Patent Application
20210393277
The present disclosure generally relates to devices and methods for removing acute blockages from blood vessels during intravascular medical treatments. More specifically, the present disclosure relates to an expandable tip for a retrieval aspiration catheter.
Aspiration and clot retrieval catheters and devices are used in mechanical thrombectomy for endovascular intervention, often in cases where patients are suffering from conditions such as acute ischemic stroke (AIS), myocardial infarction (MI), and pulmonary embolism (PE). Accessing the neurovascular bed in particular is challenging with conventional technology, as the target vessels are small in diameter, remote relative to the site of insertion, and are highly tortuous.
In delivering effective devices to the small and highly branched cerebral artery system, conventional catheters must try and balance a number of factors. The catheter must be sufficiently flexible to navigate the vasculature and endure high flexure strains, while also having the axial stiffness to offer smooth and consistent advancement along the route. Additionally, abrupt stiffness or geometric changes can hinder trackability, introduce significant stress concentrations, and increase the likelihood of device kinking or buckling.
Some designs for aspirating clot retrieval catheters, such as those with fixed mouths, can have difficulty directing the full suction of aspiration to the volume of fluid and clot distal to the mouth. When aspirating with a catheter which is incapable of sealing with the target vessel, a significant portion of the aspiration flow ends up coming from vessel fluid proximal to the catheter tip, as opposed to the distal vessel regions with the clot. This significantly reduces aspiration efficiency and lowers the success rate of clot removal. Furthermore firm, fibrin-rich clots can often be difficult to extract as they can become lodged in the tip of traditional fixed-mouth catheters. This lodging can cause softer portions to shear away from the firmer regions of the clot.
Designs for aspirating catheters which feature a larger or expandable mouth for improved efficiency must balance the flexibility for delivery with adequate radial force and atraumatic deployment. Catheter elements must survive the severe mechanical strains imparted but also generate a sufficient radial force when expanded to prevent collapse under the suction of aspiration. To meet these requirements, the mouth of some aspiration catheters have been designed with diameters that are considerably larger than the typical delivery catheter or sheath. These designs can fail to effectively balance the competing requirements to truly be effective and safe for a wide variety of procedural conditions
The present designs are aimed at providing an improved retrieval catheter with an expansile tip which incorporates features to address the above-stated deficiencies.
The designs herein can be for an expandable distal tip of a clot retrieval catheter capable of providing local flow restriction/arrest within the target vessel with a large clot-facing mouth. The catheter can be sufficiently flexible so as to be capable of navigating highly tortuous areas of the anatomy, such as the neurovascular, to reach an occlusive clot. The expandable tip of the catheter can also be compatible with relatively low-profile access sheaths and catheters for deliverability advantages.
The clot retrieval catheter can have a substantially tubular support tube defining a longitudinal axis. A large central catheter lumen can be configured for the passage of guidewires, microcatheters, stent retrievers, and other such devices. The lumen can also direct aspiration to the catheter tip. The tubular body can terminate at a distal end, at which an expansile tip can be integrally formed or fixedly connected.
The catheter can have a self-expanding mouth framework with a plurality of interconnected struts formed into a porous framework. The mouth framework can be configured to expand from a collapsed delivery configuration to an expanded deployed configuration when deployed at the site of an occlusive thrombus. In the expanded deployed configuration, the tip can assume a substantially conical or funnel shape. The funnel shape formed by the tip can improve aspiration efficiency, arrest unwanted flow, and lessen the risk of vessel trauma from snagging on vessel openings.
In the deployed state the expansile tip is tapered such that a proximal end of the tip has a first radial dimension and a more distal portion of the tip has a second radial dimension larger than the first radial dimension. The second radial dimension can be larger than the diameter of the target blood vessel. At least a portion of the tip can have a radial dimension in the expanded deployed configuration greater than an inner diameter of an outer catheter.
