Implantable stent

Abstract

The present disclosure relates to an implantable stent (100) including a plurality of junctions (105), a circumferential row of at least one larger cell (103) and smaller cell (104) connected via at least two junctions (105). And defining a tubular body having a proximal end (100a) and a distal end (100b) with a lumen extending therebetween. Each of the larger cell (103) and smaller cell (104) includes a proximal portion "P", distal portion "D" and a central portion "C" disposed therebetween. A window (106) is defined by the two adjacent junctions (105) connecting both central portion "C" of both consecutive cells. Each cell includes two struts (103a, 103b, 104a, 104b) extending from proximal end (100a) to distal end (100b) in an irregular curved profile, bent towards the lumen at the proximal portion "P".

Description

IMPLANTABLE STENTFILED OF THE INVENTION

[0001] The present disclosure relates to a medical device. More particularly, the present disclosure relates to an implantable stent.BACKGROUND OF THE INVENTION

[0002] Carotid arteries are mainly responsible for supplying oxygen-rich blood to the face and brain. Each carotid artery splits into an internal carotid artery and external carotid artery at a carotid bifurcation as shown in Fig. 1. Just above the carotid bifurcation, a carotid sinus is present which is a dilated area at the base of the internal carotid artery just superior to the bifurcation of the internal carotid and external carotid. The carotid sinus is sensitive to pressure changes in the arterial blood as baroreceptors are present in this area.

[0003] Over a period of time, any of the carotid artery may be partially or fully clogged. A fully clogged carotid artery can lead to severe complications including strokes, paralysis, brain damage, etc. while a partially clogged carotid artery may result in hypertension.

[0004] Hypertension is a condition in which a patient is in a constant state of elevated blood pressure. Baroreceptors located in the carotid sinus act to regulate blood pressure. They do so by sending information to the central nervous system (CNS) regarding the extent to which the blood vessel walls are stretched by the pressure of the blood flowing through. In response to these signals, the CNS adjusts certain parameters so as to maintain a stable blood pressure.

[0005] To resolve any of the aforesaid partial or complete clogged carotid artery condition and to restore blood flow to the brain or prevent reshaping of artery walls due to high blood pressure, a stent is deployed in order to regulate the blood flow in the clogged carotid artery. Deployment of a stent may also be helpful in preventing or treating a stroke. The stent maybe deployed via for example, a standard percutaneous method and angio-graphic visualization. Stents and other endovascular tools are sometimes placed in the internal carotid artery ("ICA") or other vasculature using guiding sheaths that do not have balloons.

[0006] Currently deployable stent designs obstruct blood flow of another artery once deployed in a parent artery and are non-retractable once deployed using a delivery system.

[0007] Hence, there arises a need of a stent that overcomes the problems associated with the conventional stent.SUMMARY OF THE INVENTION

[0008] Particular embodiments of the present disclosure are described herein below with reference to the accompanying drawings; however, it is to be understood that the disclosed embodiments are mere examples of the disclosure, which may be embodied in various forms. Well-known functions or constructions are not described in detail to avoid obscuring the present disclosure in unnecessary detail. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present disclosure in virtually any appropriately detailed structure.

[0009] The present disclosure relates to an implantable stent. In an embodiment, the stent includes a plurality of junctions, a circumferential row of cells containing at least one larger and one smaller cell. Each smaller and larger cell includes a proximal portion, distal portion and a central portion therebetween. The shorter and longer cells are connected via at least two junctions forming a tubular body. Two adjacent junctions form a window in the central portion. Each cell of the stent includes two irregular profiled struts extending from proximal end to distal end and a portion bent towards lumen extends from proximal end to distal end.BRIEF DESCRIPTION OF DRAWINGS

[0010] The summary above and the detailed description of descriptive embodiments, is better understood when read in conjunction with the apportioned drawings. For illustration of the present disclosure, exemplary constructions of the disclosure are shown in the drawings. However, the disclosure is not limited to specific methods and instrumentality disclosed herein. Moreover, those in the art will understand that the drawings are not to scale.

[0011] Fig. 1 depicts an anatomical structure of a human body, specifically, the carotid arteries.

