Hybrid stent

Abstract

The stent includes a high radial force / high pressure collapse force segment and a high flexibility segment. In one embodiment, a plurality of first ring struts are connected so that each of the plurality of first rings includes a sinusoidal pattern with a plurality of peaks and valleys, and each first ring is connected to an adjacent first ring by at least one connector. The connectors extend from a ring strut of a first ring near a peak of the first ring to a ring strut of the adjacent first ring near the peak of the adjacent ring. The second stent segment includes a plurality of second rings connected to each other to form a series of second rings.

Description

Technical Field

[0001] This specification discloses stents for implantation into the body, as well as methods for delivery and / or introduction. Certain embodiments disclosed herein may be used in procedures for treating May-Thurner syndrome, and / or deep vein thrombosis, and the resulting post-thrombotic syndrome.

Background Art

[0002] May-Thurner syndrome, also known as iliac vein compression syndrome, is a condition in which compression of the common venous outflow tract of the left lower limb can cause various adverse effects including, but not limited to, discomfort, swelling, pain, and / or deep vein thrombosis (DVT), well known as blood clots. May-Thurner syndrome occurs when the left common iliac vein is compressed by the overlapping right common iliac artery, leading to blood obstruction and potentially causing blood clot formation in some individuals. Other less common variants of May-Thurner syndrome, such as compression of the right common iliac vein by the right common iliac artery, have been described.

[0003] May-Thurner syndrome is thought to account for 2-5% of lower extremity venous disorders, but is often unrecognized. However, it is generally recognized that May-Thurner syndrome is approximately three times more common in women than in men and typically manifests between the ages of 20 and 40. Patients presenting with both hypercoagulability and left lower extremity thrombosis may be at risk of having May-Thurner syndrome. To confirm the diagnosis, it may be necessary to rule out other causes of the hypercoagulable state, for example, by assessing the levels of antithrombin, protein C, protein S, factor V Leiden, and prothrombin G20210A.

[0004] In contrast to the right common iliac vein, which runs almost vertically and parallel to the inferior vena cava, the left common iliac vein takes a more horizontal course. Along this course, the left common iliac vein lies beneath the right common iliac artery, which may compress the left common iliac vein against the lumbar spine. Compression of the iliac vein is a common anatomical variation, and it is thought that about 50% of the lumen of the left iliac vein is compressed in about one quarter of healthy individuals. However, compression of the left common iliac vein is clinically significant only if such compression causes significant hemodynamic changes in venous flow or venous pressure, or leads to acute or chronic deep vein thrombosis, which will be discussed in more detail below. In addition to other problems related to compression, due to the effect of the compressive force of chronic pulsation from the artery above, fibrous protrusions within the lumen may also develop in the vein.

[0005] Due to the narrowed turbulent flow path associated with May-Thurner syndrome, affected patients may be more prone to thrombosis. Also, due to the impaired blood flow, collateral vessels often form, and most often, collaterals that traverse the pelvis horizontally are formed, connecting both internal iliac veins and potentially causing further outflow through the right common iliac vein. In some cases, vertical collaterals are formed, most often on the side of the lumbar vertebrae, which may cause neurological symptoms such as stabbing pain and numbness.

[0006] The best current ways to treat and / or manage May-Thurner syndrome vary according to the severity of the clinical findings. Leg swelling and pain are best evaluated by vascular specialists such as vascular surgeons, interventional cardiologists, and interventional radiologists, who diagnose and treat arterial and venous diseases to ensure that the cause of limb pain is properly evaluated. The diagnosis of May-Thurner syndrome is generally confirmed by one or more imaging techniques, which may include magnetic resonance venography and venography. Compressed / flattened left common iliac veins are usually identified using intravascular ultrasound because they may not be visible or detectable using conventional venography. To prevent downstream swelling or persistent pain resulting from congestion of the left common iliac vein, it is necessary to improve / increase blood flow out of the leg. Early or uncomplicated cases can be managed simply with compression stockings. Late or severe May-Thurner syndrome may require thrombolysis if there is a recently developed thrombosis, followed by iliac vein angioplasty and stenting after the diagnosis is confirmed using venography or intravascular ultrasound. Stents may be used to support the area to prevent further compression after angioplasty. However, the currently available stent placement options are subject to several complications, including severe shortening, lack of flexibility (which may over-straighten the blood vessel), vessel abrasion and eventual perforation, increased load on the stent resulting in early fatigue failure and stent deformation, and / or blood flow impairment of the overlapping left iliac artery, which may cause peripheral arterial disease. The compressed and stenosed outflow tract present in May-Thurner syndrome can cause blood stasis, which is an important factor in deep vein thrombosis.

[0007] Patients with Mayer - Turner syndrome may or may not present with thrombosis. However, even patients without thrombotic symptoms can develop thrombosis at any time. In cases where a patient has extensive thrombosis, pharmacological and / or mechanical (i.e., pharmacomechanical) thrombectomy may be required. The congestion caused by Mayer - Turner syndrome has been clearly associated with an increased incidence of deep vein thrombosis ("DVT").

[0008] Deep vein thrombosis or deep venous thrombosis is mainly the formation of blood clots (thrombi) within the deep veins of the legs. The right and left common iliac veins are common sites for deep vein thrombosis, but it also often occurs in other locations. Nonspecific symptoms associated with this condition may include pain, swelling, redness, warmth, and superficial vein congestion. Pulmonary embolism, a life - threatening complication of deep vein thrombosis, occurs when part or all of the thrombus breaks off and migrates to the lungs. Post - thrombotic syndrome, another long - term complication associated with deep venous thrombosis, is a medical condition caused by reduced venous blood returning to the heart and may include symptoms such as chronic leg pain, swelling, redness, and ulcers or varicosities.

[0009] The formation of deep vein thrombosis usually begins inside the venous valves of the calf, where the blood becomes relatively oxygen - deficient, activating certain biochemical pathways. Some medical conditions, including cancer, trauma, and antiphospholipid syndrome, increase the risk of deep vein thrombosis. Other risk factors include aging, surgery, immobility (such as that experienced by bed rest, orthopedic casts, and sitting during long - haul flights), combined oral contraceptives, pregnancy, the postpartum period, and genetic factors. These genetic factors include deficiencies of antithrombin, protein C, and protein S, the mutation of factor V Leiden, and the characteristic of having a non - O blood type. The proportion of new cases of deep vein thrombosis increases dramatically from infancy to old age, with approximately 1 in 1000 adults developing this condition each year in adulthood.

[0010] The common symptoms of deep vein thrombosis include pain or tenderness, swelling, warmth, redness or discoloration, and surface vein dilation, but about half of those with this condition have no symptoms. Signs and symptoms alone do not have sufficient sensitivity or specificity to make a diagnosis, but when considered together with known risk factors, they can help determine the likelihood of deep vein thrombosis. Deep vein thrombosis is often excluded as a diagnosis after evaluating the patient. This is because suspicious symptoms are more often due to other unrelated causes such as cellulitis, Baker's cyst, musculoskeletal injury, or lymphedema. Other differential diagnoses include hematoma, tumor, venous or arterial aneurysm, and connective tissue disease.

[0011] Anticoagulation, which prevents further clotting but does not act directly on existing blood clots, is the standard treatment for deep vein thrombosis. Other, sometimes adjunctive, treatments may include compression stockings, selective exercise and / or stretching, inferior vena cava filters, thrombolysis, and thrombectomy.

