Description: FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(Section 10 and Rule 13)

1. TITLE OF THE INVENTION:
EXTENSION STENT GRAFT
2. APPLICANT:
Meril Life Sciences Pvt. Ltd., an Indian company of the address Survey No. 135/139 Bilakhia House, Muktanand Marg, Chala, Vapi-Gujarat 396191, India.

The following specification particularly describes the invention and the manner in which it is to be performed:

 
FIELD OF INVENTION
[1] The present invention relates to a medical implant. The invention particularly relates to an extension stent graft.
BACKGROUND OF THE INVENTION
[2] Stent grafts are designed for a variety of medical applications, each tailored to specific clinical needs. Some stent grafts provide structural support, while others facilitate the removal of obstruction or elongate patency. For instance, specialized stent grafts are used in cases of calcification to provide structural support in hardened arteries, while others are designed for clearing blockages and restoring blood flow. Drug-eluting stent grafts help prevent restenosis by releasing medication, whereas bare-metal stent grafts provide mechanical support without medication. Additionally, bioresorbable stent grafts gradually dissolve over time, offering temporary support without leaving a permanent implant. The choice of a stent graft depends on parameters, such as, the nature of the disease, vessel condition, anatomical structure, intended treatment outcome, etc. In other words, stent grafts are designed for diverse medical applications, each having a specific structural and functional characteristic tailored to its intended clinical use.
[3] The aorta is a cane-shaped artery and is the largest blood vessel in the body. The aorta is responsible for transporting nutrient-rich blood to the systemic circulation following ejection from the left ventricle of the heart. In other words, the aorta delivers oxygenated blood from the heart to the rest of the body.
[4] The aorta extends from the left ventricle of the heart to the proximal iliac bifurcation in the abdomen. The aorta may be divided into various segments depending on route/path and location including, the aortic root (not shown), the aortic valve, the thoracic aorta and the abdominal aorta, as shown in Fig. 1a. The aortic root is the section of the aorta that is attached to the heart. The aortic root is the widest part of the aorta. The entire structure at the base of the aorta where the aortic valve is located is referred as the aortic root.
[5] The aortic valve includes three flaps of tissues (leaflets) that snap open and shut to release oxygen-rich blood from the heart. The thoracic aorta consists of the ascending aorta, the aortic arch, and the descending aorta. The ascending aorta is the upward curve of the aorta after the aorta leaves the heart. The aortic arch is the curved segment that bridges the ascending aorta and the descending aorta. The curved segment of the aortic arch gives the aorta its cane-like shape. The descending aorta passes through the diaphragm’s aortic hiatus and continues as the abdominal aorta. The abdominal aorta terminates as it bifurcates into common iliac arteries, which subsequently provide arterial supply to the pelvis and lower limbs.
[6] An aortic aneurysm refers to a localized and abnormal dilation or bulging in the wall of the aorta. This condition occurs due to a weakening or thinning of the aortic wall. Over time, the wall of the aorta may become less resilient or weaken, and under the force of blood flow, it may start to expand or bulge, resulting in an aneurysm. If left untreated, this bulging can cause significant risks, such as rupture or dissection, which may be life-threatening.
[7] Aortic aneurysms can occur in different parts of the aorta. The most common types are thoracic aortic aneurysms (TAA) and abdominal aortic aneurysms (AAA), as shown in Fig. 1b.
[8] A thoracic aortic aneurysm (TAA) occurs in the part of the aorta that runs through the chest. It forms when the aortic wall weakens, leading to a bulge. This can cause complications like chest pain, hoarseness, or difficulty in swallowing, as the aneurysm may affect nearby structures.
[9] An abdominal aortic aneurysm (AAA) occurs in the section of the aorta that passes through the abdomen. AAAs are more common than TAAs and are often linked to conditions like atherosclerosis, high blood pressure, or smoking. Symptoms may include lower back or abdominal pain. If an AAA ruptures, it is a medical emergency, often causing severe internal bleeding.
[10] In some cases, an aortic aneurysm can affect both the thoracic and abdominal aorta, creating a thoracoabdominal aortic aneurysm (TAAA). This occurs when the aneurysm extends through both the descending aorta and the abdominal aorta. In these cases, the aneurysm may affect the major branches of the aorta that supply blood to critical organs such as the kidneys, intestines, and spinal cord.
[11] To maintain patency/ structure of blood vessels, stenting in the blood vessel is performed. This process is known as endovascular aneurysm repair (EVAR). Stenting is a minimally invasive procedure where a stent (a fabric tube supported by metal mesh) is delivered to the aneurysm site and deployed to seal the aneurysm, redirecting the blood flow through the stent, as shown in Fig. 1c. The stent reinforces the weakened portion of the aorta, and keeps a vessel lumen intact to facilitate normal blood flow.
[12] However, endoleaks may occur after an EVAR procedure when blood continues to flow into the aneurysm sac. This happens due to several reasons such as, for example, in case of type I endoleaks, one of a proximal end or a distal end of the stent, fails to create a tight seal with the aortic wall (as shown in Fig. 1d). A poor seal at the top or bottom edge of the stent allows blood to enter the aneurysm sac directly from the aorta. Over time, the stent may shift or migrate, particularly if it is not securely fixed at the ends, resulting in seal failure and the development of endoleaks.
[13] Alternately, type III endoleaks may happen due to disconnection between modular components of a multipiece graft, potentially leading to direct pressurization of the aneurysm (as shown in Fig. 1e). These leaks can prevent complete isolation of the aneurysm, allowing blood flow into the sac, which may lead to expansion, rupture, or other complications.
[14] To overcome the problem of endoleaks, an extension stent graft is used to extend the primary stent and to ensure the repair of the aneurysm. The extension stent extends the primary stent (as discussed above) into healthier sections of the aorta or iliac arteries to ensure a secure seal.
[15] Conventional extension stent grafts may fail to fully seal the vessel wall. These issues primarily arise from limitations in design, deployment, or the interaction of extension stent graft with complex vascular anatomies or with the primary stent. Poor sealing of the edge of the extension stent with the aortic vessel and/or the lumen of the primary stent may lead to increased endoleaks risk.
[16] Therefore, there is a need for an extension stent graft which overcomes the drawbacks of the existing ones.
SUMMARY OF THE INVENTION
[17] The present invention relates to an extension stent graft (hereinafter, stent graft). The stent graft is to be inserted in a primary stent. The stent graft has a proximal section, a distal section. In an embodiment, the extension stent graft comprises a stent and a wrapper. The stent includes a proximal end and a distal end defining a length therebetween. The stent includes a flared portion towards one of the proximal end or the distal end. The wrapper is disposed at least on the flared portion of the stent. The wrapper is configured to provide a leak-proof extension stent graft. Wherein, a shape-set expanded diameter of a non-flared portion of the stent graft snug fits an expanded inner diameter of the primary stent.
