Stent Delivery System and Method

Abstract

The present invention describes a stent, a stent delivery system, and a method of delivering a stent that enables the porosity of the stent to be dynamically changed during delivery. Different from previous stents and procedures configured to have a preset porosity, a doctor can create regions of high stent porosity on certain vascular features and regions of low stent porosity on other vascular features, and can vary these porosities on at least one stent or stent layer.

Description

[0001] Related Application

[0002] This application claims priority to U.S. Provisional Application Serial No. 62 / 934,410, filed on November 12, 2019, entitled "Dynamic Stent System", the entire content of which is incorporated herein by reference. Background Art

[0003] Stents are deployed in a patient's vascular system for various different therapeutic purposes, such as expanding a stenotic portion of a blood vessel, covering the opening of an aneurysm, or similar vascular defects. A doctor typically selects a stent for treating a patient based on one or more characteristics of the stent, such as the expanded diameter, length, porosity, and ease of deployment, among others. Thus, stents of different diameters, lengths, and porosities are typically manufactured to best suit the treatment needs of the patient.

[0004] Porosity refers to the volume fraction of the pores, gaps, or openings in the stent wall, typically expressed as a percentage. A relatively high porosity is associated with a larger opening area (e.g., having larger sized and / or higher frequency pore openings), while a relatively low porosity is associated with a smaller opening area (e.g., having smaller sized and / or lower frequency pore openings). The desired porosity of the stent wall can be determined by one or more different characteristics of the stent, such as the wire diameter of the stent wall, the braiding pattern, and the number of layers that make up the stent wall.

[0005] In some therapeutic situations, it is desirable for the stent to have a relatively high porosity such that many and / or relatively large openings pass through the sidewalls of the stent. For example, Figure 1A illustrates an aneurysm 12 that bulges outward along the sidewall of a patient's blood vessel 10. For aneurysm 12, it is sometimes treated by delivering an embolization material (e.g., small-sized coils sometimes referred to as microcoils) into the aneurysm 12. An intraluminal support or "coil-assisted" stent 100 is typically deployed at the opening of the aneurysm 12 to help contain the embolization material (before or after the embolization material is delivered). The intraluminal support stent 100 is typically composed of relatively thick wires to help it hold its position in the blood vessel and to enable the embolization delivery catheter to pass through if the embolization material is delivered after the stent. Thus, these stents also tend to be relatively porous in structure (e.g., having larger pore openings) and do not always prevent or significantly reduce blood flow into the aneurysm 12.

[0006] Alternatively, it may be desirable for the stent to have a relatively low porosity such that there is little and / or relatively small openings through the sidewalls of the stent. To further reduce blood flow into the aneurysm 12, a doctor may deploy a second shunt stent ( Figure 1A not shown in) within the already deployed endoluminal support stent 100, or by deploying the endoluminal support stent 100 within a previously deployed shunt stent, which second shunt stent has far fewer pores. In other words, the shunt stent can be located inside or outside the endoluminal support stent 100. Alternatively, some endoluminal support stents, such as the stent 111 in Figure 1B , may have an attached inner shunt layer 113, as shown in U.S. Patent No. 9,439,791, the content of which is incorporated herein by reference. These types of stents are referred to as shunts, which reduce blood flow to the aneurysm 12 through the low-porosity shunt layer 113. This is an alternative treatment method and does not necessarily require embolization coils as described above. In this way, the shunt stent 111 with a lower porosity is distinguished from the endoluminal support stent 100 with a higher porosity.

[0007] However, depending on the vascular anatomy of the patient's treatment site, the doctor may not wish to block blood flow in the immediate vicinity of the opening of the aneurysm 12. Returning to the examples of Figure 1A and Figure 1B , other blood vessels 14 may flow into or out of the blood vessel 10. Although the endoluminal support stent 100 may have a high enough porosity to allow blood to flow between the blood vessels 10 and 14, the shunt stent 111 with fewer pores may undesirably block the nearby blood vessels 14. In the case of a cerebral aneurysm, the blood vessels in the brain are usually very small, which makes it difficult to adjust the shunt stent in a way that covers the aneurysm without covering the adjacent blood vessels.

[0008] In addition, although stent manufacturers typically offer a range of stent sizes, the doctor may not always be able to easily obtain a shunt stent with the required size and required porosity during the operation. In this regard, there is not always a single stent that can meet all the doctor's support requirements and blood shunting property requirements.

[0009] In addition, most stents on the current market are configured with a single porosity throughout their entire length. Thus, these stents with uniform porosity are not designed to have regions with different porosities and therefore can generally only achieve one specific treatment function (e.g., either low porosity for shunting or high porosity for coil-assisted stent treatment - but not both at the same time).

[0010] Therefore, there is a need for a stent, a stent delivery system, and / or a stent delivery method to enable the doctor to better control the region with reduced porosity in the patient's body and the porosity of that region. SUMMARY OF THE INVENTION

[0011] This embodiment generally relates to a stent, a stent delivery system, and a method of delivering a stent that can individually or jointly adjust the porosity of the stent during delivery. During delivery, a doctor can form a high-porosity region of the stent at certain vascular features (such as adjacent vascular openings), form a low-porosity region of the stent at other vascular features (such as aneurysms), and can vary these porosities on at least one stent or stent layer. Thus, a doctor can use a single stent in some procedures where multiple stents were previously required and can dynamically adjust the porosity of the stent during the procedure as needed.

