JP2022546151A - Absorbable intravascular device that provides a decrease in radial stiffness of a vessel over time - Google Patents

Abstract

Vascular stents can be used to maintain or enhance vessel patency. By using a plurality of separate balloon-expandable stent elements, multi-element stents can be stronger than conventional self-expanding stents, but due to their multi-element construction, conventional balloon-expandable stents do not. can be more flexible than The stent elements are formed from a bioabsorbable polymeric material. The radial stiffness of the stent is configured to decrease after implantation into a vessel as the polymer is resorbed. The stent thickness, cell geometry, polymeric material, and/or treatment of the polymeric material are configured to provide a high initial radial stiffness to the vessel upon implantation and a decrease in radial stiffness of the vessel over time. can be done. [Selection drawing] Fig. 1

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is related to U.S. Provisional Patent Application No. 62/914,260, entitled "ABSORBABLE INTRAVASCULAR DEVICES THAT PROVIDE A DECREASE IN RADIAL RIGIDITY OF THE VESSEL OVER TIME," filed Oct. 11, 2019. Claiming the benefit and priority of No. 1, the entire disclosure of the above referenced application is incorporated herein by reference.

This application relates generally to the field of medical devices. More specifically, this application relates to the design and manufacture of intravascular stents intended to maintain patency (blood flow) of blood vessels (arteries and veins).

Atherosclerosis, or "arteriosclerosis," is the world's leading cause of death and disability, accounting for nearly one-third of all human mortality. Although some developed countries have made significant progress in modifying risk factors and changing lifestyle behaviors, some estimates indicate that the global prevalence of atherosclerotic disease is still rising, and by 2030 More than 23 million people are expected to die annually by then. The economic burden is staggering, with an estimated annual cost of treating atherosclerosis and its sequelae exceeding $200 billion in the United States alone.

Atherosclerosis is a pathological process of arterial aging. At an early age, the supple elastin fibers within the arterial medium provide the structural elasticity and flexibility necessary for arterial pulsation and pulse wave transmission. Over decades, however, sustained pressure and exercise slowly denature structural matrix proteins, causing fatigue and destruction of elastin. The result is a slow but relentless loss of compliance and chronic stiffening of the arterial wall. Loss of pulsatility and pulse wave reflection leads to blunted velocity profiles, loss of flow reversal, and attenuation of anterograde flow coefficients. This results in prolonged relative stagnation during diastole, resulting in longer residence times in wall particles and cells. The dysfunctional wall below the stagnant boundary layer begins to accumulate circulating atherogenic cholesteryl fatty acyl ester and triglyceride particles, particularly apolipoprotein B-containing lipoproteins. Oxidative modification of lipoproteins activates the overlying endothelium to secrete chemokines, which attract blood-borne monocytes rolling along the endothelium and become sticky upon exposure to adhesion molecules and tissue factor. tethered to the blood vessel surface. Tightly adherent monocyte extravasation traps cells within the thickened subendothelial space. The ongoing pathological process thus initiated is characterized by continuous recruitment and infiltration of cholesterol-laden foam cells, inflammatory and hematopoietic cells, and progressive accumulation of lipid matrix and smooth muscle proliferation via fatty Producing an occlusive lesion, which slowly rises the endothelium and begins to invade the arterial lumen. When atherosclerotic plaques grow large enough to reduce the flow of blood and oxygen to vital organs, they can cause chest pain (angina pectoris), mini-strokes (transient ischemic attacks), and circulation. Causes a chronic clinical syndrome of insufficiency (claudication). More complex plaques with stiffened cores and degenerated fibrous caps can rupture suddenly leading to acute occlusion of the arteries in which they reside. These lead to severe life-threatening clinical events of heart attack (myocardial infarction), stroke (cerebrovascular accident) and gangrene (critical limb ischemia).

Intravascular Metallic Stents The first stent type widely applied to treat atherosclerotic plaque was the balloon expandable stent (BES), designed as an open mesh tube made of stainless steel. When crimped onto the angioplasty balloon, it could be coaxially advanced through the arterial tree and deployed directly into the plaque. Stent implantation created a larger, more durable passageway compared to balloon angioplasty alone.

Today, balloon-expandable stents are deployed in nearly all cases of percutaneous coronary intervention (PCI) and about half of all peripheral interventional procedures.

A peripheral BES is a rigid medical device to support large open arteries and avoid excessive recoil and deformation. These typically have pressures of 0.5-2×10 ⁵ Pa (375-1500 mmHg, 0.05-0.2 N/mm ² ), well above the intra- or extravascular pressures observed in the human body. Designed to withstand non-physiological forces. In fact, the BES is more than ten times stiffer than the vessels it occupies. Because they are so rigid, BES have been implanted only in a limited number of anatomical locations, those with minimal or easily predictable arterial motion, such as the coronary, renal, and common iliac arteries. obtain. Therefore, BES implantation is strongly discouraged in many important peripheral vascular beds, including the carotid, subclavian, external iliac, common femoral, superficial femoral, and popliteal arteries.

The stiffness of BES also severely limits the usable length. Implanted stents that are too long can twist or tear the moving artery, leading to restenosis, thrombosis, formation of pseudoaneurysms, and possibly failure and migration of the device. Recognizing the danger, stent manufacturers have made devices available in limited lengths. Atherosclerotic lesions in peripheral arteries can be several hundred mm long, but the longest available BES is only 60 mm. They are clearly inadequate for intervention in the leg, where lesions over 200 mm routinely occur.

As early as 1969, it was theorized that intravascular stents should be flexible rather than rigid. An equiatomic nickel-titanium alloy called Nitinol, originally developed for aerospace applications, was thought to exhibit ideal mechanical properties for vascular scaffolding. One property was superelasticity, the ability of the metal to return to its original shape after significant deformation. This ensured flexibility within moving arteries in the human body. Another property was shape memory, the ability of the alloy to anneal at a temperature, deform sufficiently at low temperatures, and then return to its original shape upon heating. This allowed the nitinol stent to be cryogenically compressed into a delivery system and then released and expanded within a warm mammalian environment upon implantation.