In another example, at least a portion of the struts forming the perimeter of the mouth framework can extend radially inward in a distal direction from the peak maximum radial size of the mouth framework, such that the maximum radial size occurs at an axial location intermediate the proximal end and the distal end of the framework. Such a configuration can allow the tip to contact vessel walls in the expanded state with a large and gentle radius so as to avoid vessel trauma and reduce friction. When expanded and unconstrained, the diameter of the tip framework can range from 1 mm to 10 mm, and preferably closer to 3 mm.
The strut framework of the mouth can be a cut pattern of sheet or tube stainless steel, or a superelastic shape memory alloy such as Nitinol. The struts of the mouth framework can connect to form closed cells, loops, or undulating patterns. A plurality of distal hoops or crown struts can form the circumferential perimeter of the tip mouth opening. One or more support arm struts can extend longitudinally between the proximal and distal ends of the mouth framework to link adjacent hoops where they meet at hoop troughs, and the support arms can extend proximally from the hoop troughs to connect the expansile tip with the support tube and form a substantially conical surface about the longitudinal axis.
The catheter body can feature a combination of ribs and spines to define a substantially tubular shape. The expandable mouth can be formed integrally with the support tube for a monolithic structure, such as through machining the tube and mouth together from the same hypotube stock. In another example the tubular body can be of a metallic or polymeric braid/mesh or of coiled wire construction.
The support arms may be axisymmetric with the longitudinal axis of the catheter, or they can be twisted or situated in a helical fashion about the axis. Individual support arms can attach independently to a most distal rib or can extend from or align with one of the one or more axial spines of the support tube. As an alternative, some of the support arms can connect via slots, eyelets, or some other non-rigid connection such that the arms do not add stiffness to the strut framework.
The struts of the hoops and support arms can also contain features such as narrowed segments, curves, and/or undulations to enhance or tailor the flexibility of the structure. The support arms can take a waveform or sinusoidal pattern circumferentially to allow more freedom of bending along the axis of the arms. In another case, the struts of support arms can have a portion which is narrower in width than another portion of the support arms, or the support arms can have a width different than the width of at least part of the distal hoops or crowns making up the mouth perimeter.
The struts of the hoops and support arms of the mouth framework can intersect at multiple troughs located at various axial and clocking positions around the longitudinal axis. The number and location of trough intersection points can, in part, help determine the localized stiffness of the framework. For example, a support arm can terminate proximally at a support trough and distally at a hoop trough to form a closed cell. In one case, adjacent support arms can share one or more cells. In another example, support arms can extend proximally from an intersection with one or more hoops at a hoop trough and terminate at a spine, or at the most distal rib, of the support tube to form closed cells. These cells can help the mouth framework to elongate or shorten longitudinally under tensile or compressive loads during the thrombectomy procedure.
When the tip is in the collapsed delivery configuration the troughs of the framework can serve as hinges about which the strut framework folds. When expanded, the support arms of the mouth framework can form an angle with the longitudinal axis, the angle determining the rate of taper for the conical funnel shape of the expanded tip. The angle can, for example, have a range from approximately 10 degrees to approximately 45 degrees. In another example, the taper can shallow and the angle between the support arms and the longitudinal axis can be approximately 30 degrees.
The strut framework can be a cut pattern of sheet or tube stainless steel, or a superelastic shape memory alloy such as Nitinol. The funnel shape formed by the tip can improve aspiration efficiency, reduce friction, and lessen the risk of vessel trauma from snagging on vessel openings. A funnel shape also means in the deployed state the expansile tip is tapered such that a proximal end of the tip has a first radial dimension and a more distal portion of the tip has a second radial dimension larger than the first radial dimension. The second radial dimension can be larger than the diameter of the target blood vessel.
The catheter can further have a flexible elastomeric cover disposed radially so that if forms a sleeve around the at least part of the support tube and expandable tip of the clot retrieval catheter. The cover can be homogenous or can have multiple layers. As an alternative, the cover can be one or more polymer jackets.