[0012] In any case, the treatment of various venous diseases, including those described above, can be improved using stents. Therefore, an improvement in stents for use in veins is desired.

Summary of the Invention

Problems to be Solved by the Invention

[0013] Accordingly, the present invention is directed to an intravascular stent that prevents one or more of the problems resulting from the limitations and drawbacks of the related art.

[0014] In an aspect of the present invention, the stent comprises a first stent segment having a first radial force / crush force RF1 and a first diameter D1, and a second stent segment having a second radial force / crush force RF2 and a second diameter D2, where RF1 > RF2.

[0015] In another aspect of the invention, the stent system comprises a first stent having a first stent segment with a radial force / crush force RF1 and a diameter D1, and a second stent segment with a radial force / crush force RF2 and a diameter D2, where RF1 > RF2, and an additional stent having a radial force / crush force RF4 and having an end region configured to overlap a portion of the second stent segment in vivo.

[0016] Another embodiment includes a method of delivering a stent having a first segment with a first radial force / crush force RF1 and a first diameter D1, and a second segment with a second radial force / crush force RF2 and a second diameter D2. The method includes clamping the stent to a catheter, the clamping step including radially compressing and expanding a plurality of rings connected by a flexible connector, placing the first segment at a target location and expanding the first segment, and then placing the second segment and expanding the second segment, where RF1 > RF2.

[0017] Further embodiments, features, and advantages of the intravascular stent, as well as the structure and operation of various embodiments of the intravascular stent, are described in detail below with reference to the accompanying drawings.

[0018] It should be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the claimed invention.

[0019] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an intravascular stent. Together with the description, the figures further serve to explain the principles of the intravascular stent described herein, thereby enabling one of ordinary skill in the art to make and use the intravascular stent.

Brief Description of the Drawings

[0020]

Figure 1

[0021]

Figure 2

[0022]

Figure 3

[0023]

Figure 4

[0024]

Figure 5

[0025]

Figure 6

[0026]

Figure 7

[0027]

Figure 8

[0028]

Figures 9A-9C

[0029]

Figure 10

[0030]

Figure 11

[0031]

Figure 12

[0032]

Figure 13

[0033]

Figure 14

[0034]

Figures 15A-15B

[0035]

Figure 16

[0036]

Figures 17A-17C

[0037]

Figure 18

[0038]

Figure 19

[0039]

Figure 20

[0040]

Figure 21

DETAILED DESCRIPTION OF THE INVENTION

[0041] Accurate placement is ideal in any medical intervention, but it is essential when the initially introduced end is in a critical area. Such areas include vascular bifurcations and branching vessels, so the implant should not enter or obstruct the vascular portions that do not require treatment. Such bifurcations exist in the inferior vena cava, and as will be described in more detail later, at this location, the inferior vena cava bifurcates into the right and left common iliac veins.

[0042] May-Thurner syndrome, or iliac vein compression syndrome, occurs in the peripheral venous system when the iliac artery compresses the iliac vein against the spine, as shown in FIG. 1. FIG. 1 shows the vertebrae, the right and left common iliac arteries near the bifurcation of the abdominal aorta, and the right and left common iliac arteries near the bifurcation of the inferior vena cava. The bifurcation generally occurs near the L5 lumbar vertebra. Thus, it can be seen that FIG. 1 shows a lower posterior view of the L5 lumbar vertebra and the bifurcation of the abdominal aorta and inferior vena cava.

[0043] As shown, a strong right common iliac artery has been compressing the iliac vein, causing stenosis of the iliac vein. This is a possible, if not typical, finding of May-Thurner syndrome. Over time, such stenosis can cause vascular scarring, which can in turn change the lumen and potentially cause outflow obstruction of the iliac-femoral vein and / or deep vein thrombosis. As noted above, venous insufficiency (i.e., a state in which blood flow through the veins is weak) can ultimately lead to various adverse medical conditions including, but not limited to, pain, swelling, edema, skin changes, and ulcers. Venous insufficiency is usually caused by venous hypertension resulting from persistent venous disorders and malfunctioning (or insufficient) venous valves. Current treatments for venous outflow obstruction include anticoagulation, thrombolysis, balloon angioplasty, and stent placement.

[0044] Figure 2 shows a standard overlap of the right common iliac artery over the left common iliac vein. The arteries shown include the abdominal aorta 1500, which bifurcates into the left common iliac artery 1501 and the right common iliac artery 1502. The veins shown include the inferior vena cava 1503, which bifurcates into the left common iliac vein 1504 and the right common iliac vein 1505. The general view shown in Figure 2 represents a view looking down on a supine patient (i.e., a view of the patient in the anteroposterior direction at the level of the bifurcation of the abdominal aorta 1500 and the inferior vena cava 1503). The relatively strong and muscular right common iliac artery 1502 overlaps over the left common iliac vein 1504, causing the vein 1504 to be pushed down and crushed against the spine, restricting blood flow and ultimately causing May-Thurner syndrome by causing thrombosis of the left common iliac vein 1504 and any portion upstream thereof (i.e., particularly the venous system of the left leg), and potentially causing partial or total clotting thereof.

[0045] Figure 3 shows a cross-section of the arteriovenous system shown in Figure 2, taken along the gray dotted line. Schematically shown are the right common iliac artery 1600, the left common iliac vein 1601, and the vertebra 1602 of the spine (presumably the L5 lumbar vertebra of the lumbar spine). As can be seen from the figure, the right common iliac artery 1600 is substantially cylindrical due to its strong muscular structure (among other potential factors). That strong muscular artery has pushed down the left common iliac vein 1601, and ultimately the left common iliac vein has almost completely lost its patency. That is, the left common iliac vein is almost completely pinched. It will be understood that May-Thurner syndrome can actually occur when the underlying left common iliac vein 1601 is pinched / crushed this severely against the vertebra 1602 of the lumbar spine. However, it will also be understood that May-Thurner syndrome can occur when the underlying left common iliac vein 1601 is pinched / crushed much less severely against the vertebra 1602. In fact, the embodiments disclosed herein are suitable for treating various degrees of May-Thurner syndrome, including complete crushing / pinching of the left common iliac vein 160 1 by the right common iliac artery 1600. Other embodiments disclosed herein are suitable for treating various degrees of May-Thurner syndrome, including those where the crushing / pinching of the underlying left common iliac vein 1601 is about 10 - 95%, about 15 - 90%, about 20 - 85%, about 25 - 80%, about 30 - 75%, about 35 - 70%, about 40 - 65%, about 45 - 60%, and about 50 - 55%, or any other crushing / pinching worthy of treatment using one or more of the devices disclosed herein, but are not limited thereto.

[0046] Generally, disclosed herein is a stent including a circumferential ring of alternately interconnected struts connected by flexible connectors. The stent may have open-cell or closed-cell configurations of various shapes formed from an expandable material. The final expanded, implanted configuration can be achieved by mechanical expansion / actuation (e.g., balloon-expandable) or by self-expansion (e.g., nitinol). Exemplary embodiments of the stents described herein are self-expanding implants including superelastic alloy materials or shape memory alloy materials, but the stents are not so limited and may be formed of balloon-expandable materials. According to aspects of the present disclosure, the expandable stent has radial forces, crush resistance, and flexibility of various sizes at different positions along the length of the stent, and at the same time, these different positions have the same or similar diameters in the expanded configuration of the stent.

