Patent Application
20220202428
The present disclosure generally relates to devices and methods for removing acute blockages from body vessels during intravascular medical treatments. More specifically, the present disclosure relates to a clot retrieval device for removing a clot from a blood vessel.
Mechanical devices and methods can be used for removing acute obstructions from blood vessels. Acute obstructions may include a clot, misplaced devices, migrated devices, large emboli, and the like. Thromboembolism occurs when part or all of a thrombus breaks away from the blood vessel wall. This clot (now called an embolus) is then carried in the direction of blood flow, which can result in many complications. An ischemic stroke may result if the clot lodges in the cerebral vasculature. A pulmonary embolism may result if the clot originates in the venous system or in the right side of the heart and lodges in a pulmonary artery or branch thereof. Clots may also develop and block vessels locally without being released in the form of an embolus, and this mechanism is common in the formation of coronary blockages. The devices and methods herein are particularly suited to removing clots from cerebral arteries in patients suffering acute ischemic stroke (AIS), from pulmonary arteries in patients suffering from pulmonary embolism (PE), from coronary native or graft vessels in patients suffering from myocardial infarction (MI), and from other peripheral arterial and venous vessels in which a clot is causing an occlusion.
There are a number of access challenges that can make it difficult to deliver devices to a target site. In cases where access involves navigating the aortic arch (such as coronary or cerebral blockages) the configuration of the arch in some patients makes it difficult to position a guide catheter. The tortuosity challenge is even more severe in the arteries approaching the brain. It is not unusual at the distal end of the internal carotid artery that the device will have to navigate a vessel segment with several extreme bends in quick succession over only a few centimeters of travel. In the case of pulmonary embolisms, access may be gained through the venous system and then through the right atrium and ventricle of the heart. The right ventricular outflow tract and pulmonary arteries are delicate vessels that can easily be damaged by inflexible or high-profile devices. For these reasons it is desirable that a clot retrieval device be compatible with as low profile and flexible access catheters as possible.
Stent-like clot retriever devices are being increasingly used to remove a clot from cerebral vessels of acute stroke patients. These devices often rely on a pinning mechanism to grab the clot by trapping it between the self-expanding stent-like body and the vessel wall. This approach has a number of disadvantages.
A stent-like clot retriever depends on its outward radial force to retain its grip on the clot during retraction. This compressive force will tend to dehydrate the clot, which in turn can increase its coefficient of friction, making it more difficult to dislodge and remove from the vessel. If the radial force is too low the stent-like clot retriever can lose its grip on the clot, but if the radial force is too high the stent-like clot retriever may damage the vessel wall and require too much force to withdraw. Therefore stent-like clot retrievers that have sufficient radial force to deal with all clot types may cause vessel trauma and serious patient injury, and stent-like clot retrievers that have appropriate radial force to remain atraumatic may not be able to effectively handle all clot types in diverse thrombectomy situations. Pinning the clot between the stent-like clot retriever and the vessel wall also results in high shear forces against the side of the clot as it is removed, potentially releasing fragments of the clot. If these fragments are not retained by the device, they may migrate leading to further blockages in the distal vasculature.
Certain conventional thrombectomy device designs also do not retain their expanded shape very well when placed in tension in vessel bends, due to the manner in which their strut elements are connected to one another which results in the struts being placed in tension during retraction. This tension is due to friction between the device and the blood vessel and is increased if an additional load is applied load such as the resistance provided by a clot. This can result in a loss of grip on the clot as the stent-like clot retriever is withdrawn proximally around a bend in a tortuous vessel, with the potential for the captured clot to escape. In a bend, the struts on the outside of the bend are placed in higher tension than those on the inside. In order to attain the lowest possible energy state, the outside surface of the clot retrieval device moves towards the inside surface of the bend, which reduces the tension in the struts, but also reduces the expanded diameter of the device.
In seeking procedural efficiency in this environment, clot retrieval devices with multiple bodies have often been preferred. Such devices can have an outer body capable of scaffolding a target vessel and an inner body for embedding and capturing a clot. These devices can perform well in engaging with and dislodging a clot but having a larger and often stiffer network of struts can potentially make it more difficult to retract the device and partially or fully collapse to re-sheath it within an outer catheter. Additionally, since these devices are designed so the clot is typically required to migrate radially inward through the outer member, the device can have a less firm grip on peripheral regions of a clot.
