This invention relates to devices intended for removing acute blockages from blood vessels. The invention especially relates to means of rendering such devices visible under xray or fluoroscopy. Acute obstructions may include 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. 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—this mechanism is common in the formation of coronary blockages. The invention is particularly suited to removing clot from cerebral arteries in patients suffering acute ischemic stroke (AIS), from coronary native or graft vessels in patients suffering from myocardial infarction (MI), and from pulmonary arteries in patients suffering from pulmonary embolism (PE) and from other peripheral arterial and venous vessels in which clot is causing an occlusion.
Clot retrieval devices comprising a self-expanding Nitinol stent-like member disposed at the end of a long shaft are commonly used to remove clot from blood vessels, particularly from patients suffering from acute ischemic stroke. These devices are typically provided with small marker bands at either end of the self-expanding member which help to indicate the device's position. It would be very beneficial to a physician to be able to see the full expandable body of such a device under fluoroscopy, and thus receive visual information on the device's condition as rather than simply its position. Clot retrieval procedures are conducted under an x-ray field in order to allow the user visualise the anatomy and at a minimum the device position during a procedure. It is desirable, and enhances the user experience to be able to visualise the device state as well as position structure during a procedure, for example if the device is in an expanded configuration or a collapsed configuration. This means that the radopiaque sections must move closer to the device axis in a collapsed configuration and further from a device axis in an expanded configuration. It is generally desirable to make interventional devices such as clot retrieval devices more flexible and lower profile to improve deliverability in interventional procedures. This may be achieved by reducing the dimensions for device features, and the level of contrast seen under x-ray is generally reduced as the device dimensions are reduced. Radiopaque materials generally comprise noble metals such as gold, tantalum, tungsten, platinum, iridium and the like, and generally have poor elastic recovery from a strained condition and are therefore not optimal material for devices, particularly for the regions of these devices undergoing high strain in moving from a collapsed to an expanded state and vice versa. Radiopaque materials may be added through coating a structure comprising a highly recoverable elastic material such as Nitinol, but coating the entire structure has a dampening effect that inhibits device performance.
This invention overcomes limitations associated with the dampening effect of adding radiopaque material to an expandable clot retrieval device, while making the structure sufficiently radiopaque to allow full visualisation of the device condition as well as position.
Various devices and method are described in our PCT/IE2012/000011 which was published under the number WO2012/120490A. This PCT application claims the benefit of U.S. Provisional 61/450,810, filed Mar. 9, 2011 and U.S. Provisional 61/552,130 filed Oct. 27, 2011. The corresponding U.S. National stage is U.S. application Ser. No. 13/823,060 filed on Mar. 13, 2013. The entire contents of all of the above-listed applications are herein incorporated by reference. In addition, we hereby incorporate by reference in its entirety our U.S. Provisional Application No. 61/785,213 (Client Ref. 00007-0009-00600) entitled “A Clot Retrieval Device for Removing Occlusive Clot from a Blood Vessels” filed on Mar. 14, 2013.
This invention is particularly applicable to clot retrieval devices comprising expandable bodies made from a metallic framework. Such a framework might be a Nitinol framework of interconnected struts, formed by laser (or otherwise) cutting a tube or sheet of material, and may thus comprise a structure with a pattern of strut features and connector features. In some embodiments the clot retrieval device may comprise an inner expandable member and an outer expandable member, which may define a flow lumen through a clot and engage a clot.
In order to go from a collapsed to an expanded configuration, portions of the device undergo recoverable deformation and varying levels of strain. Some portions require a higher level of recoverable strain than others in order to work effectively. Where teh framework or expandable member comprises a pattern of strut features and connector features, the struts typically comprise inflection regions or connection regions generally referred to as crowns, which typically experience higher strain than the struts or connectors when the device is collapsed or expanded.
The term detector is generally referred to as the part of the equipment which collects the beam for processing into useful images, and can include for example flat panel detectors or image intensifiers. X-ray beams are filtered through an anti-scatter grid during processing. This filters out scattered beams which deflect significantly from the trajectory of the source beam, and beams less significantly deflected off the original trajectory pass through the anti-scatter grid creating areas of overlap between non-scattered photon beams and scattered photon beams, referred to herein as shadow areas.
In an embodiment of this invention discrete markers are placed in low strain regions of the clot retrieval device members, and high strain regions comprise a super elastic material with little or no radiopaque material.