[0012] Fig. 2 depicts a stent 100 in a deployed state in a carotid sinus according to an embodiment of the present invention.

[0013] Fig. 3 depicts a perspective view of the stent 100 in an expanded configuration for deployment according to an embodiment of the present invention.

[0014] Fig. 4 depicts a flat pattern view of the stent 100 according to an embodiment of the present invention.DETAILED DESCRIPTION OF DRAWINGS

[0015] Prior to describing the disclosure in detail, definitions of certain words or phrases used throughout this patent document will be defined: the terms "include" and "comprise", as well as derivatives thereof, mean inclusion without limitation; the term "or" is inclusive, meaning and / or; the phrases "coupled with" and "associated therewith", as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have a property of, or the like. Definitions of certain words and phrases are provided throughout this patent document, and those of ordinary skill in the art will understand that such definitions apply in many, if not most, instances to prior as well as future uses of such defined words and phrases.

[0016] Reference throughout this specification to "one embodiment," "an embodiment," or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases "in one embodiment," "in an embodiment," and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment, but mean "one or more but not all embodiments" unless expressly specified otherwise. The terms "including," "comprising," "having," and variations thereof mean "including but not limited to" unless expressly specified otherwise. An enumerated listing of items does not imply that any or all of the items are mutually exclusive and / or mutually inclusive, unless expressly specified otherwise. The terms "a," "an," and "the" also refer to "one or more" unless expressly specified otherwise.

[0017] Although the operations of exemplary embodiments of the disclosed method may be described in a particular, sequential order for convenient presentation, it should be understood that the disclosed embodiments can encompass an order of operations other than the particular, sequential order disclosed. For example, operations described sequentially may in some cases be rearranged or performed concurrently. Further, descriptions and disclosures provided in association with one particular embodiment are not limited to that embodiment, and may be applied to any embodiment disclosed herein. Moreover, for the sake of simplicity, the attached figures may not show the various ways in which the disclosed system, method, and apparatus can be used in combination with other systems, methods, and apparatuses.

[0018] Furthermore, the described features, advantages, and characteristics of the embodiments may be combined in any suitable manner. One skilled in the relevant art willrecognize that the embodiments may be practiced without one or more of the specific features or advantages of a particular embodiment. In other instances, additional features and advantages may be recognized in certain embodiments that may not be present in all embodiments. These features and advantages of the embodiments will become more fully apparent from the following description and apportioned claims, or may be learned by the practice of embodiments as set forth hereinafter.

[0019] The present disclosure relates to an implantable stent. The stent of the present disclosure is delivered via a percutaneous method under angio-graphic visualization in a native human annulus. The stent is designed to provide precisely the proper amount of radial strength to the artery and to exert just enough radial force on a vessel wall so as to reshape the wall in the diastolic phase, and prevent migration of the stent in the systolic phase.

[0020] Though the teachings of the present disclosure have been explained below in the context of a carotid stent, the teachings of the present disclosure can equally applicable to any other peripheral segments.

[0021] Now referring to the figures, Fig. 2 illustrates a stent 100 in a deployed state (as in expanded state) inside a blood vessel. In an embodiment, the blood vessel is a carotid artery. The carotid artery includes a common carotid artery (CCA) 400 and a bifurcation (CAB) 500, where the common carotid artery 400 bifurcates into an internal carotid artery (ICA) 200 and the external carotid artery (ECA) 300 (also shown in Fig. 1). The base of the internal carotid artery (ICA) 200 includes a carotid sinus (CAS) 600.

[0022] In an embodiment, the stent 100 is implanted in the carotid sinus 600 of the internal carotid artery 200. The stent 100 includes a body having a proximal end 100a and a distal end 100b. The proximal end 100a of the stent 100 is placed at the bifurcation (CAB) 500 from where the body of the stent 100 extends along the internal carotid artery (ICA) 200 as depicted. The stent 100 is configured to align with the arterial wall to enhance pulsatility of the vessel wall and decrease blood pressure.

