Patent Application
20230011734
The present invention relates to devices for implantation within the body for improving vessel or duct patency and stent performance as well as for delivery and/or deployment of such devices in the venous system and/or the arterial system.
Coronary stenting and most other stenting situations in the human body occur in relatively stable environments with limited flexure, allowing for stents to be designed to address the specific challenge posed by the environment without too much concern for the flexibility of the stent or its resistance to kinking.
With the development of venous stenting, a number of challenges have been encountered associated with the large capacity and variability of the venous system compared to the arterial system; vein diameter and shape varies highly across the venous system as well as within a vein. The challenges associated with the variability of the venous system are multiplied by the pelvic anatomy, for both arterial and venous interventions due to the high degree of mobility and vessel movement that occurs within this defined zone. This is compounded by the variability of the interaction and location of the pelvic arteries and veins relative to one another and the fixed ligaments and bony protrusions of the pelvis and spine, making the design of an all-purpose “one size fits all” approach highly complex. Variations between men and women as well as between individuals can be quite considerable also. Indeed, current approaches for pelvic vessel stenting necessitates the use of multiple stents of variable design, material, manufacturer, delivery system to try to “replicate” normal anatomy with each stent overlapping each other to accommodate for “slippage” and flex whilst maintaining a continuous apposition to the vessel wall. This results in clinicians often having to adopt a case-by-case approach with solutions patched together from the resources available at the time. Another issue is the lack of predictability for stent placement for extrinsic venous compression. That is, an artery impinging upon a vein requires that a venous stent apply a certain amount of force to displace the artery and restore a near normal venous cross-sectional flow aspect ratio (i.e. closer to unity which is more optimal). Current practice is to place the selected stent hoping for some clinical improvement but little predictability or good options to adjust or improve the outcome after the index venous stent is placed. The net result is that procedures are unnecessarily long or complex, lack predictability or adjustability and can result in post-operative complications.
For example, in U.S. Pat. Nos. 9,192,491 and 8,636,791, modular stent systems are discussed for deployment in the venous system. These systems make use of multiple, overlapping and connected stent to provide differing properties. To facilitate the joining of the two stents, a sealing collar, sometimes in the form of a helical element, is deployed in the region of overlap between the two stents, purely to aid with sealing and joining the two adjacent stents together. While modular stent systems such as this do provide variable properties, they are still prone to slippage and the layering of multiple stents and helical elements may lead to a reduction in luminal diameter. Creating an unnatural obstruction to the flow of blood through the stent may in turn cause turbulence as well as a range of further complications.
It is an object of the invention to provide devices that address at least some of the disadvantages associated with the prior art, particularly in providing improved configurability, restoration and maintenance of vessel patency with minimal complexity.
The present invention provides in a first aspect . . . .
A first aspect of the invention provides for a stent system comprising:
wherein the at least one secondary stent element is configured to apply a chronic outward radial force to the interior surface of the primary stent so as to effect modification of or to resist change to an aspect ratio of the lumen of the target vessel at the location where the secondary stent element is deployed.
A second aspect of the invention provides for a stent system for restoring patency to a fully or partially occluded target vessel within the body of a subject, the system comprising:
wherein the plurality of secondary stent elements are configured to apply a chronic outward radial force to the interior surface of the primary stent so as to effect modification of an aspect ratio of the lumen of the target vessel at the location where the secondary stent elements are deployed.
A third aspect of the invention provides a percutaneous device for deploying a stent element within a vessel located within an individual subject, the device being of elongate configuration having a proximal end and a distal end, the device comprising:
wherein at least one of the proximal and distal releasable anchor points is configured to be movable relative to the other along the longitudinal axis of the device.
A fourth aspect of the invention provides a stent element comprising:
A fifth aspect of the invention provides a method of treating an occlusion of a vessel or duct within the body of a subject, the method comprising:
Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.
One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:
All references cited herein are incorporated by reference in their entirety. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
Prior to setting forth the invention, a number of definitions are provided that will assist in the understanding of the invention.
As used in this description, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, the term “a sensor” is intended to mean a single sensor or more than one sensor or to an array of sensors. For the purposes of this specification, terms such as “forward,” “rearward,” “front,” “back,” “right,” “left,” “upwardly,” “downwardly,” and the like are words of convenience and are not to be construed as limiting terms. Additionally, any reference referred to as being “incorporated herein” is to be understood as being incorporated in its entirety.
As used herein, the term “comprising” means any of the recited elements are necessarily included and other elements may optionally be included as well. “Consisting essentially of” means any recited elements are necessarily included, elements that would materially affect the basic and novel characteristics of the listed elements are excluded, and other elements may optionally be included. “Consisting of” means that all elements other than those listed are excluded. Embodiments defined by each of these terms are within the scope of this invention.
