Description:TECHNICAL FIELD
[1] The present disclosure relates to medical devices, particularly to kink-resistant, self-expanding stent graft used in vascular interventions.
BACKGROUND
[2] Transjugular Intrahepatic Portosystemic Shunt (TIPS) procedures are utilized for managing complications of portal hypertension, including variceal bleeding, gastropathy, refractory ascites, and hepatic hydrothorax. TIPS procedures involve creating a shunt between the portal and hepatic veins to reduce portal pressure. The placement of stent graft during TIPS procedures presents challenges due to a curved and complex anatomy of the hepatic vasculature. The curvature between the hepatic and portal veins can lead to kinking of conventional stent grafts, resulting in reduced blood flow, increased risk of thrombosis, and potential stent graft failure. In TIPS procedures, maintaining consistent blood flow through the shunt contributes significantly to the effectiveness of the procedure and the long-term outcomes of the patient. The ability to sustain uniform blood flow impacts the overall success of the intervention and influences the post-procedural health trajectory of the patient.
[3] Several stent graft designs have been developed to address the challenges of the stent graft placement in curved vessels, including bare metal stents, covered stents, and self-expanding nitinol stents. However, limitations persist in the application of current designs to the curved vessels. For example, the bare metal stents often experience tissue ingrowth and reduced long-term patency. Further, the covered stents, while reducing tissue ingrowth, may lack the flexibility required to conform to curved anatomies without kinking. On the other hand, the self-expanding nitinol stents offer improved flexibility, but many designs struggle to maintain a consistent lumen diameter when deployed in highly curved vessels. Additionally, existing stent grafts often experience significant foreshortening during deployment, complicating precise placement and potentially necessitating multiple stents or reinterventions.
[4] Therefore, in light of the foregoing discussion, there exists a need to overcome the aforementioned drawbacks.
SUMMARY
[5] The present disclosure provides a stent graft configured to maintain patency in curved blood vessels while minimizing the risk of kinking, making the stent graft suitable for Transjugular Intrahepatic Portosystemic Shunt (TIPS) procedures and other applications involving curved vasculature. The present disclosure provides a solution to the technical problem of how to maintain an intended shape and a structure of the stent graft during the deployment of the stent graft in the blood vessels. An aim of the present disclosure is to provide a solution that overcomes at least partially the problems encountered in the prior art and provides an improved stent graft for deployment in a vascular anatomy without kinking in the regions of the vascular anatomy with significant curvature.
[6] One or more objectives of the present disclosure is achieved by the solutions provided in the enclosed independent claims. Advantageous implementations of the present disclosure are further defined in the dependent claims.
[7] The stent graft includes a tubular stent body having a proximal end, a distal end, and a lumen extending between the proximal end and the distal end. The tubular stent body includes a proximal section with a first plurality of interconnected struts forming a pattern of closed cells. The tubular stent body includes a middle section and a distal section. The middle section includes a second plurality of interconnected struts forming a pattern of crowns. The distal section includes a third plurality of interconnected struts arranged to form an open cell pattern. The third plurality of interconnected struts includes a first set of struts alternating with a second set of struts. The pattern of crowns in the middle section and, the first set of struts, and the second set of struts in the distal section are arranged such that a substantially constant internal cross-sectional area of the lumen of the tubular stent body is maintained when the stent graft is deployed in a curved vessel.
[8] The radiopaque markers in the proximal section improve the visibility of the stent graft under fluoroscopy, enabling accurate positioning during deployment. Strategically placed radiopaque markers can provide information about the orientation of the stent graft.
[9] The pattern of crowns of the giant cells formed in the middle section is configured to provide radial and columnar strength to the stent graft. The arrangement of crowns contributes to the overall radial strength of the stent graft. The giant cells enhance the kink resistance by distributing forces evenly along the length of the stent graft. The giant cells help to maintain vessel patency without exerting excessive pressure on any single point of the vessel wall. The enhanced kink resistance facilitates maintaining a constant lumen cross-section throughout the vascular curvature regions.
[10] The open cell pattern in the distal section provides longitudinal flexibility. The longitudinal flexibility is beneficial in accommodating the natural movements and pulsations of blood vessels. The alternating strut sets in the distal section, when placed in a curved vessel, respond differently to the bending forces. The differential response helps in maintaining a constant lumen cross-section throughout the vascular curvature regions. The alternating strut design in the distal section helps in reducing the overall foreshortening of the stent during deployment. As one set of struts expands, the other can compensate, helping to maintain the intended length of the stent graft.