Another expandable mouth for a clot retrieval catheter can have a self-expanding mouth framework disposed around a longitudinal axis. The mouth framework can have a collapsed delivery configuration when being delivered to a target site constrained within an outer catheter, and an expanded deployed configuration when the outer catheter is retracted to uncover the framework. The mouth framework can have a plurality of interconnected struts, and the struts can form petal-like shapes disposed circumferentially around the longitudinal axis. Each petal can have longitudinal arm struts behaving in a similar fashion to the support arms previously described. The petals can have undulations or have variable width with narrowed segments for enhanced flexibility. These features can encourage bending and flexing along axis of each arm. The longitudinal arms can extend individually, or one or more longitudinal arm struts can split to form one or more closed cells linked by distal hoops. The cells can allow the petals to elongate independently so as to avoid having the support tube pull the mouth framework proximally during clot retraction.
A polymeric membrane or cover can be disposed over, around, or encapsulating the mouth framework so that support is given to the membrane when the suction force of aspiration is directed through the catheter during a thrombectomy procedure. The cover can be taut so that it expands under the radial force of the mouth framework when the tip expands to the deployed configuration, or it can be loose or baggy so all the radial force can be directed to the vessel walls.
The petals of the self-expanding mouth framework can be made more flexibly by connecting the longitudinal support arms proximally at troughs, connecting struts, common spines, or individually to a most distal rib of the catheter support tube. The distal peak of each petal can be a crown or hoop member which is not connected circumferentially to adjacent petal crowns, so that each petal is independently sprung from its proximal connection or connections. As a result, petals can react to forces and clot morphologies separately so that each petal can flex individually without the constraint of adjacent petals.
In a further example, an expandable mouth for a clot retrieval catheter can have a proximal end, a distal end, and a radial strand array forming a closed cell mesh disposed around a longitudinal axis and extending from the proximal end to the distal end. The mesh array can be made of wire or shape memory alloy such that the mouth can expand from a collapsed delivery configuration to an enlarged deployed configuration. When unconstrained by an outer catheter in the enlarged deployed configuration, the cell mesh can form a substantially conical surface about the longitudinal axis. Similar to other examples, a flexible polymeric membrane can cover some or all of the closed cell mesh of the catheter tip.
The closed cell mesh array of the mouth framework can be a continuous polygonal pattern such as triangular or quadrilateral cells which are interlocked through the vertices of the adjacent cells. The pattern can be one of those commonly seen in stenting applications, where a minimally invasive mesh is used to support and hold open vessel passages. In one case, an elongated quadrilateral pattern forms cells pores where local array peaks mark the shared vertices. The pattern can repeat in an axial and radial fashion and the distalmost array peaks of adjacent pores can be joined by curved distal hoops or crowns to mark the perimeter of the expandable mouth.
The density of the closed cell mesh pattern can vary. A denser mesh can have a greater stiffness and radial force, but also provide more support for an overlaying cover or membrane. In one example, the pattern can be sufficiently dense to where blood flow across the mesh is impeded by the small size of the pores. In this situation a membrane cover may not be necessary as the pattern of the pores is fine enough to function as seal to block off blood within the vessel which is proximal of the tip.
In order to allow for smooth delivery of the clot retrieval catheter through an outer catheter, the closed cell mesh of the tip and/or the outer surface of the membrane or outer jackets can be coated with a low-friction, such as PTFE or FEP, or a or hydrophilic lubricious material such as those offered by Surmodics, DSM, and Harland medical. The coating can prevent a buildup of static or dynamic friction, mitigating the risk of the catheter binding or kinking in tortuous areas of the vasculature.
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 an expandable mouth for a clot retrieval catheter capable of providing both local flow restriction/arrest with a large distal facing mouth that is tailored to provide sufficient radial force and high flexibility to be capable of navigating tortuous areas of the vasculature within an outer catheter to reach an occlusive clot. The large mouth designs offer substantially greater aspiration efficiency and flow restriction capabilities. Such advantages can also be especially beneficial in the case of stroke intervention procedures, where vessels in the neurovascular bed are particularly small, circuitous, and fragile. As a result, a tailored axial and bending stiffness profiles of the expandable mouth tip can inhibit kinking and binding while tracking through these vessels. The tip can have a collapsed state so the clot retrieval catheter can be compatible with relatively low-profile access sheaths and outer catheters, so that a puncture wound in the patient's groin (in the case of femoral access) can be easily and reliably closed. The expandable mouth can also feature internal and/or external low-friction liners, and an outer polymer jacket or membrane disposed around the supporting structure. These improvements can lead to safe and more rapid access of a catheter and other devices to complex areas in order to more reliably remove occlusions and shorten procedure times.