[0023] The stent 100 has a central longitudinal axis 130 that is substantially aligned with a central longitudinal axis 130 of the artery when placed. In the expanded configuration, the stent 100 defines a lumen / opening 101 through which the blood can flow. The lumen 101 extends from the proximal end 100a to the distal end 100b. The body of the stent 100 may be tubular in shape and may have a uniform diameter or tapering diameter. In the latter case, as an example, theend portions of the stent 100 may taper. Alternately, the stent 100 may taper from the proximal end 100a to the distal end 100b as needed basis the blood vessel where it is to be deployed.

[0024] The body of the stent 100 may be radially expandable and collapsible. That is, the body of the stent 100 can be collapsed to a form a narrow profile configuration of the stent 100 for delivery to a target site such as the common carotid artery 400. When placed in the target site such as the carotid sinus 600, the stent 100 can expanded from the narrow profile configuration to a wide profile configuration.

[0025] Fig. 3 depicts a perspective view of the stent 100 in an expanded configuration according to an embodiment of the present disclosure. The stent 100 includes a plurality of cells, for example, closed cells. At least some of the cells of the stent 100 overlap with the carotid sinus 600 that in turn includes baroreceptors ensuring baroreceptors are exposed. The baroreceptors are stretch-sensitive fibres in the aortic arch and carotid sinus 600. The baroreceptors measure changes in blood pressure-induced strain in the arterial walls. The baroreceptors may be unevenly distributed around the circumference of the blood vessel for a given central longitudinal location along the axis of the artery. The stent 100 of the present disclosure exhibits adequate radial strength due to which the stent 100 exerts just enough radial force on the vessel wall to reshape the wall in the diastolic phase, and prevents migration of the stent 100 in the systolic phase once the pressure is released. This ensures that undue strain on the arterial walls is not built and the baroreceptors transmit proper signals to the CNS.

[0026] In an embodiment, the cells are shaped to allow the native vessel wall to pulsate. The plurality of cells is arranged in a ring thereby forming a tubular structure or tubular body of the stent 100. The plurality of cells may include at least two larger cells (103), and at least two smaller cells (104) as depicted more clearly in Fig. 4. Each of the cell of the plurality of cells is aligned with a respective vessel wall to increase deflection of the vessel wall. Further, due to the combination row of the shorter and larger cells (103, 104), the stent 100 profile is reduced and the cells provides adequate grip to the vessel wall. The reduced profile of the stent 100 allows the blood to flow easily from the CAB 500 without any restriction.

[0027] In an embodiment, the stent 100 includes four cells with two cells being larger cells 103 while two cells being smaller cells 104. The larger cells 103 of the stent 100 are placed on a lower edge of the bifurcation (CAB) 500 in the common carotid artery 400. The smaller cells 104 are placed in the internal carotid artery 200 near the upper edge of the bifurcation (CAB) 500 of the common carotid artery 400. Due to this, minimal blood flow obstruction after placement of thestent 100 in the artery is achieved. The length of the smaller cells 104 is 10 mm to 25 mm while the length of the larger cells 103 is 15 mm to 35 mm. It is to be noted that the number of cells and types thereof may vary from application to application. For example, depending upon the place of deployment, the number of cells in the stent 100 may vary between a minimum of 3 cells to a maximum of 6 cells depending upon the application.

[0028] In an embodiment, the plurality of cells is flexible. Each of the plurality of cells is shaped to form the tissue to increase pulsatility of the vessel wall.

[0029] Each cell (larger cell 103 or smaller cell 104) includes a distal portion "D", a proximal portion "P" and a central portion "C" sandwiched between the distal portion "D" and the proximal portion "P" (shown in Fig. 4). Further, each cell includes two struts extending from the proximal end 100a to the distal end 100b. In an embodiment, a strut may be defined of multiple strut portions (103a & 103d, 103b & 103c, 104a & 104d, 104b & 104c).

[0030] The proximal portion "P" and distal portion "D" of a cell include V-shaped structures formed by a plurality of strut portions (103a & 103d, 103b & 103c, 104a & 104d, 104b & 104c). For example, two strut portions (103a & 103d, 103b & 103c, 104a & 104d, 104b & 104c) connect at a joint, thereby forming V-shaped structures as depicted.