In use, it is desirable to maximise visibility and therefore maximise the area and volume of radiopaque markers located in the clot retrieval device. Increasing the ratio of radiopaque material to Nitinol generally improves radiopacity. For the effective operation of the device in moving between expanded an collapsed configurations, it is desirable to maintain a ratio of Nitinol to radiopaque material such that strain levels from an expanded to a collapsed configuration are substantially in the elastic region. This creates a conflict of requirements, and the solutions provided herein overcome this conflict.
Discrete markers placed in close proximity create overlapping shadow areas, referred to as intersection zones herein, which give the illusion under x-ray imaging of a continuous marker thereby providing fuller visual information to the user in an x-ray image.
Various embodiments of the invention are described in more detail below. Within these descriptions various terms for each portion of the devices may be interchangeably used. Each of the described embodiments are followed by a list of further qualifications (preceded by the word “wherein”) to describe even more detailed versions of the preceding headline embodiment. It is intended that any of these qualifications may be combined with any of the headline embodiments, but to maintain clarity and conciseness not all of the possible permutations have been listed.
One embodiment of a device of this invention comprises a clot retrieval device comprising an elongate shaft and an expandable section, the expandable section comprising a framework of interconnected strut elements, the connection region between adjacent strut elements comprising crown elements, said framework formed from a substrate material, at least a portion of a plurality of said strut elements coated with a coating material, and at least a portion of a plurality of said crown elements not coated with said coating material.
Another aspect of this invention comprises a method of manufacturing the expandable body of a clot retrieval device, the expandable body comprising a substrate material and a coating material, the method comprising:
a first step of applying the coating material to the substrate material,
a second step of removing at least a portion of said coating material from at least one area of said substrate material,
and a third step of cutting away regions of both coating and substrate material to form an interconnected pattern of coated and uncoated regions.
Another embodiment of a device of this invention comprises a clot retrieval device comprising an elongate shaft and an expandable section, the expandable section formed from a substrate material, at least a portion of the substrate material coated with a first coating material and at least a portion of the first coating material coated with a second coating material;
Another embodiment of a device of this invention comprises a clot retrieval device comprising an elongate shaft and an expandable member, the expandable member comprising a proximal section, a body section and a distal section, the body section comprising a metallic framework of a first (or substrate) material, the metallic framework comprising a plurality of strut elements, said strut elements comprising an outer surface, an inner surface and side wall surfaces, at least one of said surfaces comprising a smooth surface and recessed features, at least some of said recessed features at least partially filled with a second (coating) material.
Another aspect of this invention comprises a method of manufacturing the expandable body of a clot retrieval device, the expandable body comprising a substrate material and a coating material, the method comprising: a first step of removing material from discrete areas of the substrate material to form recesses, a second step of applying the coating material to the substrate material and recesses, and a third step of removing some or all of the coating from the non-recessed areas of the substrate.
Another aspect of this invention comprises a method of applying a radiopaque coating to selective areas of the expandable body of a clot retrieval device, the method involving a masking material and comprising:
a first step of applying a masking material to selective areas of the expandable body,
a second step of applying a coating material to the expandable body, and a third step of removing the masking material from the expandable body.
Another aspect of this invention comprises a method of manufacturing the expandable body of a clot retrieval device, the expandable body comprising a substrate material and a coating material, the method involving a masking material and comprising:
a first step of applying the masking material to the substrate material,
a second step of removing at least a portion of said masking material from at least one area of said substrate material,
a third step of cutting away regions of both masking and substrate material to form an expandable body with masked and unmasked regions,
a fourth step of applying a coating material to the expandable body, such that the coating material adheres to the unmasked areas but does not adhere to the masked areas of the expandable body,
and a fifth step of removing the masking material from the expandable body.