The first self-expanding Nitinol stent (SES) approved for clinical use was a simple coiled wire made of Nitinol. It was introduced to the American market in 1992. Shortly after seamless tubes of nitinol became available, the development of laser-cut tubular nitinol stents became possible. Today, tubular Nitinol SES is the most common device deployed in long, flexible vessels such as the external iliac and superficial femoral arteries.

Since SES does not generate as much force as BES, it rarely fully dilates the vessel. In order to expand them more fully, SESs are periodically post-expanded with a large diameter balloon after deployment. However, even after repeated balloon dilatations, the relatively weak SES fails to overcome the inward force of the recoil artery, resulting in an insufficient post-treatment diameter. This occurs surprisingly frequently after SES deployment, especially in peripheral arteries suffering from significant atherosclerotic disease. In one study, underdilation of the target lesion (≥30% residual stenosis) was observed in 70% of cases after implantation of SES in calcified arteries.

A second drawback to the use of Nitinol SES is its disturbing tendency to breakage. Although rarely observed in BES, SES failure is surprisingly common, as high as 65% in one clinical report. Although not fully understood, one attractive hypothesis for this phenomenon is that failure may be a function of the inherent biomechanical forces on stents in the lower extremities. Leg motion is a complex movement, and hip and knee loads during walking can repeatedly axially compress arteries and even produce multidimensional bends, twists, and kinks. The result is failure of a single or multiple struts or, in severe cases, complete severance of the stent. Fractures are more common after implantation of long and/or overlapping stents and possibly in more active patients. Although intravascular stent failure is clearly associated with restenosis, it is controversial whether the relationship is related or causal.

The unique mechanism and design of SES ensures that the chronic force pattern on stented arteries is significantly different from that of BES. After BES deployment, the force on the artery is static and temporary. The artery is disturbed by the initial stretch and stent deployment, but heals completely and returns to rest upon recovery. However, vessels housing Nitinol SES are continuously exposed to chronic outward force (COF) exerted by the ever-expanding tortuous device. COF accompanies all SES transplants, since by definition the SES must be "oversized" at the time of transplantation. That is, the nominal diameter of the stent must in all cases exceed the reference vessel diameter (RVD) of the target lesion, so that the flexible, unanchored device stays in place after deployment. stay. Since the final diameter of the device is always smaller than its nominal "shape memory" diameter as manufactured, it exerts an outwardly expanding force on the vessel wall until its nominal diameter is reached (very rare). continue. Combined with the motion of the vessel in which SES is typically implanted, this ensures continuous and chronic perturbation of the vessel wall for many years after deployment of the device. Arteries respond with chronic inflammation, foreign body reaction, smooth muscle cell proliferation and restenosis. This is particularly troublesome in anatomical regions that are prone to bending and kinking, such as the common femoral artery. This problem is so prevalent that implanting Nitinol SES in the hip or knee is surgically discouraged.

Finally, although nitinol SES is much more flexible than its BES counterpart, it is certain that continued thickening of SES-treated arteries will ultimately lead to stiffer stented arteries. . Even arteries treated with so-called "flexible" stents develop significant foreign body reactions, stiffening and inducing kinks and twists in the non-stented portion. Exaggerated motion of the remaining arteries may still allow restricted motion and maintain patency, but the resulting abnormal flow patterns and compliance may lead to thrombosis and dysfunction. are very many.

Given the non-physiological nature of SES in the highly resistant peripheral vasculature, their overall low efficacy is not surprising. One-year primary patency of superficial femoral arteries treated with SES remains dismal at 60% and continues to decline over the years.

Absorbable Intravascular Stents Stents that slowly dissolve after deployment have long been envisioned to address the myriad of problems associated with permanent metal implants. So-called “bioabsorbable vascular scaffolds” (BVS) are (1) effective scaffolds without the permanence of metal implants, (2) reducing inflammation and chronic foreign body reaction leading to reduced restenosis and enhanced long-term patency. (3) supporting adaptive vascular remodeling; (4) restoring physiological vasoactive function; and (5) facilitating imaging and monitoring during follow-up. Potentially offers advantages.

The original bioabsorbable device was the "gut" surgical suture, first evidence in the historical record about 4,000 years ago. Gut sutures, derived from the dried intestines of sheep, goats, or cows, were probably also used as strings for musical instruments sometimes called "kits," hence the name "gut cord." Catgut sutures can be classified as bioabsorbable because they are enzymatically degraded and resorbed in vivo. More modern bioabsorbable surgical sutures are synthetic. Other recently developed bioabsorbable medical devices include bioabsorbable screws and fracture plates for the treatment of traumatic injuries, indwelling scaffolds that serve as the basis for tissue engineering and regenerative medicine, and chemotherapy for tumor treatment. Included are carrier polymers, inert synthetic wraps for the prevention of postoperative peritoneal adhesions, bioabsorbable scaffolds for stenting the upper airway and ear canal, and bioabsorbable intravascular scaffolds (stents). Unfortunately, recent longer-term results have raised questions regarding the safety and efficacy of first-generation absorbable coronary stents.

Thus, in order to maximize the expansion and scaffolding of arteries, in the vasculature, which is stiff at the time of implantation, but whose stiffness is slowly reduced to allow the vessels to return to their original healthy and flexible state. It would be advantageous to have a stent for use. At least some of these objectives will be met by the embodiments described below.

Embodiments herein describe devices for placement within a blood vessel to maintain or enhance blood flow through the vessel. The device may include a plurality of balloon-expandable bioabsorbable vascular stent elements configured to be implanted within a vessel as a multi-element stent. The stent elements can be spaced apart such that the stent elements do not contact each other. The stent elements are formed from a bioabsorbable polymeric material. The radial stiffness of the stent is configured to decrease after implantation into a vessel as the polymer is resorbed. In some embodiments, the stent is configured to provide an initial radial stiffness to the vessel upon implantation of greater than or equal to about 15 N/cm. The stent can be configured to provide a reduction in radial stiffness of the vessel to less than 1 N/cm over about two years. The stent thickness, cell shape, polymeric material, and treatment of the polymeric material can be configured to provide a reduction in the radial stiffness of the vessel over time.

