FIBRIN RICH / SOFT CLOT MECHANICAL THROMBECTOMY DEVICE

Abstract

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 cells. The designs can feature a constrained delivery configuration and an expanded deployed configuration. An outer cage can have wide opening struts to allow for 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 in it. 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 for safer and more efficient flow restoration.

Claims

1. A device for removing a clot from a blood vessel, comprising: a proximal tubular shaft comprising a lumen extending therethrough; a framework of struts having a constrained delivery configuration, an expanded clot engaging deployed configuration, and an at least partially constrained clot pinching configuration, the framework of struts comprising: an elongate inner body comprising a distal end, a longitudinal axis, and one or more clot pinching cells configured to pinch the clot on movement from the deployed configuration to the clot pinching configuration; an outer cage connected to the distal end of the elongate inner body and expandable to a radial extent greater 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 an inverted clot housing configuration.

2. The device of claim 1, the inner body and outer cage monolithically formed through laser cutting a single continuous tube.

3. The device of claim 1, each pinching cell comprising a horseshoe shaped saddle point at the proximal and distal ends of the cell.

4. The device of claim 1, the pull wires connected to the outer cage at a linkage point by at least one of a crimp clamp, a weld, or a braid.

5. The device of claim 1, the struts of the outer cage being configured to invert proximally when the outer cage is moved from the expanded deployed configuration to the inverted clot housing configuration.

6. The device of claim 5, the struts of the outer cage enclosing the clot and the elongate inner body in the inverted clot housing configuration.

7. The device of claim 1, the proximal tubular shaft having an outer diameter of less than or equal to 0.021 inches.

8. The device of claim 1, the elongate inner body having an outer diameter of approximately 2.25 mm in the expanded deployed configuration.

9. The device of claim 1, the outer cage having an outer diameter of approximately 5 mm in the inverted clot housing configuration.

10. A clot retrieval device for removing both firm 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 pinching configuration; an inner body comprising struts forming a series of clot receiving cells, the cells extending in a generally sinusoidal wave 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 pinch the clot on movement from the deployed configuration to the clot pinching configuration; and a tapered strut mesh connected to the distal end of the outer cage, the strut mesh comprising a closed end and configured as a barrier to clot fragments.

11. The device of claim 10, each cell of the outer cage comprising a horseshoe shaped saddle point at the proximal and distal ends of the cell, the saddle points configured to compress and pinch at least a portion of the clot as the device is moved to the clot pinching configuration.

12. The device of claim 10, the inner body having an outer diameter in the range of 1.25 mm-1.5 mm in the expanded deployed configuration.

13. The device of claim 10, the outer cage having an outer diameter of approximately 5 mm in the expanded deployed configuration.

14. The device of claim 10, the clot pinching configuration achieved by advancing a catheter over the proximal ends of the inner body and the 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 claim 10, the segments of the outer cage hingedly joined to adjacent segments by a flexible connector strut, the connector strut being the only point of contact between respective segments.

16. The device of claim 10, the cells of the inner body comprising at least one bend configured to embed and stabilize at least a portion of the clot.

17. The device of claim 10, the proximal end of the outer cage comprising a tubular outer collar.

18. The device of claim 17, the inner body being monolithically formed by laser cutting a tube with an outer diameter less than an inner diameter of the outer collar of the outer cage.

19. A method for removing both firm and soft clots, the method comprising the steps of: delivering a clot retrieval device having a constrained delivery configuration, an expanded deployed configuration, and an at least partially constrained clot pinching configuration to a blood vessel with a clot, the clot retrieval device comprising: an inner body monolithically formed by laser cutting a tube, the inner body comprising struts forming cells configured to embed with at least a portion of a clot; and an outer cage extending along a longitudinal axis and comprising expandable to a radial extent greater than the inner body, the outer cage comprising struts forming cells configured to embed with at least a portion of a clot; embedding at least one of the cells of the outer cage and at least one of the cells of the inner body in a clot by expanding the device from the constrained delivery configuration to the expanded deployed configuration; advancing an outer catheter so that the outer catheter engages with the inner body and outer cage to pinch in compression at least a firm portion of the clot with the cells of the inner body and the cells of the outer cage; withdrawing the outer catheter to redeploy and embed the clot retrieval device in a soft clot if no pinch is achieved; and removing the clot retrieval device and the captured clot from the patient.