[0047] As shown in FIG. 6, an exemplary stent 10 includes a high radial force / high crush force segment 14, a high flexibility segment 18, and a transition segment 22 between the high radial force / high crush force segment 14 and the high flexibility segment 18. The exemplary stent 10 shown in FIG. 6 may include a reinforcing ring 26 at the ends of the stent 10, which, for example, is adjacent to the high flexibility segment 18 (configuration shown) or adjacent to the high radial force / high crush force segment 14 (configuration not shown). In embodiments according to the principles described herein, the stent 10 having the high radial force / high crush force segment 14 and the high flexibility segment 18 may be cut from a single tube, such as nitinol, but may also be formed or cut from flat sheets that are welded to each other at their long edges to form a tubular structure. Although a transition segment is illustrated herein, it should be noted that hybrid stents without a transition segment are considered to be within the scope of the present disclosure.

[0048] Generally speaking, the radial force refers to both or either of the radial resistance force (RRF) and the chronic outward force (COF). As shown in FIG. 4, the radial resistance force is an external force acting on the stent (towards the center of the stent) around the circumference of the stent. The chronic outward force is the force exerted by the stent outward from the direction of the center of the stent. Due to the chronic outward force of the stent, the stent will apply a force to the blood vessel into which it is inserted, resist collapse, and keep the blood vessel in an open state. FIG. 5 shows the pressure resistance and breakage used in this specification. The pressure resistance and breakage is the force of the stent when receiving a flat plate load / local crushing load. The vector direction of the radial force in FIG. 6 indicates the chronic outward force, but the radial force according to the principle of the present disclosure may be the radial resistance force, which is more deeply related to the pressure resistance and breakage than the chronic outward force. The vectors shown in the figure indicate the direction and not the magnitude. The radial force and the pressure resistance and breakage may be related, but they do not necessarily drive each other. Therefore, the stent may be designed to have a high (flat plate / local) pressure resistance and breakage but not a high radial force. These attributes can be tested independently in different test configurations.

[0049] The reinforcing ring can be a region with higher rigidity / pressure resistance and breakage at the end portion of the stent. Here, "higher rigidity" means having higher rigidity / pressure resistance and breakage than a part of the stent adjacent to the reinforcing ring. A reinforcing ring with higher rigidity can achieve good inflow through the blood vessel that enters the stent and has an implant therein. Although described herein as a "reinforcing ring", the region with higher rigidity may be provided by an additional structure (such as a "ring") overlapping the end of the stent, or instead, the region forming the region with higher rigidity may be a region where the strut structure is actually strong for reasons such as the material originally being harder, having a denser cell structure, or being a thicker strut. For example, the reinforcing ring may have different stent shapes, such as different strut widths, or may simply be a completely connected ring.

[0050] An exemplary embodiment of the reinforcement ring is shown in FIG. 7. As can be seen from FIG. 7, the ring struts that make up the reinforcement ring are connected to adjacent rings by flexible connectors / bridges in a greater number than in the adjacent highly flexible segments.

[0051] Returning to the stent structure shown in FIG. 6, the length of the stent 10 having a length L0 has a high radial force segment 14 having a radial force and / or pressure resistance RF1 and a flexibility F1 along the length L1 of the high radial force / high pressure resistance segment 14. That is, the radial / pressure resistance RF1 of the high radial force / high pressure resistance segment 14 may be relatively higher than the remaining portion of the stent 10 and may be, for example, in the range of 0.75 to 1.00 N / mm. Also, the flexibility F1 of the high radial force / high pressure resistance segment 14 may be relatively lower than the remaining portion of the stent 10. Flexibility is evaluated / measured by the angle of deflection. According to the principles described herein, the high radial force / high pressure resistance segment may be designed to withstand a long-term durability (fatigue) test in a bending range of 0 to 60 degrees.

[0052] The relatively high radial force / pressure resistance segment 14 is intended to be placed intravascularly in areas of blood vessels that are prone to compression or crushing, such as the pinching / crushing of the left common iliac vein 1601 against the vertebra 1602 caused by May-Thurner syndrome, as shown in FIG. 3. The high radial force / high pressure resistance segment has a diameter D1.

[0053] The length L0 of the stent also includes a highly flexible segment 18, which has a high radial force / high pressure resistance along the length of the highly flexible segment 18 Force sensor segment 14It has relatively higher flexibility. Further, according to the principles of the present disclosure, the highly flexible segment 18 has a length L2, a diameter D2, as well as a radial force, a pressure resistance RF2, and a flexibility F2, where RF2 < RF1 and F2 > F1, whereby the highly flexible segment is more flexible than the high radial force / high pressure resistance segment 14. According to the principles described herein, the highly flexible segment may be designed to withstand a long-term durability (fatigue) test in a bending range of 0 to 140 degrees. The radial resistance RF2 of the highly flexible segment 18 may be in the range of, for example, 0.50 to 0.70 N / mm.

[0054] The length of the stent 10 may also include a transition segment 22 between the high radial force / high pressure resistance segment 14 and the highly flexible segment 18, where the transition segment 22 has a length L3, a diameter D3, as well as a radial force or radial resistance (pressure resistance) RF3, and a flexibility F3, where RF1 > RF3 > RF2 、F2 > F3 > F1. The radial force or radial resistance (pressure resistance) RF3 and the flexibility F3 of the transition segment 22 may vary over the length L3 of the transition segment 22 or may be constant along the length L3 of the transition segment 22.

[0055] Each of the high radial force / high pressure breakage segment 14, the transition segment 22, and the highly flexible segment 18 has different radial forces, pressure breakage resistance, and flexibility, which may be provided by different ring structures in each segment of the stent 10. As can be seen in FIG. 6, the high radial force segment 14 may have a relatively high periodic cell structure compared to the radial force or pressure breakage resistance of the highly flexible segment, in order to impart a desired radial force or pressure breakage resistance, and may be formed from more rigid ring struts and flexible connectors, and / or may have a more closed cell structure or other structure. For example, a higher radial strength is provided by the strut shape, thicker / wider struts, and the number of vertices around the perimeter of the stent / ring shape can increase or decrease the radial force overall, and the radial force can be increased by being configured / connected to adjacent rings via bridge connectors and more ring connectors. Similarly, the highly flexible segment 18 may have a cell structure with relatively low periodicity, may be formed from relatively flexible ring struts and flexible connectors, and / or may have a more open cell structure. The transition segment may have a cell structure that transitions the shape of the ring struts and flexible connectors of the high radial force / high pressure breakage segment to the shape of the highly flexible segment, or the transition segment may have a cell structure different from that of the high radial force / high pressure breakage segment and the highly flexible segment. In embodiments according to the principles described herein, a stent having a high radial force / high pressure breakage segment, a transition segment, and a highly flexible segment may be cut from a single tube such as nitinol, for example, but may be formed by any other suitable means.