[0012] One embodiment includes a stent having at least a first region with a relatively high longitudinal compression resistance and a second region with a relatively low longitudinal compression resistance. In one example, the region configured with relatively low longitudinal compression resistance is softer than the other region configured with relatively high longitudinal compression resistance. Additional high- and low-resistance stent regions can also be included, so that there is one or more high-resistance regions and one or more low-resistance regions (e.g., 1, 2, 3, 4, 5 or more in each region).

[0013] The longitudinal compressive resistance of different regions of the stent can be achieved in several different ways, such as including wires with a larger diameter to increase resistance, including wires with a smaller diameter to decrease resistance, changing the braiding pattern to increase / decrease resistance, changing the material of the wires, or changing the coating or plating of a portion of the wires. These methods can be used alone or in combination with each other.

[0014] Another aspect of this embodiment relates to a method that can generate longitudinal compression on the stent during delivery by pushing an elongate stent pusher and retracting an outer delivery catheter. The pushing and pulling manner can result in a net increase in longitudinal compression on the stent (i.e., push is greater than pull), which causes at least one region of the stent to be longitudinally compressed, thereby reducing the porosity or increasing its metal coverage. Different porosities can be obtained according to the push-pull ratio. This pushing and pulling can be performed simultaneously or sequentially. In addition, this technique can be used for stents configured with higher and lower longitudinal compressive resistances or for braided stents with generally uniform longitudinal compressive resistance.

[0015] Another aspect of this embodiment relates to a delivery system that facilitates indicating or causing a push / pull movement of the pusher relative to the delivery catheter. In one example, the pusher and / or the delivery catheter can include a number of measurement marks along their lengths to indicate their relative movement, thus serving as a guide for a doctor to understand how much push and pull is achieved.

[0016] In another example, one or more handle devices may be used to push the stent pusher and retract the delivery catheter, or both. The one or more handle devices may be configured to provide a preset push / pull ratio between the stent pusher and the delivery catheter. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] These and other aspects, features, and advantages of the embodiments of the present invention will become apparent and be elucidated in the following description of the embodiments of the present invention. Please refer to the accompanying drawings, wherein:

[0018] Figure 1A is a side view of a stent placed across an aneurysm.

[0019] Figure 1B is a side view of a flow diversion stent placed across an aneurysm.

[0020] Figure 2 is a side view of a stent having a reduced porosity region according to one embodiment.

[0021] Figure 3 Illustrates a side view of a stent having different longitudinally compressive strength regions according to one embodiment.

[0022] Figure 4 Illustrates a side view of a stent having different longitudinally compressive strength regions according to one embodiment.

[0023] Figure 5 Illustrates a side view of a stent having different longitudinally compressive strength regions according to one embodiment.

[0024] Figure 6 Illustrates a side view of a stent delivery method according to one embodiment.

[0025] Figure 7 Illustrates a side view of a stent delivery method according to one embodiment.

[0026] Figure 8A and Figure 8B Illustrates a view of changing the braiding angle according to one embodiment.

[0027] Figure 9 Illustrates a graph of the percentage of metal surface coverage of an exemplary stent versus the braiding angle according to one embodiment.

[0028] Figure 10 Illustrates a graph of the percentage of metal surface coverage of an exemplary stent versus the braiding angle according to one embodiment.

[0029] Figure 11 Illustrates a graph of the stent length versus the braiding angle of an exemplary stent according to one embodiment.

[0030] Figure 12 Side view of a delivery system according to one embodiment is illustrated.

[0031] Figure 13 Side view of a delivery system according to one embodiment is illustrated.

[0032] Figure 14 Side view of a delivery system according to one embodiment is illustrated.

[0033] Figure 15 Side view of a delivery system according to one embodiment is illustrated. DETAILED DESCRIPTION

[0034] Specific embodiments will now be described with reference to the accompanying drawings. However, these embodiments may be embodied in many different forms and should not be construed as limited to the embodiments described herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. The terms used in the detailed description of the embodiments shown in the drawings are not intended to limit the embodiments. In the drawings, the same numbers represent the same elements. Although different embodiments are described, the features of each embodiment can be interchanged with those of the other described embodiments. In other words, all features in each embodiment can be mixed and matched with each other, and the embodiments do not have to be rigidly construed as only including the features shown or described.

[0035] This embodiment generally relates to stents, stent delivery systems, and methods of delivering stents that are capable of adjusting the porosity of the stent individually or in combination during delivery. During delivery, a doctor can create regions of high stent porosity over certain vascular features (such as adjacent vascular openings) and regions of low stent porosity over other vascular features (such as aneurysms), and can vary these porosities over at least one stent or stent layer. In other words, the stent as a whole can have a generally uniform braiding angle during delivery, and a doctor can change the braiding angle in certain regions during delivery to adjust the porosity. Thus, a doctor can use a single stent in some procedures where multiple stents were previously required and can dynamically adjust the porosity of the stent during the procedure as needed. The braiding angle will be discussed in more detail later in this specification.

[0036] Although this embodiment is generally described in connection with treating aneurysms (e.g., for shunting, or for stent-assisted coiling techniques), it should be understood that these stents and delivery methods can be used to treat a variety of other medical conditions, such as treating vascular stenosis, treating vasospasm (both of which involve treating the narrowing or constriction of blood vessels). Thus, while these stents and delivery methods may be particularly helpful in treating aneurysms, this embodiment should not be limited solely to such treatment.