[18] A method of fabricating the stent graft having a flared portion provided towards one of a proximal end or a distal end is disclosed. In an embodiment, the method includes providing a stent on a mandrel. The method further includes flaring one of a proximal end of the stent at a first predefined temperature for a first predefined time period. Thereafter, the method includes wrapping a wrapper around the stent a plurality of times. The method further includes laminating the stent with the wrapper on the mandrel at a second predefined temperature for a second predefined time period with a heat shrink tube. Thereafter, the mothed involves cooling the laminated stent graft at a third predefined temperature for a third predefined time period.
[19] The foregoing features and other features as well as the advantages of the invention will become more apparent from the following detailed description, which proceeds with reference to the accompanying figures.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
[20] The summary above, as well as the following detailed description of illustrative embodiments, is better understood when read in conjunction with the apportioned drawings. For the purpose of illustrating the present disclosure, exemplary constructions of the disclosure are shown in the drawings. However, the disclosure is not limited to specific methods and instrumentalities disclosed herein. Moreover, those in the art will understand that the drawings are not to scale.
[21] Figs. 1a-1e depicts an anatomical diagram of the aorta extending between the heart and abdomen.
[22] Figs. 2a-2b depict perspective views of a stent graft 200, according to an embodiment of present disclosure.
[23] Fig. 3a depicts a stent 300 in a collapsed state, according to an embodiment of the present disclosure.
[24] Figs. 3b-3c depict the stent 300 in an expanded state, according to an embodiment of the present disclosure.
[25] Fig. 4a depicts a stent 400 in the collapsed state, according to an alternate embodiment of the present disclosure.
[26] Figs. 4b-4c depict the stent 400 in the expanded state, according to an alternate embodiment of the present disclosure.
[27] Figs. 5a-5b depict the wrapper 500 disposed on the entire length of the stent (300, 400), according to an embodiment of the present disclosure.
[28] Fig. 6 illustrates a method 600 of fabricating the stent graft 200, according to an embodiment of the present disclosure.
[29] Fig. 7a depicts the stent (300, 400) provided on a first mandrel 700, according to an embodiment of the present disclosure.
[30] Fig. 7b depicts the stent (300, 400) provided on a second mandrel 750, according to an embodiment of the present disclosure.
[31] Fig. 8 illustrates a flowchart of a method 800 of deploying the stent graft 200 at a target site, according to an embodiment of the present disclosure.
[32] Fig. 9 depicts a delivery system 900 for delivering the stent graft 200 at the target site, according to an embodiment of the present disclosure.
[33] Figs. 10-11 depict delivery of the stent graft 200 at the target site using the delivery system 900, according to an embodiment of the present disclosure.
DETAILED DESCRIPTION OF THE INVENTION
[34] Prior to describing the invention 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.
[35] 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.
[36] 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.
[37] Furthermore, the described features, advantages, and characteristics of the embodiments may be combined in any suitable manner. One skilled in the relevant art will recognize 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.
[38] A primary stent graft refers to the main endovascular stent graft initially deployed to treat one or more of AAA, TAA or TAAA. The primary stent graft bypasses an aneurysm sac and restores vessel integrity.
[39] An extension stent graft refers to an additional endovascular stent graft used to extend the length of the primary stent graft, enhancing the coverage or sealing of the primary stent graft in the treatment of AAA/TAA/TAAA. The extension stent graft is deployed when the primary stent graft fails to provide adequate seal or coverage, often due to improper positioning or endoleaks.
[40] The present invention relates to an extension stent graft (hereinafter, stent graft) and methods of manufacture thereof. The stent graft prevents endoleaks, thereby eliminating build-up of an aneurysm or its rupture on overinflation due to blood flow. The stent graft may be balloon-expandable or self-expandable. Although, the stent graft of the present disclosure is exemplified for use in type III endoleaks that occur in abdominal aortic aneurysm, the teachings of the present disclosure are equally applicable to type I endoleaks in abdominal, thoracic or thoracoabdominal aortic aneurysm and are within the scope of the teachings of the present disclosure.
[41] In an embodiment, the stent graft includes a wrapper and a stent. In an exemplary embodiment, the stent is designed with enhanced radial strength and anti-kinking properties to ensure long-term performance after deployment. In an exemplary embodiment, the stent includes a plurality of struts (hereinafter, struts) and a plurality of linkages. The struts are arranged in a plurality of circumferential rows as per a pre-defined pattern to form a tubular structure. The plurality of rows of struts are interlinked by at least one linkage of the plurality of linkages to form a plurality of open units and a plurality of closed units. The plurality of linkages is configured to provide structural support, increases radial strength and introduces anti-kinking properties in the stent. Thus, the stent maximizes the expansion of the stent graft and promotes the structural integrity of the stent graft during and/or post deployment stages, and prevents blood leakage post-deployment.
[42] In an embodiment, the stent graft includes a predefined length, a predefined outer diameter and a predefined inner diameter. In an expanded state, the stent graft having a uniform diameter throughout the predefined length includes an expanded length, an expanded outer diameter and an expanded inner diameter. The expanded outer diameter of the stent graft is larger than an expanded inner diameter of the lumen of the primary stent.
[43] Further, the stent graft maybe pre-flared. In one embodiment, the stent graft is designed to have a flared portion in one of a proximal or distal end of the stent graft. The flared portion of the stent graft provides a large surface area to anchor the stent graft in the aortic vessel. The flared portion ensures a continuous and leak-proof seal between the stent graft and the vessel wall.
[44] A non-flared portion of the stent graft is configured to be positioned into a lumen of a primary stent. For example, one of a proximal section or distal section of the stent graft may include a non-flared portion. The non-flared portion is configured to overlap with at least a proximal and/or distal portion of the primary stent. In one embodiment (e.g., in endoleaks 1), the proximal section of the stent graft includes a non-flared portion and is configured to be positioned into the lumen of the distal portion of the primary stent. In another embodiment (e.g., in endoleaks 3), the distal section of the stent graft having non-flared portion is configured to be positioned into the lumen of the proximal portion of the primary stent.
[45] In an expanded state, the stent graft having a non-uniform diameter throughout the predefined length (i.e., the stent graft having a flared portion at one end and a non-flared portion at another end) has a shape-set expanded length and a corresponding shape-set outer and inner diameter. The flared portion of the stent graft has a shape-set expanded outer diameter and a shape-set expanded inner diameter. Similarly, the non-flared portion of the stent graft includes a shape-set expanded inner diameter and a shape-set expanded outer diameter. The shape-set expanded outer diameter of the stent graft is larger than an expanded inner diameter of the lumen of the primary stent. This variation in expanded outer diameter allows snug insertion of the proximal/distal section of the stent graft (in expanded state) into the respective portion of the lumen of the primary stent (in expanded state).