Another embodiment of a device of this invention comprises a clot retrieval device comprising an expandable body and an elongate shaft, the expandable body comprising a proximal section, a body section and a distal section, the body section comprising a framework of strut elements and at least one fibre assembly, the fibre assembly comprising a radiodense material.
a is an isometric view of a portion of a clot retrieval device comprising standard material under x-ray imaging
b is a representation of an x-ray image of
c is an isometric view of a portion of another clot retrieval device comprising a radiopaque material under x-ray imaging
d is a representation of an x-ray image of
a is an isometric view of a portion of another clot retrieval device comprising standard material and radiopaque material under x-ray imaging
b is a representation of an X-ray image
a is a cross section view of a strut feature of a clot retrieval device comprising standard material and radiopaque material
b is a representation of an x-ray image of
a is a cross section of a strut feature of a clot retrieval device comprising standard material and spaced apart radiopaque material features
b is the a representation of an x-ray image from
a is an isometric view of a portion of a clot retrieval device
b is a developed plan view of the portion of a clot retrieval device from
a is a view of a portion of a clot retrieval device.
b is a detail view of a region of the device shown in
c is an isometric view of the device shown in
a is an isometric view of a tube used to form a part of a clot retrieval device.
b is an isometric view of a tube used to form a part of a clot retrieval device.
a is a side view of an element of a clot retrieval device
b is a view of the element shown in
a is a side view of an element of a clot retrieval device
b is a view of the element shown in
a is a stress-strain curve of a material used in the construction of a clot retrieval device.
b is a stress-strain curve of another material used in the construction of a clot retrieval device.
c is a stress-strain curve of an element of a clot retrieval device.
d is a stress-strain curve of another element of a clot retrieval device.
a is a side view of part of a clot retrieval device of this invention.
b is a side view of part of a clot retrieval device of this invention.
c is a side view of part of a clot retrieval device of this invention.
a is an isometric view of part of a clot retrieval device of this invention.
b is a detail view of a region of the device of
c is a section through one embodiment of a part of
d is a section through another embodiment of a part of
Specific embodiments of the present invention are now described in detail with reference to the figures, wherein identical reference numbers indicate identical or functionality similar elements. The terms “distal” or “proximal” are used in the following description with respect to a position or direction relative to the treating physician. “Distal” or “distally” are a position distant from or in a direction away from the physician. “Proximal” or “proximally” or “proximate” are a position near or in a direction toward the physician.
The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Although the description of the invention is in the context of treatment of intracranial arteries, the invention may also be used in other body passageways as previously described.
Positional visualization of this device may be provided by proximal Radiopaque coil 109 and distal radiopaque markers 108. User visualization of device 100 would be enhanced by providing visual information to the user on device expansion in a vessel or clot. This information may allow the user to visualise the profile of a clot and provide a fuller map of the luminal space created upon device deployment. As the device is withdrawn, the user will see the device response as it tracks through the anatomy with clot incorporated. It is therefore desirable to add radiopaque materials to outer member 102 and/or to inner tubular member 101 to provide the highest quality information to the user. One of the challenges with incorporating radiopaque material in such a manner is the dampening effect such materials have on superelastic Nitinol. The inventions disclosed in this document facilitate incorporation of radiopaque material and therefore product visualization without compromising the superelastic response of the outer member or inner tubular member. It is intended that any of the designs and inventions disclosed may be adopted to enhance the radiopacity of a clot retrieval device such as shown in
In the embodiment shown the radiopacity of the outer member is enhanced by the presence of Radiopaque elements 107, which are attached to the outer member by supporting fibres 106. These fibres may be connected to the framework of the outer member by a variety of means, including threading the fibres through eyelets or attachment features. Radiopaque elements 107 may comprise tubes, beads or coils of a radiodense material such as Gold, Tungsten, Tantalum, Platinum or alloy containing these or other high atomic number elements. Polymer materials might also be employed, containing a Radiopaque filler such as Barium Sulphate, Bismuth SubCarbonate, Barium OxyChloride or Tantalum.
a is an isometric view of a portion of a clot retrieval device 1001 with strut feature 1002 and crown feature 1007 comprising a superelastic material such as Nitinol. The portion of the clot retrieval device is shown is an expanded configuration. It can appreciated that in the collapsed configuration, for clot retrieval device delivery, the struts 1002 may move to a position adjacent each other. During an interventional procedure, such as a neurothrombectomy procedure, the patient anatomy and device location in visualized with the aid of x-ray equipment such as a fluoroscope. Source x-ray beam 1003 originates at a photon beam source and targets device 1001. Partially scattered x-ray beam 1004 is the photon beam deflected by device 1001 which passes to detector 1008. Partially scattered x-ray beam generically refers to a photon beam which may be absorbed or scattered by a material (e.g. photoelectric absorption or Compton scattering). For materials, such as Nitinol that is relatively non-radiopaque relative to the treatment environment, source photon beams 1004 may pass through the device relatively uninterrupted, without being absorbed, changing trajectory, or without a significant wavelength change.