In some embodiments, the stent is poly(L-lactic acid) (PLLA), poly(D-lactic acid) (PDLA), poly(D,L-lactic acid) (PDLLA), semi-crystalline polylactide, polyglycolic acid (PGA), poly(lactic-co-glycolic acid) (PLGA), poly(desaminotyrosyl iodide-tyrosine ethyl ester) carbonate, polycaprolactone (PCL), salicylate-based polymer, polydioxanone (PDS), poly(hydroxy butyrate), poly(hydroxybutyrate-co-valerate), polyorthoester, polyanhydride, poly(glycolic acid-co-trimethylene carbonate), poly(iodinated desaminotyrosyl-tyrosine ethyl ester) carbonate, poly phosphoesters, polyphosphoester urethanes, poly(amino acids), cyanoacrylates, poly(trimethylene carbonates), poly(iminocarbonates), polyalkyleneoxalates, polyphosphazenes, polyiminocarbonates, and aliphatic polycarbonates, fibrin, fibrinogen, Polyurethanes, including cellulose, starch, collagen, polycarbonate urethanes, polyethylene, polyethylene terephthalate, ethylene vinyl acetate, ethylene vinyl alcohol, silicones, including polysiloxanes and substituted polysiloxanes, polyethylene oxides, polybutylene terephthalate-co-PEG, PCL-co- It may be formed from materials including PEG, PLA-co-PEG, PLLA-co-PCL, polyacrylate, polyvinylpyrrolidone, polyacrylamide, or combinations thereof.

In one embodiment, the stent includes a therapeutic agent. A therapeutic agent may prevent or attenuate inflammation, cell dysfunction, cell activation, cell proliferation, neointima formation, hypertrophy, late atherosclerotic changes, or thrombosis.

In one embodiment, the radial stiffness of the stent slowly decays as its structural polymers are debonded and metabolized, so that the stent slowly becomes more flexible and vascular adaptation and remodeling. as well as causing restoration of elasticity of blood vessels.

This and other aspects of the disclosure are described herein.

The present embodiments have other advantages and features that will become more readily apparent from the following detailed description and the appended claims, taken in conjunction with the accompanying drawings.

Figure 2 shows a typical radial resistance force of an intravascular stent. Figure 2A illustrates one embodiment of a multi-component stent. Figure 2B is an enlarged view of the stent element of Figure 2A. 1 depicts deployment of a balloon-expandable multi-element stent. A multi-element stent implanted in the popliteal artery is shown with the hip and knee fully flexed. 4B depicts the implanted device of FIG. 4A in three dimensions; 4 shows an embodiment of a stent pattern; FIG. 5A is a two-dimensional representation of the element. 5B, 5D and 5E are enlarged views of the cell of FIG. 5A. Figures 5C and 5F show the stent element of Figure 5A in cylindrical form. FIG. 6A is a two-dimensional representation of an element with a leaflet cell structure. FIG. 6B is an enlarged view of the cell of FIG. 6A. FIG. 6C shows the stent element of FIG. 6A in cylindrical form. FIG. 7A is a two-dimensional representation of an element with a ratchet configuration. FIG. 7B is an enlarged view of the cell of FIG. 7A. FIG. 7C is an isometric view of the cell of FIG. 7A. Figure 7D is a cross-sectional view of the cell of Figure 7C showing the ratchet. FIG. 7E is an enlarged view of the ratchet of FIG. 7D. FIG. 7F is an alternate view of the ratchet in cross section. FIG. 8A is a two-dimensional representation of an element having a bistable spring band configuration. FIG. 8B is an enlarged view of the cell of FIG. 8A. Figure 8C is an isometric view of the cell of Figure 8A. Figure 8D is a cross-sectional view of the cell of Figure 8C showing the curvature of the bistable strut. FIG. 8E is an enlarged view of the bistable strut of FIG. 8D. FIG. 8F is an alternative view of the bistable strut in cross section. FIG. 9A is a two-dimensional representation of an element having a pivot configuration. FIG. 9B is an enlarged view of the cell of FIG. 9A. 1 is a schematic illustration of a microstereolithograph used to fabricate a stent, according to one embodiment; FIG. FIG. 4 shows an angiographic image of a porcine iliofemoral artery treated with a device described herein. FIG. 11B is an angiogram of the iliofemoral artery of the same pig as FIG. 11A with a self-expanding nitinol stent. Figure 2 shows the radial resistance of stented arteries over time.

Although the present invention has been disclosed with reference to specific embodiments, it will be appreciated by those skilled in the art that various changes can be made and equivalents substituted without departing from the scope of the invention. . In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the scope of the invention.

Throughout the specification and claims, the following terms take the meanings explicitly associated with them, unless the context clearly dictates otherwise. The meanings of "a," "an," and "the" include plural references. The meaning of "middle" includes "middle" and "upper". Referring to the drawings, like numbers refer to like parts throughout the figures. Additionally, singular references include plural references unless stated otherwise or consistent with the disclosure herein.

The word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any implementation described herein as "exemplary" is not necessarily to be construed as advantageous over other implementations.

Various embodiments are described herein with reference to figures. The figures are not drawn to scale and are only intended to facilitate the description of the embodiments. They are not intended as an exhaustive description of the invention or as a limitation on the scope of the invention. Additionally, an illustrated embodiment need not have all the aspects or advantages shown. Aspects or advantages described in connection with a particular embodiment are not necessarily limited to that embodiment, and may be implemented in any other embodiment, even if not so illustrated.

FIG. 1 shows a typical radial resistance force of an intravascular stent. A typical “bioabsorbable vascular scaffold” (BVS) or absorbable stent has a radial force of less than 2 N/cm. Similarly, a typical self-expanding metal stent (SES) has a radial force of less than 2 N/cm. A typical balloon expandable metal stent (BES) has much higher radial resistance, which can exceed 18 N/cm.