[0056] In the embodiment of FIG. 6 shown, each segment of the stent has substantially the same diameter, such that D1≈D2≈D3. In another embodiment, the stent may taper such that D1>D2>D3. As described herein, one stent can treat the diameters of various venous blood vessels. This stent structure allows for treatment of multiple vessel sizes with a single stent because the force applied to the blood vessel is kept fairly constant over a variety of diameters (3 - 4 mm). Most conventional stents need to be specially sized to the blood vessel being treated (i.e., an oversize of 0.5 mm - 1.0 mm), so this is different from conventional stents. Thus, most conventional stents are provided in increments of 2 mm (e.g., 10 mm, 12 mm, 14 mm, etc.). The adaptable diameters according to the principles described herein simplify sizing for the physician and allow a single stent to treat a long segment of vein because the diameter of the vein generally decreases in the proximal direction.

[0057] The length L2 of the highly flexible segment 18 is intended to be longer than the length L1 of the high radial force segment, and the high radial force / high pressure breakage segment is intended to be longer than the length L3 of the transition segment.

[0058] The structure of an exemplary embodiment of a stent 110 according to the principles of the present disclosure is shown in FIG. 8. As shown in FIG. 8, the diameter DS along the stent 110 in a given ring 112 is substantially the same (D1≈D2≈D3). In the embodiment shown in FIG. 8, each of the high radial force / high pressure breakage segment (main Turner syndrome "MTS" section) 114, the transition segment (transition section) 122, and the highly flexible segment (body section) 118 has a similar cell pattern. In such cases, the radial force or pressure resistance RF of the segment may be varied by changing the thickness of the strut and / or flexible connector 132, or the angular relationship of the strut to other struts and / or flexible connectors, and / or the angulation of the flexible connector itself.

[0059] It should be noted that terms such as "vertical", "thickness", "same", "similar", and other terms related to dimensions and shapes should not be considered exact or perfect in their applicable cases. Instead, the designations related to shapes and other dimensions should be interpreted based on the allowable manufacturing tolerances and the correlation with the functional requirements of the stent 110 in which those terms are used. For example, the term "vertical" should be understood as having a reasonable amount of angular variation due to manufacturing imperfections or the actual intentional curves cut or formed in the stent design 110. Also, any thickness, width, or other dimension should be evaluated based on design tolerances and functional requirements rather than ideal measurements.

[0060] On the other hand, the thickness of the strut 128 is its radial depth, which is generally perpendicular to the width of the strut as shown in FIG. 8. The thickness of the strut 128 typically corresponds to the wall thickness of the tube (the difference between the outer diameter and the inner diameter), and after etching, grinding, and other processes, the stent 110 is laser cut from that tube. However, the stent embodiments disclosed herein are not necessarily limited to being laser cut from a cylindrical tube having a predetermined wall thickness. The stent can also be formed or cut from flat sheets that are welded to each other at their long edges to form a tubular structure.

[0061] Each of the rings 112 comprises a plurality of ring struts 128 interconnected so as to alternately form peaks or vertices 120 and valleys 124. As shown in FIG. 8, each of the ring struts 128 is generally linear. In one embodiment shown in FIGS. 8-9, the stent 110 includes a plurality of rings 112 connected by a plurality of flexible connectors 132. The rings 112 are arranged in a spaced relationship along the major axis 116 of the stent 110. The connectors 132 extend between pairs of adjacent rings 112. Each of the rings 112 and the connectors 132 comprises a plurality of interconnected struts. The dimensions and orientations of these struts are designed to provide flexibility and radial / crush stiffness in accordance with the principles of the present disclosure.

[0062] The exemplary hybrid stent 110 shown in FIG. 8 may be made from a superelastic nitinol tube according to ASTM F2063. The specifications of the stent may further be as follows after electropolishing. The AF temperature of the part is 19 degrees Celsius + / - 10 degrees. The hybrid stent may be designed to treat various iliofemoral veins in the range of 12 mm to 20 mm in size. These dimensions are exemplary and stents according to the principles of the present disclosure are not so limited.

[0063] FIGS. 9A, 9B, and 9C show details of the strut and connector structures of the high radial force / high crush force segment 114 (FIG. 9A) and the high flexibility segment 118 (FIG. 9B) of the embodiment of FIG. 8 at the position shown in FIG. 8. FIG. 9C shows the detailed dimensions of the shape of the eye 119, where a radiopaque (RO) marker is inserted to assist the physician with the introduction position of the stent under fluoroscopy.

[0064] FIG. 9A shows the ring struts 128a of the high radial force / high crush force segment 114. FIG. 9B shows the ring struts 128b of the high flexibility segment 118.

[0065] As can be appreciated, stent shortening can be particularly problematic for stent placement. In fact, more flexible stents tend to shorten more. Precise placement is desirable in any medical intervention, but it is particularly important in critical regions where the initially introduced end is located. Such regions include vascular bifurcations and branching vessels, and thus the implant should be configured so as not to enter or obstruct portions of the vessel that do not require treatment. Such bifurcations exist in the inferior vena cava, and as will be described in more detail below, at this location the inferior vena cava bifurcates into the right and left common iliac veins.

[0066] As described herein, stents according to the principles described herein include high radial force / high pressure burst segments and highly flexible segments. The high radial force / high pressure burst segments are of a more rigid construction and thus exhibit less shortening, which can result in more precise placement within the vessel in which they are implanted. FIG. 10 shows a general placement of a stent according to the principles of the present disclosure. FIG. 10 shows the inferior vena cava 1503 bifurcating into the left common iliac vein 1504 and the right common iliac vein 1505. The general view shown in FIG. 10 represents a view looking down on a supine patient (i.e., a view of the patient in the anterior-posterior direction at the location of the bifurcation of the inferior vena cava 1503). For simplicity, the abdominal aorta and its branches are not shown in FIG. 10 but are shown in FIG. 2 above. In the embodiments described herein, the peak and valley configurations (e.g., when used in highly flexible segments) may not shorten appreciably.

[0067] As shown in FIG. 10, a multi-segment stent 10 according to the principles described is placed in the left common iliac vein 1504. The high radial force segment 14 of the stent 10 may extend into the iliac vein 1503, but the end of the high radial force segment is intended to be placed at the junction of the left common iliac vein 1504 and the iliac vein 1503. The highly flexible segment 18 extends away from the high radial force segment 14 and the transition segment 22 between the highly flexible segment 18 and the high radial force / high pressure burst segment 14.

[0068] To facilitate placement of the stent 10 at the junction of the left common iliac vein 1504 and the iliac vein 1503, the stent 10 may have a flared end adjacent to the high-diameter direction force segment 14, as shown in FIG. 11. The distal flared section is controlled by a radius "r". Exemplary flare sizes include 2.5 mm × 5.0 mm and 5.0 mm × 5.0 mm, but the stent flare according to the principles of the present disclosure is not so limited. The flared distal end of the stent is Left It may be used to place a stent at the bifurcation of two blood vessels, such as the common iliac vein 1504 and the iliac vein 1503. The stent configuration pre-embedded in the delivery system described herein allows the distal flared section of the stent to be partially introduced from the delivery system, enabling the operator to position the flared section of the stent at the bifurcation of the two blood vessels. The delivery catheter is advanced to the center of the blood vessel bifurcation to be treated, in this case the left common iliac vein 1504. If a radiopaque marker is provided on the implant, the operator can use the radiopaque marker to seat the flared section of the partially introduced stent at the bifurcation junction. When the central flared end of the partially introduced stent reaches the appropriate introduction position and seats at the bifurcation junction, the remaining part of the stent can be introduced.