[11] It is to be appreciated that all the aforementioned implementation forms can be combined. All steps that are performed by the various entities described in the present application, as well as the functionalities described to be performed by the various entities, are intended to mean that the respective entity is adapted to or configured to perform the respective steps and functionalities. It will be appreciated that features of the present disclosure are susceptible to being combined in various combinations without departing from the scope of the present disclosure as defined by the appended claims.
[12] Additional aspects, advantages, features, and objects of the present disclosure would be made apparent from the drawings and the detailed description of the illustrative implementations construed in conjunction with the appended claims that follow.
BRIEF DESCRIPTION OF THE DRAWINGS
[13] The summary above, as well as the following detailed description of illustrative embodiments, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the present disclosure, exemplary constructions of the disclosure are shown in the drawings. However, the present 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. Wherever possible, like elements have been indicated by identical numbers.
[14] Embodiments of the present disclosure will now be described, by way of example only, with reference to the following diagrams wherein:
FIG. 1 is a diagram illustrating a stent graft, in accordance with an embodiment of the present disclosure;
FIG. 2A is a diagram illustrating a collapsed configuration of the stent graft, in accordance with an embodiment of the present disclosure;
FIG. 2B is a diagram illustrating an expanded configuration of the stent graft, in accordance with an embodiment of the present disclosure;
FIG. 3A is an enlarged diagram illustrating a proximal section of the stent graft, in accordance with an embodiment of the present disclosure;
FIG. 3B is an enlarged diagram illustrating a middle section of the stent graft, in accordance with an embodiment of a present disclosure;
FIG. 3C is an enlarged diagram illustrating a distal section of the stent graft, in accordance with an embodiment of the present disclosure; and
FIG. 4 is an enlarged diagram illustrating the deployment of the stent graft 100 from a transjugular vein, in accordance with an embodiment of the present disclosure.
[15] In the accompanying drawings, an underlined number is employed to represent an item over which the underlined number is positioned or an item to which the underlined number is adjacent. A non-underlined number relates to an item identified by a line linking the non-underlined number to the item. When a number is non-underlined and accompanied by an associated arrow, the non-underlined number is used to identify a general item at which the arrow is pointing.
DETAILED DESCRIPTION OF EMBODIMENTS
[16] The following detailed description illustrates embodiments of the present disclosure and ways in which they can be implemented. Although some modes of carrying out the present disclosure have been disclosed, those skilled in the art would recognize that other embodiments for carrying out or practicing the present disclosure are also possible.
[17] FIG. 1 is a diagram illustrating a stent graft, in accordance with an embodiment of the present disclosure. With reference to FIG. 1, there is shown a stent graft 100, which is used for treating vascular conditions, particularly in Transjugular Intrahepatic Portosystemic Shunt (TIPS) procedures. The stent graft 100 includes a tubular stent body 102 having a proximal end 104, a distal end 106, and a lumen extending between the proximal end 104 and the distal end 106.
[18] The stent graft 100 is a medical device designed to be inserted into a body lumen or vessel to maintain patency and ensure adequate flow. The stent graft 100 is a tubular structure composed of a mesh-like arrangement of struts and links. The links connect the struts to form a pattern. The tubular stent body 102 exhibits minimal shortening during expansion. The stent graft 100 features a hybrid design to provide enhanced flexibility and resistance to kinking, particularly in highly curved anatomical regions. In accordance with an embodiment, the stent graft 100 further includes a graft layer 108 of a polymeric material covering over at least a portion of the tubular stent body 102. In some implementations, the polymeric material is expanded Polytetrafluoroethylene (ePTFE). In another implementation, the polymeric material may be a biocompatible material depending on the desired flexibility and compatibility for specific applications. The graft layer 108 provides a smooth surface to reduce the risk of blood clot formation and enhances biocompatibility while maintaining the structural integrity and functionality of the stent graft 100. In present embodiment, polymeric material ePTFE is covered on the outer part of the stent graft 100. More preferably the polymeric material ePTFE is covered both on the outer and inner side of the stent graft 100. The polymeric material ePTFE is covered with the heat shrink process. The advantage of ePTFE on both the sides is to allow smooth passes of blood flow or divert the blood flow from the hepatic to the portal vein.
