Patent ID: 12213691

DETAILED DESCRIPTION

The objective of the disclosed designs is to create a clot retrieval device capable of providing more effective and efficient removal of obstructions in the vasculature while maintaining a high level of deliverability and flexibility during procedures. The designs can have an outer expandable member within which runs an inner expandable member. The disclosed devices share a common theme of dual layer construction where the inner member has a clot pinching capture capability and minimal interference in this capability from the outer member. Both members can be directly or indirectly connected to an elongate shaft, and a distal net or scaffold configured at the distal end of the device can prevent the escape of clot fragments. This distal net may be appended to either the shaft, the inner or the outer members, or to multiple of these.

This dual layer construction is intended to allow a clot to enter through the large openings or gaps in the outer expandable member and reside in the reception space provided between the two expandable members. At least a portion of the inner member can have a denser scaffold than that of the outer member such that the clot is prevented from entering its lumen, creating a flow channel across the clot once the device is deployed across it.

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. The material can be in many forms such as wire, strip, sheet, or tube. 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.

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.

Accessing the various vessels within the vasculature 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, such as angiographic materials, rotating hemostasis valves, delivery access catheters, and guidewires are 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.

Referring toFIG.1, a clot retrieval device100can have an elongate shaft6and an expandable structure configured at the distal end of the elongate shaft6having inner and outer members. The members can be an outer cage210and an elongate inner body110to capture a clot and facilitate the restoration of blood flow through the clot after the clot retrieval device100is deployed at a target site. The outer cage210can be a scaffolding structure with large cells through which the clot may pass and enter the reception space9defined by the annular region between the elongate inner body110and the outer cage. A fragment protection element14can be positioned approximate the tapered end218of the outer cage210near the distal end4of the device100. The outer cage210and elongate inner body110can have a collapsed configuration for delivery within a microcatheter and an expanded configuration for clot retrieval, flow restoration and fragmentation protection.

The inner and outer members are preferably made of a super-elastic or pseudo-elastic material such as Nitinol or another such alloy with a high recoverable strain. Shaft6may be a tapered wire shaft, and may be made of stainless steel, MP35N, Nitinol or other material of a suitably high modulus and tensile strength. Shaft6and device100can have indicator bands or markers 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.

The shaft6may 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 the outer cage210and elongate inner body110.

A dual-layer, multi-diameter device100as shown in various figures throughout this disclosure has several advantages. The inner body110with a smaller radial size can embed firmly in a target clot for a secure grip with a steep opening angle, while the larger radial size of the outer cage210can remain in contact with and appose the vessel walls and protect against distal migration of the clot as the device is retracted proximally into progressively larger diameter vessels.

A top view of the compound device100with dual inner and outer expandable members ofFIG.1is illustrated inFIG.2. The inner body110and outer cage210can both be monolithic structures, where the outer cage is configured to substantially encapsulate the inner body. The cells of the outer cage210serve as inlets for the clot and allow the outer cage, 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 axis8). This means that the outward radial force applied to the vasculature can be kept to a minimum. By configuring the outer cage210so as to encourage a clot to traverse to the reception space9the device can more effectively disengage clot from the wall of the vessel. The outer cage210can also have an enclosed distal end218defining a surface configured to work with the fragment protection element14as a clot fragment barrier surface.

The elongate inner body can have multiple regions to provide both a strong grip on a clot and a strong opening force to create a lumen to restore flow on deployment. The elongate inner body110can have a proximal clot pinching section120which can provide a strong grip on the clot for the critical initial step of disengaging the clot from the vessel, enabling the outer cage210to be configured with a low radial force.

A distal section of the elongate inner body110can be a porous inner channel130configured to create a flow lumen through at least a portion of the clot. This flow lumen can reduce the pressure gradient across the clot, making it easier to dislodge and remove. The porous inner channel130can be a tubular shape and have a diameter when expanded that may be tailored so as to reduce the risk of a reperfusion injury. The restricted blood flow through the lumen can ensure that the pressure applied to blood vessels immediately after flow restoration is lower than normal thereby reducing the risk of bleeding in the vascular bed. Full perfusion can be subsequently restored by removing the device and the captured clot.