Additionally, conventional thrombectomy devices are usually aimed at removing 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 the introduction of a thrombectomy device, preventing a user from knowing which device would improve the probability of a first pass success to reduce risk to the patient. Furthermore, clot heterogeneity can mean a clot can include fibrin rich cores in proximal, central, or distal portions of the overall clot anatomy, making a uniform and secure grip more difficult.
The challenges described above need to be overcome for any device to provide a high level of success in removing a clot of any type, restoring flow and facilitating good patient outcomes. The present designs are aimed at providing an improved clot retrieval device to address the above-stated deficiencies.
The disclosed designs resolve these questions by providing a flexible dual-layer clot retrieval device in which the inner and outer members work in unison to capture and remove a clot. The designs can be intended for use as first pass devices with features that are just as effective at capturing fibrin rich and sticky clots as they are soft, friable clots.
The designs can feature a constrained delivery configuration and an expanded deployed configuration. The outer member can have wide opening struts to allow for clot integration into the device. Both the inner and outer members can be configured and shaped to pinch a clot in addition to embedding in it. In some examples, at least some portions of the devices are capable of folding and inverting proximally after engaging with a target clot to internalize and protect it. These actions can increase the security of the device's grip on a clot during all phases of retrieval, allowing safer and more efficient flow restoration.
The device can have a proximal tubular shaft for manipulation with a lumen extending therethrough. The shaft can be various sizes depending on the application. In one example, the shaft is a hypotube having an outer diameter of less than or equal to 0.021 inches. In another example, the shaft can have an outer diameter of approximately 0.026 inches. Distal of the shaft can be a framework of struts having a constrained delivery configuration, an expanded clot engaging deployed configuration when deployed at a target site, and an at least partially constrained clot pinching configuration.
In some examples, the framework of struts can form an elongate inner body and an 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 pinching cells configured to pinch the clot when the device is transitioned from the deployed configuration to the clot pinching configuration. The outer cage can be arranged around the inner body, can extend from the distal end of the inner body, or be some combination of these. The outer cage can be expandable to a radial extent greater than the expanded inner body, or it can have the same or similar radial dimensions.
The clot pinching structure can take a variety of forms. The pinching 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 a horseshoe shaped saddle point at the proximal and distal ends of the cell so that the cells are capable of constricting portions of a clot in the cells when the struts are in radial compression. These patterns allows a microcatheter or outer catheter to be advanced over the proximal end of the pinching structure cells in order to compress and grip a clot between the tip of the catheter and at least a portion of the struts of the cells as the device is transitioned from the expanded deployed configuration to the partially-constrained clot pinching configuration. In another example, the clot pinching structure can be a flat pattern of struts arranged in an undulating or spiral fashion.
The properties of the inner body and outer cage can be tailored independently of each other. The outer cage can be coaxial with the inner body or can be radially offset. The inner body can be arranged substantially within the lumen of the outer cage.
In some examples, pull wires can extend through the lumen of the proximal tubular shaft and be fixedly connected to the outer cage at linkage points. The linkage points can be at least one of a crimp clamp, a weld, or a braid. A user manipulating the pull wires at the proximal end of the shaft can transition the outer cage from the expanded deployed configuration to an inverted clot housing configuration. During this transition, the pull wires can invert the outer cage so that at least part of it folds at transition points and back proximally over the inner body. The struts of the outer cage can thus enclose a clot and the inner body in the clot housing configuration. This inversion can internalize and contain both soft and firm portions of the clot for subsequent retraction and removal. In some cases, a remaining distal portion of the outer cage can also flare radially outward on activation of the pull wires to function as a fragment protection element during clot retrieval.
In some examples, the radial sizes of the inner body and outer cage can be heat set and varied depending on the application and the location of potential target occlusions within the vasculature. For targets in the neurovascular, 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 the inverted clot housing configuration.
Another design for 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 pinching configuration. After being deployed across a clot, the clot pinching configuration can be 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 inner body, the outer cage, or a combination of the inner body and outer cage.
In some examples, the inner body can have struts forming a series of clot receiving cells. The cells can be heat set to extend in a generally sinusoidal wave pattern along the longitudinal axis in the expanded deployed configuration. In another example, the cells form a spiral pattern around the axis. In one case, the cells of the inner body are configured to embed with and stabilize a clot when expanded. In another case, the cells of the inner body can have at least one bend configured embed with and stabilize at least a portion of the clot. The inner body can be a range of radial sizes. In some examples, the inner body can have an outer diameter in the range of 1.25 mm-1.5 mm in the expanded deployed configuration.