[19] In operation, the stent graft 100 is initially in a collapsed configuration, constrained within a delivery catheter. In the collapsed configuration, the diameter of the stent graft 100 is significantly reduced, allowing for minimally invasive insertion into a vascular system. The stent graft 100 is inserted into the affected blood vessel through minimally invasive procedures. The stent graft 100 is released from the delivery catheter when the stent graft 100 reaches a pre-determined location. The stent graft 100 has a pullback delivery system, which results in an expanded configuration of the stent graft 100 in the affected blood vessel. The stent graft 100 is expanded towards the pre-set diameter, pressing against the vessel walls. The radial force exerted by the stent graft 100 after expansion anchors the stent graft 100 in place and maintains the patency of the vessel lumen. The stent graft 100 continues to adapt to any changes in vessel shape or movement. The balanced design between flexibility and radial strength helps in long-term kink resistance.
[20] In an implementation, the tubular stent body 102 of the stent graft 100 is configured to expand from the collapsed configuration to the expanded configuration. The stent graft 100 is longitudinally collapsed, allowing the stent graft 100 to fit within a low-profile delivery system. The struts in the different sections of the stent graft 100 are arranged closely one above another in the collapsed configuration of the stent graft 100. In the expanded configuration, the stent graft 100 radially enlarges to the pre-set diameter, with the struts moving outward to form the designed cell patterns in each section of the stent graft 100. The expansion results in achieving the full length and diameter of the stent graft 100, allowing the stent graft 100 to conform to the vessel wall and maintain patency of the lumen. The proximal section, middle section, and distal section of the stent graft 100 each expand to the pre-set dimensions. The primary application of the stent graft 100 is to treat vascular conditions, particularly in Transjugular Intrahepatic Portosystemic Shunt (TIPS) procedures.
[21] FIG. 2A is a diagram illustrating a collapsed configuration of the stent graft, in accordance with an embodiment of the present disclosure. FIG. 2A is described in conjunction with the elements of FIG. 1. With reference to FIG. 2A, there is shown a collapsed configuration of the stent graft 100.
[22] FIG. 2B is a diagram illustrating an expanded configuration of the stent graft, in accordance with an embodiment of the present disclosure. FIG. 2B is described in conjunction with the elements of FIG. 1. With reference to FIG. 2B, there is shown an expanded configuration of the stent graft 100.
[23] Referring to FIGs. 2A and 2B, the tubular stent body 102 includes a proximal section 202 with a first plurality of interconnected struts forming a pattern of closed cells. The proximal section 202 of the stent graft 100 is configured to provide enhanced anchoring and sealing capabilities. The first plurality of interconnected struts forming a pattern of closed cells in the proximal section 202 helps in maintaining radial force while reducing the vessel injury. The closed cells are connected through a first link. The interconnection of the first plurality of struts forms the first link. In accordance with an embodiment, the proximal section 202 further includes radiopaque markers 204, positioned entirely within a length 206 of the tubular stent body 102. The radiopaque markers 204 serve as visual guides during fluoroscopic imaging, assisting in the precise positioning of the stent graft 100. In an implementation, the radiopaque markers 204 in the stent graft 100 are small, highly visible components made of materials like platinum or tantalum. The radiopaque markers 204 are attached to specific points on the stent graft 100. The radiopaque markers 204 improve visibility under X-ray or fluoroscopy, allowing doctors to position the stent graft 100 precisely during implantation. Each radiopaque marker 204 has an inner radius and an outer radius. The inner radius defines the curvature of the inner surface of the radiopaque marker 204. The curvature of the inner surface of the radiopaque marker 204 interfaces with the first plurality of struts. The outer radius defines the external curvature of the radiopaque marker 204.