The outer cage member210can be a plurality of struts forming expandable bodies configured to self-expand upon release from a restraining sheath (such as a microcatheter) to a diameter larger than the radial size of the inner body110, as shown inFIG.3. Proximal expandable bodies216can be disposed around the clot gripping or pinching section120of the inner body110and distal expandable bodies217disposed around the porous inner channel130. Proximally, the outer cage210can have support arms222joined at a proximal junction212to the shaft6and flare radially to form a proximal expandable body216. The support arms222may have a tapered profile as shown to ensure a gradual stiffness transition from the shaft6to the clot-engaging expandable bodies. Support arms222can be oriented to form a network of closed cells at discrete positions around the longitudinal axis8of the device100so that there are large circumferential gaps between adjacent arms. For example, two sets of arms222can be largely diametrically opposed to each other by approximately 180 degrees as shown, or three sets of arms can be spaced 120 degrees apart.

The proximal portion of the outer cage210can have expandable bodies216with cells which are not completely circumferential around the device. providing a level of scaffolding that is less than that of the distal expandable bodies217. Portions of a clot can pass into the gaps between the cells and support arms222of the proximal expandable bodies216so they are engaged by clot pinching structure120. Having cells in the proximal expandable bodies216which are not completely circumferential can result in a lower surface contact area and a radial force which allows the clot to more easily protrude into the gaps in this section of the device. When the device is withdrawn into an outer catheter, the clot pinching structure120can maintain a secure grip on the clot without interfering impingement from the struts of the arms222of the outer cage210. Support arms222can also have bends or crowns which would bias movement away from, or at least not in the same direction as, the clot pinching element so that the support arms do not shear portions of the clot when the proximal portion of the device is partially constrained by an outer catheter.

The proximal expandable body or bodies216can be connected to the most proximal body of the distal expandable bodies217by coupling struts233. In one example these coupling struts233can be generally straight struts running parallel to the central longitudinal axis8of the device. In other examples the coupling struts233may have a plurality of struts configured in one or more cells or may have curved or spiral arms. The regions between adjacent expandable bodies216,217can form inlets214through which the clot or portions of the clot may pass and enter the reception space9between the elongate inner body110and the outer cage210.

The distal-most portion of the outer cage210can have a tapered end218which slims down radially in a substantially conical profile to a distal junction213. The tapering and convergence of struts at the tapered end218reduces the pore size of the openings between struts to create a fragment capture zone. These struts can be end crown struts237connected to the distal-most distal expandable body217via connecting struts234, as shown inFIG.3. The end crowns237can be convexly bulged or flared so the end of the outer cage210is rendered atraumatic to the vessels in which it is used. The struts making the bulge or flare might not be parallel to those of the adjacent portions of the outer cage, forming a joint or hinge through which the tapered end218can bend or flex about the distal expandable bodies217. The junction213can be a twisted or coiled collection of struts of fibers which can have, or be given, radiopaque properties to mark the terminal end of the device100during a procedure.

Distal expandable bodies217can in turn be connected by one or more connecting arms234, which can extend from a proximal junction239to a distal junction240, as seen in the side view of the outer cage210inFIG.4. The connecting arms234can be generally straight and run parallel to the longitudinal axis8of the device100. In other cases, the connecting arms may be a plurality of struts configured in one or more cells or can have a curved or spiral profile. The region between the distal expandable bodies217can define inlets214through which a clot may pass and enter the reception space9. The connecting arms234between the distal expandable members217may be substantially aligned with the coupling struts233between the proximal and distal expandable bodies216,217to align the neutral axis of the bodies during bending.

The proximal and distal expandable bodies216,217of the outer cage210can have a series of interconnected struts to form the closed cells, with certain struts such as crown strut232terminating in crowns or distal apices236with no distal connecting elements to any adjacent closed cells, and other body struts such as242terminating in body junction points244. The distal apices236can be offset from the longitudinal axis8of the device100and can be close to the cylindrical plane defined by the outer cage210when expanded. The crown struts232which join at a distal apex236can be broadly curved in order to maximize the offset and spacing between apices in order to achieve a desirable balance between clot scaffolding and device flexibility. Having the free apices236with no distal connections at some junctions can provide greater bending flexibility for the device. This is because, in addition to the flexing of the struts forming each cell, the apices themselves can flex to accommodate bends in the vasculature and have some capacity to react to clot forces.