20. The method of claim 19, further comprising the step of inverting the struts of the outer cage proximally to internalize the clot and the inner body.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The above and further aspects of this invention are further discussed with reference to the following description in conjunction with the accompanying drawings, where like reference numbers indicate elements which are functionally similar or identical. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating principles of the invention. The figures depict one or more implementations of the inventive devices, by way of example only, not by way of limitation.

[0032] FIG. 1 is a view of a clot retrieval device according to aspects of the present invention;

[0033] FIG. 2 shows the clot retrieval device of FIG. 1 with the struts of the outer cage inverted proximally using pull wires according to aspects of the present invention;

[0034] FIGS. 3A-3C illustrate a method of use for a clot retrieval device for capturing a clot having both soft and firm components according to aspects of the present invention;

[0035] FIGS. 4A-4B demonstrate a method of use for a clot retrieval device for capturing a soft clot according to aspects of the present invention;

[0036] FIGS. 5A-5B depicts the continuation of the method steps in FIGS. 4A-4B according to aspects of the present invention;

[0037] FIG. 6 is a plan view of another example of a clot retrieval device according to aspects of the present invention;

[0038] FIG. 7 is an elevation view of the clot retrieval device of FIG. 6 according to aspects of the present invention;

[0039] FIG. 8 shows a perspective view of the inner body of the clot retrieval device of FIG. 6 according to aspects of the present invention;

[0040] FIG. 9a illustrates a plan view of the inner body of FIG. 6 according to aspects of the present invention;

[0041] FIG. 9b depicts an elevation view of the inner body of FIG. 6 according to aspects of the present invention;

[0042] FIG. 10 is a view of an example proximal joint for the clot retrieval device of FIG. 6 according to aspects of the present invention;

[0043] FIG. 11 is a flow diagram outlining a method of use for a clot retrieval device according to aspects of the present invention.

DETAILED DESCRIPTION

[0044] The objective of the disclosed designs is to create a clot retrieval device capable of providing more effective and efficient removal of clots of various composition in the vasculature while maintaining a high level of deliverability and flexibility during procedures. The designs can be first pass clot retrieval devices that can be used to the removal of any clot type, whether they be firm and sticky, soft and friable, or a combination of the two.

[0045] The designs can have an outer expandable cage within which runs an inner expandable body. The inner body and outer cage can have large openings where a radial force allows portions of the clot to migrate into the openings. The cells of one or both of the inner body and outer cage can have features configured to pinch at least a portion of the clot when an outer catheter is advanced distally upon the device. These pinching designs increase the grip security of the clot retrieval device. The devices can also be configured so that at least a portion of the device can invert proximally to internalize and protect the clot during retrieval.

[0046] Both the inner and outer expandable members are desirably made from a material capable of recovering its shape automatically once released from a highly strained delivery configuration. A suitable manufacturing process can be to laser cut a Nitinol tube and then heat set and electropolish the resultant structure to create a framework of struts and connecting elements. A range of designs are envisaged for each of these elements as described, and it is intended that any of these elements can be used in conjunction with any other element, although to avoid repetition they are not shown in every possible combination.

[0047] Accessing the various vessels within the vascular to reach a clot, whether they are coronary, pulmonary, or cerebral, involves well-known procedural steps and the use of a number of conventional, commercially available accessory products. These products are well understood and widely used in laboratory and medical procedures. When these or similar products are employed in conjunction with the disclosure of this invention in the description below, their function and exact constitution are not described in detail.

[0048] Specific examples of the present invention are now described in detail with reference to the Figures. While the description is in many cases in the context of mechanical thrombectomy treatments, the designs may be adapted for other procedures and in other body passageways as well.

[0049] Referring to FIG. 1, a clot retrieval device 100 can have an elongate shaft 6 from which distally extends a strut framework 102 with an inner body 110 and an outer cage 210 expandable from a collapsed or constrained delivery configuration to an expanded deployed configuration at the target site of a vessel occlusion or clot. The delivery method can be through, for example, a microcatheter 13 or other outer catheter or sheath depending on the access requirements of the target location. Upon being exposed beyond the distal end of the microcatheter 13, the device 100 can self-expand to the deployed configuration depicted in FIG. 1. The occlusion is typically a thrombus (blood clot) impeding blood flow in the vessel. Having a configuration with both an inner body 110 and outer cage 210 allows the clot to be retained inside the device which can minimize the risk of vessel damage during removal.