[24] Each closed cell is characterized by specific dimensional attributes that contribute to the overall performance of the stent graft 100. A radius is configured to provide a smooth transition from the stent graft 100 to the vessel wall. A radius of the struts at the proximal end 104 refers to the curvature at the outermost part of the proximal section 202. A placement length of the radiopaque markers 204 refers to the longitudinal distance occupied by the radiopaque markers 204 on the first plurality of struts. The placement length is carefully determined to provide adequate visibility without compromising the structural integrity or flexibility of the stent graft 100. A strut width of closed cells in the proximal section 202 balances the need for radial strength with the requirement for a low profile and flexibility. The strut width is uniform across the non-curved portions of the first plurality of struts forming the closed cells. A link length of closed cells in the proximal section 202 refers to the longitudinal distance between adjacent closed cells. The link length is optimized to provide sufficient flexibility for the stent graft 100 to conform to vessel curvature while maintaining the significant radial support and cell closure.
[25] The tubular stent body 102 includes a middle section 208. The proximal section 202 transitions into the middle section 208. The tubular stent body 102 features a pattern of crowns. The arrangement of the pattern of crowns provides radial and columnar strength to the stent graft 100. In an implementation, each crown of the pattern of crowns is formed by a set of interconnected struts from the second plurality of interconnected struts. The second plurality of interconnected struts is arranged to create a set of peaks and valleys. The links at preselected peaks or preselected valleys connect the adjacent crowns. The connection between the proximal section 202 and the middle section 208 is facilitated by a series of links that create a gradual transition in the structure of the stent graft 100. The links connect every other peak of the last row of closed cells in the proximal section 202 to the corresponding valleys of the first row of crowns in the middle section 208. The middle section 208 includes a second plurality of interconnected struts forming a pattern of crowns. The giant cells are formed by the second plurality of interconnected struts that are connected at specific angles. The giant cells enhance the kink resistance by distributing forces evenly along the length of the stent graft 100. The giant cells help to maintain vessel patency without exerting excessive pressure on any single point of the blood vessel wall. The closed cells in the proximal section 202 are larger than the giant cells in the middle section 208. Three giant cells together form a crown in the middle section 208. Each crown is connected to another crown, thereby constituting the middle section 208. Each crown is connected to another crown through a second link. The interconnection of the second plurality of struts forms the second link. Each giant cell is characterized by specific dimensional attributes that contribute to the overall performance of the stent graft 100. The giant cells have a horizontal length, measured as the distance between one end of the giant cell and a first curvature end. The first curvature end refers to the point on the giant cell where the structure first begins to curve or bend after extending horizontally. The arrangement of giant cells within the middle section 208 is further defined by an angle between the two consecutively connected struts of the giant cell. The angle formed is significant for optimizing the expansion characteristics of the giant cell and the ability to conform to vessel walls. Each giant cell has a width, defined as the thickness of the struts forming the cell. Each giant cell has an inner radius and an outer radius at the corners. The inner radius is the curvature on the inside of a corner of the giant cell, and the outer radius is the curvature on the outside of the corner of the giant cell. An angle between the two giant cells is measured between the longitudinal axes of adjacent giant cells, defining the overall arrangement of giant cells in the middle section 208. Further, each giant cell has an inclined length. The inclined length is the length of the strut measured along the angled path rather than horizontally. A total link length refers to the length of the link that connects two consecutive crowns. The total link length provides flexibility and strength to the middle section 208. Within the pattern of crowns, each crown has a horizontal length, measured as the distance between the outermost points of the crown parallel to the longitudinal axis of the stent body 102. Moreover, thickness of the strut in curvature refers to the width of the strut material at the curved portions of the crown. Finally, vertical length of the crown is the height of the crown measured perpendicular to the longitudinal axis of the tubular stent body 102.
[26] The tubular stent body 102 includes a distal section 210. The middle section 208 transitions into the distal section 210. The distal section 210 includes a third plurality of interconnected struts arranged to form an open cell pattern. The connection between the middle section 208 and the distal section 210 is facilitated by a series of links that create a gradual transition in the structure of the stent graft 100. The linking pattern follows an alternating design, where every other crown peak in the last row of the middle section 208 connects to a corresponding valley point of the first row of open cells in the distal section 210. The crowns that are not directly linked to the open cells remain free, potentially allowing for greater flexibility at the transition point from the middle section 208 to the distal section 210. The peaks of the crowns in the middle section 208 align vertically with the valley points of the open cells in the distal section 210, creating a seamless transition in the overall structure. The open cell pattern refers to the largely spaced cells arranged with one another in the distal section 210. The open cell pattern creates larger, less constrained spaces between the struts. The open cell pattern allows for increased flexibility and conformability of the stent graft 100 in the distal section 210. The third plurality of interconnected struts includes a first set of struts 212 alternating with a second set of struts 214.