The outer cage210can expand and contact the vessel wall as the microcatheter is retracted during device deployment. The contact provides stability to the device100and minimizes twisting as the inner elongate body110and any spiral portions of the pinching section120is unsheathed in the vessel. This facilitates uniform deployment and expansion of the device100in the obstruction or clot.

Expansion of the outer cage210can 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 will urge the clot towards the opening. The clot itself can have many degrees of freedom and can move in a variety of different directions. By providing an outer cage210whose length is substantially as long as the length of the occlusive clot or longer, many of the degrees of movement freedom available to the clot are removed. Inlet openings214are provided in the outer cage210to guide the primary movement freedom available to the clot and so the expansion of the outer cage urges the clot into the reception space9. This allows the clot to be retrieved without being excessively compressed. This is advantageous because compression of the clot can cause it to dehydrate, which in turn increases the frictional properties and stiffness, which makes the clot more difficult to disengage and remove from the vessel. This compression can be avoided if the clot easily migrates inward through the cells or the gaps in the proximal portion of the outer cage as the outer cage expands outward towards the vessel wall.

Another advantage of using self-expanding bodies is that because of the volumetric properties and stiffness of a target clot, resistance can cause the device100to initially expand to only a fraction of its freely expanded diameter when deployed across the clot. This gives the outer cage210the capacity to further expand to a larger diameter while being retracted so that it can remain in contact with vessel walls as it is retracted into progressively larger and more proximal vessels.

FIG.5shows the inner elongate body110of the device100fromFIG.2. The clot engaging pinching section120and porous inner channel130can be formed integrally from a single strip or tube of a shape memory material such as Nitinol which is then laser cut to form the strut pattern. Alternately, they can be formed independently and later attached to allow both members to take on varied shapes. The inner body110can also have a proximal joint or transition between the proximal end121of the pinch section120and an elongate shaft6on which the device is mounted.

The elongate inner body110can be configured to expand to a lesser diameter than that of the smallest vessel in which it is intended to be used. When the inner body is non-tapered, this diameter is typically less than 50% that of the expanded outer cage diameter and in some cases may be as low as 20% or less of the outer cage diameter. This allows portions of the inner body can be constructed with a very small volume of material, as it is only required to expand to a fraction of the diameter of the outer cage and can thus be highly flexible in both the collapsed and expanded states. This flexibility can advantageously allow the inner body to be displaced in one direction by one portion of the clot and another direction by another portion of the clot.

The clot pinching section120can be an engaging element in the more proximal region of the inner elongate body110of the device100. The pinching section120is intended to facilitate clot retrieval by expanding between the clot and the vessel wall in such a way as to engage with a clot over a significant surface area and do so with minimal compression of the clot. The overall clot compression is minimized because the section can be constructed to have rings of high compression with deep strut embedding interspersed with areas of minimal clot compression and low radial force. A portion of a clot can protrude into the area of low compression and be pinched between the tip of a catheter and the struts of the device. The pinch is achieved by forwarding a microcatheter or outer catheter over the proximal end121of the pinching section120until a portion of clot is compressed between the tip of the catheter and a crown or strut of the pinching section. This pinch facilitates removal of the clot as it increases the grip of the device on the clot, particularly for fibrin rich clots. It may 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 during 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.

Distal of the clot pinching section120, the inner channel130can be generally tubular, planar, or some other shape, with a luminal structure being smaller in diameter than the surrounding portions of the outer cage210. In one example, the distal inner channel130can transition from the distal end122of the clot pinching section to form a barrel shape so that this section is a smaller or larger radial size than that of the proximal pinch section120in the illustrated expanded configuration. This allows a flow channel to be created across very long clots without overly compressing the clot or engaging the inner channel130with the vessel wall. The inner channel130can be formed monolithically with the pinching section or can be formed separately and connected through a collar or other mechanical joint. In other cases, the inner channel130may have a non-cylindrical cross-section, may be non-uniform in diameter, and may have tailored strut patterns to provide regions of differing radial force or flexibility.