Another advantage of using and having a clot retrieval catheter with an expanding mouth delivered through an outer catheter is that once the clot has entered the distal end of the clot retrieval catheter, the clot retrieval catheter can be retracted through the outer catheter such that the outer catheter is left in place to maintain access at the target treatment location. While it is appreciated that certain clots may also require that the outer catheter be retracted with the clot and inner clot retrieval catheter, the majority of clots are likely to be removed through the inner clot retrieval catheter. With this combination there will be greater confidence that the lumen of the outer catheter is clean of debris for reduced risk during contrast injection that potential thrombus remnants may be dislodged from the catheter. With traditional catheters, a user would often have to remove the outer catheter to flush any thrombus remnants outside of the body prior to injecting contrast, at the cost of losing access to the target treatment location. The present invention provides 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.
Specific examples of the present invention are now described in detail with reference to the Figures. It should be appreciated that when used herein, tip framework, mouth framework, support frame, etc. are interchangeable and all refer to the same structure. The designs can often have a polymeric membrane cover, which is typically not shown for clarity of the underlying framework. 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 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, 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 to
The support tube 35 of the clot retrieval catheter can be of many different configurations. The support tube 35 can have one or more axial spines 42 extending the length of the support tube. For example, the support tube 35 illustrated in
The support tube 35 can be formed from laser-cutting a hypotube or other tube stock, or of otherwise similar construction including a braid with overlaid or interwoven spine(s). This enables the support tube 35 to have good push and torque characteristics, small bend radii, kink resistance, and solid resistance to tensile elongation. Commonly used materials include Nitinol and familiar medical-grade stainless-steel alloys like 304 and 316. Hypotubes of different materials, such as stainless-steel for the proximal section of the tubular support and Nitinol for a distal portion of the tubular support tube and for the expansile mouth, said different materials being joined by welding, bonding or by holding interlocking features in place with inner and/or outer polymer jacket materials.
The funnel design of the expandable tip 100 of the disclosed examples can be an integral lattice laser cut directly and integrally with the support tube 35 of the catheter shaft. Alternately, the expansile tip lattice can be injection molded support or mesh frame constructed as a single piece and attached to the support tube through heat welding, adhesives, or similar means. The tip can be designed to expand to a wide range of target vessel diameters, such as a carotid terminus (3.2-5.2 mm), a horizontal M1 segment of the Middle Cerebral Arteries (1.6-3.5 mm), and/or the Internal Carotid Artery (ICA, 2.7-7.5 mm). If the catheter is then retracted from an M1 segment to the ICA (or another route with a proximally increasing vessel inner diameter), the expandable tip 100 will continue to seal the vessel across a range of vessel sizes. Further, a tip capable of a range of target vessel diameters can also seal at vessel bifurcations which can have a wider cross-sectional area than the vessel proximal and vessels distal to the bifurcation. Preferably, the expandable tip 100 of the catheter is expanded at the treatment location to avoid having to advance the expanded tip through the vasculature.
Arranging the expandable tip 100 to have connections in-line with one or more of the spines 42 of the support tube 35 allows advancement forces to be directly transmitted through the spines to the tip during advancement through an outer catheter for enhanced pushability. An in-line connection can also allow other circumferential portions of the support tube 35 to be kept free of joints to adjacent ribs or the tip in order to limit effects on the deliverability of the catheter through increased friction with the outer catheter.
The catheter can also have a cover or membrane (not shown) disposed around or encapsulating at least a part of the support tube 35 and expandable tip 100. Suitable membrane materials can include elastic polyurethanes such as Chronoprene, which can have a shore hardness of 40 A or lower, or silicone elastomers. A single- or variable-stiffness cover can be extruded or post-formed over the support tube 35 and tip 100. The cover can also be laminated, or heat welded to the structure.