[0069] In an aspect of the invention, a separate expandable stent 50 may be included with the stent 10. An embodiment of the separate expandable stent 50 is shown in FIG. 12. As shown in FIG. 12, the separate expandable stent 50 is tubular and may be a highly flexible segment similar to the highly flexible segment 18 of the hybrid stent 10 described above. In an aspect of the present disclosure, the separate expandable stent 50 may include a plurality of rings 152, which include a plurality of ring struts 158 interconnected to alternately form crests or vertices 160 and valleys 164. As shown in FIG. 12, each of the ring struts 158 is generally linear. The ring struts 158 may be connected to flexible connectors 162. The rings 152 are arranged in a spaced relationship along the long axis 116 of the stent 110. The flexible connectors 162 extend between pairs of adjacent rings. The separate expandable stent 50 may also include reinforcing rings at either or both ends of the tube. The dimensions and orientations of these struts are designed to provide flexibility and radial / crush stiffness according to the principles of the present disclosure. Each of the rings 152 and the connectors 162 includes a plurality of interconnected struts. The separate expandable stent is made from an expandable or self-expanding material such as nitinol. The separate expandable stent 50 may be cut from a single tube such as nitinol, for example, but may also be formed or cut from a flat sheet that is welded together at the long edges to form a tubular structure.

[0070] An exemplary expandable stent is shown in FIG. 13. The expandable stent shown in FIG. 13 may be made from a superelastic nitinol tube according to ASTM F2063. The specifications of the stent may further be as follows after electropolishing. The AF temperature of the part is 19 degrees Celsius + / - 10 degrees. The expandable stent may be designed to treat various iliac femoral veins in the range of 8 mm to 16 mm in size. These dimensions as well as the dimensions shown in the figure are exemplary and stents according to the principles of the present disclosure are not so limited.

[0071] As shown in FIG. 14, a separate expandable stent 50 is disposed in the left iliac vein 1504 adjacent to the highly flexible segment 18 of the hybrid stent 10 and may overlap the end of the hybrid stent 10. The overlapping region in the figure is indicated by reference numeral 200. The placement of the hybrid stent 10 and the separate expandable stent 50 may be performed simultaneously using the same delivery device. A second delivery catheter with the expandable stent pre-crimped may be introduced into the treatment vessel and may approach the proximal end of the previously introduced hybrid stent. The catheter with the expandable stent crimped thereon is inserted into the proximal end of the hybrid stent and positioned, and the stent is introduced using radiopaque markers on both stents so that, for example, a suitable overlap of 1 cm is achieved. In another aspect, the expandable stent can be implanted as a separate stent.

[0072] The expandable stents described herein may be used in combination not only with the hybrid stent 10 but also with other stents as "main stents". When used, the expandable stents can be used to allow for variations in placement.

[0073] Furthermore, the expandable stent may include a reinforcing ring, where the reinforcing ring can be a region of higher rigidity / resistance to pressure collapse at the end portion of the stent. Here, "higher rigidity" means having higher rigidity than a portion of the stent adjacent to the reinforcing ring. A reinforcing ring having higher rigidity can achieve good inflow through the blood vessel into which the stent is inserted and which has an implant therein. The reinforcing ring can, for example, facilitate the placement of the expandable stent relative to the main stent by alleviating the crushing of the ends when the expandable stent and the main stent are overlapped. Further, to facilitate placement, the ends of the expandable stent and / or the ends of the stent adjacent to which the expandable stent is to be placed may be coated with a polymer such as urethane or PTFE. Also, the expandable stent may include fixtures, eyelets, radiopaque markers, or other features to assist in the placement of the expandable stent. The expandable stent may also be delivered together with the main stent or separately into the blood vessel.

[0074] The expandable stent may be delivered through a suitable access site (e.g., the neck, popliteal fossa, etc.). The expandable stent can be made to be "bidirectional", whereby it can be pre-loaded into the delivery catheter without particular regard to the direction of delivery (e.g., the neck, popliteal fossa, etc.). For example, delivery can be performed from above or from below the treatment area. Such bidirectionality can be facilitated by making the shape of the expandable stent symmetric such that the ends of the expandable stent have the same shape. The stent may be delivered by a coaxial delivery catheter. In another aspect of the present disclosure, the novel delivery device may include a cartridge that can be incorporated into the catheter and a hybrid stent that is also incorporated into the catheter. The operator can reverse the cartridge so that it moves backward or forward. The stent may be pre-loaded into the delivery catheter in the direction of delivery (e.g., the neck, popliteal fossa, etc.).

[0075] For clarity, the stent 10 includes a first section having a relatively higher radial force or burst resistance than a second section of the stent, and as long as the second section has a relatively higher flexibility than the first section, the actual ring shape of the stent may differ from that disclosed herein. Also contemplated is that a separate expandable stent 50 may have a flexibility similar to that of the highly flexible segments of the hybrid stent 10. Exemplary stent shapes for segments of the hybrid stent 10 and the expandable stent 50 are taught in U.S. Patent Application Nos. 15 / 471,980, and 15 / 684,626, which are hereby incorporated by reference herein for all purposes as if fully set forth herein.

[0076] FIGS. 15A and 15B show "cut-away" views (plan views / flat views) of an exemplary embodiment of a high radial force / high burst force segment of a stent in a compressed state, according to the principles of the present disclosure. FIG. 15A shows the stent shape of a high radial force / high burst force segment 214 of a stent, according to the principles described herein. FIGS. 15A and 15B show exemplary high radial force / high burst force segments in a compressed state. FIG. 15B shows an enlarged view of the apex of the high radial force / high burst force segment of the embodiment shown in FIG. 15A, according to the principles of the present disclosure. The exemplary high radial force / high burst force segment 214 includes a plurality of rings 212 connected by a plurality of connectors 232. The rings 212 are arranged in a spaced relationship along the long axis of the high radial force / high burst force segment 214 of the stent. The connectors 232 extend between pairs of adjacent rings 212. Each ring 212 comprises a plurality of interconnected struts 228. The dimensions and orientations of these struts are designed to provide a relatively high radial force / burst force such that the stent segment has a higher burst resistance than adjacent transition segments or highly flexible segments (see FIGS. 6 and 8).

[0077] Each ring 212 consists of a plurality of ring struts 228 interconnected to alternately form peaks or vertices 240 and valleys 242. As shown in FIGS. 15A and 15B, each ring strut 228 is generally linear and has a major strut width 224 and a strut length 230. The major strut width 224 is the width of the strut adjusted to be approximately perpendicular to the edge of the strut in the circumferential direction. In other words, the major strut width 224 is a measurement from edge to edge corresponding to the outermost circumferential surface of the strut of the ring 212.