[46] The wrapper is disposed at least partially along a predefined length of the stent of the stent graft. The wrapper is configured to enhance sealing and fixation of the stent graft within the vessel wall and the lumen of the primary stent. In an embodiment, the wrapper is made of a single sheet. The sheet is wrapped around the stent to provide a leak-proof seal between the stent graft and the vessel wall. The sheet includes a plurality of pores. The plurality of pores allows controlled tissues ingrowth and adaptation post-deployment, promoting long-term stability while minimizing thrombogenic risks.
[47] Now referring to figures, Figs. 2a-2b depict an extension stent graft 200 (hereinafter, stent graft 200), according to an embodiment of the present disclosure. The stent graft 200 is configured to be inserted into a primary stent graft and extend the length of the primary stent graft, enhancing the coverage or sealing of the primary stent graft. The stent graft 200 is a tubular structure having a proximal end 200a and a distal end 200b. The stent graft 200 includes a proximal section 200c and a distal section 200d provided towards the proximal end 200a and distal end 200b, respectively. The stent graft 200 includes a middle section 200e provided between the proximal section 200c and a distal section 200d.
[48] The stent graft 200 is configured to undergo shape shifting and structural deformity, radially, between a collapsed state and an expanded state, as explained later. For example, the stent graft 200 may be deformed to the collapsed state to load over a suitable delivery device (not shown). Upon delivery of the stent graft 200 at the target site, the stent graft 200 is configured to regain its expanded state.
[49] The stent graft 200 has a predefined length and a predefined diameter. In the collapsed state, the predefined length (hereinafter, referred as collapsed length) may range between 30 mm and 100 mm. In the expanded state, the predefined length (hereinafter, referred as expanded length) may range between 20 mm and 80. In an embodiment, the collapsed length and the expanded length of the stent graft 200 are 50 mm and 40mm, respectively.
[50] In the collapsed state, the stent graft 200 includes a collapsed inner diameter ranging from 02 to 04 and a collapsed outer diameter ranging from 1.50 to 4.50. In the expanded state, the stent graft 200 has an expanded inner diameter ranging from 15 to 19 and an expanded outer diameter ranging from 16 to 20.
[51] In the depicted embodiment, the stent graft 200 is in the expanded state (as shown in Fig. 2a and 2b). The stent graft 200 may have a uniform or non-uniform tubular structure. In one depicted embodiment, the stent graft 200 has a uniform tubular structure, as shown in Fig. 2a. In other words, the expanded outer diameter of the stent graft 200 remains the same throughout a predefined length of the stent graft 200. The expanded outer diameter of the stent graft 200 may vary based on the anatomical structure of the patient (i.e., the inner diameter of the aortic vessel) and an inner expanded diameter of the primary stent (as shown in Fig. 1c).
[52] The expanded outer diameter of the stent graft 200 is larger than the expanded inner diameter of the lumen of the primary stent. One of the proximal section 200c or the distal section 200d is configured to be positioned into a lumen of a primary stent. The proximal section 200c or the distal section 200d of the stent graft 200 is configured to overlap with at least one of a proximal/distal portion of the primary stent. In an embodiment, the proximal section 200c of the stent graft 200 is configured to be positioned in the distal portion of the lumen of the primary stent. The proximal section 200c of the stent graft 200 is configured to at least partially overlap on the distal portion of the primary stent. The exact length for overlapping may vary depending upon the anatomical structure. The overlapping portions between the proximal section 200c of the stent graft 200 and the distal portion of the primary stent provide a secure connection therebetween and ensure a continuous and leak-proof seal.
[53] The expanded outer diameter of the stent graft 200 is designed to be larger than the expanded inner diameter of the lumen of the primary stent, ensuring snug insertion of the proximal section 200c/distal section 200d of the stent graft 200 into the respective portion of the lumen of the primary stent. The larger expanded outer diameter of the stent graft 200 provides a reinforcement against the expanded inner diameter of the primary stent and creates a tight seal therebetween, thereby preventing migration of the stent graft 200 from the primary stent. By creating a tighter seal between the stent graft 200 and the primary stent, the endoleaks are minimized.
[54] In another depicted embodiment, the stent graft 200 has a non-uniform tubular structure having a proximal end 200a and a distal end 200b, as depicted in Fig. 2b. In an embodiment, one of the proximal section 200c or the distal section 200d of the stent graft 200 may flare outwards from a longitudinal axis of the stent graft 200 to form a flared portion 200f. In the depicted embodiment, the flared portion 200f is provided towards the distal section 200d of the stent graft 200. In an embodiment, the distal section 200d extends between the distal end 200b and the first end A. The flared portion 200f is formed by shape-setting the stent graft 200 using an exemplary method, which has been explained later.
[55] The flared portion 200f includes a predefined inner diameter and a predefined outer diameter. In the collapsed state, the flared portion 200f has a shape-set collapsed inner diameter and a shape-set collapsed outer diameter. In the expanded state, the flared portion 200f has a shape-set expanded inner diameter and a shape-set expanded outer diameter. In the depicted embodiment, the stent graft 200 is in expanded state, as shown in Fig. 2b.
[56] The shape-set expanded outer diameter of the distal section 200d at the distal end 200b is larger than the shape-set outer diameter of the first end A. The shape-set expanded outer diameter of the distal section 200d is configured to decrease gradually from the distal end 200b to the first end A, thus forming the flared portion 200f of the stent graft 200.
[57] The first end A of the flared portion 200f smoothly transits into the proximal section 200c of the stent graft 200. In the depicted embodiment, a portion of the stent graft 200 between the first end A and the proximal end 200a is a non-flared portion. The non-flared portion includes a shape-set expanded outer diameter and a shape-set expanded inner diameter. The shape-set expanded outer diameter of the non-flared portion in the stent graft 200 helps snug fit the expanded inner diameter of the primary stent. The shape-set expanded outer diameter of the flared portion 200f at the distal end 200b and the first end A, and the expanded outer diameter of the non-flared portion may range between 18 mm and 22 mm, and 16 mm and 20 mm, respectively. In an embodiment, the shape-set expanded outer diameter of the flared portion 200f at the distal end 200b and at the first end A, and the shape-set expanded outer diameter of the non-flared portion of the stent graft 200 is 18mm, 20mm, 22 mm and 16mm, 18mm, 20mm, respectively. The transition between the distal section 200d and the proximal portion 200c forms the non-uniform tubular structure of the stent graft 200.
