segments to locally open to an increased diameter to maintain a good grip on the clot between the inner body 310 and the outer cage 410. The ability to locally increase to a larger diameter can be particularly useful in situations where part or all of the target clot is located within a difficult anatomical structure, such as a bifurcation, allowing the clot to be retained within the vessel.

[0065] The outer cage 410 can also have a final segment with a tapered mesh end 420 to prevent small fragments from breaking away from the main clot and reoccluding smaller, more distal vessels. The mesh end 420 can also help protect against clot compartments separating as they roll or change shape during retrieval. The distal struts forming this segment 420 can bulge or flare so that the distal end of the outer cage 410 is atraumatic to the vessel in which it is used. The tapering and converging of these struts can also reduce the pore size of the mesh to create an effective fragment capture zone.

[0066] A perspective view of the inner body 310 of the device 300 from Figures 6 and 7 is shown in Figure 8. The sinusoidal design of the body cells 316 is visible as the struts include bends 319 between the amplitude peaks 317 of the pattern. The bends 319 of the cells 316 can bias movement away from, or at least not in the same direction as, the clot-clamping cells 416 of the outer cage 410, so that when the proximal portion of the device is partially restrained in the clot-clamping configuration, the inner body 310 stabilizes but does not shear portions of the clot. The bends or crowns can also help provide a better grip on the clot by embedding and balancing with the clot for the crucial initial step of disengaging the clot from the vessel, allowing the outer cage 410 to be configured with a lower radial force.

[0067] The undulating shape of the cells 316 and inner body 310 may allow the device to accommodate slight length differences through stretching without applying significant tensile or compressive forces to the joints. Length differences may occur, for example, when the device is expanded, collapsed, or deployed in small vessels. The undulating configuration of the struts of the inner body cells 316 also allows the cells to extend and shorten sufficiently so that the lengths of the inner body 310 and outer cage 410 may be substantially the same when loaded into a microcatheter and when freely expanded at the target site. However, the cells may still have sufficient structural rigidity so that the device 300 can be advanced or retracted without excessively extending and shortening the inner body 310 and outer cage 410.

[0068] The inner body 310 can also transition distally from a single cell sinusoidal pattern to a collection of radially expanded struts 318. In the example shown, four expansion struts 318 can be positioned equally spaced 90 degrees apart about the longitudinal axis. The flared or expanding struts can assist the distal mesh section segment 420 of the outer cage 410. The expansion struts can also align the foreshortening of the inner body 310 and outer cage 410 during crimping of the device onto an insertion tool or microcatheter.

[0069] 9A and 9B provide top and side views, respectively, of the inner body 310 of FIG. 8 , independent of the outer cage 410 of the device 300. FIG. 9A shows the sequence of cell openings 316 within the inner body 310. Each cell opening 316 may have a single cell opening 316. The cells may have a diameter of approximately 1.25 to 1.5 mm, or may have slightly different diameters determined by the difference in shortening of the inner body 310 and outer cage 410 during crimping of the device onto an insertion tool or microcatheter. The expansion struts 318 near the distal end 314 may have a larger outer diameter (much closer to the expanded outer diameter of the outer cage) than the cells 316 of the inner body 310; as a result, these struts may also account for a significant amount of the take-up length required between the inner body and outer cage.

[0070] 9B illustrates a side view of FIG. 9A clearly showing the sinusoidal pattern 315 of cells 316 of the inner body 310. The proximal-most cell of the pattern can terminate in a connecting strut 330 that connects it to a partially circumferential inner collar 328 at the proximal end 312 of the inner body. The inner body struts can be monolithically formed with the collar 328 by cutting and machining a single hypotube having an outer diameter 324 equal to the outer diameter of the collar. At the distal end 314 of the inner body 310 can be a radiopaque coil 310 or marker band for marking the end of the device during a procedure.