[0078] Each connector 232 itself consists of a connector strut 234. In this embodiment, the connector is a single connector strut 234, but the design of the connector is not necessarily limited to a single strut. As shown in FIG. 15A, the end 236 of each connector strut 234 is connected to each ring strut 228. Each of the plurality of connector struts 234 extends from the end of the connector strut 234 connected to the respective ring strut 228 of each ring 212 towards the adjacent ring 212. The connector strut 234 extends in a direction that is neither parallel nor perpendicular to the longitudinal axis of the high-diameter-direction force / high-pressure breaking force segment 214 of the stent. As shown in FIG. 15A, in this aspect of the high-diameter-direction force segment of the illustrated embodiment, the connector 232 is connected to the ring strut 228 of an adjacent ring that is offset in the latitude direction from the original ring strut that extends. That is, as shown, the connector 234 is connected from the ring strut 228 as a starting point to the ring struts of the two rings on the other side from the immediately adjacent ring strut, and in the illustrated embodiment, there are two unconnected vertices between the two connected vertices. In other words, in some embodiments, each ring strut 228 is not necessarily connected by a connector to another ring strut of an adjacent ring. In another aspect, each vertex 240 can be connected to the vertex 240 of the adjacent ring 212. In some cases, as shown in detail in FIG. 15B, the connection to the vertex can be made by a connector 232 that is offset from the actual apex of the vertex 240. In some embodiments, the connector 232 is not directly connected to or at the vertex 240 of the ring 212. Instead, the connector 232 is offset somewhat along the length of the ring strut 228 to which it is connected. Also, in some embodiments, as shown in FIG. 15A, the connectors 232 on both sides of the ring 212 are "wound" in opposite directions (e.g., clockwise and counterclockwise) in a compression configuration.

[0079] Similar to the exemplary ring strut 228, the connector strut 234 has a relatively constant width except at the connection points to the ring 212. Similar to the ring strut 228 described above, the width of the connector strut 234 may increase somewhat as it integrates with the connection to the ring 212. As shown in FIG. 15B, for example, each connector 232 also includes a main connector width 256 (between the arrows) and an apex connector width 258 (between the arrows). The main connector width 256 is Ring · the width of the strut 228, which is typically the minimum width of the strut between the ring 212 and the connector apex 240, or the width presenting the most flexible region. The apex connector width 258 is the width of the connector apex 240 at any location along its bend, for example at the center of the bend. In either case, the apex connector width 258 can be the region that structurally presents the high flexibility of the connector apex 240.

[0080] FIG. 16 shows an exemplary embodiment of the high radial force / high pressure breakage segment of the stent in the expanded state according to the principles of the present disclosure. As shown in FIG. 16, when the compressed high radial force segment 228 shown in FIG. 15A is expanded, due to the design of the length of the connector 232, the rings 212 rotate such that the apexes of each ring 212 are circumferentially aligned between the apexes of the adjacent rings 212. In some embodiments, such as larger stents (e.g., with an outer diameter in the range of approximately 16 - 20 mm), the flexible connector between the MTS section and the transition section may have a "linear" connector (in the expanded state), e.g., a connector that extends substantially axially of the stent. Another embodiment, such as a smaller stent (e.g., with an outer diameter in the range of approximately 12 - 14 mm), may have an inclined Connector , for example, extending in a direction that is not substantially axial of the stent Connector . Although these embodiments are mentioned here, it is possible for stents of any size to have "linear" connectors and / or "inclined" connectors in the expanded state.

[0081] FIG. 17A shows a plan view / flat view of an exemplary embodiment of a flexible segment and an exemplary embodiment of a reinforcing segment of a stent in a compressed state according to the principles of the present disclosure. FIG. 17B shows an enlarged view of the apex of the flexible segment of the embodiment shown in FIG. 17A according to the principles of the present disclosure. FIG. 17C shows an enlarged view of the apex of the reinforcing ring of the embodiment shown in FIG. 17A according to the principles of the present disclosure.

[0082] As shown in FIG. 17A, an exemplary flexible segment 318 includes a plurality of rings 312 connected by a plurality of connectors 332. The rings 312 are arranged in a spaced relationship along the major axis of the flexible segment 318 of the stent. The connectors 332 extend between pairs of adjacent rings 312. Each ring 312 consists of a plurality of interconnected struts 328. The dimensions and orientations of these struts are designed to provide relatively high flexibility such that the stent segment has higher flexibility than adjacent transition segments or high radial force / high pressure break segments (see FIGS. 6 and 8).

[0083] Each ring 312 consists of a plurality of ring struts 328 interconnected to alternately form peaks or apices 340 and valleys 342. As shown in FIGS. 17A and 17B, each ring strut 328 is generally linear and has a major strut width 324 and a strut length 330. The major strut width 324 is the width of the strut adjusted to be approximately perpendicular to the edge of the strut in the circumferential direction. In other words, the major strut width 324 is the edge-to-edge measurement corresponding to the outermost circumferential surface of the strut of the ring 312.

[0084] Each connector 332 itself consists of a connector strut 334. In this embodiment, the connector 332 is a single connector strut 334, but the design of the connector is not necessarily limited to a single strut. As shown in FIG. 17A, the end 336 of each connector strut 334 extends from the valley 342 to the apex of the adjacent ring 312. In an exemplary embodiment, the connector strut 334 extends in a direction substantially parallel to the longitudinal axis of the flexible segment 318 of the stent. As shown in FIG. 17A, in this aspect of the flexible segment of the illustrated embodiment, the valleys 342 are connected by connectors 332 to the apexes 340 of the adjacent rings 312 in groups of four. That is, as shown, three adjacent valleys are not connected by connectors 332 to the adjacent rings. In other words, in some embodiments, each valley is not necessarily connected by a connector to the apex 340 of the adjacent ring. In another aspect, it is possible for each valley 342 to be connected to the apex 340 of the adjacent ring 312. Although not shown, in some embodiments, the connector 332 may not be directly connected to or at the valley 342 or apex 340 of the ring 312. Instead, the connector 332 is somewhat offset along the length of the ring strut 328 to which it is connected. Also, in some embodiments, as shown in FIG. 15A, the connectors 332 on both sides of the ring 212 are "wound" in opposite directions (e.g., clockwise and counterclockwise).

[0085] Similar to the ring strut 328 of the exemplary embodiment, the connector strut 334 has a relatively constant width except at the connection points to the ring 312. The width of the connector strut 334 may increase somewhat as it integrates with the connection to the ring 312. FIG. 18 shows an exemplary embodiment of the flexible segment 318 of the stent in an expanded state according to the principles of the present disclosure.

[0086] The exemplary reinforcement ring segment 426 includes a plurality of rings 412 connected by a plurality of connectors 432. The rings 412 are arranged in a spaced relationship along the long axis of the reinforcement ring 426. The connectors 432 extend between pairs of adjacent rings 412. Each ring 412 consists of a plurality of interconnected struts 428. The dimensions and orientations of these struts are designed to provide a relatively large radial force so that the stent segment has a higher pressure resistance than adjacent transition segments or highly flexible segments (see FIGS. 6 and 8). This figure shows the connector 432 as being horizontal / parallel to the axial direction of the stent, but the connector 432 may be inclined, and the adjacent rings may be oriented such that the vertices between the rings are not aligned as shown in FIG. 21. This connection pattern may be used at the end rings of the expandable stent 50.

[0087] Each ring 412 consists of a plurality of ring struts 428 interconnected to alternately form peaks or vertices 440 and valleys 442. As shown in FIGS. 17A and 17C, each ring strut 428 is generally linear and has a main strut width 424 and a strut length 430. The main strut width 424 is the width of the strut adjusted to be approximately perpendicular to the edge of the strut in the circumferential direction. In other words, the main strut width 424 is the edge-to-edge measurement corresponding to the outermost circumferential surface of the strut of the ring 312.