[0031] The strut portions include an irregular curved profile (referred as irregular strut portions). Due to this, in an embodiment, the entire strut attains an irregular curved profile. The irregular strut portions (103a & 103d, 103b & 103c, 104a & 104d, 104b & 104c) include a curved profile for example, inwards and / or outwards along the length of the struts. The irregular strut portions (103a & 103d, 103b & 103c, 104a & 104d, 104b & 104c) help in proper positioning of the stent 100 in the walls of the blood vessels as the blood vessel walls have a substantially polygonal crosssection. Further details on irregular strut portions (103a & 103d, 103b & 103c, 104a & 104d, 104b & 104c) are provided in Fig. 4.

[0032] The central portions 'C' of each cell act as a connecting bridge between two adjacent cells. Together, the distal portion 'D', the proximal portion 'P' and the central portion 'C' of a cell may have any suitable cross-section including without limitation, polygon, hexagonal, diamondshaped, etc. In an embodiment, the cell is shaped to be of a substantially polygonal cross-section or leaf shaped. The shape and size of the cell impacts pulsatility of the vessel wall. For example, larger cells 103 increase the pulsatility of the vessel wall.

[0033] As mentioned above, the cells are coupled to each other around their central portions 'C'. For example, two adjacent cells are coupled via one or more junctions 105 formed between the central portions 'C' of the two adjacent cells. The number of junctions 105 depends upon the length of the central portions 'C' of the cells. In case the length of the central portions is long, three junctions 105 may be formed as in the case of larger cells 103. In the case of smaller cells 104, only two junctions 105 may be formed connecting the central portions 'C' of the respective smaller cells 104. In case of adjacent cells of unequal lengths, namely one smaller cell 104 and one larger ce 11103, three junctions 105 may be formed connecting the respective central portions 'C'.

[0034] Further, the junctions 105 may include a curved profile. Other shapes of profile include V-shaped, straight shaped, U-shaped with perpendicular sharp edges etc. The length of a junction105 ranges from 0.5 to 1.5 mm. In an embodiment, the length is 0.85mm. Each of the plurality of junctions 105 are configured to distribute pressure to the vessel wall and allow the endothelium of the vessel wall to grow over the junction 105 in order to increase biocompatibility.

[0035] Between two junctions 105, a window 106 is formed. For example, a window 106 is formed between the central portions 'C' of two adjacent cells and two junctions. For example, between two adjacent larger cells 103, two windows 106 are formed while between two adjacent smaller cells 104, a single window 106 is formed. In case of coupling of a larger cell 103 and a smaller cell 104, two windows 106 are formed as depicted. The formation of windows 106 maintains the pulsatility and ensuring proper signal flow in baroreceptors. Further, the windows106 may be of same or varied dimensions. For example, the window 106 formed between longer cells may be longer compared to windows 106 formed between smaller cells 104. Various such permutations of the dimensions of the windows 106 are within the teachings of the present disclosure.

[0036] Fig. 4 depicts a flat cross-sectional view of the implantable stent 100 of Fig. 3 in accordance with an embodiment.

[0037] Each of the irregular strut portions (103a & 103d, 103b & 103c, 104a & 104d, 104b & 104c) may be bent towards the lumen 101. For example, the irregular strut portions (103a & 103d, 103b & 103c, 104a & 104d, 104b & 104c) at the proximal portion "P" are bent at an angle ranging from 0 to 10° towards the lumen 101. Similarly, the irregular strut portions at the distal portion "D" are bent at an angle ranging from 0 to 10° towards the lumen 101.

[0038] Further, two adjacent irregular strut portions (103a & 103d, 103b & 103c, 104a & 104d, 104b & 104c) form an angle with each other. For example, angle between the irregular strut portions 104b of adjacent smaller cells 104 at the proximal end 100a P ranges from 30° to 70°, say 50° while angle between the irregular strut portions 104c of adjacent smaller cells 104 at the distal end 100b D of the stent 100 is an acute angle that ranges from 30° to 60°, say 42°. Similarly, angle between the irregular strut portions (103a, 103b) of adjacent larger cells 103 at the proximal end 100a P ranges from 30° to 60°, say 42° while angle between the irregular strut portions (103c, 103d) of adjacent larger cells 103 at the distal end 100b D of the stent 100 is an acute angle that ranges from 30° to 60°, say 45°. The angle between the irregular strut portions (104a, 103a) & (104a, 103b) of adjacent smaller cell 104 and longer cell 103 at the proximal end 100a P ranges from 30° to 60°, say 42° while angle between the irregular strut portions (103c, 104d) and (103d, 104d) of adjacent smaller cell 104 and longer cell 103 at the distal end 100b D of the stent 100 is an acute angle that ranges from 30° to 60°, say 42°.