[58] In an embodiment, the flared portion 200f of the stent graft 200 is positioned into the aortic lumen. The flared portion 200f provides a large surface area to anchor the stent graft 200 in the aortic vessel. The flared portion 200f is configured to conform with the lumen of the aortic vessel and accommodate variations in aortic vessel diameter, thus making it suitable for irregular anatomies. The flared portion 200f ensures a continuous and leak-proof seal to aneurysm in the vessel wall. The flared portion 200f is configured to provide a uniform radial force against the aortic wall, which helps in accommodating natural variations in the lumen size of the aortic vessel. The close conformation of the flared portion 200f to the aortic vessel wall reduces micromovements of the stent graft 200 from the vessel wall that could create small channels for leakage, thus preventing blood from escaping into the aneurysm region (i.e., reducing the risk of endoleaks).
[59] The gradual decrease in the shape-set expanded outer diameter of the flared portion 200f between the distal end 200b and the first end A is configured to maintain a smoother transition for the blood to flow from the natural vessel into the stent graft 200. In other words, the flared portion 200f is configured to prevent abrupt diameter changes between the stent graft 200 and the natural vessel, and mitigate the volumetric restrictions within the stent graft 200, ensuring a smoother flow transition and minimizing turbulence in the blood flow. This ensures unobstructed blood flow and minimizes blood vessel stress that might otherwise allow blood to seep through, thereby lowering the risk of vessel injury.
[60] In an exemplary embodiment, the stent graft 200 includes a stent and a wrapper 500.
[61] The stent is a mesh-like structure extending between the proximal end 200a and the distal end 200b of the stent graft 200. The stent includes a plurality of struts. The struts may be designed in a predefined pattern to form the mesh structure of the stent. The struts may be formed using techniques, such as, without limitation, laser cut, 3-D printing, braiding technique, welding, machining, etc. In an embodiment, the struts are formed using a laser cutting technique to form the mesh structure of the stent.
[62] The present disclosure describes two exemplary stents; however, these embodiments are provided for illustrative purposes and do not limit the scope of the present disclosure. A person skilled in the art may modify or design around these embodiments without departing from the scope of the invention. Additionally, other stent designs may be applied, provided they achieve the similar functional outcomes.
[63] Figs. 3a-3c illustrate a first embodiment of a stent 300. In an embodiment, the stent 300 includes a proximal end 300a and a distal end 300b, thereby defining a length. The proximal end 300a and the distal end 300b of the stent 300 aligns with the proximal end 200a and distal end 200b of the stent graft 200. The stent 300 includes a proximal section and a distal section provided towards the proximal end 300a and distal end 300b, respectively. The stent includes a middle section provided between the proximal section and the distal section.
[64] The stent 300 is configured to undergo shape shifting between a collapsed state and an expanded state. The stent 300 includes a plurality of rows of struts 330 arranged in a predefined pattern to form the mesh-like structure. The rows of struts 330 are arranged parallelly. The plurality of rows of the struts 330 extend in a circumferential direction and are coupled to form a tubular structure of the stent 300. In an embodiment, in each row, the struts 330 are joined to form alternating peaks (p) and troughs (t). The struts 330 of each row may be arranged in a predefined pattern, such as, curved chevron pattern, zig-zag pattern, chevron pattern, etc. In an embodiment, the struts 330 of each row are formed continuously in a curved chevron pattern. Each strut 330 may have a straight profile or curved profile. In an embodiment, each strut 330 has a curved profile. The continuous curved chevron pattern of the struts 330 gives a near appearance of cuspidate shape of an apex of a leaf. In an embodiment, the peaks (p) of one row are aligned with the troughs (t) of an adjacent row.
[65] The stent 300 includes a plurality of linkages. The plurality of linkages is configured to interconnect two adjacent rows of struts 330 to form a plurality of closed units (301, 303) and a plurality of open units (305). In the depicted embodiment, a plurality of first linkages 317 (hereinafter, referred as first linkages 317) of the plurality of linkages is configured to interconnect two adjacent rows of struts 330 provided in the proximal section at the proximal end 300a. Specifically, each peak (p) of a first row of struts 330 is interlinked with an adjacent trough (t) of an adjacent second row of struts 330 via a first linkage 317, thus forming closed units 301 at the proximal end 300a. Similarly, two adjacent rows of struts 330 provided in the distal section at the distal end 300b of the stent 300 are interlinked by the first linkages 317 to form the closed units 303.
[66] The closed units (301, 303) at the proximal end 300a and at the distal end 300b provide stability to the stent 300 within the aortic vessel and the primary stent. The closed units (301, 303) provide rigidity to the proximal end 300a and the distal end 300b of the stent 300.
[67] At least the proximal portion of the stent 300 having the closed units (301) is configured to overlap with the distal/proximal portion of the primary stent. The closed units (301, 303) at the proximal end 300a and the distal end 300b provide uniform sealing within the aortic vessel and within the lumen of the primary stent, respectively.
[68] The first linkages 317 forming the closed units (301, 303) are configured to enhance radial strength at the proximal end 300a and the distal end 300b of the stent 300. The first linkages 317 allow uniform expansion of the ends of the stent 300 during the deployment. The first linkages 317 forming the closed units (301, 303) allows the stent 300 to conform with the aortic vessel and the distal portion of the primary stent, respectively. Thereby, maintaining the shape of the stent 300 against a vessel recoil or external forces, and preventing collapse of the stent post-deployment. In other words, the first linkages 317 forming the closed units (301, 303) are configured to provide resistance to the stent 300 against external compression (for example, pulsatile expansion during blood flow).
[69] The plurality of rows of struts 330 provided in the middle section (i.e., between the closed units (301 and 303)) are interlinked to form a plurality of open units 305. A plurality of second linkages 320 (hereinafter, second linkages 320) and a plurality of third linkages 340 (hereinafter, third linkages 340) are configured to interlink the plurality of struts 330 provided between the closed units (301 and 303). In the depicted embodiment, two adjacent rows of struts 330 are interlinked by one of the second linkages 320 or the third linkages 340, thereby forming open units 305. A plurality of second linkages 320 (hereinafter, second linkages 320) and a plurality of third linkages 340 (hereinafter, third linkages 340) are configured to selectively interlink peaks (p) of one row of struts 330 with a trough (t)/ peak (p) of the adjacent row of struts 330. The selection of interlinking peaks (p) of one row with a trough (t)/ peak (p) of the adjacent row may depend upon the requirement of the radial strength and anti-kinking property in the stent 300.
[70] The plurality of linkages involved in forming the open units 305 are configured to provide radial strength and introduce anti-kinking in the stent 300. The plurality of linkages prevents foreshortening of the stent graft 200 during the deployment and post-deployment. The plurality of linkages prevents formation of sharp curves or twists in the stent graft 200 during or post deployment in the aortic vessel, which otherwise may cause collapse of the stent graft 200 post-deployment and lead to migration of the stent graft 200.