b is a representation of resulting image 1011 captured by detector 1008 in
c is an isometric view of a portion of a clot retrieval device 1021 with strut feature 1022 and crown feature 1027 comprising a radiopaque material, or a superelastic material such as Nitinol fully covered with radiopaque material through a process such as electroplating or sputtering. Source x-ray beam 1023 is a source photon beam between and x-ray source and device 1021. Highly scattered x-ray beam 1025 is the photon beam between device 1001 and detector 1008. As an source x-ray beam 1023 passes through radiopaque materials, such as noble metals such as gold, platinum, and the like, the level of scattering of a beam is relatively much greater than the level of scattering of either an adjacent non-radiopaque device comprising Nitinol or relative to the treatment environment where source x-ray beams 1023 pass through relatively uninterrupted.
d is a representation of resulting image 1031 captured by detector 1028 in
a is an isometric view of a portion of a clot retrieval device 1041 with strut feature 1042 and crown feature 1047. The device structure substantially comprises superelastic Nitinol material, especially at crown feature 1047 where a high level of elastic recovery is desirable for effective device operation. Discrete radiopaque marker 1045 is located on strut feature 1042 as an example of a location on a structural feature of the device which deflects less and requires less elastic recovery than other features of the device, for example crown feature 1047. Several embodiments of devices incorporating discrete radiopaque marker 1045 are disclosed later. Source x-ray beam 1043 is used to image device 1041 and in this example a mixture of highly scattered x-ray beam 1046 and partially scattered x-ray beam 1044 reach detector 1048.
b is a representation of x-ray image 1051 of device 1052 captured by detector 1048 (
a and
b is an illustration of x-ray image 1071 with low contrast image 1074, high contrast image 1073, and shadow zone 1075. Shadow zone 1075 in
a is a cross section view of a portion of a clot retrieval device 1091 with strut feature 1092 and a plurality of discrete radiopaque markers 1095. The device structure substantially comprises superelastic Nitinol material, especially strut feature 1092 and especially areas where a high level of elastic recovery is desirable for effective device operation such as crown features not shown in this drawing. A plurality of discrete radiopaque markers 1095 are located on strut feature 1092 as an example of a location on a structural feature of the device which deflects less and requires less elastic recovery than other features of the device. Source x-ray beam 1093 is used to image device 1091 and in this example a mixture of highly scattered x-ray beams 1096 and partially scattered x-ray beam 1094 reach detector 1098 after filtration through an anti-scatter grid.
b is a representation of x-ray image 1101 of device 1092 (
a and
a is a sectioned plan view of a portion of partially coated clot retrieval device 1501 having crown feature 1510, uncoated strut feature 1516, and partially coated strut feature 1511 partially covered in a radiopaque coating 1515. The strut and crown features may comprise a highly elastic material such as Nitinol, and the radiopaque material may comprise noble metals such as gold or platinum or the like or a polymer material such as polyurethane, pebax, nylon, polyethylene, or the like, filled with radiopaque filler such as tungsten, barium sulphate, bismuth subcarbonate, bismuth oxychloride or the like or an adhesive filled with radiopaque filler. Strut features and crown features may comprise Nitinol material with strut sidewall recess feature 1512. In the example shown, strut sidewall recess feature comprises a series of grooves in the sidewall of the strut. Grooves may be incorporated in a sidewall using cutting process such as laser cutting or other cutting means of incorporated through mechanical abrasion, cutting, grinding, or selective chemical etching. Other recess features may be incorporated such as dimples, knurls, or highly roughened surface to achieve a non-planar, textured, or rough surface. The coating can be applied as a single step (a partially coated device is shown for illustration purposes) through a process such as electroplating, sputtering, dipping, spraying, cladding, physical deposition, or other means.
b is a detailed view of partially coated strut feature 1511 showing uncoated groove 1512 for illustration purposes on one side and coating 1515 on the other side. Device 1501 has strut sidewall recess feature 1512 and device 1501 is preferentially coated in these areas with thick coating section 1513 resulting, which is located in a low-strain area for effective operation. The elastic recovery dampening effect of coating material 1515 has less impact on low strain strut features. Crown feature 1510 has a thin coating 1514 and is less preferentially coated because of its non-recessed, non-textured, or smooth surface, so potential dampening effect of radiopaque coating is minimised in parts of the clot retrieval device 1501 features requiring more elastic recovery such as crown feature 1510.