[0037] Figure 1A and Figure 1B illustrates an exemplary treatment site where an aneurysm 12 is connected to the sidewall of a blood vessel 10. A treatment for the aneurysm 12 sometimes involves first delivering an endoluminal support stent 100 through an opening of the aneurysm 12, and then delivering embolization material (e.g., small coils sometimes referred to as microcoils) through the stent 100 into the aneurysm 12. The endoluminal support stent 100 typically consists of relatively thick wires to help it hold its position in the blood vessel, and thus also tends to be relatively porous in its structure (e.g., larger pore openings).

[0038] However, depending on the vascular anatomy of the patient's treatment site, the doctor may not want to block blood flow in the immediate vicinity of the opening of the aneurysm 12. For example, other blood vessels 14 may flow into or out of the blood vessel 10. Although the endoluminal support stent 100 may have a high enough porosity to allow blood to flow between the blood vessels 10 and 14, a shunt stent with fewer pores may block such nearby blood vessels 14, as Figure 1B shown.

[0039] Currently available stents on the market typically have a continuous porosity distribution. In other words, after the stent is manufactured (e.g., woven and heat-set), when it is deployed in a relatively straight and uniform container, the stent is capable of forming a uniform porosity over almost its entire length. Thus, a typical stent does not allow the doctor to determine the porosity of various parts of the stent during the procedure. For example, if treating a Figure 1B vascular condition with a shunt stent 111 (e.g., in a situation where a low porosity is used to reduce blood flow into the aneurysm 12), the continuous porosity distribution of a typical stent will ensure that the low porosity region also covers the nearby blood vessels 14, because the entire stent has a similar porosity distribution. Although a low porosity distribution is helpful near the aneurysm 12 (e.g., in the case where the stent 111 is used for shunting), it may not be beneficial for the nearby blood vessels 14, because the low porosity distribution may result in a reduced blood flow to the blood vessels 14.

[0040] To address this problem, some embodiments presented herein utilize stents in which the doctor can create portions or regions of different porosities in the stent during the treatment.

[0041] Figure 2 illustrates a stent 120 according to one embodiment, which has been delivered to regions of lower and higher porosity. Specifically, the exemplary stent 120 includes proximal and distal regions 120A that have a relatively high porosity compared to an intermediate region 120B of relatively low porosity. Alternatively, regions of relatively lower porosity may be created in the proximal or distal regions 120A, the proximal and distal regions 120A, or even most or all of the regions of the entire stent 120.

[0042] As discussed further in detail below, the delivery of the scaffold 120 with different porosity regions can be achieved in the following ways: 1) during delivery and deployment, the scaffold 120 is constructed in such a way that regions with greater longitudinal compression of the scaffold are formed, 2) the scaffold 120 is delivered by a push-pull combination of an internal delivery pusher and an external delivery catheter, or 3) a combination of scaffold construction and delivery methods. In some embodiments, the scaffold 120 can be delivered to regions with different porosities such that the scaffold 120 initially has a first (e.g., uniform) porosity and then is capable of forming one or more regions with different porosities after delivery. Although scaffolds with regions of reduced longitudinal compression resistance may facilitate such porosity changes during the procedure, scaffolds with substantially uniform longitudinal compression resistance can also be used.

[0043] Longitudinal compression refers to the reduction in distance between the proximal and distal ends (left and right in the figure) of a scaffold region. Longitudinal compressive resistance refers to the resistance of a scaffold region to such longitudinal compression.

[0044] First is the construction of the scaffold. The fabrication of the scaffold 120 makes certain regions more prone to longitudinal compression while other regions are relatively more resistant to compression. During the deployment of the scaffold 120 (e.g., pushing distally), regions with stronger resistance to longitudinal compression typically resist significant compression, while regions with weaker resistance undergo greater longitudinal compression, depending on how much distal longitudinal force the doctor applies during delivery.

[0045] Figure 3 An exemplary embodiment of a scaffold 130 is shown, which has proximal and distal regions 130A that are more resistant to longitudinal compression and an intermediate region 130B that is less resistant to longitudinal compression. Specifically, the scaffold 130 is woven from one or more wires that are relatively more resistant to bending than the remaining woven structure wires 101.

[0046] In one example, the compressive regions 130A can each be woven together with one or more longitudinal support wires 132, and the diameter of the longitudinal support wires 132 is greater than that of the remaining structural wires 101. For example, the diameter of the wires 132 can vary from 1% to 50% greater than the diameter of the remaining wires 101. In another example, the diameter of the wires 132 may be approximately 0.0005 inches to 0.001 inches greater than the diameter of the remaining wires 101. The wires 132 with a larger diameter tend to be stronger than the remaining smaller-diameter structural scaffold wires 101 and thus have better compressive resistance. Therefore, the compressive resistance of the regions 130A is better than other regions of the scaffold 130.

[0047] In one example, the body of the stent (e.g., the entire length of stent 130) can be braided with a single wire or multiple wires 101, and at least one wire 132 can also be braided between one or more of the wires 101 in regions (e.g., region 130A) designed to resist longitudinal compression. In this way, one or more wires 101 can be braided throughout the stent 130, and one or more wires 132 of larger diameter can be selectively braided in the compression-resistant region 130A of the stent 130.