[71] The struts 330 may be made of shape memory, biocompatible materials, such as, without limitation, brasses, copper-aluminum, nickel-titanium (NiTi), etc., or a combination thereof. In an embodiment, the struts 330 are made of a nickel-titanium (NiTi) material. The shape memory property of the struts 330 allows the stent to shape shift and undergo structural deformity, radially, between the collapsed state (as shown in Fig. 3a) and the expanded state (as shown in Fig. 3b). For example, the stent 300 may be deformed to the collapsed state to load the stent graft 200 over a suitable delivery device (not shown).
[72] The stent 300 has a predefined length and a predefined diameter. Due to foreshortening of the stent, the predefined length of the stent 300 may vary upon expansion.
[73] In the collapsed state, the stent 300 is crimped, reducing the profile of the stent graft 200 for a minimal invasive delivery. The collapsible nature allows the stent 300 to remain crimped while the stent graft 200 passes through the narrow delivery systems. In the collapsed state, the stent 300 may have a collapsed inner diameter and a collapsed outer diameter.
[74] Upon delivery of the stent 300 at an intended zone, the stent 300 is configured to regain its expanded state, adapting to the aortic vessel without compromising its mechanical strength and structural integrity. In the expanded state, the stent 300 may have an expanded inner diameter and an expanded outer diameter.
[75] Each closed unit (301, 303) includes an extension 310. The extension 310 has a predefined shape, such as, but not limited to diamond shape, c shape, crown shape, U shape, etc. In an embodiment, the extension 310 has an elongated crown shape. The extensions 310 helps maintaining the position of the stent 300 at its deployed location. The extensions 310 provide additional support to the stent 300 in the deployed state. This ensures anchorage of the stent 300 within the vessel wall and the expanded primary stent. The extensions 310 have smooth surface that prevents rupturing of the vessel wall.
[76] In an embodiment, the stent 300 includes two or more marker cavities 310a provided on the extension 310. Each extension 310 may be provided with a marker cavity 310a. In the depicted embodiment, a marker cavity 310a is provided on one extension 310, followed by two extensions 310 without a marker cavity. Alternately, alternate extensions 310 may include a marker cavity 310a. The two or more marker cavities 310a may be slots, holes, grooves, etc. The marker cavities 310a may include any suitable shape, such as, but not limited to, circular, triangular, ellipse, square, rectangle, ellipse, pyramid, etc. In an embodiment, the marker cavities 310a have a circular shape.
[77] Each marker cavity 310a may be coupled to a radiopaque marker or components that are visible under medical imaging, helping healthcare providers in accurately positioning the stent 300 at an intended zone. In an embodiment, each marker cavity 310a is coupled to a corresponding radiopaque marker (not shown) having a corresponding shape by using techniques, such as, without limitation, welding, riveting, crimping, clamping, hooking, welding, brazing, mechanically, laser cutting, etc. In an exemplary embodiment, each marker cavity 310a is welded to a corresponding radiopaque marker by using welding technique.
[78] A portion towards the proximal end 300a or distal end 300b may be flared to form the flared portion 200f of the stent graft 200. In the depicted embodiment, the distal portion towards the distal end 300b of the stent 300 is flared to form the flared portion 200f of the stent graft 200, as shown in Fig. 3c. The flared portion 200f of the stent graft 200 is formed by shape-setting the stent 300 using an exemplary method, which has been explained later.
[79] In an embodiment, the distal portion towards the distal end 300b having closed units 303 is shape-set to include a flared portion 300f. Upon flaring the stent 300, the closed units 303 at the distal portion provide structural support, facilitating controlled flaring during deployment. Thus, enhancing stability and ensuring proper the apposition to the vessel wall post-deployment. In the collapsed state, the flared portion 300f of the stent 300 may have a shape-set collapsed inner diameter and a shape-set collapsed outer diameter. In the expanded state, the flared portion 300f of the stent 300 may have a shape-set expanded inner diameter and a shape-set expanded outer diameter.
[80] In the depicted embodiment, the proximal portion towards the proximal end 300a having closed units 301 is shape-set to include the non-flared portion of the stent graft 200. The non-flared portion of the stent 300 includes a shape-set expanded outer diameter and a shape-set expanded inner diameter.
[81] Figs. 4a-4c depict a second exemplary embodiment of the stent 400. In the depicted embodiment, the stent 400 includes a proximal end 400a and a distal end 400b, thereby defining a length therebetween. The proximal end 400a and the distal end 400b aligns with the proximal end 200a and distal end 200b of the stent graft 200. The stent 400 includes a proximal section, a distal section and a middle section therebetween. The stent 400 is functionally similar to the stent 300 and also shared some structural similarities. For example, the depicted embodiment of the stent 400 includes a plurality of rows of the struts 430. The rows of the struts 430 are arranged parallelly. The plurality of rows of the struts 430 coupled in a circumferential direction to form a tubular structure of the stent 400. The arrangement of the rows of struts 430 is same as that of the rows of struts 330 of the stent 300, hence can be referred from the context of the stent 300. Similar to the stent 300, the stent 400 is configured to undergo shape-shifting between the collapsed state and the expanded state.
[82] The dimensional changes that occur in the stent 400 during the shape-shifting (including, the collapsed inner diameter, collapsed outer diameter, expanded inner diameter and expanded outer diameter) is also same as that of the stent 400, and hence is not repeated for the sake of brevity.
[83] The stent 400 includes a plurality of linkages configured to interconnect two adjacent rows of struts 430 to form a plurality of closed units (401, 403) and a plurality of open units 405. Two rows of struts 430 provided respectively in the proximal section at the proximal end 400a and distal section at the distal end 400b are interlinked by first linkages 417, thus forming the closed units (401, 403). The interlinkage is similar to the interlinkage between two rows of struts 330 at the proximal end and distal end (300a, 300b) in the stent 300, and can be referred from the context of the stent 300.
[84] The plurality of rows of struts 430 provided in the middle section (i.e., between the closed units (401, 403)) are interlinked to form a plurality of open units 405. A plurality of second linkages 420 (hereinafter referred as second linkages 420) of the plurality of linkages is configured to interlink plurality of rows of struts 430 provided between the closed units (401, 403). In an embodiment, the second linkages 420 are configured to selectively interlink peaks (p) of one row of struts 430 with a trough (t)/ peak (p) of the adjacent row of struts 430, thereby forming open units 405. The selection of interlinking peaks (p) of one row with a trough (t)/ peak (p) of the adjacent row may depend upon the requirement of the radial strength and anti-kinking property in the stent 400.
[85] In an embodiment, the stent 300 has more radial strength and anti-kinking property that the stent 400. This is due to the difference in the selection of the interlinking peaks (p) of one row of struts with the peak (p)/ trough (t) of the adjacent row of struts. Depending upon the anatomical structure of the anatomical structure of the aorta, the stent may be chosen having an appropriate radial strength and anti-kinking property.