[0039] The combination of the larger cells 103 and smaller cells 104 in the stent 100 may be alternate, consecutive or interchanging. The combination of larger cells 103 and the smaller cells 104 are consecutive as depicted in Fig. 4. The cells are leaf-shaped to minimize the blood flow obstruction in the common carotid artery 400.

[0040] The stent 100 may include one or more eyelets 107 at one or both the proximal end 100a and the distal end 100b of the stent 100. Specifically, the eyelets 107 may be coupled to the proximal end 100a or distal end 100b of a cell, for example, at the point of intersection of the V- shaped struts (103a & 103d, 103b & 103c, 104a & 104d, 104b & 104c). The eyelet 107 may be but not limited to circular, or semi-circular, square, rectangular etc. in shape. In the depicted embodiment, the eyelets 107 are of circular shape. The eyelets 107 comprises a cavity 107a for hosting a radiopaque marker by a suitable method of coupling such as but not limited to welding, bonding, fusing, brazing, soldering etc.

[0041] In an embodiment, the eyelets 107 may be placed on alternate ends of the larger cells 103 and smaller cells 104 (shown in Fig.4). For example, in the smaller cells 104, the eyelets 107 may be placed at the proximal end 100a while in the larger cells 103, the eyelets 107 may be placed at the distal end 100b. Alternately, irrespective of the size of the cells, the eyelets 107 may alternate from cell to cell, that is, in a first cell, an eyelet 107 may be placed at the distal end 100b while in an adjacent cell, the eyelet 107 may be placed at the proximal end 100a and so on.In yet another embodiment, some of the cells may include eyelets 107 while other cells include V-shaped structures.

[0042] Optionally, an eyelet 107 includes one or more markers. The markers may be made of materials such as tantalum, platinum-iridium, platinum-tungsten, etc.

[0043] Axial and / or rotational adjustments may help to achieve a desired orientation of the stent 100 implantation, to assist operators in determining the location of stent 100 within the common carotid artery 400 relative to a known or suspected region of baroreceptor concentration and configured to aid in accurate positioning and visualization of the stent 100 during medical procedures. Additional parts can be provided on the implantable stent 100 to help an operator to achieve a desired placement, such as markers for handling the stent 100 with a tool, or providing the markers of the stent 100 on V-shaped structures at the proximal end 100a and the distal end 100b.

[0044] When the self-expanding carotid stent 100 expands from a narrow profile to an expanded profile, each of the cells is expanded while the openings remain in a substantially fixed arrangement. The V-shaped structures can be urged apart so as to define the plurality of cells while the irregular strut portions remain substantially undeflected. In alternate embodiments, the junctions 105 deflect when the V-shaped structures expand. This stent 100 is capable of meeting pressures during systole and diastole cycles in order to enhance stretching and stimulation of the baroreceptors.

[0045] The stent 100 may be made of biocompatible metals including, but not limited to, medical-grade formulations of platinum, stainless steel, cobalt, titanium, nitinol, and / or cobaltchromium, and / or alloys containing these metals and / or biocompatible polymers. In an embodiment, the stent 100 is made of a self-expanding material, nitinol.

[0046] The stent 100 may include a shape of but not limited to a sphere, tubular, taper, cone, torus etc. In the said embodiment, the stent 100 depicts a hollow tubular structure.

[0047] It may be noted that the stent 100 in accordance with the teachings of the present disclosure may be manufactured by laser cutting a tube to required dimensions and shape to yield a singular structure. The stent 100 includes a smooth surface to ensure minimum trauma to the patients.