[0050] 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 a high radial force when expanded to assist with interpenetrating and embedding the cells within the clot. The proximal and distal end of each cell can taper into substantially a “U” or horseshoe shaped saddle points 118. This shape of the saddle points 118 allows the cells 116 to contract radially when the microcatheter 13, or another outer catheter, is advanced over the proximal end of the device. This contraction can pinch a firm portion of a clot embedded within the cell or cells.

[0051] Having multiple pinching cells 116 can be beneficial for capturing clots which have fibrin cores in the proximal, center, and/or distal locations within the clot. The cells can grip the clot tightly as the device is retracted into the outer catheter until resistance is felt, indicating a pinch grip that can be further secured with aspiration.

[0052] The pinch facilitates removal of the clot by increasing the grip of the device on the clot, particularly in the case of substantially fibrin rich clots. The pinch can also elongate the clot, thereby reducing the dislodgement force by pulling the clot away from the vessel wall during the dislodgement process. Retention of the clot can be improved during retraction to the microcatheter or outer catheter by controlling the proximal end of the clot and preventing it from snagging on a side branch vessel.

[0053] The ends of adjacent cells 116 can be connected by flexible connecting struts 117. The connecting struts 117 can act as a hinge between cells and can be the only point of contact between adjacent cells. As a result, the individual cells can flex independently as the device is advanced or retracted through bends in the vasculature and can respond locally to the forces exerted on the device by a captured clot.

[0054] 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 4. In some examples, the inner body 110 and outer cage 210 can be formed monolithically, whereby the struts of the inner body transition to become struts of, and take on the shape of, the outer body. This is illustrated in FIG. 1 where transition points 115 at the distal end 114 of the inner body 110 make the transition to the broadly looped structure of the outer body 210. Cutting and heat setting the inner body 110 and outer cage 210 from the same tube can simplify the manufacturing process and remove potential kink points from stiffness gradients in the device.

[0055] The struts of the outer cage 210 can be very flexible with low radial force to allow the struts to be manipulated by pull wires 218 or other suitable actuation method to change the shape of the outer cage as desired. The flexibility of the struts also allows the outer cage 210 to be collapsed to the outer diameter 122 of the inner body 110 for navigation through narrower vessels.

[0056] The inner body 110 and outer cage 210 can be preferably made of a super-elastic or pseudo-elastic material such as Nitinol or other such alloy with a high recoverable strain and suitably high modulus and tensile strength. An advantage of using self-expanding bodies with these materials is that because of the volumetric properties and stiffness of a target clot, resistance can cause the device 100 to initially expand to only a fraction of its freely expanded diameter when deployed across the clot. This gives the outer body 210 the capacity to further expand to a larger diameter while being retracted so that it can appose vessel walls as it is retracted into progressively larger and more proximal vessels

[0057] In one example, the inner body 110 and outer cage 210 can be laser cut from a single continuous pieces of tubing which also serves as the shaft 6. Having a shaft 6 which doubles 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 as necessary.

[0058] The tubing can be in raw material form, for example a Nitinol hypotube so that the struts of the inner body 110 and outer cage 210 can be laser cut and heat set to the desired shapes and dimensions. For example, the inner body 110 can be heat set to have an outer diameter 122 of approximately 2.25 mm when expanded to the deployed configuration. Similarly, in the same deployed configuration the outer cage 210 can be heat set to have an outer diameter 222 of approximately 5.00 mm. The device can thus be effectively spring loaded within a microcatheter and expand to these dimensions when deployed at the target site.

[0059] The radial size of the outer cage 210 can allow it to remain in contact with and appose the vessel walls as well as protecting against distal migration of the clot as the device is retracted proximally into progressively larger diameter vessels. Apposition with the vessel walls can also reduce the axial force necessary to initially dislodge a clot from the vessel.

[0060] FIG. 2 shows an example configuration for the device 100 of FIG. 1 after the capture of a clot (not shown). The cells 116 of the inner body 110 can serve as inlets to stabilize the clot and allow the device, when retracted, to apply a force to the clot in a direction substantially parallel to the direction in which the clot is to be pulled from the vessel (i.e. substantially parallel to the longitudinal axis 8). This also means that any outward radial force applied to the vasculature by the outer cage 210 can be kept to a minimum.