In another example, the shape can be substantially tubular and have a plurality of struts converging away from and towards the axis8of the device in intervals as shown inFIG.5, the struts forming cells132configured to engage with and define a flow lumen through the clot in its expanded state. When expanded, the cells132can interpenetrate the clot and give additional grip to assist in the initial dislodgement of the clot while also scaffolding the flow lumen through the clot to prevent the liberation of fragments.

The distal end136of the inner channel130can transition to or be connected with a tether or shaft to a fragment protection structure14. The fragment protection structure14can be a plurality of struts configured in a volumetric pattern, in a weave or entangled mesh filter, or in a basket-like or conical shape to impede or collect fragments from travelling distal of the device. The structure14can also be a bundle of fibers in a spherical or similar shape, and in the expanded state at least a portion of the fragment protection structure has a radial size larger than the flow channel130and pinching section120and can be similar in size to the diameter of the target blood vessel. The distal end of the fragment protection element14can have a radiopaque coil element16, which can be laser cut from the same tubing used in the construction of the inner channel130during processing.

The inner elongate body110and outer cage210can be joined proximally at the shaft6and also distally during assembly so as to minimize tension between the members during use. The struts of the clot pinching segment120, the inner channel130, or both, can lengthen and shorten so that the lengths of the inner body and outer cage are substantially the same when loaded in a microcatheter and when freely expanded at the target site. The closed cells of the inner body and outer cage, along the coil element16, can 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.

An enlarged and magnified view of the clot pinching section120of the inner elongate body110ofFIG.5is shown inFIG.6. Alternative ring segments145can be formed by overlapping struts and form intermediate crowns147at local apices. Section of low density fluting146can extend between and be bounded by consecutive ring segments145, where longitudinally extending bridge struts exert a lower level of scaffolding and reduced radial force compared to that generated by the ring segments145. The overlapping of the struts as the pinching section120expands or contracts can allow each ring segment145to twist relative to its adjacent rings, but where each twist can counterbalance the next so that minimal overall twisting occurs in the pinching section at the distal end122relative to the proximal end121. Minimal twisting helps to ensure that the grip on a pinched clot is not lost.

The longitudinal length of the bridge struts in the low density fluting146between the ring segments145can vary. When used in the middle cerebral artery, for example, the longitudinal spacing can be approximately 3-6 mm. This spacing allows the clot to protrude between the struts where it engages the pinching section in the expanded deployed configuration. The total length and/or number of ring segments145and fluting sections146can be optimized for the expected length and density for optimum embedding in the clot. The bridge struts144between the ring segments145can be straight and parallel with the axis8of the device for better pushability to ensure the device can be delivered through tortuous anatomy.

Struts in the pinching section120can also have one or more bends148at various axial positions along their length. The “dog-leg” type shape created by these bends148in the struts144can be repeated around the circumference or radial direction of the section to form cells. The angle formed by the bends148or the length of the struts144can be varied in places, or different struts in the pattern can also have different widths so that various segments can have higher expansion force for improved engagement with the clot in the expanded deployed configuration. This structure can be produced by laser cutting Nitinol stock and heat-setting the shape so that it assumes the desired profile when expanded.

Another example of an inner elongate body110which has a proximal engaging element configured as a clot engaging pinching section120and a distal inner channel130is illustrated inFIG.7. When fully expanded, the pinching section120can have the same or different radial size than the inner channel130, but the two structures can be formed monolithically so there is not a significant stiffness transition at the distal end122of the pinching section. A fragment protection element14can be formed or otherwise attached to the distal end136of the inner channel130and be configured to transition to an expanded radial size greater than both the clot pinching section120and inner channel when the device100is deployed across a clot.

The pinching section120can have more densely spaced ring segments145along portions of its length as compared to that inFIG.5. As discussed, this segment120can have rings145of struts and areas of low radial force and strut density146. Having adjacent ring segments145spaced close together at certain axial locations of the pinching section120can increase the effect of the pinch between rings in the clot pinching configuration as a microcatheter or outer catheter is advanced.