The term ‘braided stent’ refers to a metal or metal alloy stent that is produced using a plain weaving technique. The stent comprises a lumen capable of stretching in the longitudinal direction while circumferentially, the multiplicity of filament-like elements intersect a plane that is perpendicular to the longitudinal direction when in the expanded position.
The term ‘kink resistance’ refers to a stent's ability to withstand mechanical loads from the surroundings depending upon the position in the body. Usually, this is based upon the smallest radius of curvature a stent can withstand without the formation of a kink. In areas of high tortuosity within the body it is necessary for a stent to have increased kink resistance to prevent a reduction in lumen patency or even total occlusion.
The term ‘crush resistance’ refers to the ability of a stent experiencing external, focal or distributed loads to resist collapse. These loads ultimately lead to stent deformation and even full or partial occlusion which can result in adverse clinical consequences.
The term ‘venous ulcers’ refers to skin sores that form due to the persistent elevation of venous pressure. Often, they present in association with venous valve regurgitation. They are most commonly found on the lower limbs. It is thought that when venous valves become mechanically blocked or veins become engorged and the valve leaflets cannot co-opt to prevent regurgitation of blood, venous congestion worsens and the hydrostatic forces cause both extravasation of fluid from the veins into interstitium, and activation of inflammatory cytokines. This accumulation of fluid pressure and inflammatory cytokines contributes to skin break down, chronic ulceration and predisposes to local infections.
The term ‘venous obstruction’ refers to any occurrence whereby the diameter (or ‘caliber’) of a vein is reduced when compared to a normal, i.e. non-occluded, state. Venous obstruction can occur through the narrowing (stenosis) of the vein, through blockage or through externally applied pressure causing a localised compression of the vein. The term also includes venous occlusion, whereby the vein's lumen is partially or totally obstructed to the flow of blood. Occlusion may result from thrombosis (e.g. deep vein thrombosis (DVT)) or may be due to tumour incursion.
The term ‘venous return’ is defined by the volume of blood returning to the heart via the venous system, and is driven by the pressure gradient between the mean systemic pressure in the peripheral venous system and the mean right atrial pressure of the heart. This venous return determines the degree of stretch of heart muscle during filling, preload and is a major determinant of cardiac stroke volume.
The term ‘venous compression’ refers to the external compression of the vein. The source of external compression may be caused by an adjacently located artery compressing the vein against another fixed anatomical structure, which can include the bony or ligamentous structures found in the pelvis, the spine itself, or overlapping arterial branches.
The term ‘May-Thurner syndrome’ (MTS) also known as iliac venous compression syndrome (which includes Cockett's syndrome) is a form of ilio-caval venous compression wherein the left common iliac vein is compressed between the overlying right common iliac artery anteriorly and the lumbosacral spine posteriorly (fifth lumbar vertebra). Compression of the iliac vein may cause a myriad of adverse effects, including, but not limited to discomfort, swelling and pain. Other less common variations of May-Thurner syndrome have been described such as compression of the right common iliac vein by the right common iliac artery; this is known as Cockett's syndrome. More recently, the definition of May-Thurner syndrome has been expanded to include an array of compression disorders associated with discomfort, leg swelling and pain, without the manifestation of a thrombus. Collectively, this has been termed non-thrombotic iliac vein lesions (NIVL).
The term ‘infraluminal thickening’ (also referred to as venous spurs or intraluminal spurs) is related to this external compression of the left common iliac vein by the right common iliac artery against the fifth lumbar vertebra. Venous spurs arise due to the chronic pulsation of the right common iliac artery, this ultimately results in an obstruction to venous outflow. Venous spurs are internal venous obstructions consequent to chronic external compression of veins by adjacent structures.
The term ‘Deep Vein Thrombosis’ (DVT) refers to the formation of blood clots or thrombus within the venous segment, and in itself is not life threatening. However, it may result in life threatening conditions (such as pulmonary embolism) if the thrombus were to be dislodged and embolize to the lungs. Additionally, DVT may lead to loss of venous valvular integrity, life long venous incompetence and deep venous syndrome which includes rest and exercise pain, leg swelling and recurrent risk of DVT and emboli. The following is a non-limiting list of factors that reflect a higher risk of developing DVT including prolonged inactivity, smoking, being dehydrated, being over 60, undergoing cancer treatment and having inflammatory conditions. Anticoagulation which prevents further coagulation but does not act directly on existing clots, is the standard treatment for deep vein thrombosis. Other potentially adjunct, therapies/treatments may include compression stocking, selective movement and/or stretching, inferior vena cava filters, thrombolysis and thrombectomy.
Stents were first designed for use in the cardiovascular space in the mid-1980s and have since undergone major refinements in design and composition. The indications for stenting and locations of their use in the human body has also developed; stenting of arterial and venous vessels is a regular occurrence in hospitals.