[0088] Each connector 432 itself consists of a connector strut 434. In this embodiment, the connector 432 is a single connector strut 434, but the connector design is not necessarily limited to a single strut. As shown in FIG. 17A, the end 436 of each connector strut 432 extends from the vertex 440 to the vertex 440 of the adjacent ring 412. In an exemplary embodiment, the connector 432 extends in a direction substantially parallel to the longitudinal axis of the reinforcing ring 412 of the stent. As shown in FIG. 17A, in this aspect of the reinforcing segment 426 of the illustrated embodiment, all vertices 440 are connected by the connector 432 to the vertices 440 of the adjacent ring 412. In other words, in some embodiments, each vertex is connected by the connector 432 to the vertex 440 of the adjacent ring. In another aspect, it is conceivable that not all vertices 440 are connected to the vertices 440 of the adjacent ring 412. Although not shown, in some embodiments, the connector 432 may not be directly connected to or at the vertex 440 of the ring 412. Instead, the connector 432 is somewhat offset along the length of the connecting ring strut 428.

[0089] Similar to the ring strut 428 of the exemplary embodiment, the connector 432 has a relatively constant width except at the connection points to the ring 412. The width of the connector strut 432 may increase somewhat as it is integrated into the connection to the ring 412 or the ring vertex 440. FIG. 18 shows an exemplary embodiment of the reinforcing ring segment 426 of the stent in an expanded state according to the principles of the present disclosure.

[0090] FIG. 17A also shows a transition portion where the flexible segment 318 is connected to the reinforcing segment 426. As shown by the connection of the third ring 512 from the right in FIG. 17A, the connector 332 extends from the ring 312 of the flexible segment 318 starting from the valley 340 and is connected to the apex 540a of the adjacent ring 512 (the second ring from the right in FIG. 17A). On the opposite side of the ring 512, each apex 540b of the ring 512 is connected to the apex 440 of the adjacent ring 412. Thus, the transition from the flexible segment 318 to the reinforcing segment 426 is realized.

[0091] The hybrid stent 510 having separate segments with different radial force / crush force and flexibility according to the principles described herein can benefit from a smooth transition between the segments. In this aspect of the hybrid stent, the high radial force / high crush force segments may include rings designed to rotate relative to each other along the length of the stent, and the transition regions and flexible regions where the stent opens more uniformly may not need to rotate. Thus, to address the crimping and deployment problems that occur when the last ring of the high radial force / high crush force segment is twisted and causes twisting in the adjacent transition / flexible segment region, one aspect can enable a smooth transition between two adjacent regions / segments of the stent. FIG. 19 shows an embodiment of the transition between segments, which can connect a segment having rotating / twisting rings when crimped / crimped or during expansion during deployment to a segment having additional means that are flexible but not twisted. FIG. 19 shows a linear connection transition from a rotating segment (left), such as the high radial force segment 518, to a non-rotating segment (right), such as the transition segment 522. The linear connection in this exemplary embodiment includes a plurality of linear connectors 532. The linear connection at its junction enables uniform crimping and reduces or eliminates twisting and crimping problems.

[0092] FIG. 20 shows an exemplary connection between a high radial force segment (MTS segment) (left) 618 and a transition section (right) 622 according to the principles described herein, which connection may be applicable to smaller hybrid stents, such as stents of 12-14 mm. However, the illustrated connection, and each of the corresponding segments illustrated, are of one stent configuration.

[0093] It should be noted that rings and struts of flexible connectors having structures that include regions of expanded or reduced width or thickness may be used, taking into account venous applications. As another example, it should be noted that venous applications benefit from a configuration that improves flexibility while maintaining sufficient rigidity to resist the pressure exerted on the venous structure in selected regions (such as May-Thurner syndrome) due to the higher elasticity of venous applications.

[0094] In particular, the stents herein are not necessarily limited to venous applications unless explicitly required by the claims. The disclosed stents can be utilized, for example, in arterial and biliary applications. However, the disclosed stents are particularly suitable for the need for a relatively soft structure that defines a lumen that undergoes much more bending, twisting, elongation, and other torsions and loads than a typical arterial lumen.

[0095] To introduce the implant, the implant may be radially compressed / crimped to a smaller diameter and incorporated onto / into a delivery catheter. The implant may be crimped to cover a balloon of an inner core of the delivery system, and the balloon may then be inflated to expand the crimped implant to the desired diameter.

[0096] Implants such as those described above advantageously provide an adaptable diameter and / or flexibility to accommodate the dynamic movement of the peripheral veins of the leg / pelvis, thereby facilitating the treatment of both iliac vein compression syndrome and iliofemoral vein outflow obstruction.

[0097] Rather than straightening the blood vessel with a stent, it may be desirable to have a stent that conforms to an existing venous pathway. It may also be desirable to have a high radial / crush stiffness of the stent so as to resist crushing of the stent under the crushing load and to maximize the resulting diameter of the blood vessel treated at the stent introduction location. In most stent configurations, there is a direct relationship between the radial stiffness and the axial stiffness.

[0098] Common commercially available balloon-expandable stents undergo a dramatic change in length since a balloon is used to expand the stent within the blood vessel. Common commercially available self-expandable stents do not undergo as dramatic a change in length, but there is still a substantial change, which increases as the length of the stent increases. Since the length changes between the configuration within the delivery system and when introduced into the blood vessel, it becomes difficult to accurately position / land the stent at the target location. When the stent is delivered in its crimped configuration and then introduced or expanded, the shortening of the length causes the target introduction location of the stent to have to be displaced from the target deployment location. The magnitude of this effect depends on the cross-section of the lumen along the length of the target deployment location and is neither controllable nor easily predictable (the cross-section is frequently unexpectedly affected by remaining stenosis, abnormal shapes due to external objects, and / or forces, etc.). When the target lesion connects to the junction of the left and right iliac bones entering the IVC, this makes it difficult to place the stent so that it is fully deployed within the iliac bone along the entire length to the junction to the inferior vena cava without crossing the inferior vena cava. By placing a high radial force / high crush force segment at the junction, it is not only easier to cope with crushing due to May-Thurner syndrome, but it is also easier to reduce the shortening from the target location.

[0099] The embodiments disclosed herein can be used in both balloon-expandable and self-expandable stent designs. This stent design can be used in any stent intervention treatment, including coronary artery, peripheral vascular, carotid artery, nerve, bile duct, and especially venous applications. Further, this may also be beneficial for stent-grafts, percutaneous valves, and the like.

[0100] Currently available implants are typically incorporated and held in a delivery system in a crimped configuration and then navigated and introduced into the desired anatomical location where the implant is expanded into an implanted configuration. The final implanted configuration can be achieved by mechanical expansion / actuation (e.g., balloon-expandable) or self-expansion (e.g., nitinol). Self-expandable implants are manufactured from superelastic or shape memory alloy materials. The accurate and precise introduction of self-expandable implants can be difficult due to several inherent design attributes associated with self-expandable implants. The implant may pop out / advance from the distal end of the delivery system during introduction due to the elastic energy of the accumulated material. Further, the implant may shorten during introduction due to the change in the diameter of the implant from the crimped configuration to the expanded configuration. Finally, physiological and anatomical configurations, such as placement at or near a bifurcation of a body lumen, can affect the accurate placement of the implant. When the implant is placed within a body lumen, there is a risk that the expansion may be uneven or that the implant may not be circumferentially juxtaposed with respect to the body lumen, which can result in movement, migration, or in certain severe cases, implant embolization.