During retraction, the pinch of a fibrin rich clot may be lost, or the clot may contain red blood cell rich ‘soft’ segments which are not fully gripped on the proximal pinch section120. In these scenarios, the struts of the distal porous inner channel130can provide engagement with the clot and retrieve it through the increased diameter vessels, past the bends and branches to the microcatheter or outer catheter. Further, the expanded cells and/or struts of the fragment protection element14engage with any liberated fragments or ungripped clot sections with minimal shear.

Referring toFIG.8, there is illustrated another inner elongate body110which has some features which are similar to other devices described above. The inner elongate body110can be attached proximally to a shaft6. This connection can be a collar or some other axial constraint which allows at least partial relative rotation between the outer cage210and the inner body. Radiopaque markers (not shown) can also be used at this location to mark the proximal terminating point for the expandable portion of the device100during a procedure.

The inner body110can have a proximal clot engaging element120and a more distal tubular inner channel130. A three-dimensional mesh-like structure or basket can be formed from wire or fiber into a fragment protection element14, which is retained at the distal end136of the distal inner channel130and within the outer cage210. The wire or fibers may be randomly curled and/or twisted to occupy the space within the structure, or they may be shaped into a specific pattern.

The clot engaging element120can have struts forming a plurality of adjacent segments152, where differing shapes of the adjacent segments results in the radial force generated by successive adjacent segments being unequal. Some struts can have bends148(such as those seen inFIG.6) so that adjacent struts144can compress the clot as the clot engaging element is transitioned from the expanded deployed configuration to the partially constrained clot pinching configuration. Struts in portions of the adjacent segments152can overlap at angles to the longitudinal axis8of the device so they can slide in different directions relative to each other when positioned in or moving through bends in the vasculature. Additionally, portions of adjacent segments152can have features which bias collapse along certain planes or change lengths in the axial or radial direction. The differences in strut length ensure that the radial force applied to a clot by the pinch section120varies to achieve good grip on the clot while facilitating clot retrieval in association with a microcatheter or outer catheter.

In another example of the device100shown inFIG.9, the strut pattern of the clot pinching section120of the inner elongate member110can be formed by laser cutting a largely flat, two-dimensional sheet and wrapping the resultant flat pattern around a cylindrical mandrel prior to heat setting. The centerline of the device can then form a helical or spiral pattern around the longitudinal axis8, similar to the process of wrapping a ribbon around a cylinder. At the proximal end the clot pinching structure120can be connected to a shaft6. The inner channel130connected at the distal end122of the clot pinching section120can also be a flat pattern, have a curved or profiled cross section, or be a generally tubular shape as shown in other disclosed examples.

When deployed across a clot, portions of the clot can migrate through the inlets214and cells of the expandable bodies216,217of the outer cage210, or the spaces between expandable bodies, and into the reception space9or the device. Here, the clot can protrude into areas of low strut density and also into the central lumen of the helical spiral pattern of the clot pinching structure120. The gaps and lower scaffolding of the proximal expandable bodies216facilitate ingress to the spiral of the clot pinching structure120. When the device100is subsequently retracted, this spiral can improve grip and dislodgement performance and facilitate the clot pinching action when an outer catheter is forwarded distally to transition the device from the expanded deployed configuration to the partially constrained clot pinching configuration. Such an effect can also be increased if the clot pinching structure120of the device100was constructed from two or more helical spiral components.

A helical spiral shape can also allow portions of the clot pinching structure120to elongate under tension, stretching parts of the clot during dislodgement. The proximal end of the clot can be pinched and constrained on the clot pinching structure120while the distal end of the clot can be positioned on the inner channel130to embed and open a flow channel. If the distal end of the clot remains stuck in the vessel, the inner channel130and outer cage210can remain static while the clot pinching section120expands in some sections and contracts in others in response to clot forces. This action can help peel the clot from the vessel wall and reduce the dislodgement force during the procedure.

A fragment protection element14can be connected by a tether or shaft134to the distal end136of the inner channel130. The protection element14can be a volumetric pattern which expands to a larger radial size than the radial size at any point along the cross section of the elongate inner body110. The shape of the element can be a conical basket as shown or a mesh element or fibrous bundle occupying sufficient space to impede the distal passage of clot or thrombus fragments.