Alternatively, the cover can also be a formed from a series of polymer jackets. Different jackets or sets of jackets can be disposed at discrete lengths along the axis 111 of the support tube 100 in order to give distinct pushability and flexibility characteristics to different sections of the tubular portion of the catheter. By configuring the jackets in an axial series, it is possible to transition the overall stiffness of the catheter from being stiffer at the proximal end to extremely flexible at the distal end. Alternately, the polymer jackets of the cover can be in a radial series disposed about the support tube in order to tailor the material properties through the thickness. In a further example, transitions between jackets can be tapered or slotted to give a more seamless transition between flexibility profile of abutting jackets in longitudinal series.
In an example shown in
The support arms 116 can be V- or Y-shaped struts extending from the support tube 35 merging to two connections to the spines 42 or the support tube at the proximal end 112 of the expandable tip 100 and four connections to the distal hoops 118. The V- or Y-shaped support arms 116 can give the frame 110 similar support to a device with four or more support arms, while reducing the number of connections to the support tube 35. Having two connections to the support tube spaced 180 degrees apart allows the support frame 110 to hinge about the connections when collapsed within an outer catheter during advancement through tortuous vasculature, or when deployed in curved vessels to fully appose the vessel walls with the hoops 118. The hinging action biases bending along a plane extending radially through the two connections and the longitudinal axis 111 of the frame 110. It can be appreciated that support frames 110 with two connections to a support tube 35 can have additional support arms extending from a single connection where distal hoops 118 with more than four proximal troughs 121 are used.
The stiffness and changes in stiffness for the mouth support frame 110 is important in situations where distances and tortuosity can be significant, such as when it must be advanced from a patient's inner thigh, over the cardiac arch, and up into the neurovascular inside the skull. To further tailor the stiffness, the strut width of the support arms 116 and distal hoops 118 can be varied along the length of the strut by incorporating one or more narrowed segments 124. For example, greater width at the peak of a V-shaped support arm 116 can give greater radial force capability while narrowed mid-sections can help to reduce lateral stiffness to aid in bending to track through tortuous vasculature. Having a greater width adjacent to the proximal troughs 121 of the distal hoop 118 can also give increased radial force. Narrowed segments 124 at the distal hoop peaks 119 can soften the distal end of the expandable tip 100 to improve the atraumatic characteristics of the tip, and the narrowed segments 124 can also aid the hoop 118 in collapsing back into the mouth of an outer catheter by reducing the force required to collapse the distal peaks 119 of the frame 110.
Turning to
Another support frame 110 can have six Y-shaped support arms 116 and six hoops 118 with six distal peaks 119, as shown in
The V-shaped support arms 154 provide additional surface area to support an outer cover or membrane (not shown). The outer membrane can reduce the likelihood of the proximal peaks 117 of the V-shaped arms 154 of snagging on branching vessels or the mouth of an outer catheter during retraction. In another example, the proximal peaks 117 of the arms 154 can be more rounded or U-shaped similar to the distal peaks 119 of the support hoops 118.
In another example, a mouth support framework 110 for a clot retrieval catheter can have six distal hoop peaks 119, two Y-shaped support arms 152, and four V-shaped support arms 154, as seen in
Similar to other examples, this design can provide a closed-cell structure for the distal hoop 118 to provide enhanced radial force while the eyelets 127 and link members 128 mean there are only two rigid connections with the Y-shaped arms 152 to the support tube at the proximal end 112. Spacing the connections between the support tube 35 and Y-shaped arms 152 at diametrically opposed positions of the tube allows the frame 110 to hinge about the connections for trackability through an outer catheter and to better conform when the target location is in a curved vessel.
The array of link members 128 reduce the likelihood of the free proximal peaks 117 of the V-shaped support arms 154 snagging on the mouth of an outer catheter when the expandable tip 100 is retracted. The connections of the link members to the eyelets 127 at the proximal peaks 117 of the V-shaped arms 154 and the eyelets of the support tube are not rigid, allowing the members to move through the eyelets 127 of these connections in a loose manner so the support frame 110 can flex easily in tortuous vessels. If the link members 128 are made flexible, they will not contribute to the bending stiffness of the tip 100 in a collapsed state but can become taut once the distal support hoop 118 is expanded. Flexible members can be sufficiently tough to support an outer cover or membrane to counteract the negative pressure forces exerted on the cover during aspiration.