[27] In an implementation, each of the first set of struts 212 and the second set of struts 214 in the distal section 210 has a length greater than the struts in the proximal section 202 and the middle section 208. The open cells in the distal section 210 are larger than the giant cells in the middle section 208 and the closed cells in the proximal section 202. The open cells help in maintaining natural blood flow patterns at the distal end 106 of the stent graft 100, reducing the blood flow disturbances. The progression from smaller to larger cells in the stent graft 100 allows for a gradual reduction in radial force from the proximal end 104 to the distal end 106, mimicking the natural decrease in vessel wall thickness and stiffness often observed in vascular anatomy. The open cells in the distal section 210 are formed by alternating the first set of struts 212 and the second set of struts 214, creating a pattern of diamond-shaped cells. The open cells are vertically aligned, with each peak connecting to the valley of the open cell above. Adjacent columns of open cells are horizontally offset from each other, creating a staggered pattern. The offset arrangement contributes to the flexibility and the ability to conform to the curved vessels. The pattern is symmetrical both vertically and horizontally, the symmetry aids in even distribution of forces and uniform expansion. Each open cell is connected to the adjacent open cell through a third link. The interconnection of third plurality of interconnected struts in distal section 210 forms the third link. The links are at points where the first set of struts 212 meets the second set of struts 214. The open cells in the distal section 210 are characterized by specific dimensional attributes that contribute to the overall performance of the stent graft 100. A length of the open cell in the distal section 210 refers to the longitudinal distance between the peak and valley of an individual open cell. The length of the open cell is calibrated to provide the right balance between flexibility and structural integrity. The open cells offer increased flexibility, allowing the distal section 210 to better conform to curved or tortuous vessel segments. A link width refers to the thickness of the connecting elements between adjacent open cells. The interconnection of the third plurality of struts in the distal section 210 forms the links.
[28] The pattern of crowns in the middle section 208 and, the first set of struts 212 and the second set of struts 214 in the distal section 210 are arranged such that a substantially constant internal cross-sectional area of the lumen of the tubular stent body 102 is maintained when the stent graft 100 is deployed in a curved vessel. The crowns in the middle section 208 have struts arranged in a manner such that the giant cells adjust themselves to collapse and expand based on the curvature of the vessel. The alternating strut pattern in the distal section 210 forms the open cells that are configured to mimic the natural vessel wall shape, thus contributing to maintaining the internal cross-sectional area of the lumen of the tubular stent body 102 constant. Maintaining the internal cross-sectional area constant is necessary for preventing kinking or folding of the stent graft 100 and ensuring consistent blood flow through the stent graft 100.
[29] FIG. 3A is an enlarged diagram illustrating a proximal section 202 of the stent graft 100, in accordance with an embodiment of the present disclosure. FIG. 3A is described in conjunction with the elements of FIGs. 1 to 2B. With reference to FIG. 3A, there is shown an enlarged diagram illustrating the proximal section 202 of the stent graft 100.
[30] In an implementation, a width M of the distal and proximal end curve strut is between 0.20 mm and 0.40mm. In an example, the distal and proximal end curve strut width M is 0.27 mm. The width M provides significant strength for the end sections of the stent graft 100.
[31] In an implementation, the proximal end strut has a radius N ranging between 0.040 mm and 0.070 mm. In an example, the radius N is 0.057 mm. In another implementation, the proximal end close cell has a length O ranging between 11 mm and 14 mm. In some examples, the length O of the proximal end close cell is 13 mm. The dimensions such as the radius N and the length O contribute to the smooth profile of the proximal end 104 of the stent graft 100. The smooth profile helps in reducing the risk of vessel injury during and after deployment.
[32] In an implementation, the radiopaque marker 204 has an inner radius P ranging between 0.20 mm and 0.40 mm and an outer radius Q ranging between 0.30 mm and 0.60 mm. In an example, the inner radius P of the radiopaque marker 204 is 0.25 mm, and the outer radius Q of the radiopaque marker 204 is 0.47 mm. The inner radius P and the outer radius Q ensure that the marker is clearly visible under fluoroscopy while maintaining a low profile.