[0071] The proximal connections of the inner body 310 and outer cage 410 to the elongate shaft 6 may be constructed so that the inner body and outer cage can have some small amount of independent translation relative to one another. The translation may be, for example, linear translation along an axis, rotation of one body relative to the other, or some combination thereof. An example of a coupling where this may be achieved with a collar assembly 426 is illustrated in the exploded view of FIG. 10 . The proximal end 413 of the outer cage 410 may have a tubular collar 427 that surrounds the elongate shaft 6. The proximal end 312 of the inner body 310 may have a partially circumferential inner collar 328 that rides on the elongate shaft 6, as described above. The partially circumferential inner collar 328 may be cut from a hypotube having an outer diameter 324 that is smaller than the inner diameter 428 of the tubular collar 427 of the outer cage 410. Such a configuration may allow the inner collar 328 to be located radially inward of the tubular outer collar 427, which may allow a small amount of rotation of either the inner body 310 or the outer cage 410 relative to the other. The partially circumferential setup also allows the inner collar 328 to be assembled onto the shaft 6 with the fully circumferential outer collar 427.

[0072] The coaxial collar assembly 426 of the partial inner collar 328 of the inner body 310 and the outer collar 427 of the outer cage 410 can allow the two bodies to be substantially aligned with the neutral axis of the device 300 during flexion within the vasculature. The possibility of rotation between the outer cage 410 and the inner body 310 allowed by the collar assembly 426 can also help prevent clot shear that could otherwise occur with a static and fixed connection.

[0073] 11 diagrammatically illustrates method steps for performing a thrombectomy procedure using such a device. The method steps may be implemented by any of the exemplary devices described herein and known to those skilled in the art, or by suitable alternatives. The method may have some or all of the steps described, although in many cases the steps may be performed in a different order than disclosed below.

[0074] Referring to method 11000 outlined in FIG. 11 , step 11010 may include delivering a clot retrieval device across a target clot of unknown composition. The clot may be hard and fibrin-rich, soft and friable, or some combination of the two. The clot retrieval device may be delivered through a microcatheter or other suitable delivery catheter and may have a collapsed configuration during delivery and an expanded, deployed configuration when the delivery catheter is retracted. An elongate shaft may be used to manipulate the device by a user.

[0075] The strut expandable element can be attached to a distal end of the elongate shaft and have outer cage cells and inner body cells within a lumen of the outer cage. Step 11020 can include embedding at least one of the outer cage cells and at least one of the inner body cells within the clot by expanding the device from a constrained delivery configuration to an expanded, deployed configuration. A radial force from the expansion of the outer cage can displace at least a portion of the clot radially inward.

[0076] In step 11030, a microcatheter or other outer catheter can be advanced distally to engage at least some of the cells of the inner body and outer cage to compress and clamp at least a solid portion of the clot. The cells of the inner body and / or outer cage can be shaped to have bends at their axial apexes that are shaped to radially fold the cells when the device is partially resheathed. Thus, the saddle points can exert a firm grip on any fibrin-rich core within the clot composition.

[0077] Distal advancement of the outer catheter can continue until resistance is felt by the user indicating that clamping has been achieved, or no resistance is felt indicating the absence of a fibrin-rich portion of the clot. If clamping has not been achieved, step 11040 can include withdrawing the outer catheter and redeploying the device to embed within the clot. This redeployment stabilizes the soft clot within the cells of the device.

[0078] In step 11050, some or all of the struts of the outer cage can be everted proximally, folding back over the clot and inner body to internalize the clot and inner body. Everting can protect the clot and reduce possible interaction or snagging due to friction, bifurcations, and / or sharp bends within the vasculature. The struts can be retracted and pulled proximally by the user by utilizing pull wires running through the lumen of the device shaft, or by other suitable means. For example, the pull wires can extend through the hypotube device shaft and be actuated from a handle positioned on the proximal end of the shaft. Additionally, the proximal joints of the inner body, outer cage, and elongate shaft can be configured to allow some relative movement between them, reducing retraction forces and the risk of clot shear.

[0079] Step 11060 may include removing the clot retrieval device and trapped clot from the patient. This may be accomplished, for example, by retrieving the device into the outer catheter with the aid of suction. If clamping is achieved, it may be maintained by maintaining the relative positions of the device and outer catheter during withdrawal. Optionally, if additional segments of occlusive clot are present or if further passes are required for complete recanalization, the device may be rinsed and gently washed with saline before being reloaded into the microcatheter for reintroduction into the vasculature.

[0080] The present invention is not necessarily limited to the examples described, which may vary in configuration and details. The terms "distal" and "proximal" are used throughout the foregoing description and are meant to refer to a location and direction relative to the treating physician. Thus, "distal" or "distally" refers to a location away from or a direction away from the physician. Similarly, "proximal" or "proximally" refers to a location closer to or a direction toward the physician. Furthermore, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0081] The term "about" or "approximately" used herein in connection with any numerical value or range of values ​​indicates a suitable dimensional tolerance that enables a portion of a component or a collection of components to function for its intended purpose as described herein. More specifically, "about" or "approximately" may refer to a range of values ​​of ±20% of the recited value, e.g., "about 90%" may refer to a range of values ​​of 71% to 99%.