Another mouth frame 110 example can have distal support hoops 118 with six peaks 119 around the perimeter of the mouth, as illustrated in
For optimized lateral flexibility, the support frame 110 can be constructed so that the struts forming the waveform pattern 130 of the support arms 116 form an angle between 45 degrees and 135 degrees with respect to the central longitudinal axis 111 when the frame is in a flat pattern or plan view. In this configuration, the more longitudinally oriented portions of the support arms 116 can bias bending about the struts extending between the peaks of the waveform pattern 130 when the frame is subjected to torsional moments, making the support arms more reliant on torsional flexibility than lateral flexibility. It can be appreciated that the angle formed by the struts of the pattern can fall outside the 45-135-degree range if it is desired to trade some torsional flexibility for additional lateral flexibility in bending.
In a similar example seen in
Another support frame 110 of an expandable tip 100 similar to that of
The frame 110 can have an additional strut or struts acting one or more torsional members 132 extending between proximal hoop troughs 121 of the support hoops 118. The torsional members 132 can extend in a circular fashion about a central longitudinal axis 111 of the device as shown such that it can move distally under torsional loading during retraction into an outer catheter, This movement can aid the frame 110 in pinching a stiff clot that may be otherwise restricted from entering the catheter lumen 44 fully so that the grip on the clot is secure as the catheter is withdrawn through the vasculature. In another example, a portion of the hoop peaks 119 and/or the torsional members 132 can have an axially rounded or curved profile, or the struts can intersect at an intermediate point to serve as hinges and reduce the transmission of the torsional moment as the frame 110 is collapsed. This reduced moment can be beneficial in devices where the outer cover or jackets are constructed from stiffer materials with reduced elastic strain capacity and elongation at break, as the cover would not be required to move as much as the frame folded or collapsed into an outer catheter.
A further example of a support frame 110 having distal hoops 118, four support arms 116, and four hoop peaks 119 is disclosed in
The struts of the distal hoops 118 can also have a different width than those of the support arms 116. For example, wider or thicker struts of the hoop approximate the hoop peaks 119 can provide the support frame 110 with greater radial force capability at the hoop and more flexible support arms. Narrower struts near the peaks 119 can allow the hoops to be more compliant when sealing with the walls of a vessel.
Another support frame 110 having four branching support arms 116 and four hoop peaks 119 is illustrated in
Various views for a design where an expandable support frame 110 has elongated connector struts 136 between the distal hoops 118 and support arms 116 is shown in
Depending on the location of an occlusive clot and the requisite pushability and flexibility demands on the support frame, other advantages can be gained by varying the strut width of the support arms of the frame. A support frame 110 with four support arms 116 having enlarged closed cell openings and struts of variable thickness can be seen in
When flexibility characteristics are added to the support arms 116 of the tip framework 110, the radial force capabilities of the tip 100 can be maintained through a more generous support arm angle, α, to the longitudinal axis 111. The radial force can be tuned so that an adequate seal can be maintained without contributing to vessel trauma. For example, when the tip framework 110 is heat set with an angle α equal or greater than 30 degrees, a larger component of the expansion forces can be exerted in the radial direction.
Various views of a similar design for an expanding support frame 110 with a less tapered funnel shape and four support arms 116 with a decreased support arm angle θ is depicted in
Alternatively, the support arm angle θ can be in a range that is less than 45 degrees so that the catheter tip 100 will be less likely to expand further when advanced distally in an outer sheath or blood vessel, but greater than 10 degrees so that the mouth framework 110 of the catheter will be kept relatively short in length. Optimizing the support arm angle θ can also help the tip 100 to seat against the distal tip of an outer catheter and the walls of a target vessel.