[86] Similar to the stent 300, the stent 400 may an extension 410. The extension 410 may be provided in each closed unit (401, 403). The extensions 410 may have the same or different shape as that of the extensions 310 in the stent 300. Each extension 410 may include a marker cavity 410a. Alternatively, alternate extensions 410 may include the marker cavity 410a. The marker cavity 410a is coupled to a marker using the same technique.
[87] Similar to the stent 300, the stent 400 may be flared to form the flared portion 200f of the stent graft 200, and hence can be referred from the context of the stent 300. As shown in Fig. 4c, the distal portion of the stent 400 includes a flared portion 400f provided towards the distal end 400b, using the same exemplary method, which has been explained later. The dimensions of the flared portion 400f of the stent 400 during the shape-setting (including, the shape-set collapsed inner diameter, shape-set collapsed outer diameter, shape-set expanded inner diameter and shape-set expanded outer diameter) is also same as that of the stent 400, and hence is not repeated for the sake of brevity. In the depicted embodiment, the proximal portion towards the proximal end 400a having closed units 301 is shape-set to include the non-flared portion of the stent graft 200. The non-flared portion of the stent 400 includes a shape-set expanded outer diameter and a shape-set expanded inner diameter.
[88] Figs. 5a and Fig. 5b depict the wrapper 500 disposed around the stent (300, 400) respectively. The wrapper 500 is disposed at least on the flared portion (300f, 400f) of the stent (300, 400). In an embodiment, the wrapper 500 is longitudinally wrapped around an outer surface of the stent (300, 400) between the proximal end (300a, 400a) and the distal end (300b, 400b). In other words, the wrapper 500 is wrapped around an entire expanded length of the stent (300, 400). The wrapper 500 is configured to act as a barrier, minimizing blood seepage through the stent graft 200 while allowing necessary permeability for integration with the vessel wall.
[89] In an embodiment, the wrapper 500 includes a single sheet (not shown). The single sheet may be made of made of biocompatible materials, such as, without limitation, polytetrafluoroethylene (PTFE), silicone, expanded polytetrafluoroethylene (ePTFE), polyurethane, etc., or a combination thereof. In an embodiment, the single sheet is made of a combination of ePTFE and silicone.
[90] The ePTFE used in making the single sheet provides flexibility to the wrapper 500. The wrapper 500 is stretchable, allowing it to accommodate the expansion and collapse of the stent (300, 400) during both loading and deployment of the stent graft 200 at the target site. In other words, in the collapsed state, the wrapper 500 crimps around the stent (300, 400). And, upon deployment, the wrapper 500 regains its structure, adapting to the expanded shape of the stent (300, 400) without compromising its mechanical strength and structural integrity.
[91] Silicone provides resistance to wrapper 500 against displacement or migration. The wrapper 500 is configured to conform to the lumen of the primary stent and the natural irregularities of the aortic vessel wall. In an embodiment, the wrapper 500 has resistance to displacement or migration. In other words, the wrapper 500 provides resistivity to the stent graft 200 against displacement or migration from the deployed position in the aortic vessel. The wrapper 500 is configured to provide surface friction to prevent movement of the stent graft 200. This ensures tight seal of the stent graft 200 with the aortic vessel wall and the primary stent.
[92] The single sheet may have a predefined thickness ranging between 4500 nm and 9500 nm. In an embodiment, the predefined thickness of the single sheet is 7620 nm. The wrapper 500 includes two or more layers of the single sheet. In other words, the single sheet may be wrapped around the stent (300, 400) for plurality of times to form the wrapper 500. In an exemplary embodiment, the wrapper 500 includes 8 layers of the single sheet. The single sheet is wrapped around the stent (300, 400) using an exemplary process, which has been explained later. The wrapping process ensures uniform distribution of the sheet around the stent (300, 400), maintaining consistent thickness while preventing uneven layering. The multilayering of the single sheet provides the wrapper 500 having a predefined thickness. The predefined thickness of the wrapper 500 may range between 4500 nm and 9500 nm. In an embodiment, the predefined thickness of the wrapper 500 is 7620 nm. The multilayering of the single sheet provides a leak-proof wrapper 500 and prevent unintended fluid leakage. The multiple layers of the single sheet create a controlled permeability profile, allowing for selective fluid movement when required while ensuring structural integrity. Additionally, the multiple layering of the sheet is configured to adapt to irregularities in the vessel wall, ensuring a secure fit and reducing the risk of small leaks. Thus, the wrapper 500 is configured to provide a leak-proof stent graft 200.
[93] In an embodiment, the single sheet includes a plurality of pores. The plurality of pores (or porosity) may include a predefined size ranging between 1.5 microns and 3.5 microns. In an embodiment, the predefined size of the plurality of pores is 2.5 microns. The plurality of pores allows controlled tissue ingrowth and adaptation post-deployment, promoting long-term stability while minimizing thrombogenic risks. This ensures effective sealing of the stent graft 200 with the vessel wall and the primary stent, while maintaining sufficient structural flexibility to accommodate vessel movement and pressure variations. The plurality of pores helps balance sealing and integration, preventing leakage while allowing tissue growth.
[94] Fig. 6 illustrates a flowchart of a method 600 for fabricating the stent graft 200, according to an embodiment of the present disclosure.
[95] At step 602, a stent (300, 400) may be held or clamped onto a mandrel. For example, in the depicted embodiment, the stent (300, 400) is provided on a first mandrel 700. The first mandrel 700 has a straight profile having an outer diameter that corresponds to the expanded inner diameter of the stent (300, 400), as shown in Fig. 7a. The straight profile of the first mandrel 700 helps in maintaining consistent dimensions throughout the length of the stent (300, 400).
[96] Alternately, one of a proximal section or a distal section of the stent (300, 400) may be flared. To achieve flaring, a mandrel with a corresponding contour is chosen to achieve the desired flare in the stent (300, 400). In one depicted embodiment, the stent (300, 400) is held to a second mandrel 750, as shown in Fig. 7b. The second mandrel 750 has a first portion 750a and a second portion 750b. An outer diameter of the first portion 750a is different from an outer diameter of the second portion 750b. In the depicted embodiment, the first portion 750a is narrower than the second portion 750b of the second mandrel 750. The outer diameter of the first portion 750a corresponds to the expanded inner diameter of the proximal portion of the stent (300, 400) towards the proximal end (300a, 400a). The outer diameter of the second portion 750b corresponds to the expanded inner diameter of the distal portion of the stent (300, 400) towards the distal end (300b, 400b) (in other words, the portion (proximal/distal) that is intended to be flared, is provided on the second portion 750b of the second mandrel 750.