[0061] When the cells 116 of the inner body 110 have been embedded within a clot, the pull wires 218 can be tensioned and retracted to invert the flexible struts of the outer cage 210 proximally as shown to internalize the inner body and clot. The pull wires 218 can be retrieved using a handle positioned at the proximal end of the device shaft. The wires 218 can pull the larger diameter outer cage 210 while the inner body 110 is left in position so that a pinch can be maintained between the saddle points 118 of the inner body cells 116, microcatheter 13, and at least a firm portion of the clot as described.

[0062] When inverted, the outer cage 210 can feature a series of broad loop segments 216 disposed around the longitudinal axis 8 and inner body 110. At the inner body distal end 114, the inner body/outer cage transition points 115 can form distal crowns 220 to act as a fragment protection element during clot removal to prevent the distal migration of debris. The crowns 220 can also have a flared diameter similar to that of the target vessel so that it can help to securely capture fragments from friable parts of the clot.

[0063] The shaft 6 can be a stock tubing size chosen to be compatible with commonly available delivery sheaths. In one example, the outer diameter 9 of the shaft 6 can be less than approximately 0.021 inches to ensure compatibility with a 0.021 inch inner diameter microcatheter. In another example, the shaft 6 can have a slightly larger outer diameter of approximately 0.026 inches to be compatible with 0.027 inch inner diameter microcatheter.

[0064] The shaft 6 and other portions of the device 100 can also have indicator bands or markers (not shown) to indicate to the user when the distal end of the device is approaching the end of the microcatheter during insertion or mark the terminal ends of the device during a procedure. These indicator bands can be formed by printing, removing, or masking areas of the shaft for coating, or a radiopaque element visible under fluoroscopy, so that they are visually differentiated from the remainder of the shaft.

[0065] The shaft 6 can also be coated with a material or have a polymeric jacket to reduce friction and thrombogenicity. The coating or jacket may consist of a polymer, a low friction lubricant such as silicon, or a hydrophilic/hydrophobic coating. This coating can also be applied to some or all of the outer cage 210 and inner body 110.

[0066] FIGS. 3A-3C illustrate a method for using the device 100 in the vasculature 40 to capture a non-homogenous clot 20, 22 with both firm and soft components. In FIG. 3A, the device can be deployed from a microcatheter 13 in a clot with the cells 116 of the inner body 110 section exposed to the clot. The microcatheter 13 can then be advanced distally to re-sheath at least a portion of the cells 116 of the inner body 110 and the pull wires 218. Alternatively, another outer catheter or sheath can be used. The saddle points 118 can form a natural inflection point for the cells 116 to fold down radially. If a fibrin rich portion 20 of the clot is present, the cells 116 can achieve a pinch on this section of the clot between the inner body 110 and microcatheter, as shown in FIG. 3B.

[0067] Once a pinch is achieved and the user feels the resulting resistance, the pull wires 218 can be retracted through the shaft 6. The wires pull the larger diameter heat set portion of the outer cage 210 proximally at linkage points 219 while leaving the inner body 110 in position to maintain the pinch. The retrieval of the pull wires 218 withdraws the loop segments 216 of the outer cage 210 over both the firm portions 20 and soft portions 22 of the clot to internalize the entire clot within the outer cage, as depicted in FIG. 3C. The full device can then be withdrawn with the clot into a guide catheter or other outer sheath.

[0068] The bond between the pull wires 218 and struts of the outer cage 210 at the linkage points 219 can be by a number of methods. In some examples, a mechanical connection such as a crimp, braid, or bulb/eyelet combination can be utilized. In other cases, a thermal process such as a weld or braze can be used.

[0069] FIGS. 4A-4B and FIGS. 5A-5B demonstrate a method for using the device if only a soft clot 22 is present. The device can be deployed in the clot 22 so that the cells 116 of the inner body 110 can be exposed to and embed in the clot as shown in FIG. 4A. In FIG. 4B, the microcatheter 13 can be advanced distally to re-sheath at least a portion of the cells 116 of the inner body 110 and the pull wires 218 to attempt to pinch the clot as seen in FIG. 4B. If the user does not feel the resistance of a pinch between the inner body 110 and microcatheter, it suggests the clot 22 is soft (no fibrin rich portion or portions). The device can then be redeployed out of the microcatheter 13 to embed the inner body 110 and stabilize the clot (FIG. 5A). The user can then tension the pull wires 218 and draw them proximally to invert the outer cage 210 while leaving the inner body 110 in position to internalize the soft clot 22 (FIG. 5B). The crowns 220 can prevent distal migration of clot fragments while the full device and clot is withdrawn into the guide catheter.