[33] In an implementation, the radiopaque marker 204 has a placement length R ranging between 1.10 mm and 1.25 mm. In an example, the placement length R is 1.17 mm. The placement length R allows for optimal positioning of the marker for visibility during deployment and follow-up imaging.
[34] In an implementation, closed cells in the proximal section 202 has a strut width S ranging between 0.10 mm and 0.30 mm. In an example, the strut width S is 0.20 mm. The strut width S provides the significant strength for the closed cell design of the proximal section 202 while maintaining flexibility.
[35] In an implementation, the closed cells in the proximal section 202 has a link length T ranging between 1.1 mm and 1.5 mm. In an example, the link length T is 1.3 mm. The link length T allows for optimal connection between cells, contributing to the overall structural integrity and flexibility of the proximal section 202.
[36] FIG. 3B is an enlarged diagram illustrating a middle section 208 of the stent graft 100, in accordance with an embodiment of the present disclosure. FIG. 3B is described in conjunction with the elements of FIGs. 1 to 2B. With reference to FIG. 3B, there is shown an enlarged diagram illustrating the middle section 208 of the stent graft 100.
[37] In an implementation, each giant cell in the middle section 208 has a horizontal length A ranging between 1.5 mm and 3.5 mm. In some examples, the horizontal length A of the giant cell in the middle section 208 is 2.890 mm. The horizontal length A contributes to the overall flexibility and radial strength of the middle section 208.
[38] In an implementation, each giant cell in the middle section 208 has an angle B between 40 degrees and 50 degrees. In some examples, the angle B of each giant cell is 45 degrees. The angle is formed between the two consecutively connected struts. The angle formed is necessary for optimizing the expansion characteristics and the ability to conform to the vessel walls of the giant cells.
[39] In an implementation, each giant cell in the middle section 208 has a width C ranging between 120 microns and 160 microns. In some examples, the width C of each giant cell is 140 microns. The width is essential for maintaining the structural integrity of the stent graft 100 while allowing for compressibility during deployment.
[40] In an implementation, each giant cell in the middle section 208 has an inner radius D ranging between 0.03 mm and 0.06 mm. In some examples, the inner radius D of each giant cell is 0.05 mm.
[41] In an implementation, each giant cell in the middle section 208 has an outer radius E ranging between 0.025 mm and 0.029 mm. In some examples, the outer radius E of each giant cell is 0.027 mm. The inner radius D and the outer radius E contribute to the smooth profile of the stent graft 100 and the interaction with the vessel wall.
[42] In an implementation, the middle section 208 has an angle F between two giant cells that ranges between 220 degrees and 260 degrees. In some examples, the angle F between two giant cells is 245 degrees. The angle F allows for optimal cell distribution and the flexibility of the stent graft 100.
[43] In an implementation, each giant cell in the middle section 208 has an inclined length G ranging between 2.00 mm and 3.00 mm. In some examples, the inclined length G of each giant cell is 2.70 mm. The dimension of the inclined length G contributes to the ability to expand radially while maintaining longitudinal stability of the stent graft 100.
[44] In an implementation, total link length H that links two consecutive crowns is between 0.5 mm and 1.0 mm. In some examples, the total link length H is 0.80 mm. The link length H plays a significant role in maintaining the overall structure of the stent graft 100 while allowing for significant flexibility.
[45] In another implementation, each crown in the middle section 208 has a horizontal length I ranging between 4.5 mm and 6.5 mm. In an example, the horizontal length I of the crown in the middle section 208 is 6.0 mm. In yet another implementation, each giant cell in the middle section 208 is made up of struts and a thickness J of the strut in curvature is between 0.20 mm and 0.40 mm. In an example, the strut thickness J in curvature is 0.27 mm. The thickness J is significant for balancing the radial strength of the stent graft 100 with the compressibility for delivery.
[46] In an implementation, each crown in the middle section 208 has a vertical length K ranging between 5 mm and 11 mm. In some examples, the vertical length K of the crown in middle section 208 is 8.00 mm. In another implementation, a ratio of a horizontal length I to a vertical length K of each crown in the middle section 208 is between 1:1.5 and 1:2, optimizing the shape of the crown for both flexibility and radial strength. The ratio of the horizontal length I to the vertical length K of each crown in the middle section provides significant radial strength to the structure of the stent graft 100. The ratio values help in calibrating giant cells of size suitable for reducing the kink in the stent graft 100. In another implementation, each crown constituted from a set of giant cells is joined with another crown through the link with a width L between 0.30 mm and 0.60 mm. In some cases, the link width is 0.43 mm. The link width L is optimized for maintaining structural integrity while allowing for the significant flexibility of the stent graft 100.