[0048] Alternatively, at least one wire can be connected in a manner different from braiding. As seen in the stent 144 of Figure 5 , the wire 146A can be longitudinally connected along the length of the stent 130 by a plurality of loosely configured ties (not shown). The ties enable each end of the wire 146A to slide along the wire 101 to which it is connected, such that the longitudinal wire 146A does not prevent or limit radial expansion and the consequent shortening (i.e., the longitudinal contraction of the stent that occurs as the stent expands radially). In other words, the sliding ties enable the wire 146A to slide and adapt to the shortening during expansion. The longitudinal wire can alternatively include multiple wire segments 146B (also seen in Figure 5 ), which can be arranged linearly or non-linearly with respect to the longitudinal axis of the stent 144. The wire 146A, 146B, or a combination of both can be used to create a region 144A with a higher resistance to longitudinal compression and a region 144B with a lower resistance to longitudinal compression.

[0049] In another embodiment, the previously described wire 132 can be made of a material different from that of the wire 101 to provide a difference in the ease of longitudinal compression. This material difference can be a supplement to or an alternative to the diameter difference described above. In one example, the stent wire 101 can be composed of Nitinol, while the compression-resistant wire 132 is composed of stainless steel, tantalum, or platinum. Additionally, a material difference can be created in other ways, such as coating or electroplating a first material onto a wire formed of a second material.

[0050] In another example, some or all of the wire 101 can consist of a drawn filled tube. A drawn filled tube wire can include a radiopaque core material (such as platinum or tantalum) and a shape memory sheath or outer layer (such as nitinol). One advantage of a drawn filled tube wire stent is that, since the wire contains radiopaque material, there is some radiopacity visibility along the entire length of the stent, which may reduce or eliminate the need to add additional radiopaque markers. Additionally, since drawn filled tube stents are generally softer than conventional stents, the middle portion can even be more conformable, thus being suitable for the geometry of the treatment location. In this way, since no separate radiopaque material is required for visualization, drawn filled tube stents can potentially be smaller in size and generally less stiff than conventional stents. As discussed in other parts of this specification, other methods can be used to increase the longitudinal compressive resistance of certain regions of a stent mainly composed of drawn filled tubes. An example of a stent composed of drawn filled tube wires can be found in U.S. Application No. 16 / 685,995, filed on November 15, 2019, the content of which is incorporated herein by reference.

[0051] Because a stent composed of drawn filled tube wires provides relatively weak longitudinal compression (e.g., relative to some other metal wires, such as nitinol), and the drawn filled tube wires are radiopaque, when applying the required amount of longitudinal compression to the stent, a doctor can particularly easily observe the entire stent under fluoroscopic visualization or a similar technique (the compression technique will be discussed later in this specification). The doctor can use the visualization technique to observe the porosity of the entire stent and compress the stent until the porosity of one or more regions of the stent reaches the desired change. In other words, the doctor can not only easily see which region of the stent they are longitudinally compressing, but also see the relative amount of compression applied and the relative porosity. In this regard, one embodiment of this specification also includes a method for visualizing a drawn filled tube wire stent, applying longitudinal compression, and determining when the desired porosity change has been achieved. By comparing the uncompressed region and the compressed region of the stent (e.g., through visual inspection), or by using a guiding or measuring device (e.g., built into the fluoroscope) to measure the pore size of the stent, the desired porosity can be relatively determined.

[0052] In one embodiment, the structural wire 101 of the stent is metallic (e.g., nitinol, stainless steel, or cobalt-chromium alloy), and it includes one or more wires wound into a single-layer tube. In one embodiment, the stent consists of one or more drawn filled tube wires wound into a braided single-layer tube.

[0053] In another example, different regions 130A and 130B can have different braiding patterns that increase or decrease the resistance to longitudinal compression by different amounts. For example, helical braiding, circumferential braiding, and multi-layer braiding can be used in various regions of the stent 130.

[0054] As Figure 4 shown, most or all of the wires in regions 140A, 140B of the stent 140 may have properties that enhance or reduce longitudinal compression. For example, the proximal and distal regions 140A are almost entirely braided from partial wires that resist longitudinal compression, while the intermediate region 140B can be almost entirely braided from partial wires with relatively weaker resistance to longitudinal compression.

[0055] These regions 140A and 140B can be created in different ways. For example, different regions can be braided separately and then connected to each other (e.g., by welding or wire lacing). Each region can be wound with one or more wires of different diameters, different materials, different braiding patterns, or any combination of these techniques.

[0056] In another instance, a single wire can be formed from wire segments of different materials or different diameters. The different segments have certain lengths and spacings such that segments of a particular material / size are aligned in different regions of the stent. For example, when the wire is braided on a mandrel, the first segment of the wire is aligned with segment 140A, while the second segment with a different diameter / material is aligned with region 140B.

[0057] In another instance, the stent 140 can first be braided with one or more wires 101 and then processed to cause dimensional or material changes in various regions of the stent 140. In one technique, the stent 140 can be braided from one or more structural wires 101, and the intermediate region 140B can be electropolished to reduce the diameter of portions of one or more wires 101 in region 140B, thereby reducing the longitudinal compression resistance of region 140B relative to the adjacent regions 140A. Alternatively, the stent 140 can be braided from one or more wires 101, and the proximal and distal portions 140A can be electroplated or coated to increase the diameter of portions of one or more wires 101 in those regions 140A - thereby increasing the compressive resistance along region 140A. Such coating or electroplating can form a new material layer on the wire portion 142 that is the same as portion 101, or can coat / plate a different material on the wire portion 142.