[0082] In describing exemplary embodiments, technical terminology is employed for the sake of clarity. Each term is intended to have its broadest meaning as understood by one of ordinary skill in the art and is intended to include all technical equivalents that operate in a similar manner to accomplish a similar purpose without departing from the scope and spirit of the present invention. It should also be understood that a reference to one or more steps of a method does not preclude the presence of additional or intervening method steps between those explicitly identified steps. Similarly, some steps of a method can be performed in a different order than set forth herein without departing from the scope of the disclosed technology. For the sake of clarity and conciseness, not all possible combinations have been listed; such variations will often be apparent to those skilled in the art and are intended to be within the scope of the following claims.

[0083] [Embodiment] (1) A device for removing a blood clot from a blood vessel, comprising: a proximal tubular shaft having a lumen extending therethrough; 1. A strut framework having a constrained delivery configuration, an expanded clot engaging deployment configuration, and an at least partially constrained clot clamping configuration, the strut framework comprising: an elongate inner body having a distal end, a longitudinal axis, and one or more clot clamping cells configured to clamp the clot upon movement from the deployed configuration to the clot clamping configuration; an outer cage connected to the distal end of the elongate inner body and expandable to a greater radial extent than the elongate inner body; and one or more pull wires extending through the lumen of the proximal tubular shaft and fixedly connected to the outer cage, the pull wires configured to move the outer cage from the expanded, deployed configuration to the inverted, clot-containing configuration. (2) The device of embodiment 1, wherein the inner body and the outer cage are monolithically formed through laser cutting of a single continuous tube. (3) A device as described in embodiment 1, wherein each clamping cell has horseshoe-shaped saddle points at the proximal and distal ends of the cell. (4) A device as described in embodiment 1, wherein the pull wire is connected to the outer cage at a connection point by at least one of a crimp clamp, welding, or braiding. (5) A device as described in embodiment 1, wherein the struts of the outer cage are configured to invert proximally when the outer cage is moved from the expanded, deployed configuration to the inverted, clot-containing configuration.

[0084] (6) A device as described in embodiment 5, wherein the struts of the outer cage surround the clot and the elongated inner body in the inverted clot-accommodating configuration. (7) The device described in embodiment 1, wherein the proximal tubular shaft has an outer diameter of 0.533 mm (0.021 inches) or less. (8) The device of embodiment 1, wherein the elongate inner body has an outer diameter of approximately 2.25 mm in the expanded, deployed configuration. (9) The device described in embodiment 1, wherein the outer cage has an outer diameter of approximately 5 mm in the inverted clot-containing configuration. (10) A clot retrieval device for removing both hard and soft clots from a blood vessel, comprising: a longitudinal axis; a proximal shaft; a constrained delivery configuration, an expanded deployed configuration, and an at least partially constrained clot clamping configuration; an inner body including struts forming a series of clot-receiving cells, the cells extending in a generally sinusoidal pattern along the longitudinal axis in the expanded, deployed configuration; an outer cage comprising a series of segments, each segment comprising two cells configured to clamp the clot upon movement from the deployed configuration to the clot clamping configuration; a tapered strut mesh connected to the distal end of the outer cage, the strut mesh having a closed end and configured as a barrier against clot fragments.

[0085] (11) The device of embodiment 10, wherein each cell of the outer cage comprises a horseshoe-shaped saddle point at the proximal and distal ends of the cell, the saddle point configured to compress and clamp at least a portion of the clot when the device is moved into the clot clamping configuration. (12) The device of embodiment 10, wherein the inner body has an outer diameter in the expanded, deployed configuration in the range of 1.25 mm to 1.5 mm. (13) The device of embodiment 10, wherein the outer cage has an outer diameter of approximately 5 mm in the expanded, deployed configuration. (14) The device of embodiment 10, wherein the clot clamping configuration is achieved by advancing a catheter over the proximal ends of the inner body and outer cage until at least a portion of the clot is compressed between the tip of the catheter and at least a portion of the struts of the outer cage. (15) The device of embodiment 10, wherein the segments of the outer cage are hingedly joined to adjacent segments by flexible connector struts, the connector struts being the only points of contact between the respective segments.