[47] FIG. 3C is an enlarged diagram illustrating the distal section 210 of the stent graft 100, in accordance with an embodiment of the present disclosure. FIG. 3C is described in conjunction with the elements of FIGs. 1 to 2B. With reference to FIG. 3C, there is shown an enlarged diagram illustrating the distal section 210 of the stent graft 100.
[48] In an implementation, the distal section 210 has an open cell pattern of different sizes. As illustrated in FIG. 3C, there are three different lengths of open cells U, V and W. In an implementation, the length U of the open cell is between 9.00 millimetres (mm) and 11.0 mm. In some examples, the length U of the open cell is 10.0 mm. The length U of the open cell contributes to the overall flexibility of the distal section 210 while maintaining structural integrity.
[49] In an implementation, the length V of the open cell is between 7.00 mm and 8.00 mm. In some examples, the length of open cell V is 7.60 mm. The length V of the open cell helps to create a gradual transition in flexibility along the distal section 210.
[50] In an implementation, the length W of the open cell is between 7.50 mm and 9.50 mm. In some examples, the length W of the open cell is 8.90 mm. The slight variation in strut length W contributes to the asymmetric cell design, enhancing the ability to conform to irregular vessel geometries of the stent graft 100.
[51] In an implementation, each open cell constituted from a set of the first plurality of struts is joined with another open cell in the distal section 210 through the link with width X ranging between 0.200 mm and 0.270 mm. In some cases, the link width is 0.240 mm. The links connecting the open cells play a significant role in maintaining the overall structural integrity of the distal section 210 while allowing for the significant flexibility.
The specific dimensions and arrangement of struts and links in the distal section 210 work in concert to provide enhanced flexibility and conformability, particularly when the stent graft 100 is deployed in curved or tortuous vessels. The open cell pattern helps in maintaining a substantially constant internal cross-sectional area of the lumen, which is necessary for ensuring consistent blood flow and reducing the risk of kinking or folding.
[52] FIG. 4 is an enlarged diagram illustrating the deployment of the stent graft 100 from a transjugular vein, in accordance with an embodiment of the present disclosure. FIG. 4 is described in conjunction with the elements of FIGs. 1 to 3C. With reference to FIG. 4, there is shown a body 400 of a patient wherein a catheter 402 is inserted via the jugular vein and advanced towards a hepatic vein 404. The catheter 402 is further navigated into a portal vein 406 following a TIPS approach. The TIPS approach involves minimally invasive insertion of the catheter 402 through the jugular vein, which is guided under fluoroscopic imaging to reach liver 408.
[53] Referring to FIG. 4, the surgeon inserts the catheter 402, loaded with the stent graft 100 in the collapsed configuration, into the body 400 of the patient through the TIPS approach. In the collapsed configuration, the stent graft 100 has a significantly reduced diameter, constrained within the catheter 402, allowing for minimally invasive insertion into the vascular system. The catheter 402 is inserted through the jugular vein and navigated carefully into the vascular system under fluoroscopic guidance to ensure precise positioning of the stent graft 100. The distal end 106 of the catheter 402 is advanced until it reaches the hepatic vein 404. Once the catheter 402 is appropriately positioned, the stent graft 100 is released at the predetermined location using the pullback delivery system of the stent graft 100, enabling the stent graft 100 to expand radially from the collapsed to the expanded configuration. During expansion, the stent graft 100 radially enlarges to the pre-set diameter, with the struts moving outward to form the designed cell patterns. The radial force exerted by the stent graft 100 anchors it securely against the vessel walls, maintaining lumen patency and preventing kinking, even in curved vascular anatomies. The balanced design between flexibility and radial strength allows the stent graft 100 to adapt to changes in vessel shape or movement, ensuring long-term functionality. Once fully deployed, the stent graft 100 creates a stable shunt between the portal vein 406 and the hepatic vein 404, restoring proper blood flow and relieving conditions such as portal hypertension. After confirming the accurate placement and functionality of the catheter 402, the catheter 402 is carefully withdrawn from the body 400 of the patient, completing the procedure.