One of the original stents, the Wallstent (Schneider AG), was a self-expanding, stainless steel wire-mesh structure. This was superseded by the Palmaz-Schatz stent (Johnson & Johnson), which was the first FDA approved, balloon-expandable stainless steel slotted tube stent. Multiple stents and stent manufacturers followed shortly after with their own iterations that were designed to prevent elastic recoil and restenosis. These were far from optimal stent designs because they had a high metallic density that resulted in elevated rates of stent thrombosis, failed deployments, embolizations and in-stent restenosis (ISR). For example, restenosis occurred in 20% to 30% of all angioplasties.
Drug-eluting stents (DES) were developed to specifically address the issues of ISR. Seen as the next revolution in interventional cardiology, DES utilized a coating of various compounds to target proliferation of vascular smooth muscle cells, platelet activation, and thrombosis. Many compounds were tried with minimal response, including gold, carbon, heparin, and others such as oestrogen, glucocorticoids, and mineralocorticoids with modest effects. However, the greatest effect was seen in the use of anti-proliferative drugs. Drugs such as Sirolimus and Paclitaxel were the most effective in reducing ISR.
This lead to a new generation of stents, stent design, and stent coating combinations. Early signals were very positive, indicating better efficacy when compared with bare metal stents. However in 2006, a safety signal began to emerge of an increased risk of stent thrombosis (ST) in first generation DES. A redesign of the first generation DES lead to a second generation of DES with novel antiplatelet agents and polymers.
While stents were being designed in an attempt to counteract ST, the physical implantation of a stent itself acted as the perfect recipe for thrombus formation, and required the use of complex anticoagulation regimens to combat ST. This caused further problems, leading to major bleeding and vascular complications in many cases. It wasn't until the development of dual antiplatelet therapy (DAPT) that stents began to become safer to use in common practice.
Stent materials and designs have continued to be developed over the years. First generation stent materials such as stainless steel have been more recently superseded by cobalt-chromium alloys. Cobalt-chromium alloys allow for thinner stent strut designs without compromising radial strength or corrosion resistance of the stent. Other new alloys include platinum-chromium alloys, which are used for high conformability and radial strength and a thinner stent strut design.
In addition to drug coatings and drug developments, stents have also been covered with various synthetic or biological materials in order to cover perforations, aneurysms, or heavy thrombus. Bioresorbable stent scaffolds have also been designed to provide a vascular scaffold following a percutaneous coronary intervention (PCI). The bioresorbable scaffolds are gradually re-absorbed after placement, leaving the vessel in which the scaffold was placed free from any metallic caging and able to regain its normal function. A number of biodegradable compounds have been developed and utilized by various manufacturers for this purpose.
In today's stent market there exist five different types of available stents:
Their overall main purpose is to keep narrowed blood vessels open to allow adequate flow of blood or other bodily fluid. A special group of stents, called stent grafts are used in the aorta to create a smaller conduit within which the blood can flow, as the original vessel has become enlarged and at risk of rupture. Various applications of stents in the body include:
Hence, embodiments of the devices according to the invention can also be used during endoscopic and laparoscopic procedures where the vessel includes the bile duct, the intestine, the fallopian tubes, the ureter, the urethra, the oesophagus, bronchioles, or any other hollow vessel or duct within the body of an animal.
Venous stents require unique characteristics that differ from arterial stents. Veins are highly flexible and vary in diameter and luminal profile depending upon flow and surrounding structures that may impinge upon them. Veins operate at very low pressures, relative to arteries, therefore it is critical that they are able to expand to accommodate additional flow during exertion. Venous stents must likewise be self-expanding, flexible and adapt to the changing nature of the veins in which they are placed. Venous walls are prone to deformation due to normal movements such as the overlying musculature, organ function (e.g. peristalsis), as well as the respiratory and cardiac cycle. At the same time, venous stents are placed because there is some obstruction or external compression to be resisted, so they must have appropriate strength to restore luminal flow diameter at the treatment site. Of course, once a stent is implanted the walls of the vein will react to the deformation inherently caused by the device. The interplay of the stent and the externally applied forces may vary along the length of the stent resulting in irregular mechanical interactions along the longitudinal axis. These irregularities can result in stent migration and associated complications.
Despite vast improvement in stent design since the origination of stenting, the stent options currently available on the market are plagued by a number of problems including foreshortening, device collapse, device failure, device wear and eventual perforation. Some of the main underlying factors contributing to the problems with these stents include a lack of flexibility or too much flexibility. Increased load on the deformation of the stent can cause early fatigue failure, and/or impedance of flow in the overlying iliac artery, potentially causing peripheral arterial disease.