[0070] Another example of a clot retrieval device 300 capable of being a first pass device for capturing both firm and soft clots is seen in the plan view in FIG. 6. The device 300 can have a constrained delivery configuration for delivery through a microcatheter, an expanded deployed configuration, and an at least partially constrained clot pinching configuration for gripping firm 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. Similar to 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 to desired shapes when expanded. The inner body 310 and outer cage 410 can help to retain the clot inside the device to reduce the risk of damage to the vessel wall during retrieval as the clot is not brushed against the vessel wall for grip.

[0071] The inner body 310 can be configured to stabilize a clot during the removal process and add support and additional grip for particularly soft clots. The inner body 310 can be a low profile series of clot engaging cells designed with an “s-wave” or sinusoidal wave final heat set shape. The low profile design allows more clot reception space between the inner body 310 and outer cage 410 to minimize clot shearing when the device is retrieved back into an intermediate catheter or other outer catheter. In one example, the inner body 310 can have an expanded outer diameter in a range of approximately 1.25-1.5 mm. In other examples, 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 a target site.

[0072] An elevation side view of the device 300 from FIG. 6 is depicted in FIG. 7. The outer cage 410 can have an axial series of body segments 412 disposed around the inner body 310 and heat set with a substantially larger outer diameter 422 than the inner diameter 322 of the inner body. In some preferred examples 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.

[0073] The device 300 shown in FIGS. 6-7, for example, has two cells 416 per segment 412 around the longitudinal axis 8 perpendicular to each other. Note that due to the perpendicular nature of the cells 416 from the plan and elevation views as shown in FIG. 6 and FIG. 7, respectively, each cell of the body segments 412 can have 180 degrees of curvature where a flexible connector strut 417 serves as the top/bottom of the adjacent cell when the device 300 is rotated 90 degrees. The result can thus be a cylindrical shape for the outer cage 410 around the longitudinal axis 8.

[0074] Expansion of the outer cage 410 can cause compression and/or displacement of the clot during the expansion, depending on the level of scaffolding support provided by the struts. When an expandable body provides a high level of scaffolding the clot can be compressed. Alternately, when an expandable body provides an escape path or opening the expanding body urges the clot towards the opening. The clot itself can have many degrees of freedom and can move in a variety of different directions. When the device is sufficiently long, many of the degrees of movement freedom available to the clot are removed. This allows the clot to be retrieved without being excessively compressed. This is advantageous because compression of clot can cause it to dehydrate, which in turn increases the frictional properties and stiffness, which make the clot more difficult to disengage and remove from the vessel. This compression can be avoided if the clot can easily migrate inward through the cells of the outer cage.

[0075] As a result, the cells 416 from the device 300 shown in FIGS. 6 and 7 can have wide opening struts to allow a clot to migrate radially through the outer cage 410 once deployed in a clot. Similar to other examples, distally advancing a microcatheter or other catheter after deployment can compress the saddle points 418 of each cell 416 to pinch fibrin rich portions of a clot for a secure grip during removal.

[0076] Adjacent segments 412 of the outer cage 410 can be joined by a flexible connector strut 417. As the 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 respective segments. This allows segments to hinge about the connector struts to improve device flexibility and vessel wall apposition. The connector struts can also allow the cells 416 of individual segments to open locally to an increasing diameter to maintain a good grip on a clot between the inner body 310 and outer cage 410. The ability to locally increase to a larger diameter can be especially useful in situations where some or all of a target clot is located in difficult anatomy, such as a bifurcation, allowing the clot to be retained inside the vessel.

[0077] The outer cage 410 can also have a final segment with a tapered mesh end 420 for preventing small fragments from breaking away from the main clot and re-occluding in smaller, more distal vessels. The mesh end 420 can also help to protect against sections of the clot which detach as they roll over or change shape during retrieval. The distal struts forming this segment 420 can be bulged or flared so the distal end of the outer cage 410 is rendered atraumatic to the vessels in which it is used. The tapering and convergence of these struts can also reduce the pore size of the mesh to create an effective fragment capture zone.