c is a partially cut isometric view of clot retrieval device 1501. The device is shown with coating 1515 partially cut away for illustration purposes. Clot retrieval device 1501 has crown features 1510, uncoated strut feature 1516 with strut sidewall recess feature 1512 to promote thick coating layer 1513 in on low strain parts of the device and thin coating layer 1514 on high strain parts of the device.
a is an isometric view of tubing 1801 comprising Nitinol material 1803 and radiopaque cladding 1802 comprising a radiopaque material such as a gold, platinum, iridium or tantalum. This material may be processed by means such as electroplating, sputtering, or a mechanical compression process such as crimping or drawing.
b is an isometric view of tubing 1806 with comprising Nitinol material 1803 and cladding 1302 comprising rings of radiopaque material, with intermittent gaps 1304 between cladding rings 1302. Tubing 1806 may be manufactured from applying a secondary process to tubing 1801 in
a is a cross section of a structural element 2204 in a non-strained condition of clot retrieval device 2201 comprising Nitinol material, with radiopaque material coating 2202. Line 2203 represents a line or plane within structural element 2204 away from the neutral axis of bending.
b is a cross section of structural element 2204 in a strained configuration through a bending load.
a is a cross section of structural element 2304 of clot retrieval device 2301 comprising superelastic material such as Nitinol and discontinuous radiopaque coating 2302. Line 2303 is a reference line close to device surface away from the neutral axis of structural element 2304. In
Deformation, such as the applied bending load shown in
Referring now to
d is a stress-strain curve of structural element 2301M bending, taking line 2303 as an example, where the device is loaded from point A to point R and when the load is removed the device unloads from point R to point B. The magnitude of plastic strain is reduced (reduced distance between point B and A when comparing
a is a side view of Clot Retrieval Device Outer Member 2401 comprising strut features 2402 and crown features 2403. Radiopaque filaments 2405 are connected between crown features or strut features to enhance device radiopacity. Radiopaque filaments are located along the outer circumference of clot retrieval device outer member 2401 in order to enhance fluoroscopic visualisation of the expanded or collapsed configuration of the device. The circumferential location of the filaments may also aid visualisation of device interaction with a clot during use. The filaments may run parallel to the axis of the device, or in a helical path from crown to crown, crown to strut, or strut to strut in order to maintain clot reception space 2406 for clot retrieval. Radiopaque filaments may comprise single of multiple strands of radiopaque wire such as tungsten, platinum/iridium or gold, or similar materials.
b is a side view of Clot Retrieval Device Outer Member 2501 comprising strut features 2502 and crown features 2503. Filaments 2505 incorporating radiopaque beads 2506 are connected between crown features or strut features to enhance device radiopacity. Sequenced radiopaque beads 2505 along filaments 2505 do not contribute to the mechanical stiffness of the device or contribute to or detract from radial force in any way, and in a collapsed configuration wrap into inter-strut spaces in a versatile manner. The filaments may run parallel to the axis of the device, or in a helical path from crown to crown, crown to strut, or strut to strut in order to maintain clot reception space 2507 for clot retrieval as in
c is a side view of clot retrieval device outer member 2601 comprising strut features 2602 and crown features 2603. Filaments 2605 are incorporated in device outer member 2601 in a similar matter detailed in
a is an isometric view of clot retrieval device outer member 2701 comprising strut features 2702 and crown features 2703. An elongate radiopaque thread 2405 is incorporated in the structural elements, i.e. struts or crowns, of clot retrieval device outer member. Elongate radiopaque thread 2704 threads the perimeter of outer member 2704 to define the outer boundary of device in an axial and circumferential direction under fluoroscopic imaging. A plurality of radiopaque threads may be incorporated to further define the boundary of the outer member.
b illustrates a means of incorporating elongate thread 2804 in strut 2802 through eyelet 2805. Elongate radiopaque thread may be incorporated through other means such as surface adhesion.
c and
It will be apparent from the foregoing description that, while particular embodiments of the present invention have been illustrated and described, various modifications can be made without parting from the spirit and scope of the invention. Accordingly, it is not intended that the present invention be limited and should be defined only in accordance with the appended claims and their equivalents.
This application claims the benefit of U.S. Provisional Application No. 61/784,940, filed Mar. 14, 2013, the disclosure of which is incorporated herein by reference in its entirety.
Number | Date | Country | |
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61784940 | Mar 2013 | US |