The exact shape and configuration of the strut network and adjacent segments152of the clot pinching element120will determine the radial force extorted at different axial positions along the structure when the element is in the expanded deployed configuration and clot pinching configuration. The force can vary, for example, in a generally sinusoidal waveform pattern124with locally varying peaks126determining the amplitude128of force at that position. A sample plot of radial force as a function of axial position along the clot engaging element120is shown to illustrate this concept inFIG.10. The amplitude128can repeat at a patterned distance so that it is relatively equal along the length of the engaging element120, or it can decrease along the length so that the force is lower at the distal end122and higher at the proximal end121where with initial grip of the pinch allows for disengagement of the clot. The plot shows how, for example, the ring segments145which embed in the clot can have a higher radial force than the low-density fluting segments146between the rings. The effectiveness of areas of increased radial force can be increased by maximizing the angle of the struts with respect to the longitudinal axis of the vessel, which can allow the ring segments145to grip, rather than slide past, the clot. Having these regions of differing radial force allows the device100to maintain a grip on the clot in the area of the peaks126while exerting much less compression on the clot between peaks, which helps to minimize the overall force required to retract the clot.

As a microcatheter or outer catheter is advanced to increase the pinch on a clot, the user may feel the pinching as resistance and stop advancement of the catheter, or alternately may advance a fixed distance over the proximal end121of the engaging element120and the more proximal expandable bodies216of the outer cage210. The lower level of scaffolding in the proximal expandable bodies216of the outer cage210allows the relative tension between the engaging element120and catheter to be maintained so that the pinch between the engaging element and the catheter does not deteriorate during retraction of the clot.

FIGS.11a-11eand the flow diagrams ofFIG.12andFIG.13show a method of use for the disclosed designs. A guidewire11and microcatheter13are inserted and guided through the vasculature40and advanced across the obstructive clot20using conventionally known techniques. When the microcatheter13is positioned distal to the occlusive clot40, the guidewire11can be removed from the vessel40to allow the clot retrieval device100be advanced through the microcatheter. The device100is advanced in a collapsed configuration until the distal tip of the device reaches the distal end of the microcatheter. The microcatheter13can be retracted while the position of device100is maintained using the shaft6to deploy the clot retrieval device across the clot20, preferably in a manner so that the distal end of the device is positioned distal of the clot, as shown inFIG.11b. The device100expands so that the outer cage210can engage with the occlusive clot20and allow the clot to pass radially inward. The clot pinching section120and porous inner channel130can expand to embed with the clot and provide a flow channel to restore blood flow in a controlled manner. The device100may be allowed to incubate for a period of time within the clot20if desired, as the controlled flow that has been restored through the inner channel130is stabilized.

FIG.11cillustrates the clot20engaged with the device during retrieval into the microcatheter13. Advancement of the catheter causes the collar12to compress the clot20between the crowns147of the ring segments145and the bridging struts144of the low-density fluting segments146, as shown inFIG.11d. Depending on conditions, the pinching engagement can also be effected with an intermediate or other outer catheter. The clot can be partially located in the inlet openings214of the device and also partially located in the reception space9defined by the region between the inner body110and outer cage210. Clot fragments can be trapped in the distal closed tapered end218of the outer cage210and the fragment protection element14to prevent the fragments from being released in the blood flow. Flow occlusion, aspiration and other standard techniques may be used during this process.

The relative tension between the device and the microcatheter can be maintained by the user during dislodgment and retraction to ensure the pinch on the clot is maintained, as inFIG.11e. While the use of a microcatheter or intermediate catheter to pinch the clot is described as giving additional benefits when used with this invention, all the embodiments described herein can also be used to dislodge and retrieve clots without the use of catheter pinching if required. The distal closed end of the outer cage210and the expanded fragment protection element14of the device100prevents trapped clot fragments from being released in the blood flow.

FIG.12andFIG.13diagram 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 alternative 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.

Referring to a method1200outlined inFIG.12, step1210can involve providing an outer catheter which can have a tubular body and a collar at its distal end. Depending on circumstances, the outer catheter can be a microcatheter, intermediate catheter, or any other suitable sheath known to those in the art with a diameter appropriate for effecting a pinch on the device as previously described.