[0078] A perspective view of the inner body 310 of the device 300 from FIG. 6 and FIG. 7 is illustrated in FIG. 8. The sinusoidal waveform design of the body cells 316 is visible as the struts contain bends 319 between 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 pinching cells 416 of the outer cage 410 so that the inner body 310 stabilizes but does not shear portions of the clot when the proximal portion of the device is partially constrained in the clot pinching configuration. The bends or crowns can also help to provide a better grip on the clot by embedding with and balancing the clot for the critical initial step of disengaging it from the vessel, enabling the outer cage 410 to be configured with a lower radial force.

[0079] The cells 316 and waveform shape of the inner body 310 allow the device to accommodate minor length differentials through stretching without the application of significant tensile or compressive forces to the joints. Length differentials can occur when, for example, the device is expanded, collapsed or deployed in a small vessel. The waveform arrangement of the struts of the inner body cells 316 also allows the cells to lengthen and shorten enough so that the lengths of the inner body 310 and outer cage 410 can be substantially the same when loaded in a microcatheter and when freely expanded at the target site. However, the cells can still have sufficient structural rigidity so the device 300 can be advanced or retracted without excessively lengthening or shortening the inner body 310 and outer cage 410.

[0080] The inner body 310 can also transition distally from the single cell sinusoid pattern into a collection of radially expanded struts 318. In the example shown, four expanded struts 318 can be positioned spaced equally 90 degrees around the longitudinal axis. The flared or expanded struts can aid the distal mesh fragment segment 420 of the outer cage 410. The expanded struts can also align the foreshortening of the inner body 310 and outer cage 410 during the crimping of the device into an insertion tool or microcatheter.

[0081] FIGS. 9A and 9B provide a top view and side view, 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 in the inner body 310. Each wave can have a single cell opening 316. The cells can have a diameter of approximately 1.25-1.5 mm or can have a slightly different diameter determined by the difference in the foreshortening of the inner body 310 and outer cage 410 during crimping of the device into an insertion tool or microcatheter. The expanded struts 318 near the distal end 314 can be a larger outer diameter (much closer to the expanded outer diameter of the outer cage) than the cells 316 of the inner body 310, and as a result these struts can also make up a significant amount of the take-up length required between the inner body and outer cage.

[0082] FIG. 9B illustrates a side view of FIG. 9A clearly showing the sinusoidal wave pattern 315 of the cells 316 of the inner body 310. The most proximal cell of the pattern can terminate in a connecting strut 330 linking it to a partially circumferential inner collar 328 at the proximal end 312 of the inner body. The struts of the inner body can be formed monolithically with the collar 328 by cutting and machining a single hypotube with an outer diameter 324 equal to that of the collar. At the distal end 314 of the inner body 310 can be a radiopaque coil 310 or marker band to mark the terminal end of the device during a procedure.

[0083] The proximal connections of the inner body 310 and outer cage 410 to the elongate shaft 6 can be constructed so the inner body and outer cage can have some small amount of independent translation with respect to each other. The translation can be, for example, a linear translation along an axis, a rotation of one body with respect to the other, or some combination of these. An example of a joint where this can be accomplished with a collar assembly 426 is illustrated in the exploded view in FIG. 10. The proximal end 413 of the outer cage 410 can have a tubular collar 427 circumscribing the elongate shaft 6. The proximal end 312 of the inner body 310 can have the partially circumferential inner collar 328 riding on elongate shaft 6 as mentioned above. The partially circumferential inner collar 328 can be cut from a hypotube having an outer diameter 324 less than the inner diameter 428 of the tubular collar 427 of the outer cage 410. Such a configuration can allow the inner collar 328 to sit radially inboard of the tubular outer collar 427 so that a small amount of rotation of either the inner body 310 or outer cage 410 can be possible with respect to the other. A partially circumferential setup also allows the inner collar 328 to be assembled on the shaft 6 with a fully circumferential outer collar 427.

[0084] The coaxial collar assembly 426 of the partial inner collar 328 of the inner body 310 and outer collar 427 of the outer cage 410 can allow for the two bodies to be substantially aligned with the neutral axis of the device 300 during bending within the vasculature. The rotation potential between the outer cage 410 and inner body 310 allowed by the collar assembly 426 can also help to prevent clot shearing which could otherwise occur with a static and fixed connection.