[0058] Similarly, regions 130A, 130B, 140A, 140B of the stent 130 can have different from Figure 3 and 4The positions shown. For example, regions 130A and 130B can be reversed. In another example, the stent can have two, three, four, five, six or more regions with different combinations that have different longitudinal compression resistances.

[0059] Generally, regions with reduced longitudinal resistance are configured such that they are compressed with a force less than that which would cause distal movement or sliding of the deployed distal end of the stent within the patient's blood vessel. In other words, once a portion of the stent has been deployed, it is generally not desirable for it to slide within the patient's blood vessel as this can misalign the stent from its intended target location. Since applying a distal push force to the stent causes longitudinal compression, it is preferred that the regions with reduced longitudinal compression resistance be longitudinally compressed before any anchoring force at the distal end of the stent is overcome. In some examples, the regions with reduced longitudinal compression resistance are configured to longitudinally compress when a longitudinal force of about 1 to 5 pounds is applied to them by a pusher.

[0060] Although a stent can be constructed to have discrete regions with different longitudinal compression resistances, a stent with a gradually varying longitudinal compression can also be created. For example, it may be easiest to longitudinally compress in the middle of the stent (meaning the least resistance to longitudinal compression) and increase gradually towards its proximal and distal ends. For example, such a stent can be constructed by braiding a decreasing number of compression-resistant wires 132 from both ends of the stent towards the middle. Alternatively, the diameter of one or more compression-resistant wires 132 can decrease from both ends of the stent towards the middle and be braided with the wires 101 (meaning the diameter of the wires 132 is thickest at the ends and thinnest in the middle). In another alternative embodiment, the stent can have a braiding pattern that is capable of gradually reducing the longitudinal compression resistance towards the middle of the stent.

[0061] Stents 130 and 140 (or any other stent in this specification) can include radiopaque components to aid visualization during the surgical procedure and to help indicate different compression-resistant regions. For example, Figure 3 the compression-resistant wires 132 in can be composed of or coated with a radiopaque material. In another example, radiopaque markers or wire coils 122 can be fixed at positions around the circumference of the stent and near the edges of regions with different compression resistances (e.g., between regions 130A and 130B), or wound around the wires 101, 132 or 132. In a particular example, radiopaque markers are positioned at the proximal and distal ends of the regions of the stent where the longitudinal compression resistance is reduced.

[0062] The exemplary stent of this specification is depicted as an endoluminal support stent formed by at least one wire braided into a tube 101. Each end of the tube 101 has a plurality of loops 102, and a plurality of radiopaque coils 104 are provided on at least some of the loops 102. Such stents are generally detailed in U.S. Patent No. 9,439,791, the content of which is incorporated herein by reference. Other aspects, variations, and exemplary delivery mechanisms of such stents can be found in U.S. Patent Nos. 10,182,931, 10,322,020, 10,335,299, 10,617,544; the above patents are also incorporated herein by reference. However, according to this embodiment, other braided stent designs can also be used.

[0063] In some examples, if the metal surface coverage of the device (referring to the total area of the metal that makes up the stent, which is a function of the total area occupied by the stent) is at least 30%, the stent is classified as a flow diverter. Flow diverters generally have a relatively high metal surface coverage and a low porosity because these stents are designed to reduce blood flow to the aneurysm. On the other hand, the metal surface coverage of coil-assisted stents can be less than 30% (e.g., about 20%-36%), and they generally have a lower metal surface coverage and a higher porosity than flow diverters because the stent pores are typically used as access points for microcatheters, through which an embolization material (e.g., an embolization coil) is delivered into the aneurysm. In current medical practice, since stents have a fixed porosity at a given size, stents are generally classified as endoluminal support stents or flow diverter stents (in the case of treating aneurysms), so these stents are generally only used for one treatment purpose each.

[0064] In some instances, the stent can be delivered such that the stent has at least one high-porosity region, which can be regarded as an endoluminal support region, and at least one low-porosity region, which can be regarded as a flow diversion region. For example, the middle part of the stent can be delivered such that the middle part has a lower porosity and is regarded as a flow diversion region, while the two ends of the stent have a higher porosity and can be regarded as endoluminal support regions.

[0065] It should be emphasized that in some embodiments of the stent, regions with different porosities are created and controlled during delivery to enable the doctor to control where (i.e., which region of the stent) the porosity of the stent should change and to what extent the porosity should change. For at least some of the stents described in the present application, such as stents 100, 120, 130, and 140, the porosity can self-expand to be relatively uniform without significant longitudinal compression, so longitudinal compression remains an important mechanism for changing the initial porosity of the stent. For example, stents 100, 120, 130, 140 can have regions with different wire counts or wire thicknesses, but this alone may not have a significant impact on the porosity of each part - on the contrary, these methods are used to change the longitudinal compression distribution in different regions of the stent. The delivery steps described herein longitudinally compress one or more regions of the stent during stent delivery and then change the porosity distribution along different regions of the stent.

[0066] In this regard, the present embodiment also includes one or more methods of deploying a stent to create regions of the stent with different porosities. These methods can be used for standard endoluminal stents, such as stent 100, to change the porosity (i.e., a stent with relatively uniform longitudinal compression resistance), or can be used for stents with regions of different longitudinal compression strengths, such as stents 120, 130, and 140. In addition, stents with porosity variations (e.g., regions with higher porosity in a non-longitudinally compressed state) can also be used in conjunction with the construction techniques and deployment methods described herein.