[0086] (16) The device of embodiment 10, wherein the cells of the inner body include at least one bend configured to embed and stabilize at least a portion of the clot. (17) The device of embodiment 10, wherein the proximal end of the outer cage comprises a tubular outer collar. (18) The device of embodiment 17, wherein the inner body is monolithically formed by laser cutting a tube having an outer diameter smaller than the inner diameter of the outer collar of the outer cage. (19) A method for removing both hard and soft blood clots, said method comprising: delivering a clot retrieval device having a constrained delivery configuration, an expanded deployed configuration, and an at least partially constrained clot clamping configuration to a blood vessel having a clot, the clot retrieval device comprising: an inner body monolithically formed by laser cutting a tube, the inner body comprising struts that form cells configured to be embedded with at least a portion of a blood clot; delivering an outer cage extending along a longitudinal axis and expandable to a greater radial extent than the inner body, the outer cage comprising struts forming cells configured to be embedded with at least a portion of a blood clot; expanding the device from the constrained delivery configuration to the expanded deployed configuration to embed at least one of the cells of the outer cage and at least one of the cells of the inner body within a blood clot; advancing the outer catheter so that the outer catheter engages the inner body and the outer cage to compressively clamp at least a solid portion of the clot with the cells of the inner body and the cells of the outer cage; If clamping is not achieved, withdrawing the outer catheter and redeploying the clot retrieval device to embed within the soft clot; removing the clot retrieval device and the captured clot from the patient. (20) The method of embodiment 19, further comprising proximally everting the struts of the outer cage to internalize the clot and the inner body.

Claims

1. 1. A device for removing a blood clot from a blood vessel, comprising: a proximal tubular shaft having a lumen extending therethrough; an elongate inner body having a distal end and a longitudinal axis, the elongate inner body comprising two or more clot clamping cells, the two or more clot clamping cells changeable in shape between a constrained delivery configuration, an expanded clot engaging deployed configuration, and an at least partially constrained clot clamping configuration, the two or more clot clamping cells being spaced apart from one another in a direction along the longitudinal axis, each of the two or more clot clamping cells being configured to clamp the clot within the clot clamping cell when the elongate inner body changes shape from the deployed configuration to the clot clamping configuration; an outer cage connectable to the distal end of the elongate inner body and expandable to a greater radial extent than the elongate inner body, the outer cage being shape-changeable between a constrained delivery configuration, an expanded clot engaging deployment configuration, and an at least partially constrained clot clamping configuration; one or more pull wires extending through the lumen of the proximal tubular shaft and fixedly connected to the outer cage, the one or more pull wires configured to move the outer cage from the expanded, clot-engaging, deployed configuration to the inverted, clot-containment configuration; The two or more clot clamping cells include a first clot clamping cell and a second clot clamping cell adjacent to each other, the second clot clamping cell being located distal to the first clot clamping cell, the distal end of the first clot clamping cell and the proximal end of the second clot clamping cell being connected by a flexible connection, the flexible connection acting as a hinge between the first clot clamping cell and the second clot clamping cell, and the flexible connection being the only contact point between the first clot clamping cell and the second clot clamping cell.

2. A device as described in claim 1, wherein the length of the proximal and distal ends of each of the two or more clot clamping cells in a direction perpendicular to the direction along the longitudinal axis is smaller than the length of the central portion between the proximal and distal ends of the clot clamping cell.

3. The device of claim 1 , wherein the pull wires are connected to the outer cage at a juncture by at least one of welding or braiding.

4. The device of claim 1, wherein the outer cage is configured to invert proximally when the outer cage is moved from the expanded clot-engaging deployment configuration to the inverted clot-containing configuration.

5. The device described in claim 4, wherein the outer cage surrounds the clot and the elongated inner body in the inverted clot-containing configuration.

6. The device of claim 1 , wherein the proximal tubular shaft has an outer diameter of 0.533 mm (0.021 inches) or less.

7. The device of claim 1 , wherein the elongate inner body has an outer diameter of 2.25 mm in the expanded, clot-engaging, deployed configuration.

8. The device of claim 1 , wherein the outer cage has an outer diameter of 5 mm in the inverted, clot-containing configuration.

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