An underestimated but important problem experienced by stents is stent fracture. The incidence of stent fractures for coronary stents is on average around 4%. Many stent fractures may not be recorded as a number of fractures are likely asymptomatic without any sequalae. Alternatively the fractures may not be detected with conventional angiography procedures, and so are diagnosed and treated otherwise, perhaps as stent thrombosis or stenosis rather than stent fracture. Finally fractures may lead to stent thrombosis. In such cases, the first presence of a fracture may be the onset of sudden cardiac death. Again, such fractures are not recorded. Stent fractures have been identified to be more likely to occur as a result of one or more of the following:
In general, the primary stent 22 is any stent suitable for the application it is being used on. The primary stent 22 may be a braided stent, a laser cut tubular stent, or another suitable stent. The primary stent 22 may have a minimum radial resistive force, kink resistance, and/or crush resistance as appropriate, which can subsequently be augmented with stent elements. The primary stent 22 can be manufactured from any suitable material. The primary stent 22 may have any suitable dimensions relative to the vessel in which it is located. The primary stent 22 may have any suitable covering, and/or any suitable drug coating if required. The primary stent 22 may have specific or non-specific properties for the application for which it is being used. The primary stent 22 may be constructed from a variety of different strengths of wire/different weave structures specific to the location of deployment.
In some examples, the primary stent 22 may have the same mechanical properties across the entire primary stent, or may have variable mechanical properties, having defined regions of low crush resistance or flexibility and other regions of high crush resistance for example. In some examples of embodiments, the primary stent may be fully or partially tapered or exhibit a graduated luminal diameter from one terminus to the other. Some examples of primary stents may have specific locations for side apertures to prevent thrombus formation or allow formation of anastomoses to adjacent vessels. In embodiments of the invention the stent 22 may include one or more junctions, bifurcations, or anchoring sections that allow the stent to conform to local vessel anatomy,
In pursuing a more personalised or customized stent design, the inventors have identified that the design of stents itself can only be optimised to an individual patient's anatomy to a certain extent, and that changes in the vasculature of patients may result in the off-the-shelf design of stent being unsuitable for the vasculature. It is also very difficult for physicians currently to assess the potential success for a given stent to adequately restore luminal diameter. It is only after placement of the chosen stent that a physician may realize that insufficient luminal diameter has been restored, resulting in an ovalized or high aspect ratio lumen, or insufficient force to resist the external compression with no good options for correction or adjustment. Accordingly, the inventors have provided a configurable stenting system 20 having the primary stent 22 and, within the primary stent 22, at least one secondary stent 24, referred to hereafter as a ‘stent element’, that provides a localised change in the physical and/or mechanical properties of the primary stent 22. In embodiments of the invention, the stent element 24 is not in direct physical contact with the endothelial tissue of the vessel 10 when disposed in the lumen of the primary stent 22. Rather, the stent element 24, when deployed, bears upon the inner luminal surface of the stent 22.
The primary stent 22 may be designed in tandem with the stent element 24 to enable connection between the stent elements 24 and the primary stent 22. For example, as will be described later, the system 20 may comprise an anchoring mechanism for mediating an interconnection between the stent 22 with the one or more stent elements 24.
As shown in
The stent element 24 is configured to provide reinforcement to the primary stent 22. As shown in
As can be seen in
As the stent elements 24 are configured to restore or impose an optimal aspect ratio to the vessel 10 and/or the primary stent 22, the stent element 24 may be formed to have a substantially circular cross section/outline, or it may be formed to have a different polygonal cross-section or outline. For example, an elliptically shaped stent element may provide a useful counteraction to an elliptically shaped vessel. Depending upon the application, in certain embodiments the stent element may be shaped as a polygon in cross section, such as a hexagon. In such embodiments the outward radial or compressive forces are exerted at foci located at the corners of the polygon as opposed to the more even distribution of force associated with a stent element 24 having a circular configuration. Alternatively or additionally, the stent element may have a non-linear cross-section, either being tapered and/or having twists/rotations and/or comprising a combination of shapes to appropriately tailor the required radial forces to the vessel to counteract the obstruction.
Providing one or more stent elements 24 for deployment in the primary stent 22 permits a different approach to conventional stenting. Historically, as discussed above, stents have been increasingly refined in their design for highly specific applications, and as a result compromises and modifications have been made to mitigate the issues introduced by the increasing complexities.
In providing the stenting system 10 in the form of a kit of the primary stent 22 and one, two, three, four or more independently positionable stent elements 24, the complexities and associated issues of highly-specialised stent design are avoided. For one, the primary stent 22 can be a stent without a tailored design, and so can be flexible and straightforward to position and maintain. The primary stent 22 can be considered to be less intrusive and obtrusive. A reduction in the complexity of the primary stent 22 lends itself to an improved ease of manufacture and reduction in cost of production as well as associated lower burden for regulatory approval also.