[0067] One embodiment relates to a method of generating longitudinal compression on a stent during stent deployment. In an exemplary embodiment, such longitudinal compression is generated by advancing a pusher or an elongate stent deployment mechanism distally after a portion of the stent has been deployed.

[0068] In another exemplary embodiment, the longitudinal compression is generated by a combination of: 1) advancing a pusher or an elongate stent deployment mechanism distally after a portion of the stent has been deployed, and 2) retracting an outer delivery catheter surrounding the stent. The pusher and the delivery catheter can be advanced and retracted at various rates to achieve the desired porosity of the stent. This pushing and pulling can be done simultaneously or alternately. Generally, retracting the outer delivery catheter exposes a portion of the stent, while advancing the inner pusher distally forces the proximal portion of the stent to advance distally. Since the distal end of the stent expands and fixes first within the patient's blood vessel, the distal end of the stent typically remains in place, causing more proximal portions of the stent to be longitudinally compressed, thereby increasing the porosity of the region of the stent near the delivery catheter.

[0069] Figure 6 and 7Illustrates an example method of deploying a stent. Typically, a guide wire (not shown) is implanted into a patient such that its distal end is located at or near a target site, such as an aneurysm. Next, a relatively large guiding catheter 158 is advanced over the guide wire such that its distal end is located at or near the delivery site, such as Figure 5 shown, and the guide wire is removed.

[0070] Then, a delivery device is advanced through the guiding catheter. The delivery device may include a delivery catheter 150 that has an elongated lumen, passageway, or conduit between its proximal and distal ends. The delivery device may also include an elongated pusher 152 that can move longitudinally within the lumen, passageway, or conduit of the delivery catheter 150. The pusher preferably includes a mechanism on or near its distal end that can engage the stent 120 and cause the stent 120 to be pushed distally by the pusher 152. Note that while this is described with respect to the stent 120 as an example, various methods described herein can be utilized with any kind of stent embodiment to achieve stents with different porosities.

[0071] For example, the pusher may include a distally projecting protrusion 154 and a proximally projecting protrusion 156. These protrusions may be in the form of radiopaque cylinders, stars, or other similar shapes. The distal protrusion 154 is preferably sized to fit within an opening of the stent 120, such as the loop 102, while the proximal protrusion 156 is preferably sized to fit near the proximal end of the stent (e.g., the end of the stent loop 102). Thus, the stent 120 can be pushed distally and retracted into the microcatheter if desired. Additionally, various different pushers and other stent engagement mechanisms can alternatively be used, such as those seen in patents previously incorporated by reference into this specification.

[0072] As Figure 6 shown, the delivery catheter 150 is typically pushed to a position distal to the aneurysm 12 or the target site. The pusher 152 can be held in place while the delivery catheter 150 is withdrawn proximally to expose the distal end of the stent 120, and the stent 120 radially expands to engage and fix to the blood vessel 10.

[0073] As Figure 7 shown, the pusher 152 is advanced distally by the physician and the delivery catheter 150 is retracted proximally such that the stent 120 is pushed longitudinally forward, thereby forming an intermediate region 120B with a higher porosity relative to an end region 120A of an original or lower porosity. This pushing and pulling can be done simultaneously or in small alternating increments. In addition to other known factors, such as wire size, braiding pattern, stent diameter, etc., the ratio or amount of push and pull will typically determine the porosity of the higher porosity region 120B.

[0074] As the braiding angle (weaving angle) increases, the metal coverage rate of the braided stent increases exponentially, and the porosity decreases exponentially. Therefore, braided stents are usually designed and manufactured by adjusting the braiding or braiding angle according to the required metal coverage rate and opening force. For example, Figure 8A An enlarged portion of the stent 120 is illustrated, in which the first wire 101A crosses the second wire 101B, and a braiding angle 101C is formed between the longitudinal axis 103 of the stent 120 and one of the wires 101A. Figure 8B It is shown that when the area of the stent 120 is longitudinally compressed, the braiding angle 101C increases, which results in a shorter length 101D of the holes / openings in the direction parallel to the stent axis 103 (e.g., the rhombus in the figure). Since these openings or rhombuses narrow in the direction parallel to the stent axis (i.e., the left - right direction in the figure), the number of wefts per inch increases, the metal coverage rate increases, and the porosity of the longitudinally compressed area of the stent decreases.

[0075] Figure 9 An example simulation diagram is illustrated, which clarifies the change in the metal surface coverage rate when the braiding angle of a 48 - wire stent (representing a typical single - layer shunt stent due to the relatively large number of wires) changes. Figure 10 Another example simulation diagram is illustrated, which clarifies the change in the metal surface coverage rate when the braiding angle of a 16 - wire stent (representing a typical coil - assisted or intraluminal - supported stent due to the relatively small number of wires) changes. According to the braiding angle of each stent design, the percentage of metal coverage can generally be quantified. Note that although specific numbers of wires are mentioned, this "number" of wires may be partial wires located in the cross - section in the braiding pattern of the stent. For example, a single wire can be woven back and forth between the proximal and distal ends of the stent to produce 16 or 48 "wires" or wire segments (or other numbers of wires). Therefore, in this case, the term "wire" should not be literally understood as individual wire pieces.