[54] Advantageously, the stent graft 100, when deployed, provides immediate and sustained radial strength, ensuring lumen patency in curved vascular anatomies and minimizing the risk of kinking or migration, which are critical for maintaining effective blood flow. The radial force exerted by the stent graft 100 anchors it securely against the vessel walls, preventing displacement and enabling long-term stability. The stent graft 100 adapts to vessel curvature, maintaining structural integrity while accommodating vascular shape changes during physiological movement. Upon expansion, the struts of the stent graft 100 form precise cell patterns that distribute radial pressure evenly, reducing the likelihood of vessel trauma or collapse. The balanced design of the stent graft 100 between flexibility and rigidity facilitates its application in challenging vascular conditions, particularly in TIPS procedures. The deployment process, guided by radiopaque markers, allows surgeons to precisely position the stent graft 100, ensuring optimal alignment within the affected vessel. This design enhances procedural outcomes by improving blood flow, minimizing procedural complications, and ensuring long-term patency of the treated vessel.
[55] Modifications to embodiments of the present disclosure described in the foregoing are possible without departing from the scope of the present disclosure as defined by the accompanying claims. Expressions such as "including", "comprising", "incorporating", "have", "is" used to describe and claim the present disclosure are intended to be construed in a non-exclusive manner, namely allowing for items, components or elements not explicitly described also to be present. Reference to the singular is also to be construed to relate to the plural. The word "exemplary" is used herein to mean "serving as an example, instance or illustration". Any embodiment described as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments and/or to exclude the incorporation of features from other embodiments. The word "optionally" is used herein to mean "is provided in some embodiments and not provided in other embodiments". It is appreciated that certain features of the present disclosure, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the present disclosure, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable combination or as suitable in any other described embodiment of the disclosure.
, Claims:We claim:
1. A stent graft (100) comprising:
a tubular stent body (102) having a proximal end (104), a distal end (106), and a lumen extending between the proximal end (104) and the distal end (106), wherein the tubular stent body (102) comprises:
a proximal section (202) with a first plurality of interconnected struts forming a pattern of closed cells;
a middle section (208) comprising a second plurality of interconnected struts forming a pattern of crowns; and
a distal section (210) comprising a third plurality of interconnected struts arranged to form an open cell pattern, wherein the third plurality of interconnected struts includes a first set of struts (212) alternating with a second set of struts (214),
wherein the pattern of crowns in the middle section (208) and the first set of struts and the second set of struts in the distal section (210) are arranged such that a substantially constant internal cross-sectional area of the lumen of the tubular stent body (102) is maintained when the stent graft (100) is deployed in a curved vessel.

2. The stent graft (100) as claimed in claim 1, wherein each crown of the pattern of crowns is formed by a set of interconnected struts from the second plurality of interconnected struts arranged to create a set of peaks and valleys.
3. The stent graft (100) as claimed in claim 2, wherein adjacent crowns are connected by links at preselected peaks or preselected valleys.
4. The stent graft (100) as claimed in claim 1, wherein each of the first set of struts (212) and the second set of struts (214) in the distal section (210) has a length greater than the struts in the proximal section (202) and the middle section (208).
5. The stent graft (100) as claimed in claim 1, wherein the proximal section (202) comprises radiopaque markers (204), and wherein the radiopaque markers (204) are positioned entirely within a length of the tubular stent body (102).
6. The stent graft (100) as claimed in claim 1, further comprising a graft layer (108) of a polymeric material covering over at least a portion of the tubular stent body (102).
7. The stent graft (100) as claimed in claim 6, wherein the polymeric material is expanded Polytetrafluoroethylene (ePTFE).
8. The stent graft (100) as claimed in claim 1, wherein each crown in the middle section (208) has a horizontal length between 1.5 mm and 3.5 mm and wherein each crown in the middle section (208) has a vertical length between 5 mm and 11 mm.
9. The stent graft (100) as claimed in claim 8, wherein a ratio of the horizontal length to the vertical length of each crown in the middle section (208) is between 1:1.5 and 1:2.
10. The stent graft (100) as claimed in claim 1, wherein the tubular stent body (102) is configured to expand from a collapsed configuration to an expanded configuration, and wherein the tubular stent body (102) exhibits minimal shortening during expansion.