[0101] In some embodiments, self-expandable implants are provided that have a radial force or crush resistance sufficient to resist constant compression of a body lumen and are designed to achieve optimal fatigue resistance, accurate placement, and in-body fixation to prevent movement / migration. Further, various introduction methods and implantation methods are provided for treating iliac vein compression syndrome and venous insufficiency diseases.

[0102] In some embodiments, the implant includes an intentionally designed venous implant intended to locally treat compression of the iliac vein (May-Thurner syndrome). The implant may be relatively short in length (~60 mm) and may be manufactured from self-expanding nitinol with incorporated fixation features to assist in accurate placement and reduce migration after implantation. The implant and delivery system are designed to enable accurate introduction and placement at the bifurcation where the inferior vena cava becomes the left and right common iliac veins.

[0103] As another feature, the stents disclosed herein can include, for example, fixation members, radiopaque markers, or eyes, as described in co-pending U.S. patent applications Ser. Nos. 15 / 471,980 and 15 / 684,626, which are hereby incorporated by reference in their entirety for all purposes as if fully set forth herein.

[0104] Although the invention has been disclosed in the context of certain embodiments and examples, it will be understood by those skilled in the art that the invention extends beyond the explicitly disclosed embodiments to include other alternative embodiments and / or uses of the invention, as well as their obvious modifications and equivalents. Further, while multiple variations of the invention have been shown and described in detail, other modifications within the scope of the invention will be readily apparent to those skilled in the art based on this disclosure. Various combinations or sub-combinations of the specific features and aspects of the embodiments may be made, and these are still intended to be within the scope of the invention. Accordingly, it should be understood that the various features and aspects of the disclosed embodiments can be combined with or substituted for one another to form various modes of the disclosed invention. Thus, the scope of the invention herein should not be limited by the specific disclosed embodiments described above, but should be determined only by a fair reading of the following claims.

[0105] Similarly, no claim is to be construed as reflecting an intention that it requires more features than those expressly recited in that claim. Rather, as the following claims reflect, aspects of the invention lie in combinations of fewer features than all of the features of any one of the previously disclosed embodiments. Accordingly, the claims following the description of embodiments for carrying out the invention are expressly incorporated into this description of embodiments for carrying out the invention, and each claim stands on its own as a separate embodiment.

[0106] Although various embodiments of the present invention have been described above, it should be understood that these have been presented by way of example only, and not of limitation. It will be apparent to those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention. Accordingly, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only by the following claims and their equivalents.

Claims

1. A first stent segment comprising a plurality of the first rings interconnected to form a continuous first ring; A second stent segment comprising a plurality of the second rings interconnected to form a continuous second ring; A stent comprising: The first ring comprises a plurality of first ring struts interconnected such that each of the plurality of first rings includes a sine wave pattern having a plurality of vertices and valleys, and each first ring is connected to an adjacent first ring by at least one connector, the connector extending from a ring strut of the first ring to a ring strut of the adjacent first ring from a position offset from the actual apex of the apex of the first ring to a position offset from the actual apex of the apex of the adjacent first ring. The second stent segment is connected to the first stent segment; The first stent segment has a first stiffness and a first pressure resistance, and the second stent segment has a second stiffness and a second pressure resistance, wherein the first stiffness is different from the second stiffness, and the first pressure resistance is different from the second pressure resistance; A plurality of second ring struts interconnected such that each of the plurality of second rings includes a sine wave pattern having a plurality of vertices and valleys, and each second ring is connected to an adjacent second ring by at least one second connector, the second connector extending from a valley of the second ring to the apex of the adjacent second ring. The second ring is provided with a plurality of second ring struts; The at least one connector extends in a direction non-parallel to the longitudinal axis of the first stent segment; Stent.

2. The stent according to claim 1, further comprising at least one reinforcing ring connected to one of the first rings or one of the second rings so as to be an end ring of the stent, the at least one reinforcing ring having a third stiffness and a third pressure resistance, wherein the third stiffness is different from the first stiffness and the second stiffness, and the third pressure resistance is different from the first pressure resistance and the second pressure resistance.

3. The stent according to claim 1, wherein the first stent segment and the second stent segment have substantially the same diameter in the expanded state.

4. The stent according to claim 2, wherein the first stent segment, the second stent segment, and the reinforcing ring have substantially the same diameter in the expanded state.

5. The stent according to claim 1, wherein each first ring is connected to an adjacent ring by a number of connectors that is less than the number of vertices of each first ring.

6. The stent according to claim 1, wherein in the compressed state, at least one of the connectors passes through at least one vertex of the adjacent ring and extends to a connection point on the ring strut of the adjacent first ring.

7. The stent according to claim 1, wherein in the compressed state, the connectors on both sides of the first ring are wound in opposite directions.

8. A plurality of reinforcing ring struts connected such that at least one reinforcing ring includes a sine wave pattern having a plurality of vertices and valleys, the at least one reinforcing ring further comprising an additional reinforcing ring connected to the at least one reinforcing ring by a reinforcing connector, the reinforcing connector extending from a vertex of the at least one reinforcing ring to a vertex of the additional reinforcing ring, the stent according to claim 2.

9. The stent according to claim 8, wherein each vertex of the at least one reinforcing ring is connected to the additional reinforcing ring by a reinforcing connector.

10. The stent according to claim 1, wherein the second stent segment is connected to the first stent segment by a substantially straight connector that connects one of the plurality of second rings to an adjacent one of the plurality of first rings.

11. The stent according to claim 10, wherein the second ring comprises a plurality of second ring struts connected such that each of the plurality of second rings includes a sine wave pattern having a plurality of vertices and valleys, and a vertex of the adjacent one of the plurality of first rings is connected to a vertex of the one of the plurality of second rings by the substantially straight connector.

12. A plurality of vertices of one of the adjacent first rings among the plurality of first rings are connected to a plurality of vertices of one of the second rings among the plurality of second rings, and each vertex of one of the adjacent first rings among the plurality of first rings is connected by the substantially linear connector to a corresponding vertex among the plurality of vertices of one of the second rings among the plurality of second rings. The stent according to claim 11.

13. The plurality of vertices of one of the adjacent first rings among the plurality of first rings are fewer than all of the vertices of one of the adjacent first rings among the plurality of first rings. The stent according to claim 12.

14. The plurality of vertices of one of the second rings among the plurality of second rings are fewer than all of the vertices of one of the second rings among the plurality of second rings. The stent according to claim 12.

15. Each connected vertex of one of the adjacent first rings among the plurality of first rings is separated from another connected vertex of one of the adjacent first rings among the plurality of first rings by a vertex of one of the adjacent first rings among the plurality of first rings that is not connected to one of the second rings among the plurality of second rings. The stent according to claim 11.

16. Each connected vertex of one of the second rings among the plurality of second rings is separated from another connected vertex of one of the second rings among the plurality of second rings by a vertex of one of the second rings among the plurality of second rings that is not connected to one of the adjacent second rings among the plurality of second rings. The stent according to claim 11.

17. The attachment of the substantially linear connector to one of the second rings among the plurality of second rings is offset from an actual apex of the vertex of one of the second rings among the plurality of second rings. The stent according to claim 11.

Images