Embodiments herein are much larger than and comparable to those provided by a typical absorbable or self-expanding metal stent (SES) and balloon expandable metal stent (BES). We describe a novel intravascular absorbable device design that maintains long blood vessel passageways (patency) by providing temporary rigid radial support to provide temporary, rigid radial support. When implanted, the absorbable device exerts a high degree of radial force to hold the diseased artery open, roughly equivalent to a large diameter peripheral balloon expandable metal stent.

In contrast to most stent patterns designed to combine both radial force and longitudinal flexibility, the pattern described herein maximizes radial force and stiffness, Specially tailored to eliminate directional and axial flexibility.

The devices described herein are multi-component vascular stents (or "vascular scaffolds"). These stents are composed of a plurality of short rigid cylindrical stent segments or elements that are separate from each other, but are sometimes collectively referred to as multi-element stents.

Generally, each element of the multi-element stents described herein will be sufficiently stiff to provide the desired level of strength to withstand the stresses of the vessels in which they are placed, such as tortuous peripheral vessels. . At the same time, multi-element stents are also flexible because they are constructed from multiple discrete elements, and thus can be deployed in curved and tortuous vessels.

Additionally, balloon-expandable stents are typically stronger than self-expanding stents, so the multi-component stents described herein will typically be balloon-expandable rather than self-expanding. . Each balloon expandable element of the stent can have a relatively high radial force (stiffness) due to the structure and materials described. A stent element is radially stiff if it is significantly radially stronger than a self-expanding stent of similar or greater size than a conventional balloon expandable metal stent, such as steel or cobalt chromium. is defined as having

When serially mounted on inflatable balloons, they can be implanted side-by-side in long vessels at the same time. During movement of the organism, the elements can move independently and maintain their individual shape and strength, while the non-stented intervening elements of the vessel can twist, bend, and rotate unimpeded. can. The result is a treated vessel with a flow path that remains rigid and is indefinitely flexible during organism movement.

The described embodiments demonstrate that (1) rigid devices deployed via balloon expansion represent the optimal design of intravascular stents considering their temporal impact on the arterial wall and relative ease of accurate implantation; (2) long rigid devices cannot be safely implanted in arteries that bend and twist with skeletal motion; and (4) the length, number, and spacing of stent elements can be determined by the known and predictable bending properties of the target artery. and (5) arteries need scaffolding only temporarily, and the delayed dissolution of the stent has little effect on the long-term efficacy of the treatment.

To treat long occlusive lesions in bendable human arteries, such as the superficial femoral artery of the thigh, the device consists of a series of identical or nearly identical cells spaced evenly on a single long balloon. can be formed as a rigid element of The spacing of elements in a multi-element stent is described in PCT International Application No. PCT/US16/55953, entitled "RADIALLY RIGID AND LONGITUDINALLY FLEXIBLE MULTI-ELEMENT INTRAVASCULAR STENT," the full disclosure of which is incorporated herein by reference. incorporated into the book.

One embodiment of a fully assembled device is shown in FIG. 2A. A single balloon inflation and device deployment can treat long segments of diseased arteries while preserving the artery's important ability to bend with skeletal movements such as sitting or walking. Multi-element stent 200 includes multiple stent elements 201 . Individual balloon expandable stent elements 201 are crimped onto an inflatable balloon 203 to facilitate delivery. FIG. 2B is an enlarged view of stent element 201 of FIG. 2A. The individual elements 201 are positioned sequentially along the longitudinal length of the balloon 203 and are spaced apart so that the stent elements 201 do not contact each other. Further, the spacing is such that the stent elements 201 do not contact or overlap during skeletal movement after deployment. The number of elements 201, the length of the elements, and the gaps 202 between elements 201 may vary depending on the target vessel location. In one embodiment, each element 201 in multi-element stent 200 has the same length. In a multi-element stent having three or more elements 201 and thus two or more gaps 202, the gaps can be the same length.

Figures 3A-3C depict the deployment of a balloon expandable multi-element stent. In FIG. 3A, a multi-element stent mounted on a balloon has been advanced to the lesion. In Figure 3B, the balloon and stent are expanded. In FIG. 3C, the balloon is withdrawn, leaving the multi-element stent still in the artery.

FIG. 4A shows a multi-element stent implanted in the popliteal artery with the hip and knee fully flexed. FIG. 4B depicts the implanted device of FIG. 4A shown in three dimensions. The individual stent elements 401 are spaced apart so that they do not overlap even when the artery is highly tortuous. Unobstructed arterial motion is provided by flexing or stretching of the stentless gap 402 .

The stents described herein can be formed from a variety of different materials. In one embodiment, a stent may be formed of a polymer. In various alternative embodiments, the stent or stent elements are made of, for example, poly(L-lactic acid) (PLLA), polyglycolic acid (PGA), poly(iodinated desaminotyrosyl-tyrosine ethyl ester) carbonate, and the like. It may be made from any suitable bioabsorbable material, including but not limited to, non-toxic and soluble in the human body.