Furthermore, the reduction in complexity is preferable for the increase in the use of stents. As human anatomy can be variable between individuals, the design of stents for use in many patients is difficult as the exact requirements for regions of different flexibility are unlikely to be the same between any two patients. For example, pelvic venous anatomy of juveniles versus geriatric patients, or even men versus women, can be quite different. In veterinary contexts, the divergencies between various sub-species of animal, such as breeds of dogs, is also highly variable. Accordingly, the use of a flexible primary stent 22 and one or more implantable stent elements 24 allows for a faster, more personalised stent system 20.
In embodiments of the invention, the one or more stent elements 24 can be arranged within the primary stent 22, either before or after insertion, to quickly provide a personalised stent arrangement with regions having different properties. The properties are also more variable because the elements can be designed accordingly. These reinforcing stent elements 24 can be positioned exactly where changes in radial force and/or crush resistance and/or kink resistance are desired, whilst minimizing the compromise of the primary stent 22 property of flexibility in mobile regions of the body, such as the pelvic geometry.
Further benefit is provided by the elements because they are implantable after the primary stent has been inserted, and their position is variable and can be changed if the vessel's properties also change. In providing implantable stent elements, remedial action intended to address complications with existing pre-inserted stents may also benefit from the changes in mechanical properties that result from using these implantable elements. In this way the primary stent pre-implanted stent can be maintained within the vessel and invasive procedures to remove the stent are avoided.
Put simply, the stenting system 20 described herein can provide similar benefits as existing, more exotic specialised stents, but without the disadvantages associated with existing stents such as the cost, complexity of design, failure rate or the difficulties of insertion and deployment.
Typically, the stent elements 24 are, as described above, secondary stents for placement wholly within and encompassed by the primary stent. Therefore, the stent elements 24 may be formed as a stent by any suitable means and in by any appropriate method. In a specific embodiment, both the stent element 24 and the primary stent 22 may be comprised of braided wire. The stent element 24 may be formed of one or more wires, arranged to provide the optimal radial force and in the desired shape to restore the required aspect ratio of the stent and surrounding vessel. Hence, the wire may be formed of any appropriate material, in any cross-section, to provide the desired effect. Different shapes of wire in cross section (e.g. round, elliptical, hexagonal, square and/or rectangular) allows for different design characteristics in the stent element. For instance, a flat rectangular wire or ribbon, may allow for better engagement with the primary stent than a round wire which may slip. Oval wires may allow for added strength without increasing the overall thickness of the device. Two stent system embodiments 20 including specific types of stent element 24 formed of wire are shown in
According to a specific embodiment of the invention, the stent element 24 as shown in
In the embodiment depicted in
In general, the radial force and crush resistance of the stent element 24 is based on and controllable by varying the thickness and cross sectional shape of the wire, type of wire, construction of the element 24 through twists or braids, and other properties of the wire forming the stent element 24. The properties of the stent element 24 may be controlled by selecting specific braiding patterns or the specific number of coil turns or twists necessary to achieve a desired outward radial force. In embodiments of the invention, stent elements 24 of embodiments of the invention exert an outward radial force of greater than 0.25 N/cm, suitably at least 0.5 N/cm, typically at least 1.0 N/cm and optionally at least 2 N/cm. In further embodiments of the invention, the stent elements 24 exert an outward radial force of at most 25 N/cm, suitably at most 20 N/cm, optionally at most 15 N/cm. In embodiments of the invention the outward radial force is determined at greater than 50% expansion of the stent element, or alternatively at between 10% and 50% of the expansion.
In other examples that are not depicted here, the stent element may comprise material arranged otherwise than a coil 224 or S-ring 124. For example, the stent element 24 may be S-shaped in the circumferential direction so that each S forms one circumference of the element. Another alternative is a double-helix arrangement of two coils whose ends are joined.
In some stent elements 24, a combination of a coil and an S-ring may be provided. For example, the stent element may comprise two S-rings having a coil extending between them, all comprised from a single length of wire.
It is envisaged that in specific embodiments the individual stent elements 24 will be at least 1 mm, suitably 5 mm, optionally 10 mm in length; and at most 30 mm, and typically not more than 20 mm in length.
To provide a generalized discussion about the stent elements 24 and the possibilities for their use,
The element 30 of
A variation on the element 30 of
In some examples, the stent element 32 may be movable so that the space 34 between the parts can be varied to ensure an exact placement of the stent element when inserting. It will be appreciated that a coil formation lends itself to this stent element shown in
It will be appreciated that where the term ‘spring’ is used, this is intended to mean an elastic member capable of being compressed or elongated in a direction and returning to its original length. In the examples provided here, the springs are compressible and stretchable in directions that are at a tangent to the circumference of each stent element.