[0076] The metal surface coverage rate is inversely proportional to the porosity, and the metal surface coverage rate plus the porosity is theoretically about 100% in total. Among them, the porosity represents the percentage of the opening area in the stent, and the metal surface coverage rate represents the percentage of the metal stent elements covering the stent. Thus, a low percentage of metal surface coverage corresponds to a high percentage of porosity, while a high percentage of metal surface coverage corresponds to a low percentage of porosity. In this way, a larger braiding angle corresponds to a higher metal surface coverage rate, which in turn corresponds to a lower porosity.

[0077] These exemplary stents have a diameter of approximately 4 millimeters and are composed of 16 wires with a diameter of approximately 60 micrometers or 48 wires with a diameter of approximately 31.75 micrometers. Using the mathematical principles of the relationship between the braiding angle, braiding pitch, and number of braiding turns, different structures and corresponding percentages of metal surface area can be obtained. For both designs, once the braiding angle exceeds approximately 60 degrees, the metal surface coverage percentage increases exponentially. Between approximately 30 and 60 degrees, the increase is relatively stable. In one embodiment, a braided stent with a braiding angle designed to be approximately 60 degrees has a metal coverage of approximately 35%. By controlling longitudinal compression (along the long axis of the stent), the metal coverage percentage in the region of interest can be increased from approximately 35% to 80%.

[0078] Figure 11 Illustrates the interaction between longitudinal compression, changes in the device braiding angle, and changes in the device length, where the changes in the device length are achieved by keeping the total wire length constant and changing the braiding angle and pitch to simulate the compression of a 16-wire braided stent (e.g., Figure 10 ). Approximately 50% longitudinal compression will change the braiding angle from around 60 degrees to around 75 degrees and increase the metal coverage from 22% to 42% - almost doubling the metal coverage.

[0079] Table 1 below illustrates several example amounts of pushing the pusher and pulling the delivery catheter to achieve the desired braiding angle, thereby increasing the porosity or coverage percentage in the region of the stent (e.g., Figure 10 of the exemplary stent). Typical prior art stent delivery would seek to provide no net pushing or longitudinal compression. For example, the delivery catheter can be mainly withdrawn from the pusher to expose the stent and allow the stent to expand radially. Or, the doctor can push the pusher while retracting the outer delivery catheter, resulting in no net longitudinal compression on the stent, as shown in the first row of Table 1. Thus, in prior art delivery techniques, the initial braiding angle of a portion of the delivered stent is the same as the final braiding angle of the delivered stent, and the coverage percentage is not increased or the porosity is not reduced.

[0080] Table 1

[0081]

[0082] However, according to at least one embodiment, Table 1 also shows that an increase in the amount of distal pushing on the pusher 152 relative to pulling / withdrawing the proximal end of the delivery catheter 150 results in a net amount of longitudinal compression that increases the final braiding angle in the stent region, increasing the coverage percentage or reducing the porosity. The net amount of longitudinal compression applied to the stent 120 will generally determine the degree of change in the final braiding angle (e.g., Figure 8B ) relative to the initial braiding angle (e.g., Figure 8A ), and thus determine the increase in the percentage of metal coverage in a certain region of the stent 120.

[0083] In one embodiment, the doctor can perform the aforementioned pushing of the pusher 152 and pulling of the delivery catheter by manually operating the respective devices. In one embodiment, the pusher 152, the delivery catheter 150, or both can include a plurality of measurement marks that assist in indicating the position of the devices relative to each other and relative to the external guiding catheter 158.

[0084] For example, Figure 12 illustrates the proximal ends of the guiding catheter 158, the delivery catheter 150, and the pusher 152. The pusher 152 can include a plurality of measurement marks 161 along at least the proximal portion of its length to illustrate the movement of the pusher relative to the proximal end of the delivery catheter 150 (e.g., the delivery catheter hub 150A). Similarly, the delivery catheter 150 includes a plurality of measurement marks 163 along at least the proximal portion of its length to illustrate the movement of the catheter relative to the external guiding catheter 158 (e.g., the guiding catheter hemostatic valve 158A). Thus, the doctor can better determine the amount and ratio of pushing / pulling of the pusher 152 and the delivery catheter 150.

[0085] Figure 13 shows another embodiment that includes a handle 160 that is connected to the proximal portion of the pusher 152, enabling the user to more precisely advance the pusher 152 distally through user interface elements such as a thumbwheel 162. For example, the thumbwheel 162 can be connected to a gear arrangement (e.g., a rack and pinion 167) within the handle 160, which is further connected to the pusher 152 (e.g., via a clamping mechanism). In one embodiment, the thumbwheel 160 can be configured to have a plurality of rotational stops that can indicate the pusher 152 moving a specific distance (e.g., 1 millimeter) so that the doctor can better determine the amount of longitudinal compression and thus the final porosity of a certain region of the stent 120. The previously described marks can also be included to assist in further communicating the relative movement of the pusher 152 and the delivery catheter 150 to each other.

[0086] Figure 14 shows another embodiment of a handle 170 that is configured not only to move the pusher 152 but also to connect to and move the delivery catheter 150. In one instance, the handle 170 includes a tube 172 that is positioned around the pusher 152 and is connected to the proximal end of the delivery catheter (e.g., the hub 150A). This arrangement enables the handle 170 to push the pusher 152 distally and retract the delivery catheter 152 proximally.

[0087] In one embodiment, the thumbwheel 162 can control the movement of both the pusher 152 and the delivery catheter 150 simultaneously. Additionally, a gear mechanism within the handle 170 can push and pull at a preset ratio to achieve a preset porosity (e.g., one of the ratios in Table 1) in the stent region. The handle 170 can also include a ratio adjustment component (e.g., a switch, a wheel, a button, etc.) for changing the push / pull ratio. Thus, the doctor can determine the desired porosity on the handle 170 during the procedure.