In alternate embodiments, any suitable polymer can be used to construct the stent. The term "polymer" includes homopolymers, copolymers, terpolymers, etc., whether natural or synthetic, including random, alternating, block, graft, branched, crosslinked, mixtures, compositions of mixtures, and variations thereof. is intended to include the products of polymerization reactions, including The polymer can be in true solution as particles, saturated or suspended, or supersaturated in the beneficial agent. Polymers can be biocompatible or biodegradable. For purposes of illustration and not limitation, polymeric materials include poly(D-lactic acid) (PDLA), poly(D,L-lactic acid) (PDLLA), poly(iodinated desaminotyrosyl-tyrosine ethyl ester) carbonate, Poly(lactic-co-glycolic acid) (PLGA), salicylate-based polymers, semicrystalline polylactide, phosphorylcholine, polycaprolactone (PCL), poly-D, L-lactic acid, poly-L-lactic acid, poly(lactide-co- glycolide), poly(hydroxybutyrate), poly(hydroxybutyrate-co-valerate), polydioxanone (PDS), polyorthoester, polyanhydride, poly(glycolic acid), poly(glycolic acid-co-trimethylene carbonate) , polyphosphoesters, polyphosphoester urethanes, poly(amino acids), cyanoacrylates, poly(trimethylene carbonates), poly(iminocarbonates), polyalkyleneoxalates, polyphosphazenes, polyiminocarbonates, and aliphatic polycarbonates, fibrin, Polyurethanes including fibrinogen, cellulose, starch, collagen, polycarbonate urethanes, polyethylene, polyethylene terephthalate, ethylene vinyl acetate, ethylene vinyl alcohol, silicones including polysiloxanes and substituted polysiloxanes, polyethylene oxides, polybutylene terephthalate-co-PEG, PCL- May include, but are not limited to, co-PEG, PLA-co-PEG, PLLA-co-PCL, polyacrylate, polyvinylpyrrolidone, polyacrylamide, and combinations thereof. Other non-limiting examples of suitable polymers include thermoplastic elastomers in general, polyolefin elastomers, EPDM rubbers, and polyamide elastomers, as well as biostable plastic materials including acrylic polymers and their derivatives, nylons, polyesters, and epoxies. included. In some embodiments, a stent can include one or more coatings with materials such as poly(D,L-lactic acid) (PDLLA). However, these materials are merely examples and should not be considered as limiting the scope of the invention.

Stent elements can include a variety of shapes and configurations. Some or all of the stent elements may include closed cell structures formed by intersecting struts. Closed cell structures may include diamond, square, rectangular, parallelogram, triangular, pentagonal, hexagonal, heptagonal, octagonal, cloverleaf, leaflet, circular, elliptical, and/or oval shapes. Closed cells may also include slot-type geometries such as H-slots, I-slots, J-slots, and the like. Additionally or alternatively, a stent may include an open cell structure, such as a helical, serpentine, zigzag structure. Intersections of struts can form pointed, vertical, rounded, blunt-ended, flat, beveled, and/or chamfered cell corners. In one embodiment, a stent may include a plurality of different cells having different cell shapes, orientations, and/or sizes. Various cell structures are described in PCT International Application No. PCT/US16/20743, entitled "MULTI-ELEMENT BIORESORBABLE INTRAVASCULAR STENT," the full disclosure of which is incorporated herein by reference. In one embodiment, the stent element can include a plurality of closed diamond-shaped cells that are longer longitudinally than radially when in the unexpanded state. The stent element may also include a plurality of closed diamond-shaped cells that are radially longer than longitudinally in the expanded state.

One embodiment of a stent pattern is shown in Figures 5A-5F. Stent element 501 has a diamond-shaped closed cell pattern. Element 501 includes mixed diamond-shaped closed cells 504 , 505 . Diamond-shaped cells 504 may be aligned longitudinally and/or circumferentially in a repeating pattern. Similarly, diamond-shaped cells 505 may be aligned longitudinally and/or circumferentially in a repeating pattern. Additionally or alternatively, diamond-shaped cells 504 and diamond-shaped cells 505 may be spirally aligned in an alternating pattern. In one embodiment, diamond-shaped cells 504 and diamond-shaped cells 505 are circumferentially offset. Additionally, a diamond-shaped cell 205 can be formed in a central location between four adjacent diamond-shaped cells 504 . The width and/or height of the struts 506 between the two corners of the longitudinally aligned diamond-shaped cells 504 are equal to the width and/or height of the struts 507 between the two corners of the longitudinally aligned diamond-shaped cells 505. It may be larger than the width and/or height.

Returning to FIG. 2B, in this exemplary embodiment, stent element 201 has a diamond-shaped closed cell pattern. Element 201 includes mixed diamond-shaped closed cells 204 , 205 . Diamond-shaped cells 204 may be aligned longitudinally and/or circumferentially in a repeating pattern. Similarly, diamond-shaped cells 205 may be aligned longitudinally and/or circumferentially in a repeating pattern. Additionally or alternatively, diamond-shaped cells 204 and diamond-shaped cells 205 may be spirally aligned in an alternating pattern. In one embodiment, diamond-shaped cells 204 and diamond-shaped cells 205 are circumferentially offset. Additionally, a diamond-shaped cell 205 can be formed at a central location between four adjacent diamond-shaped cells 204 . The width of the struts 206 between the two corners of the longitudinally aligned diamond-shaped cells 204 is greater than the width of the struts 207 between the two corners of the longitudinally aligned diamond-shaped cells 205.

Figures 6A-6C show embodiments of stent elements having a cloverleaf or leaflet cell configuration. Although FIGS. 6A-6C depict cells with four leaflets, cells can have any number of leaflets. FIG. 6A is a two-dimensional representation of an element with a leaflet cell structure. FIG. 6B is an enlarged view of the cell of FIG. 6A. FIG. 6C shows the stent element of FIG. 6A in a cylindrical form, with the two diamond-shaped cells of FIG. 6A wrapped from left to right to form a cylinder. In this embodiment, element 600 includes interleaved leaflet-like closed cells 601 , 602 . Leaflet cells 601 may be aligned longitudinally and/or circumferentially in a repeating pattern. Similarly, leaflet cells 602 may be aligned longitudinally and/or circumferentially in a repeating pattern. Additionally or alternatively, the leaflet cells 602 and diamond-shaped cells 601 may be spirally aligned in an alternating pattern. In one embodiment, leaflet cells 602 and leaflet cells 601 are circumferentially offset. Additionally, a diamond-shaped cell 602 can be formed at a central location between four adjacent diamond-shaped cells 601 . In the embodiment shown in FIGS. 6A-6C, longitudinally aligned longitudinal leaflets 603 are larger than circumferentially aligned circumferential leaflets 604 . Alternatively, longitudinal leaflets 603 can be the same size as circumferential leaflets 604 . Longitudinal leaflets 603 of adjacent longitudinally aligned leaflet cells 1001 may be connected by longitudinally connecting struts 605 . Circumferential leaflets 604 of adjacent circumferentially aligned leaflet cells 601 may be connected by circumferentially connecting struts 606 . In one embodiment, longitudinally connecting struts 605 are wider than circumferentially connecting struts 606 . Alternatively, longitudinally connecting struts 605 may have the same width as circumferentially connecting struts 606 . Element 600 can assume a crimped configuration when attached to an unexpanded balloon. Similarly, element 600 can assume an expanded configuration when expanded by a balloon. Concave surface 607 moves away from the center of leaflet element 600 as leaflet cell 601 transitions from the crimped state to the expanded state.