[97] To retain the shape of the flaring, the stent (300, 400) is heated to a first predefined temperature for a first predefined period of time. In an embodiment, the first predefined temperature ranges between 500 degrees Celsius and 510 degrees Celsius for the first predefined period of time ranging between 02 min and 06 min. In an exemplary embodiment, the stent (300, 400) is subjected to the first predefined temperature at 505 degrees Celsius for 05 minutes.
[98] Thereafter, the stent (300, 400) is allowed to cool down for a second predefined time period, at step 610. The second predefined time period may range between 01 minutes to 03 minutes. In an embodiment, the stent (300, 400) is allowed to cool down for 02 minutes. This helps in retaining the shape-set flared portion (300f, 400f) in the stent (300, 400).
[99] At step 604, a sheet made of a biocompatible material (as explained earlier) is wrapped around the stent (300, 400) that is loaded on the mandrel. The sheet is wrapped around the stent (300, 400) for a plurality of times to form layers of the sheet. In an embodiment, the wrapper 500 is formed by 8 layers of the sheet (i.e., the sheet is wrapped around the stent (300, 400) for 8 times). Thereafter, excess sheet is cut/removed.
[100] At step 606, the wrapper 500 and the stent (300, 400) are subjected to a lamination process to obtain the stent graft 200. First, a heat-shrink tube is disposed over the sheet wrapped around the stent (300, 400). Thereafter, heat is applied at a second pre-defined temperature for a second time period using a lamination apparatus. In an embodiment, the lamination apparatus is a heat gun (a device blowing hot air at varying temperature and speed). In an embodiment, the heat gun is set at the second predefined temperature, and a predefined speed for the second predefined time period. The second pre-defined temperature may range between 150˚C and 250˚C, the second time period may range from 02 minutes to 08 minutes and the predefined speed may range from 1500 and 1700. In an embodiment, the second pre-defined temperature for the second time period and speed are 200˚C, 05 minutes and 1650 Feet Per Second.
[101] The lamination process helps the wrapper 500 to conform precisely to the shape of stent (300, 400), maintaining its functionality and durability. The lamination process ensures a tight adhesion of the wrapper 500 with the stent (300, 400), preventing delamination. As heat is applied, the heat-shrink tube is configured to contract, applying an even pressure over the wrapper 500, causing the wrapper 500 to be compressed around the stent (300, 400). The compression helps bond the wrapper 500 to the stent (300, 400). The heat-shrink tube acts as a protective layer, preventing excessive heat exposure and ensuring controlled heat distribution during the lamination process, that could otherwise damage the wrapper 500.
[102] Thereafter, the laminated stent graft 200 on the suitable mandrel (the first mandrel 700 or the second mandrel 750) provided with the stent (300, 400) and the wrapper 500, is subjected to a third predefined temperature for a third predefined time period, at step 608. The third predefined temperature and the third predefined time period may range between -25˚C and -15˚C, and 02 minutes and 08 minutes, respectively. This allows the stent graft 200 obtained from the step 604 to cool down. In an embodiment, the third predefined temperature and the third predefined time period are -18˚C and 5 minutes, respectively.
[103] At step 610, the heat-shrink tube is removed. Thereafter, excess material of the wrapper 500 on the stent (300, 400) is removed and the mandrel (the first mandrel 700 or the second mandrel 750) is withdrawn, thus obtaining a stent graft 200, where the stent graft 200 has a uniform tubular structure and/or the stent graft 200 includes the flared portion 200f towards the distal end 200b.
[104] Fig. 8 illustrates a flowchart of a method 800 of delivering the stent graft 200 at a targeted region in the aortic vessel, according to an embodiment of the present disclosure.
[105] At step 802, the stent graft 200 is preloaded within a delivery system.
[106] An exemplary delivery system 900 is illustrated in Fig. 9. In the depicted embodiment, the delivery system 900 includes a catheter. The catheter includes a proximal end 900a, a distal end 900b and a distal tip 900c. In an embodiment, the catheter includes an outer sheath 902, an inner sheath 904 and a holding member 906. The outer sheath 902 has a tubular structure extending between the proximal end 900a and the distal end 900b. The outer sheath 902 is hollow from inside and defines a lumen. The inner sheath 904 has a tubular structure extending between the proximal end 900a and the distal end 900b. The inner sheath 904 is disposed within the lumen of the outer sheath 902. The holding member 906 may be provided at the distal end 900b of the catheter. The holding member 906 is disposed between the outer sheath 902 and the inner sheath 904 at the distal end 900b of the catheter. The holding member 906 may also be provided at the distal tip 900c of the catheter. The holding member 906 may be a pusher tip or a retractable clasp.
[107] For the purpose of loading the stent graft 200 within the delivery system 900, the stent graft 200 is crimped into the collapsed state.
[108] The stent graft 200 is preloaded at the distal end 900b of the catheter. The stent graft 200 is mounted on an outer surface of the inner sheath 904. In other words, the stent graft 200 is disposed between the inner sheath 904 and the outer sheath 902 at the distal end 900b. The outer sheath 902 is configured to retain the stent graft 200 in the collapsed state during navigation. The proximal end 200a of the stent graft 200 is coupled to the holding member 906. A proximal end of the holding member 906 may be provided with one or more anchoring elements (not shown). The one or more anchoring elements help in anchoring the stent graft 200 with the holding member 906. The holding member 906 is configured to provide additional support to the collapsed stent graft 200 until the outer sheath 902 is retracted during the deployment. The holding member 906 is configured to prevent premature deployment of the stent graft 200.
[109] At step 804, the distal tip 900c of the catheter is introduced into the femoral artery of the patient and is advanced through the intricate pathways of the vessel. The distal tip 900c includes a smooth surface that reduces trauma to the vessel as the catheter is advanced. It may have a tapered or atraumatic design for ease of navigation.
[110] The distal end 900b of the catheter is maneuvered in the blood vessel using a handle 950 (as shown in Fig. 9). The handle 950 may be coupled to the proximal end 900a of the delivery system 900. The handle 950 allows the operator to manipulate and maneuver the catheter within the vasculature system during the navigation. Further, the handle 950 helps in deploying the stent graft 200 at the target site. In the depicted embodiment, the handle 950 includes a luer hub 951, a hemostatic hub 953 and a one-way stop cock 955.
[111] A guidewire (not shown) is inserted into the lumen of the inner sheath 904 through the luer hub 951. The guidewire helps to position the distal end 900b of the catheter at the target site. The guidewire is introduced into the femoral artery of the patient and is advanced towards the target site through the intricate pathways of the vessel. Thereafter, the catheter is advanced in the vasculature to the target site of the primary stent graft, using fluoroscopic guidance. The distal tip 900c of the catheter follows the guidewire to reach the target site.