[0088] Figure 15 Another embodiment is illustrated, in which the previously described handle 160 can be used to move the pusher 152, and a separate but similar handle 180 can be used to move the delivery catheter 150. These handles 160 and 180 can be configured such that they can produce one or more push / pull ratios between the pusher 152 and the delivery catheter 150, and can include an adjustment mechanism so that the user can adjust the push / pull ratio to a desired amount. Additionally, the previously described markings can also be used to assist in monitoring changes in the relative positions between these devices.

[0089] Any of the previously described handles can be manually driven by a thumbwheel or a similar mechanism, or can be driven by an electric motor. In this regard, the handle can also include an electronic interface that can monitor and display position changes and adjust or generate the desired push / pull ratio through electronic configuration. In one embodiment, an electronic interface can be included that allows the user to input characteristics of the stent, such as the manufacturer, model, number of braided wires, dilated diameter size, etc., and then input the desired porosity or percentage coverage of the stent region, and the appropriate amount of push / pull for the pusher 152 and the delivery catheter 150 can be automatically determined. The electronic interface can determine such a push / pull ratio by querying a stored database or chart, or by performing calculations based on the input information.

[0090] The concept of the handle also has some benefits when used with a DFT stent (previously described as an element that does not require additional radiopaque elements and makes the entire stent visible using one or more drawn fill tube wires). One benefit is that the doctor can use the handle to create a specific desired porosity or distribution of metal surface coverage for at least a portion of the stent, and then visually determine whether the distribution of this configuration is suitable for a particular procedure (e.g., whether the stent appears to be configured to achieve its intended purpose - for example, whether a portion of a stent configured for a shunting purpose can be shaped to accomplish this task). If further improvement is needed, the doctor can use the handle to further change the delivery shape of the stent.

[0091] In addition, if this handle concept is not used and instead the doctor uses a push / pull method (retracting the catheter while pushing the stent to change the porosity distribution of a portion of the stent), using a DFT stent will enable the doctor to visually determine how the stent will respond when using the push / pull method and then adjust the push / pull method (e.g., push the pusher more or pull the catheter more) to adjust the desired porosity distribution of the stent. In other words, for the doctor, the ability to observe in real time the changes in the shape and porosity of the stent has a practical benefit in deciding how to adjust the stent during delivery.

[0092] Note that while this is a particular advantage for highly radiopaque stents such as DFT, since the DFT stent contains DFT wires and the whole and most of the stent are visible, for other stents at least most of the stent can be seen, which is beneficial to some extent. However, one advantage of the DFT stent is that no additional radiopaque components need to be added for observation, so the entire stent itself can be easily observed simply using the DFT wires that form the structure of the stent.

[0093] While the present embodiment has been described in terms of providing a stent, system, and delivery technique to induce longitudinal compression to reduce the porosity of the stent, it should be clear that the reverse operation is also possible. Specifically, the doctor can deploy a stent that has a relatively low porosity in its original state but can have increased porosity in certain regions. For example, this can be achieved by having similar stent regions with different longitudinal compressions and a technique of pulling the pusher proximally relative to the delivery catheter.

[0094] Although the present invention has been described in terms of specific embodiments and applications, those of ordinary skill in the art can, in light of the teachings of the present invention, generate additional embodiments and modifications without departing from or exceeding the scope of the claimed invention. Accordingly, it should be understood that the figures and descriptions presented herein by way of example are for the purpose of facilitating understanding of the present invention and should not be construed as limiting the scope of the present invention.

Claims

1. A stent, which comprises: one or more structural wires braided into a tubular shape; a first stent region having a first longitudinal compressive resistance; a second stent region having a second longitudinal compressive resistance lower than the first longitudinal compressive resistance; and one or more longitudinal support wires located in the first stent region, the one or more longitudinal support wires comprising a plurality of wire segments, the plurality of wire segments being capable of being linearly arranged relative to the longitudinal axis of the stent, and wherein the first stent region and the second stent region are longitudinally adjacent; and wherein the first stent region and the second stent region are configured to be deployed at a first porosity, and wherein the second stent region is configured to be longitudinally compressible relative to the first stent region during delivery to form a second porosity lower than the first porosity.

2. The stent according to claim 1, wherein one or more longitudinal support wires are braided between one or more structural wires located in the first stent region.

3. The stent according to claim 1, wherein one or more structural wires include a first braiding pattern in the first stent region and a second braiding pattern in the second stent region.

4. The stent according to claim 1, further comprising a third stent region having the first longitudinal compressive resistance, the third stent region being adjacent to the second stent region and located on the opposite side of the first stent region.

5. The stent according to claim 4, wherein the one or more longitudinal support wires are composed of a first longitudinal support wire located in the first stent region and a second longitudinal support wire located in the third stent region.

6. The stent according to claim 5, wherein the first stent region includes the proximal region of the stent, wherein the second stent region includes the middle region of the stent, and wherein the third stent region includes the distal region of the stent.

7. The stent according to claim 5, wherein the second stent region does not include any of the one or more longitudinal support wires.

8. The stent according to claim 1, wherein the one or more longitudinal support wires are each connected to one or more structural wires by a tie such that the one or more longitudinal support wires can slide along the one or more structural wires.

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