Figures 7A-7F show embodiments of stent elements having a ratchet configuration. Although Figures 7A-7F show cells in a diamond configuration, the cells can have any closed cell configuration. FIG. 7A is a two-dimensional representation of an element with a ratchet configuration. FIG. 7B is an enlarged view of the cell of FIG. 7A. FIG. 7C is an isometric view of the cell of FIG. 7A. 7D is a cross-sectional view of the cell of FIG. 7C showing ratchet 707. FIG. FIG. 7E is an enlarged view of ratchet 707 of FIG. 7D. FIG. 7F is an alternate view of ratchet 707 in cross section. A stent element having the cell structure of FIG. 7A may have a left-to-right winding orientation to form a cylinder. In this embodiment, element 700 includes intermingled ratchet cells 701 and non-ratchet cells 702 . Ratchet cells 701 may be aligned longitudinally and/or circumferentially in a repeating pattern. Similarly, non-ratchet cells 702 may be aligned longitudinally and/or circumferentially in a repeating pattern. Additionally or alternatively, the unratcheted cells 702 and ratcheted cells 701 may be spirally aligned in an alternating pattern. In one embodiment, the non-ratchet 702 and ratchet cells 701 are circumferentially offset. Additionally, a non-ratchet cell 702 can be formed at a central location between four adjacent ratchet cells 701 . In the embodiment shown in FIGS. 7A-7F, the ratchet cells 701 can have the same or similar size as the non-ratchet cells 702 . Alternatively, ratchet cells 701 may be larger or smaller than non-ratchet cells 702 . Adjacent longitudinally aligned ratchet cells 701 may be connected by longitudinally connecting struts 705 . Adjacent circumferentially aligned ratchet cells 701 may be connected by circumferentially connecting struts 706 . In one embodiment, longitudinally connecting struts 705 may have a greater length or width than circumferentially connecting struts 706 . Alternatively, longitudinally connecting struts 705 may have the same length or width as circumferentially connecting struts 706 . Ratchet cell 701 includes longitudinally aligned ratchet posts 703 . The longitudinally aligned corners of ratchet cells 701 and/or longitudinally connecting struts 705 may include cavities 708 to accommodate linear racks 709 on ratchet struts 703 . Pawl 710 engages tooth 711 of linear rack 709 . Element 700 can assume a crimped configuration when attached to an unexpanded balloon. Similarly, element 700 can assume an expanded configuration when expanded by a balloon. Linear rack 707 moves longitudinally into cavity 708 when ratchet element 700 transitions from the crimped state to the expanded state (shown from bottom to top in FIG. 7E and right to left in FIG. 7F). Ratchet 707 may thereby increase the radial strength of element 700 .

Figures 8A-8F show embodiments of stent elements having a bistable spring band configuration. Although Figures 8A-8F show cells in a diamond configuration, the cells may have any closed cell configuration. FIG. 8A is a two-dimensional representation of an element having a bistable spring band configuration. FIG. 8B is an enlarged view of the cell of FIG. 8A. Figure 8C is an isometric view of the cell of Figure 8A. 8D is a cross-sectional view of the cell of FIG. 8C showing the curvature of bistable strut 803. FIG. FIG. 8E is an enlarged view of the bi-stable strut 803 of FIG. 8D. FIG. 8F is an alternative view of bistable strut 803 in cross section. A stent element having the cell structure of FIG. 8A may have a left-to-right winding orientation to form a cylinder. In this embodiment, element 800 includes a mixture of bistable cells 801 and non-bistable cells 802 . Bi-stable cells 801 may be aligned longitudinally and/or circumferentially in a repeating pattern. Similarly, non-bistable cells 802 may be longitudinally and/or circumferentially aligned in a repeating pattern. Additionally or alternatively, non-bistable cells 802 and bistable cells 801 may be spirally aligned in an alternating pattern. In one embodiment, non-bistable 802 and bistable cells 801 are circumferentially offset. Additionally, a non-bistable cell 802 can be formed in a central location between four adjacent bistable cells 801 . In the embodiments shown in FIGS. 8A-8F, the bistable cells 801 can have the same or similar size as the non-bistable cells 802. FIG. Alternatively, bistable cell 1301 may be larger or smaller than non-bistable cell 802 . Adjacent longitudinally aligned bistable cells 801 may be connected by longitudinal connecting struts 805 . Adjacent circumferentially aligned bistable cells 801 may be connected by circumferentially connecting struts 806 . In one embodiment, longitudinally connecting struts 805 may have a greater length or width than circumferentially connecting struts 806 . Alternatively, longitudinally connecting struts 805 may have the same length or width as circumferentially connecting struts 806 . Bi-stable cell 801 includes circumferentially aligned bistable struts 803 . The bistable strut 803 has a bistable spring band configuration. In one embodiment, bistable strut 803 has a concave-convex shape. The bistable post 803 can take a straight form or a bent form, with the bistable post 803 bending in a concave direction. The stiffness of bistable struts 803 in straight form increases the radial strength of element 800 . As shown in FIGS. 8C-8F, the concave curved surface of bistable strut 803 can be oriented longitudinally and face the proximal or distal opening of cylindrical element 800 . Element 800 can assume a crimped configuration when attached to an unexpanded balloon. Similarly, element 800 can assume an expanded configuration when expanded by a balloon. The bistable strut 803 can have a bent configuration in the crimped configuration. In the expanded state, the bistable strut can have a straight configuration.