Springs 42 may be incorporated into both coil stent elements and S-ring stent elements as appropriate and stent elements can be combined with or without spring like elements to achieve the desired properties. In particular, any of the arrangements of
Two embodiments are shown in
In each of the above embodiments, the end termini of the wire or material forming the stent element may be free. In other examples, the free ends can be joined or locked together either prior to positioning within the primary stent or once deployment of the stent element within the primary stent is complete. Joining or locking the ends prevents the free ends from perforating the vessel walls or snagging the deployment device or guide wire, adds strength to the ends of the stent elements, adds strength to the entire length of the stent element, and improves the stability of the reinforcing stent element.
Although not depicted in the Figures, the stent elements and/or the primary stent may incorporate one or more physical mechanisms to maintain the relative positions of the stent elements and primary stent. In specific embodiments the retention mechanisms may incorporate one or more hooks, teeth, barbs or splines that engage with or bear upon the primary stent and prevent malposition or subsequent migration of the stent element. In general, it is expected that friction between the stent elements and the primary stent and the outward radial bias force exerted by the stent elements on the interior face of the primary stent will be sufficient to maintain the stent elements in position. However, a further mechanism may be particularly useful to ensure that the relative positions are maintained even through the continual movement and changes in vasculature that occur with everyday activity. The mechanism may anchor the stent element to the primary stent. In some embodiments, the stent element may incorporate the mechanism so that the stent element is attached to and grips the primary stent. In some embodiments, the primary stent may incorporate a mechanism so that the stent element is gripped or anchored by the primary stent. In some embodiments, both the stent element and the primary stent incorporate parts of the mechanism so that there is an interaction between two parts of the mechanism to anchor the stent element to the primary stent.
The stent element may incorporate the anchoring mechanisms to prevent its migration relative to the primary stent. These mechanisms include but are not limited to loops, taps, bends, gripping elements, or surface modifications of various shapes and designs. The anchor mechanisms may be provided at either or both termini of the stent element or anywhere along the length of the stent element.
In a particular embodiment, the stent elements may comprise flexible hooks arranged about the circumference of a coil. Each hook faces the same direction. The stent element can therefore be mounted to and affixed to the primary stent by positioning it and rotating in the direction of the hooks so that they hook onto the primary stent.
In some embodiments, the primary stent may incorporate an engaging mechanism for engaging the stent element and maintaining its position relative to it. Similarly to the anchoring mechanism of the stent element, the engaging mechanism may comprise loops, taps, bends, gripping elements of various shapes and designs. The engaging mechanism may interact with the anchoring mechanism of the stent element or may engage the stent element without a specific anchoring mechanism.
In one example, the engaging mechanism comprises have internally-extending hooks that all face in one direction longitudinally along the stent that are configured to hook onto the wire of the stent element. To engage the stent element, the stent element is maneuvered along the primary stent, and once the correct position for the stent element is reached, it is pulled backwards slightly to engage with the hooks, thereby connecting the stent element to the primary stent.
In one embodiment of the present invention, the primary stent may include one or more coupling elements to prevent migration of the primary stent within the vessel. The coupling elements may be provided at one or both termini of the primary stent.
To aid positioning of the stent elements, radiopaque markers may be provided along the length of the primary stent to indicate relative positions.
The stent element and/or the primary stent may comprise of, either separately or in combination, stainless steel, nitinol, cobalt chromium, tantalum, platinum, tungsten, iron, manganese, molybdenum, or other surgically- and bio-compatible metal or metal alloy.
The stent element and/or the primary stent may comprise non-metal material, including a polymer such as: a bioresorbable material such as poly (l-lactide) (PLLA), polyglycolic acid (PGA), polyglycolic-lactic acid (PLGA), polycaprolactone (PCL), polyorthoesters, polyanhydrides, or another aliphatic polyester fibre material; polypropylene; polyamide; carbon fibre; and glass fibre. In some embodiments, the stent element and/or the primary stent comprise both metal and non-metal portions. The stent element and/or the primary stent may comprise radiopaque markers to assist with optimal placement and orientation longitudinally and/or radially. Such radiopaque material may include titanium, tantalum, rhenium, bismuth, silver, gold, platinum, iridium, and/or tungsten.
The primary stent or portions of the primary stent may be covered. Such covering material may include: PTFE; e-PTFE; polyurethane; silicone; papyrus; Dacron®; Goretex®; other polymeric membrane; polyhedral oligomeric silsesquioxane and poly(carbonate-urea) urethane (POSS-PCU); other Biodegradable nanofibers. The stent element or portions of the stent element may be covered. Covering material may include any of the above-referenced covering materials.
In specific embodiments of the invention, the primary stent may contain a window or cell of increased size and identified by radiopaque markers to allow for the creation of an anastomosis shunting device with an adjacent vessel or duct, without requiring the perforation of the primary stent structure.