When in the expanded state, at least part of the mouth framework 110 may taper distally from a larger peak radial dimension to a smaller radial dimension. In this configuration, the outer axial profile of the tip body can also be broadly rounded to provide a smooth interface with the vessel wall. A portion of the distal support hoops 118 can extend radially inward as shown in
The support arms 116 can be connected at the proximal end 112 of the mouth frame 110 with the support tube 35 of the catheter. One or more spines 42 of the support tube can be aligned with one or more of the support arms to allow for the smooth transmission of longitudinal forces between the spines and the frame. Support arms 116 not aligned with spines 42 can link with support arms that are aligned or terminate at points approximate the distal end of the support tube 35. In thus configuration, compressive forces generated during clot retrieval may not cause unwanted expansion of the support tube 35 or mouth frame 110 during a procedure.
Any of the mouth support frames 110 disclosed herein can be enclosed or encapsulated by an elastomeric membrane cover 50. While many of the previous figures have not shown the cover for clarity,
The thickness of the membrane cover 50 can be maintained between and over the struts of the mouth support frame 110 or it can vary in thickness along the frame 110. In one example, the cover 50 can be applied where the thickness of the membrane between struts is close to the ligament thickness of the membrane above and below the struts. In another, the cover can have a uniform wall thickness where the thickness between the struts is greater than the ligament thickness remaining above and below the struts. The membrane cover 50 can also include geometric features and/or thinned regions positioned appropriately to vary the contribution of stiffness from the membrane to the overall assembly of the support frame 110 and cover together.
The membrane cover 50 can be stitched to the struts of the support tube 35 and mouth frame 110, or it can be reflowed over and between struts (to be flush with the inner surface of the support struts, or an inner layer and an outer layer may be utilized so that the struts have membrane material above the outer surface and below the inner surface of support struts), heat shrunk and bonded to the outer surface of support struts, or welded in place in defined zones 52. The cover 50 can also be formed through a dipping process (to be flush with the inner surface of the support struts, or an inner layer and an outer layer may be utilized so that the struts have membrane material above the outer surface and below the inner surface of support struts). How the cover 50 conforms to the distal end 114 of the mouth framework 110 can also be varied, as seen in the profile examples of
The membrane cover 50 can be of a construction where it has good ductility and a high elastic strain limit so that it can be easily expanded by minimal radial forces from the underlying support frame 110, as shown in
To allow for smooth delivery of the clot retrieval catheter through an outer catheter, and auxiliary devices through the lumen of the clot retrieval catheter, the expandable tip and/or the outer surface of the membrane or outer jackets can be coated with a low-friction or lubricious hydrophilic material, or a low friction material such as a fluoropolymer like PTFE or FEP. Additionally, the inner surfaces of the struts of the expandable tip, or the inner surfaces of the membrane cover if it encapsulates the tip, can also be coated with the liner or be otherwise manufactured with low-friction properties.
In many examples, the support tube 35 can also share an external and/or internal lubricious film or coating with the tip 100. The coating can be delivered via dipping, spray, plasma, a profiled mandrel, or any other commonly used technique. Alternately, the membrane cover or jackets can be impregnated with particles having low-friction properties.
In another example, the mouth framework 110 can include an electro-spun or other porous cover that allows for reduced blood flow from the proximal side of the tip-vessel wall seal. A flow reduction between 50% to 99%, more preferably from 60% to 80%, will still direct most of the aspiration flow to the clot while allowing for a small restoring flow portion from the proximal side. This flow can help to reduce the possibility of vessel collapse under excessive aspiration, in locations where vessels have little support from surrounding tissue, or in cases where there are no side branches between a blocked vessel and the expanded tip 100 and a mechanical thrombectomy device or stentriever has not been able to open a portion of the blocked vessel.
Other mouth support frame examples can have longitudinal supports which are distally independent of one another so they can flex individually.
Similar to other disclosed examples, unconstrained, the petals 215 can expand radially so that a substantially conical surface is formed the combination of arms 216 around the longitudinal axis 111. The struts of the longitudinal arms 216 can branch to form one or more undulations or closed cells 220, allowing the petals 215 to lengthen and shorten independently in response to the forces experienced during navigation through an outer catheter or during a thrombectomy procedure when the tip 200 is deployed and expanded at a target site. Having the longitudinal arms 216 closely aligned with the longitudinal axis 111 of the tip 200 can maintain good column stiffness and pushability characteristics. The petals 215 can also include other members to enhance developed radial force and further support a membrane cover during aspiration.