Figures 9A and 9B show embodiments of stent elements having a pivot configuration. FIG. 9A is a two-dimensional representation of an element having a pivot configuration. FIG. 9B is an enlarged view of the cell of FIG. 9A. A stent element having the cell structure of FIG. 9A may have a left-to-right winding orientation to form a cylinder. In this embodiment element 900 comprises an alternating array of two larger cells 901 and a set of smaller cells 902 . The two larger cells 901 allow bending of the freely moving pivot struts 903 separating the two larger cells 901 . Element 900 can assume a crimped configuration when attached to an unexpanded balloon. Similarly, element 900 can assume an expanded configuration when expanded by a balloon. Figures 9A-9B show the unstable, less stiff configuration of the pivot strut 903 that exists when the element 900 is in the crimped state. When expanded, the apex 904 of the pivot strut 903 will transition from right to left (based on the orientation of FIGS. 9A and 9B), thereby increasing the stiffness of the pivot strut 9 and the radial direction of the element 900. Increases strength.

The devices described herein are useful for pathological endoluminal interventions such as inflammation, cell dysfunction, cell activation, cell proliferation, neointima formation, hyperplasia, late atherosclerotic changes, and/or thrombosis. Incorporation of therapeutic agents intended to prevent or lessen the consequences may be included. In various embodiments, any suitable therapeutic agent (or "drug") can be incorporated into, coated onto, or otherwise attached to the stent. Examples of such therapeutic agents include antithrombotic agents, anticoagulants, antiplatelet agents, antilipid agents, thrombolytic agents, antiproliferative agents, antiinflammatory agents, agents that inhibit hyperplasia, smooth muscle cell inhibitors. , antibiotics, growth factor inhibitors, cell adhesion inhibitors, cell adhesion promoters, antimitotic agents, antifibrin, antioxidants, antitumor agents, agents that promote endothelial cell recovery, matrix metalloproteinase inhibitors, Antimetabolites, antiallergic substances, virus vectors, nucleic acids, monoclonal antibodies, tyrosine kinase inhibitors, antisense compounds, oligonucleotides, cell penetration enhancers, hypoglycemic agents, hypolipidemic agents, proteins, nucleic acids, useful for stimulating erythropoiesis angiogenic agents, antiulcer/antireflux agents, and antiemetic/antiemetic agents, PPAR alpha agonists such as fenofibrate, selected PPAR-gamma agonists such as rosiglitazone and pioglitazone, heparin disodium, LMW heparin , heparoids, hirudin, argatroban, forskolin, bapriprost, prostacyclin and prostacillin analogues, dextran, D-phe-pro-arg-chloromethylketone (synthetic antithrombin), glycoprotein IIb/IIIa (platelet membrane receptor antagonist antibody), recombinant hirudin, thrombin inhibitor, indomethacin, phenyl salicylate, beta-estradiol, vinblastine, ABT-627 (astracentan), testosterone, progesterone, paclitaxel, methotrexate, fotemsin, RPR-101511A, cyclosporine A, vincristine, carvediol, vindesine, dipyridamole, methotrexate, folic acid, thrombospondin mimetics, estradiol, dexamethasone, metrizamide, iopamidol, iohexol, iopromide, iobitridol, iomeprol, iopentol, ioversol, ioxirane, iodixanol, and iotrolan, antisense compounds, smooth muscle cell growth inhibitors, lipid-lowering agents, radiopaque agents, antineoplastic agents, HMG CoA reductase inhibitors such as lovastatin, atorvastatin, simvastatin, pravastatin, cerivastatin, and fluvastatin, and combinations thereof, but It is not limited to these.

Examples of antithrombotic, anticoagulant, antiplatelet, and thrombolytic agents include low molecular weight heparins such as sodium heparin, unfractionated heparin, dalteparin, enoxaparin, nadroparin, reviparin, aldoparin, and sertaparin, heparinoids, hirudin , argatroban, forskolin, bapriprost, prostacyclin and prostacillin analogs, dextran, D-phe-pro-arg-chloromethylketone (synthetic antithrombin), dipyridamole, glycoprotein IIb/IIIa (platelet membrane receptor antagonist antibody ), recombinant hirudin and bivalirudin, thrombin inhibitors such as thrombin inhibitors, and thrombolytic agents such as urokinase, recombinant urokinase, prourokinase, tissue plasminogen activator, ateplase, and tenecteplase. including but not limited to.

Examples of cytostatic or antiproliferative agents include rapamycin and its analogs, including everolimus, zotarolimus, tacrolimus, novolimus, and pimecrolimus; angiotensin-converting enzyme inhibitors, such as angiopeptin, captopril, cilazapril, or lisinopril; nifedipine; Calcium channel blockers such as amlodipine, cilnidipine, lercanidipine, benidipine, trifluperazine, diltiazem, and verapamil, fibroblast growth factor antagonists, fish oil (omega-3-fatty acids), histamine antagonists, lovastatin, etoposide and topotecan. Included, but not limited to, topoisomerase inhibitors, and antiestrogens such as tamoxifen.

Examples of anti-inflammatory agents include, but are not limited to, colchicine and glucocorticoids such as betamethasone, cortisone, dexamethasone, budesonide, prednisolone, methylprednisolone, and hydrocortisone. Non-steroidal anti-inflammatory agents include flurbiprofen, ibuprofen, ketoprofen, fenoprofen, naproxen, diclofenac, diflunisal, acetominophen, indomethacin, sulindac, etodolac, diclofenac, ketorolac, meclofenamic acid, piroxicam, and phenylbuta including, but not limited to, zone.

Examples of antineoplastic agents include altretamine, bendamusine, carboplatin, carmustine, cisplatin, cyclophosphamide, fotemustine, ifosfamide, lomustine, nimustine, prednimustine, and alkylating agents including treosulfine, vincristine, vinblastine, paclitaxel, docetaxel. Mitotic drugs including antimitotics, antimetabolites including methotrexate, mercaptopurine, pentostatin, trimetrexate, gemcitabine, azathioprine, and fluorouracil, antibiotics such as doxorubicin hydrochloride and mitomycin, and promoting endothelial cell recovery such as estradiol include, but are not limited to, agents that

Antiallergic agents include pemirolast nitroprusside potassium, phosphodiesterase inhibitors, prostaglandin inhibitors, suramin, serotonin blockers, steroids, thioprotease inhibitors, triazolopyrimidines, and nitric oxide. Not limited.