The primary stent and/or the stent element may comprise of a drug coating or combination of drug coating and graft covering to promote re-endothelization; improve endothelial function; reduce inflammatory reaction; inhibit neo-intimal hyperplasia (MM2A); prevent adverse events such as in-stent restenosis and stent thrombosis through antithrombotic action of heparin.
The deployment of the stent system 20, which includes the primary stent 22 and one or more stent elements 24, is depicted in embodiments illustrated in
In
As shown in
As shown in
Once the device 25 is correctly positioned, the stent element 24 is formed within the primary stent 22. Once the stent element 24 is correctly positioned, it is disconnected from the device 25 and the device 25 is removed. As shown in
The steps of forming a coil stent element 224 according to one embodiment of the invention is shown in
The longitudinal position of one of the attachment points 64 of the stent element carrier 60 may be varied relative to the other, so that the attachment points 64, 66 can be brought closer together to create the stent element 24, as will be described below. The rotational orientation of one of the attachment points 64 may also be varied relative to the other so that the attachment point can rotate about the stent element carrier 60 relative to the other attachment point 66, thereby twisting or untwisting the wire allows the user to apply or release torque and so aid with formation of the stent element 24. At the attachment points 64, 66, a stent element release mechanism is provided configured to releasably connect the wire 62 to the stent element carrier 60 so that the stent element 24 can be detached from the device 25 and deployed. The movement of the attachment points 64, 66 and the release mechanism are controlled at the handle 50 by the user. Release may be effected via a mechanism involving pin release, clamp release or clipping/nipping off of the wire 62. In embodiments where pin release is used the stent element 24 may comprise an aperture at or near the terminus of the wire 62 (as depicted in
It will be appreciated that user control of the various functionalities described as comprised within the distal end of the device 25 are mediated through control interfaces and mechanisms located within the handle 50. Such interfaces and controls may include, but are not limited to: sliders, levers, screw threads and mechanical or electrical actuators.
The device 25 may also incorporate one or more means for positioning the catheter 52 and stent element 24.
In the method of deployment using the device 25, initially, as can be seen in
Once at the correct site, the outer sheath 58 is retracted/withdrawn, as shown in
The ends of the wire 62 are then brought closer together (i.e. more proximate to each other), as shown in
Therefore, when positioning the stent element 24, the device 25 is initially positioned so that the proximal attachment point 66, and therefore the proximal end of the wire 62 and eventually of the stent element, proximal and distal relative to proximal and distal ends of the device 25, is in the correct position as it will be when it is deployed. The formation of the stent element 24 then brings the distal end of the wire 62 at the distal attachment point 64 back towards the proximal end so that stent element 24 is formed at the correct location.
It will be appreciated that this method of forming a stent element permits a stent element of variable diameter to be formed. The diameter of the stent element may be pre-determined and the device configured to create a stent element of that diameter. Alternatively, the user of the device may judge the correct diameter when positioning the device so that the stent element is exactly the correct size for the vessel and primary stent in which the element is being positioned. The diameter can therefore be tailored exactly to the vessel and stent. Conventionally, where the stent had to incorporate the correct properties, rather than a primary stent and stent element, the stent had to be exactly the correct size for the vessel, and choosing this size would be time consuming and would require many different stents of different sizes to be maintained for use. Now, the primary stent may be of a set size, but may be further expanded by the action of the stent element so that the primary stent and the stent element are the correct size and/or aspect ratio at all times.
Once the stent element 24 is formed at
At
In embodiments where the stent element is formed as an S-ring rather than a coil element, the device may be configured to mount a compressed S-ring around its carrier element, with the outer sheath over the S-ring. The S-ring can subsequently be released once the device is correctly positioned and the outer sheath has been withdrawn, by pin or clamp release or otherwise.
It will be appreciated that alternative radial expansion mechanisms may be implemented such as by introducing the stent element over a radially expandable bladder or balloon catheter device. In such an embodiment the bladder or balloon may be located appropriately in the location for deployment within a primary stent within a vessel and expanded to position the stent element appropriately. Upon deflation of the bladder or balloon the device may be withdrawn from the vessel leaving the stent element in situ.
The above stent system including at least one primary stent and one or more stent elements may be particularly useful in the venous system. For example, the system may be particularly useful at locations of venous obstruction, which includes, at least, venous stenosis, venous congestion, and venous constriction. The stent system described herein may be used in the treatment of MTS, DVT, intraluminal thickening, venous ulcers, venous compression, and/or any other venous or arterial obstruction.