Step1220can provide for a clot retrieval device having a collapsed delivery configuration, an expanded deployed configuration, and an expandable element. A proximal shaft can be used to manipulate the device during a procedure. The expandable element can have an inner body and an outer body expandable to a greater radial extent than the inner body. The inner body can have a proximal pinching element and a distal flow channel element. The outer body can have a non-circumferential first scaffolding section disposed around the pinching element and a fully circumferential second scaffolding section around the flow channel element and connected distal of the first scaffolding section. The non-circumferential first scaffolding segment can allow for portions of the clot in the vicinity can easily pass inward through gaps in the outer body to engage with the proximal pinching element of the inner body.

Step1230can involve delivering the clot retrieval device in the collapsed delivery configuration to the occluded vessel through a microcatheter. In the case of an intracranial occlusion a variety of access routes are possible, including a direct stick into the carotid artery, a brachial approach, or a femoral access. Once access has been gained to the arterial system using conventional and well understood techniques, a guide catheter or long sheath (not shown as part ofFIGS.11a-e) is typically placed as close to the occlusive clot as practical. For example, in the case of a middle cerebral artery occlusion, the guide catheter might be placed in the internal carotid artery proximal of the carotid siphon. A microcatheter can then be advanced across a clot with or without the aid of a guidewire. Once the microcatheter tip has been advanced across and distal of the clot, the guidewire, if used, can be removed and the clot retrieval device is advanced through the microcatheter until it reaches the distal end.

The microcatheter can then be retracted allowing the clot retrieval device to expand within and either side of the clot in step1240. This step can further involve the scaffolding regions of the outer body expanding within the clot to apply a compressive force to urge the clot to flow through the inlet cells and into the space between the inner and outer bodies. As the outer body is deployed to the expanded deployed configuration, at least a portion of the clot can pass radially through circumferential gaps in the non-circumferential first scaffolding section and into contact with at least a portion of the pinching element. Because of the large cell openings in the outer body, and the gaps in the non-circumferential first scaffolding section, clot compression can be controlled and minimized. Minimizing compression on the clot reduces the forces applied radially outward to the vessel wall, which in turn reduces the frictional forces to be overcome when retracting the clot.

Continuing toFIG.13, method1300can have a step1310of inhibiting migration of the clot into the flow channel element to allow a flow of blood through the flow channel element in the expanded deployed configuration. Because the device can be configured with a two-part long inner body, upon device deployment the expansion of the flow channel element can create a flow channel through the clot, restoring flow to the vascular bed distal of the clot and reducing the pressure gradient across the clot. This reduction in pressure gradient reduces the force required to disengage the clot from the vessel wall and retract it proximally. Additionally, a flow channel allows the device can be safely left in place for a dwell period prior to withdrawal. A dwell period allows the distal vascular bed to be gently perfused with fresh oxygenated blood rather than be exposed to a sudden transient spike in pressure and flow as would be the case if the clot were immediately removed or if the device were to compress the clot so much that a very large flow channel was created upon deployment.

While rigidly maintaining the position of the clot retrieval device, step1320can involve advancing the outer catheter along the elongate shaft so that the collar of the outer catheter engages with the expandable element to pinch in compression at least a portion of the clot with the pinching element. This can be done with the aid of aspiration through the outer and/or guide catheter to assist in retaining a firm grip on the clot and avoiding fragment loss. However, the disclosed designs grip the clot securely and houses the clot safely within a reception space, with the added benefit of having a distal fragment protection element and scaffolding region. The protection element may be spaced apart from the distal end of the inner member, so it is optimally positioned to trap any fragments released from the clot during retraction.

In step1330, the outer catheter and the clot retrieval device are withdrawn in unison from the vessel while maintaining the engagement between the collar of the outer catheter and the expandable element. Along with aspiration, this engagement maintains the firm pinching grip on the clot as it is withdrawn through bends and successively larger vessel diameters.

In step1340, the clot retrieval device and the pinched clot can be removed from the patient. The device may be rinsed in saline and gently cleaned before being reloaded into the microcatheter, if required. It can then be reintroduced into the vasculature to be redeployed in additional segments of an occlusive clot, or if further passes for complete recanalization are needed.

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.

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%.

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.