The support frame 210 can also have proximal support hoops 230 extending distally from support troughs 126 which form connections with a support tube of the catheter, which is not shown for clarity. Connecting struts 236 can form the distal terminating peaks of the proximal support hoops 230 and can link the hoops with the longitudinal arms 216 of the frame.
In a similar variant,
Alternatively, a mouth support frame 210 with distally unconnected petals 215 can have direct connections to the support tube, either to a common axial strut or to the most distal rib or lip (not shown). A support frame with direct connections having eight longitudinal arms 216 joining four distal hoop members 216 to form four unconnected petals 215 is illustrated in
The longitudinal arms 216 can contain one or more closed cells 220 to sustain the necessary radial force while providing additional support for a membrane cover. The spacing of the direct proximal connections and the closed cells can be such that the petals may or may not overlap with each other when held at the desired radial shape of the frame by the cover and can collapse neatly when the tip folded into an outer catheter.
A support frame 210 can also have six longitudinal arms 216 each extending from a direct connection at the proximal end 112 to form six distally unconnected petals 215, as depicted in
As observed from
It can be appreciated that fewer unconnected petals 215 in
Several views of a support frame 210 having a plurality of undulations or waveforms 130 along the length of the longitudinal arms 216 and with an array of closed cells 220 around the longitudinal axis 111 at the distal end 114 is considered in
In another alternative construction, an expandable mouth tip 300 of a catheter can have a radial array of struts or strands organized into a closed cell mesh 310, as illustrated in
In another example, the support tube 35 can have a metal and/or polymer strand construction formed into a patterned mesh or coiled structure. The structure can form a radial array as a continuous tubular catheter body and in some cases can even be integral with the expandable tip 300. In this case the stiffness transition between the support tube 35 and tip 300 is minimized in order to approximate a singular supporting piece and better distribute strain. The tube can be coated or encapsulated with a cover or membrane to provide smooth surfaces for trackability within an outer catheter and the internal passage of ancillary devices.
The closed cell mesh array 310 making up the mouth framework can be a continuous polygonal pattern as shown such as triangular or quadrilateral cells which are interlocked through the sharing of the vertices of the adjacent cells. In one case, the array 310 can have an elongated quadrilateral pattern as seen in
The cells formed by the shared array peaks 312 define the open pores 316 of the closed cell mesh 310 structure. The pores 316 of the mesh can be sized so as to tailor the filtration properties of the expandable tip 300. For example, large pores can give the tip enhanced flexibility yielding deliverability advantages while incorporating an outer membrane cover or jacket (not shown) to block or limit blood flow from regions proximal to the tip when deployed in the expanded configuration at a target site.
Alternately, the pores 316 can be micro-sized to form a mesh array 310 which is dense enough to impede flow sufficiently to where an outer jacket or a membrane cover is not necessary. In this case, the outer cover of the support tube 35 can terminate close to or in a region just distal of the proximal end 112 of the expandable tip 300 where the diameter of the tip begins to expand in the deployed configuration. By not requiring an outer membrane cover, the expandable tip 300 can track more easily through an outer catheter and the required advancement forces can be limited. As a result, although one may still be applied, a lubricious or low-friction coating may not be required.
There are a wide variety of minimally invasive stent patterns, meshes, or screens found in commercially available products with a range of capabilities and applications. It can be appreciated that the closed cell mesh 310 of the expandable tip 300 can utilize any expanding stent pattern known in the art of stent patents and products and that the pore 316 sizes need not be restricted to those disclosed herein.
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. Similarly, it is also to be understood that the mention of one or more components in a device or system does not preclude the presence of additional components or intervening components between those components expressly identified. 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. For clarity and conciseness, not all possible combinations have been listed, and such modifications are often apparent to those of skill in the art and are intended to be within the scope of the claims which follow.