According to one non-limiting example, an individual may have no apparent signs or symptoms of leg swelling but, nevertheless, an obstruction of the veins in the ilio-caval region may be suspected. Normal anatomy in this region sees the vein assume an upward sigmoidal curve from the femoral vein to the inferior-vena cava. In
Although particular embodiments of the invention have been disclosed herein in detail, this has been done by way of example and for the purposes of illustration only. The aforementioned embodiments are not intended to be limiting with respect to the scope of the appended claims, which follow. It is contemplated by the inventors that various substitutions, alterations, and modifications may be made to the invention without departing from the spirit and scope of the invention as defined by the claims. In addition, the above described embodiments may be used in combination unless otherwise indicated.
The invention is further exemplified by way of the following clauses:
1. A stent system comprising:
wherein the at least one secondary stent element is configured to apply a chronic outward radial force to the interior surface of the primary stent so as to effect modification of or to resist change to an aspect ratio of the lumen of the target vessel at the location where the secondary stent element is deployed.
2. The stent system of clause 1, wherein the at least one secondary stent element comprises one or more anchors for engaging with the interior surface of the primary stent.
3. The stent system of clause 1 or 2, wherein the at least one secondary stent element is configured to engage the interior surface of the primary stent for modifying the aspect ratio and cross section of the lumen to be substantially circular when deployed.
4. The stent system of any one of clauses 1 to 3, wherein the at least one secondary stent element is configured to apply a substantially uniform chronic outward radial force to the primary stent around its circumference when deployed.
5. The stent system of any previous clause, wherein the at least one secondary stent element has a substantially circular cross-section when deployed.
6. The stent system of any previous clause, wherein the at least one secondary stent element has a substantially elliptical cross-section when deployed.
7. The stent system of any previous clause, wherein the at least one secondary stent element comprises an S ring.
8. The stent system of any previous clause, wherein the at least one secondary stent element comprises coil.
9. The stent system of any previous clause, wherein the system comprises more than one secondary stent element.
10. A stent system for restoring patency to a fully or partially occluded target vessel within the body of a subject, the system comprising:
wherein the plurality of secondary stent elements are configured to apply a chronic outward radial force to the interior surface of the primary stent so as to effect modification of an aspect ratio of the lumen of the target vessel at the location where the secondary stent elements are deployed.
11. The stent system of clause 10, wherein the aspect ratio of the lumen of the target vessel is modified to approximate unity in order to restore patency to the fully or partially occluded target vessel.
12. The stent system of clause 10 or 11, wherein the vessel is a vein.
13. The stent system of any one of clauses 10 to 12, wherein the at least one secondary stent element comprises an S ring.
14. The stent system of any one of clauses 10 to 13, wherein the at least one secondary stent element comprises a coil.
15. A percutaneous device for deploying a stent element within a vessel located within an individual subject, the device being of elongate configuration having a proximal end and a distal end, the device comprising:
16. The device of clause 15, wherein the distal releasable anchor point is movable relative to the proximal releasable anchor point, and the position of the proximal releasable anchor point is fixed.
17. The device of clause 15, wherein the proximal releasable anchor point is movable relative to the distal releasable anchor point, and the position of the distal releasable anchor point is fixed.
18. The device of any one of clauses 15 to 17, wherein the stent element carrier is comprised within the central lumen.
19. The device of clause 18, wherein the central lumen extends through the stent element carrier to the distal end.
20. The device of any one of clauses 15 to 19, retraction of the slidable outer sheath is controlled via a retraction mechanism comprised within the handle.
21. The device of any one of clauses 15 to 20, wherein release of the at least one wire from the proximal and distal releasable anchor points is controlled by a release mechanism comprised within the handle.
22. The device of any one of clauses 15 to 21, wherein the proximal and distal releasable anchor points may be rotated relative to each other to apply or release torque to the wire.
23. The device of any one of clauses 15 to 22, wherein the stent element carrier includes a positioning mechanism.
24. The device of clause 23, wherein the positioning mechanism comprises one or more radiopaque markers located along the stent element carrier.
25. The device of clauses 23 or 24, wherein the positioning mechanism comprises one or more ultrasound windows located along the along the stent element carrier.
26. A stent element comprising:
27. A method of treating an occlusion of a vessel or duct within the body of a subject, the method comprising:
28. The method of clause 27, wherein the vessel is a vein.
29. The method of clause 28, wherein the vein is within the iliocaval region.
30. The method of any one of clauses 28 or 29, wherein the method is to treat May-Thurner syndrome.
31. The method of any one of clauses 28 or 29, wherein the method is to treat deep vein thrombosis.
32. The method of any one of clauses 28 to 31, wherein more than one secondary stent element is deployed.
33. The method of any one of clauses 28 to 32, wherein deployment of the at least one secondary stent element changes the aspect ratio of a lumen of the vessel at the location of the occlusion to around unity.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2020/063450 | 12/4/2020 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 62944466 | Dec 2019 | US |