[112] The catheter is advanced through the vasculature to the site of the of the primary stent graft, using fluoroscopic guidance. In an embodiment, the catheter includes one or more markers (not shown). The one or more markers may be provided along a length of the outer sheath 902 of the catheter. The one or more markers of the catheter helps the operator visualize the position of the catheter using imaging techniques. The one or more markers ensure accurate placement and deployment of the stent graft 200 at the target site.
[113] The hemostatic hub 953 prevents blood leakage and stagnation, minimizing blood loss during procedures involving catheter insertion and removal. A fluid (such as, saline) is provided at the target site via the one-way stop cock 955.
[114] At step 806, upon reaching the target position, the distal tip 900c of the catheter is aligned with a tip of the guidewire with the help of fluoroscopic imaging techniques. Upon alignment of the catheter at the target site, the outer sheath 902 is gradually retracted with the help of the handle 950, exposing the stent graft 200, as shown in Fig. 10. The handle 950 may be provided with any suitable mechanism for the retraction of the outer sheath 902. The stent graft 200 remains stationary while the outer sheath 902 is pulled back (in the proximal direction) allowing the stent graft 200 to expand and engage with the vessel wall. For example, a slight retraction of the outer sheath 902 exposes the distal end 200b of the stent graft 200. Upon exposure, the distal end 200b expands and secures tight seal with the vessel wall. An entire length of the stent graft 200 gradually expands upon retracting the outer sheath 902 further.
[115] As shown in Fig. 11, in the depicted embodiment, as the stent graft 200 expands the distal portion of the stent graft 200 secures tight seal with the vessel wall. And, the proximal portion of the stent graft 200 overlaps over a distal portion of the primary stent and secure a tight seal therewith. Thereby, extending the coverage at the distal end of the primary stent to prevent blood leakage into the aneurysm site, post-expansion.
[116] At step 808, the proximal end 200a of the stent graft 200 is detached from the one or more anchoring members of the holding member 906 using a mechanism (not shown) that may be provided in the handle 950. Thereafter, the inner sheath 904 is retracted in the proximal direction and is removed from the patient’s body. Thus, deploying the stent graft 200 at the target site.
[117] 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. An extension stent graft (200) to be inserted in a primary stent, having a proximal section (200c), a distal section (200d), the extension stent graft (200) comprises:
I. a stent (300, 400) having a proximal end (300a, 400a) and a distal end (300b, 400b) defining a length therebetween, the stent (300, 400) includes a flared portion (300f, 400f) towards in one of the proximal end (300a, 400a) or the distal end (300b, 400b);
II. a wrapper (500) disposed at least on the flared portion (300f, 400f) of the stent (300, 400), configured to provide a leak-proof extension stent graft (200),
wherein, a shape-set expanded diameter of a non-flared portion of the stent graft (200) snug fits an expanded inner diameter of the primary stent.
2. The extension stent graft (200) as claimed in claim 1, wherein, the stent (300, 400) comprises:
I. a plurality of rows of struts (330, 430) extending circumferentially, and
II. a plurality of linkages configured to interlink the plurality of rows of struts (330, 430) to form:
a. a plurality of closed units (301, 303, 401,403) provided towards the proximal end (300a, 400a) and the distal end (300b, 400b); and
b. a plurality of open units (305, 405) provided between the closed units (301, 401, 303 and 403).
3. The extension stent graft (200) as claimed in claim 2, wherein each strut (330, 430) of the plurality of rows of struts (330, 430) has one of a straight profile or a curved profile.
4. The extension stent graft (200) as claimed in claim 2, wherein struts (330, 430) of each row of the plurality of rows of struts (330, 430) are arranged in one of a predefined curved chevron pattern, a zig-zag pattern, or a chevron pattern.
5. The extension stent graft (200) as claimed in claim 2, wherein the plurality of linkages comprises at least one of:
I. a plurality of first linkages (317, 417) configured to interlink two adjacent rows of struts (330, 430) of the proximal end (300a, 400a) and distal end (300b, 400b) to form the plurality of closed units (301, 303, 401,403);
II. a plurality of second linkages (320, 420) configured to interlink two adjacent rows of struts (330, 430) provided in a middle section of the stent (300, 400) to form the plurality of open units (305, 405); and
III. a plurality of third linkage (340) configured to interlink a peak (p) of one row of struts (330) with an adjacent trough (t) of an adjacent row of struts (330).
6. The extension stent graft (200) as claimed in claim 5, wherein the plurality of first linkages (317, 417) are configured to interlink each peak (p) of a first row of struts (330, 430) with an adjacent trough (t) of an adjacent second row of struts (330, 430).
7. The extension stent graft (200) as claimed in claim 5, wherein the plurality of second linkages (320, 420) are configured to interlink a peak (p) of one row of struts (330, 430) with an adjacent trough (t) of an adjacent row of struts (330, 430).
8. The extension stent graft (200) as claimed in claim 1, wherein the extension stent graft (200) includes:
I. a predefined collapsed length ranging between 30 mm and 100 mm in the collapsed state, and
II. a predefined expanded length ranging between 20 mm and 80 mm in the expanded state.
9. The extension stent graft (200) as claimed in claim 1, wherein the wrapper (500) includes a single sheet made of a biocompatible material, the biocompatible material being selected from at least one of polytetrafluoroethylene (PTFE), silicone, and expanded polytetrafluoroethylene (ePTFE), polyurethane.
10. The extension stent graft (200) as claimed in claim 1, wherein the wrapper (500) includes a single sheet wrapped around the stent (300, 400) a plurality of times to form the wrapper (500).
11. The extension stent graft (200) as claimed in claim 1, wherein, porosity of the wrapper ranges from 1.5 microns to 3.5 microns.
12. A method (600) of fabricating the stent graft (200) having a flared portion (200f) provided towards in one of a proximal end (200a) or a distal end (200b), the method (600) comprising:
I. providing a stent (300, 400) on a mandrel;
II. flaring one of a proximal end (300a, 400a) of the stent (300, 400) at a first predefined temperature for a first predefined time period;
III. wrapping a wrapper around the stent (300, 400) a plurality of times;
IV. laminating the stent with the wrapper, on the mandrel at a second predefined temperature for a second predefined time period with a heat shrink tube; and
V. cooling the laminated stent graft (200) at a third predefined temperature for a third predefined time period.
13. The method (600) of fabricating the stent graft (200) as claimed in claim 12, wherein the method (600) comprises the first predefined temperature, the second predefined temperature and the third predefined temperature range between 500 degrees Celsius and 510 degrees Celsius, 150 degrees Celsius and 250 degrees Celsius and 25 degrees Celsius and 15 degrees Celsius, respectively.
14. The method (600) of fabricating the stent graft (200) as claimed in claim 12, wherein the method (600) comprises the first predefined time period, the second predefined time period and the third predefined time period range between 2 minutes and 6 minutes, 1 minute and 3 minutes and 2 minutes to 8 minutes, respectively.