[0085] FIG. 11 diagrams method steps for performing a thrombectomy procedure with such a device. The method steps can be implemented by any of the example devices or suitable alternatives described herein and known to one of ordinary skill in the art. The method can have some or all of the steps described, and in many cases, steps can be performed in a different order than as disclosed below.

[0086] Referring to a method 11000 outlined in FIG. 11, step 11010 can involve delivering a clot retrieval device across a target clot of unknown composition. The clot can be firm and fibrin rich, soft and friable, or some combination of the two. The clot retrieval device can be delivered through a microcatheter or other suitable delivery catheter and have a collapsed configuration during delivery and an expanded deployed configuration when the delivery catheter is retracted. An elongate shaft can be used to manipulate the device by a user.

[0087] An expandable element of struts can be attached to the distal end of the elongate shaft and have an outer cage of cells and an inner body of cells within the lumen of the outer cage. Step 11020 can involve embedding at least one of the cells of the outer cage and at least one of the cells of the inner body in a clot by expanding the device from the constrained delivery configuration to the expanded deployed configuration. The radial force from the expansion of the outer cage can cause at least a portion of the clot to migrate radially inward.

[0088] In step 11030, a microcatheter or other outer catheter can be advanced distally to engage with at least some of the cells of the inner body and outer cage to pinch in compression at least a firm portion of the clot. The cells of the inner body and/or outer cage can be shaped to have bends at the axial apices shaped to fold the cell down radially as the device is partially re-sheathed. The saddle points can therefore exert a firm grip on any fibrin rich cores in the clot composition.

[0089] The distal advancement of the outer catheter can continue until resistance is felt by the user, indicating a pinch has been achieved, or no resistance is felt indicating the lack of fibrin rich portions of the clot. If no pinch is achieved, step 11040 can involve withdrawing the outer catheter to redeploy and embed the device in the clot. This redeployment stabilizes the soft clot within the cells of the device.

[0090] In step 11050, some or all of the struts of the outer cage can be inverted proximally to fold back over and internalize the clot and inner body. The inversion can protect the clot and reduce possible interactions or snags due to friction, bifurcations, and/or sharp bends in the vasculature. The struts can be pulled proximally by the user utilizing pull wires that are retracted and run through an inner lumen of the device shaft or by other suitable means. For example, the pull wires can extend through a hypotube device shaft and be actuated from a handle positioned on the proximal end of the shaft. In addition, the proximal joint of the inner body, outer cage, and the elongate shaft can be configured to allow some relative motion between them, reducing retraction forces and the risks of clot shearing.

[0091] Step 11060 can involve removing the clot retrieval device and captured clot from the patient. This can be accomplished, for example, by retrieving the device into an outer catheter with the aid of aspiration. If a pinch was achieved, it can be maintained by keeping the relative positions of the device and outer catheter during withdrawal. If required, the device may be rinsed in saline and gently cleaned before being reloaded into the microcatheter to be reintroduced into the vasculature when there are additional segments of occlusive clot, or if further passes for complete recanalization are needed.

[0092] The invention is not necessarily limited to the examples described, which can be varied in construction and detail. The terms “distal” and “proximal” are used throughout the preceding description and are meant to refer to a positions and directions relative to a treating physician. As such, “distal” or distally” refer to a position distant to or a direction away from the physician. Similarly, “proximal” or “proximally” refer to a position near to or a direction towards the physician. Furthermore, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

[0093] As used herein, the terms “about” or “approximately” for any numerical values or ranges indicate a suitable dimensional tolerance that allows the part or collection of components to function for its intended purpose as described herein. More specifically, “about” or “approximately” may refer to the range of values ±20% of the recited value, e.g. “about 90%” may refer to the range of values from 71% to 99%.

[0094] In describing example embodiments, terminology has been resorted to for the sake of clarity. It is intended that each term contemplates its broadest meaning as understood by those skilled in the art and includes all technical equivalents that operate in a similar manner to accomplish a similar purpose without departing from the scope and spirit of the invention. It is also to be understood that the mention of one or more steps of a method does not preclude the presence of additional method steps or intervening method steps between those steps expressly identified. Similarly, some steps of a method can be performed in a different order than those described herein without departing from the scope of the disclosed technology. For clarity and conciseness, not all possible combinations have been listed, and such variants are often apparent to those of skill in the art and are intended to be within the scope of the claims which follow.