The outer cage can have a series of segments extending in an axial fashion along the length of the device. Each segment can have one or more cells. In some examples, each segment can have two cells. Each cell of the outer cage can have a horseshoe shaped saddle point at the proximal and distal ends of the cell configured to compress and pinch at least a portion of the clot as the device is moved to the clot pinching configuration. The clot pinching configuration can be 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 as the struts are radially compressed. Adjacent axial segments can be hingedly joined by a flexible connector strut, which can be the only point of contact between respective segments. The segments can therefore flex independently as the device is advanced or retracted through bends in the vasculature.
The outer cage can be various 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.
The inner and outer bodies can share the same shaft and be coaxial around the longitudinal axis. At the proximal interface joint with the shaft, the outer cage can have a fully circumferential tubular outer collar circumscribing the shaft. The inner body can be formed laser cutting a tube with an outer diameter less than an inner diameter of the outer collar of the outer cage. The inner body can thus have a collar at the proximal interface that can slide within the outer collar.
A method for using the disclosed examples as first pass devices to extract both firm and soft clots from vessels can include a device having an inner body, an outer cage, and a proximal shaft. The inner body can be formed monolithically by laser cutting a tube, and have struts forming cells configured to embed with at least a portion a clot. In some cases, the outer cage can also be cut from the same continuous tube and extend distal to the inner body. In other cases, the outer cage can extend along the longitudinal axis around the inner body and be expandable to a radial extent greater 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 also allow portions 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 pinching configuration.
The method can include the step of delivering the device to a blood vessel adjacent to the site of a target clot. The clot composition can be firm, soft, or mixed with both firm and soft portions The device can be unsheathed to embed at least one of the cells of the outer cage and at least one of the cells of the inner body in the clot by expanding the device from the constrained delivery configuration to the expanded deployed configuration.
Another step can involve advancing an outer catheter distally so that the outer catheter engages with and impinges on the proximal ends of 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 the outer cage. The outer catheter can be a microcatheter, access catheter, or another suitable outer sheath. The pinch can be maintained while the device is withdrawn so the grip on the clot is not lost.
In some examples, the cells of the inner body and/or outer cage can have struts forming bends or horseshoe shaped saddle points shaped to be compressed by the distal advancement of the outer catheter. The method can then further include the step of pinching at least a portion of the clot in a horseshoe shaped saddle point of at least one of the inner body cells when engaged with the outer catheter. Alternatively, or in addition to, the method can further include the step of pinching at least a portion of the clot in a horseshoe shaped saddle point of at least one of the outer cage cells when engaged with the outer catheter.
If the clot is frangible and not stiff enough to achieve a pinch, a user can feel the lack of tactile resistance when the shaft of the device is retracted, or the outer catheter is distally advanced. In this scenario, the outer catheter can be withdrawn, and the device can be redeployed to the expanded configuration to imbed the clot. In some examples, struts of the outer cage can be inverted back over the device, and the method can involve the step of inverting the struts proximally to internalize the clot and the inner body. The inner body can be held in position while the outer cage struts are inverted so the clot is not pushed proximally.
When the firm and/or soft clot has been captured by the device, the method can involve the step of removing the clot retrieval device and the captured clot from the patient. This can be done, for example, by retrieving the device proximally into a guide catheter using aspiration. If a firm portion of the clot can be pinched, the pinch can be maintained during this step so the grip on the clot is not lost. Additionally, if the struts of the outer cage have been inverted proximally (using tensioned pull wires or other method) to internalize and help secure the clot, this configuration can also be maintained.
After retrieving some or all of the occlusive clot, an assessment can be made to the degree to which the vessel is patent. Additional passes with the clot retrieval device can be made if an obstruction remains in the vessel. Any remaining devices can then be removed from the patient once adequate recanalization of the target vessel is observed. The devices of the present disclosure, however, provide a means to minimize the number of catheter advancements required to treat a patient, thereby reducing the likelihood of vessel damage and the associated risk of vessel dissection in cases where multiple passes are required.
Other aspects and features of the present disclosure will become apparent to those of ordinary skill in the art, upon reviewing the following detailed description in conjunction with the accompanying figures.
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.
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.
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.
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.
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.
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.
Referring to
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.
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.
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.
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.
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
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.
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
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.
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.
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.
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.
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.
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.
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.
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.
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
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.
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
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.
An elevation side view of the device 300 from
The device 300 shown in
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.
As a result, the cells 416 from the device 300 shown in
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.
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.
A perspective view of the inner body 310 of the device 300 from
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.
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.
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
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.
Referring to a method 11000 outlined in
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.
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.
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.
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.
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.
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.