[0048] In an embodiment, the stent 100 is a retractable stent 100 that can be placed in a carotid artery to improve the functioning of the carotid sinus 600. Due to the eyelets 107 provided at theproximal end 100a of the stent 100, the stent 100 can be retracted if delivered pre-maturely in the vessels. The eyelet 107 includes a cavity 107a which engages with a retracting mechanism of a delivery device. This engagement between the cavity 107a of the eyelet 107 and the retracting mechanism is temporary. During placement of the stent 100 in the carotid sinus 600, first, the distal end 100b is deployed while the proximal end 100a remains in the delivery device being engaged with the retracting mechanism. The deployment of the stent 100 is not complete until the eyelets 107 at the proximal end 100a are uncovered by the retracting mechanism. Thus, as long as the eyelets 107 are covered and the stent 100 is pre-maturely deployed, the stent 100 can be retracted.

[0049] The scope of the invention is only limited by the appended patent claims. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and / or configurations will depend upon the specific application or applications for which the teachings of the present invention is / are used.

Claims

WE CLAIM:

1. A stent (100) comprising: a) a plurality of junctions (105); b) a circumferential row of at least one larger cell (103) and smaller cell (104) connected via at least two junctions, forming a tubular body, the tubular body having a proximal end (100a), a distal end (100b) and a lumen (101) extending therebetween, each of the larger cell (103) and smaller cell (104) including a proximal portion "P", a distal portion "D" and a central portion "C" disposed therebetween; and c) a window (106) defined between the two adjacent junctions (105); wherein at least two junctions (105) connect central portions of two consecutive cells; wherein each cell includes two struts (103a & 103d, 103b & 103c, 104a & 104d, 104b & 104c) extending from the proximal end (100a) to the distal end (100b); wherein the struts (103a & 103d, 103b & 103c, 104a & 104d, 104b & 104c) include an irregular curved profile; wherein portion of the struts (103a & 103d, 103b & 103c, 104a & 104d, 104b & 104c) in the proximal portion are bent towards the lumen (101).

2. The stent (100) as claimed in claim 1, wherein the stent (100) includes an eyelet (107) provided with each of the larger cell (103) and smaller cell (104) towards one of the proximal end (100a) or distal end (100b).

3. The stent (100) as claimed in claim 2, wherein the proximal portion of the smaller cell (104) includes the eyelet (107).

4. The stent (100) as claimed in claim 2, wherein the distal portion of the larger cell (103) includes the eyelet (107).

5. The stent (100) as claimed in claim 2, wherein the eyelet (107) includes a cavity (107a).

6. The stent (100) as claimed in claim 2, wherein the eyelet (107) includes one or more markers.

7. The stent (100) as claimed in claim 1, wherein the circumferential row includes two adjacent smaller cells (104) and two adjacent larger cells (103) placed between the smaller cells (104).

8. The stent (100) as claimed in claim 1, wherein two adjacent larger cells (103) are connected via three junctions (105) forming two windows (106).

9. The stent (100) as claimed in claim 1, wherein one smaller cell (104) and an adjacent larger cell (103) are connected via three junctions (105) forming two windows (106).

10. The stent (100) as claimed in claim 1, wherein the struts (103a & 103d, 103b & 103c, 104a & 104d, 104b & 104c) at the proximal portion are bent at angle ranging from 0 to 10° towards the lumen (101).

11. The stent (100) as claimed in claim 1, wherein the stent (100) is made of a self-expanding material.

12. The stent (100) as claimed in claim 1, wherein the stent (100) is a laser cut singular structure.

13. The stent (100) as claimed in claim 1, wherein the angle between adjacent struts (103a & 103d, 103b & 103c, 104a & 104d, 104b & 104c) of two smaller cells (104) at the proximal end (100a) is 50° and at the distal end (100b) is 42°.

14. The stent (100) as claimed in claim 1, wherein the angle between adjacent struts (103a & 103d, 103b & 103c, 104a & 104d, 104b & 104c) of two larger cells (103) at the proximal end (100a) is 42° and at the distal end (100b) is 45°.

15. The stent (100) as claimed in claim 1, wherein the angle between strut (103a & 103d, 103b & 103c, 104a & 104d, 104b & 104c) of a larger cell (103) and an adjacent strut (103a & 103d, 103b & 103c, 104a & 104d, 104b & 104c) of a smaller cell (104) at the proximal end (100a) is 42° and at the distal end (100b) is 42°.

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