A beneficial agent may include a solvent. The solvent can be any single solvent or combination of solvents. By way of illustration and not limitation, examples of suitable solvents include water, aliphatic hydrocarbons, aromatic hydrocarbons, alcohols, ketones, dimethylsulfoxide. , tetrahydrofuran, dihydrofuran, dimethylacetamide, acetate, and combinations thereof.

Stents can be manufactured using addition or subtraction. In any of the described embodiments, the stent or stent element may be manufactured as a sheet and rolled into a cylinder. Alternatively, the stent or stent elements can be manufactured cylindrically using additional manufacturing processes. In one embodiment, a stent may be formed by extruding material into a cylindrical tube. In some embodiments, longer stent elements may be formed during the manufacturing process and then cut into smaller stent elements/multiple elements to provide a multi-element stent. In one embodiment, a stent tube can be laser cut in a pattern to form stent elements.

Referring now to Figure 10, in one embodiment, a stent may be manufactured using a microstereolithography system 100 (or "3D printing system"). Some examples of currently available systems that can be used in various embodiments include MakiBox A6 (Makible Limited, Hong Kong), CubeX (3D Systems, Inc., Circle Rock Hill, SC), and 3D- Bioplotter (EnvisionTEC GmbH, Gladbeck, Germany), but not limited to.

A microstereolithography system may include an illuminator, a dynamic pattern generator, an imager, and a Z-stage. The illuminator may include a light source, filters, electronic shutters, collimating lenses, and reflectors that project uniformly intense light onto a digital mirror device (DMD) that produces a dynamic mask. FIG. 10 illustrates some of these components of one embodiment of microstereolithography system 100, including the DMD board, Z stage, lamp, platform, resin vat, and objective lens. Details of 3D printing/microstereolithography systems and other additional manufacturing systems are well known in the art and are not described here. However, according to various embodiments, any additional manufacturing system or process, whether now known or later developed, is potentially employed to manufacture stents within the scope of the present invention. can be used for In other words, the scope of the invention is not limited to any particular additional manufacturing system or process.

In one embodiment, system 100 may be configured to manufacture stents using dynamic mask projection microstereolithography. In one embodiment, a fabrication method may include first generating a 3D microstructured scaffold by slicing a 3D model with a computer program and solidifying and stacking the images layer by layer within the system. In one embodiment, the system's reflector is used to project uniformly intense light onto the DMD that produces the dynamic mask. The dynamic pattern generator creates images of sliced sections of the manufacturing model by generating black and white areas similar to masks. Finally, for image lamination, the resolution Z-stage moves up and down to refresh the resin surface for the next cure. In one embodiment, the Z-stage build subsystem has a resolution of approximately 100 nm and includes a platform for mounting the substrate, a vat for containing the polymer liquid solution, and a hot plate for controlling the temperature of the solution. . The Z stage creates a new solution surface with the desired layer thickness by moving deep downward, moving upward to a predetermined position, and then waiting a certain amount of time for the solution to be evenly dispersed.

Because the device is constructed entirely of bioabsorbable materials, it will slowly weaken and begin to dissolve quickly when exposed to a warm, bioactive environment. The device is designed to slowly decay its stiffness as its structural polymers are debonded and metabolized. As the device weakens, the effect on the vein wall is slowly released. Ultimately, the device has no radial impact on its host artery, thus completely eliminating any pathological stimulus for neointimal hyperplasia formation, ongoing hyperplasia and maladaptation. Lack of continued stimulation by an intravascular foreign body allows the vessel to reenter a quiescent patency until such time as additional plaque can be generated by its host.

FIG. 11A shows an angiographic image of a porcine iliofemoral artery treated with the device described herein at 1101 after one year. FIG. 11B shows an angiographic image of the iliofemoral artery of the same pig treated with a self-expanding nitinol stent at 1102, one year later. Clear neointimal hyperplasia is seen in the artery containing the self-expanding stent, but not in the artery of FIG. 11A.

FIG. 12 shows the radial resistance of a stented artery over time. A normal healthy artery has a radial force of less than 1 N/cm. An atherosclerotic artery containing plaque has a radial resistance of approximately 5 N/cm. Atherosclerotic arteries treated with conventional metallic balloon expandable stents have an initial radial resistance of about 15 N/cm. A vein containing a metal stent becomes stiffer over time. An atherosclerotic artery treated with a self-expanding stent can have an initial radial resistance of about 7 N/cm. Arteries containing self-expanding stents also become stiffer over time.

Atherosclerotic arteries treated with the devices described herein have similar initial radial resistance, about 15 N/cm, to arteries treated with metal balloon expandable stents. In other embodiments, a bioabsorbable stent can induce an initial radial resistance force in the range of 10-20 N/cm. As the bioabsorbable stent dissolves, it slowly becomes more flexible, allowing the artery to adapt and remodel, thereby restoring arterial elasticity. In one embodiment, the bioabsorbable stent dissolves over a period of about two years and reduces the radial stiffness of the stent over the same period. In other embodiments, a bioabsorbable stent can dissolve over a period of time ranging from 1.5 to 3 years. The radial resistance force of atherosclerotic arteries treated with bioabsorbable stents decreases over time, approaching the stiffness of healthy arteries of less than 1 N/cm. The stent thickness, cell geometry, polymeric material, and/or polymer treatment or treatment are configured to provide a particular dissolution rate and to provide the desired reduction in radial stiffness of the vessel over time. obtain.

Although specific embodiments have been shown and described, they are not intended to limit the invention. Various changes and modifications may be made to any of the embodiments without departing from the spirit and scope of the invention. The invention is intended to cover alternatives, modifications and equivalents.

Claims (21)

A device for placement within a blood vessel to maintain or enhance blood flow through the blood vessel, comprising:
a plurality of balloon-expandable bioabsorbable vascular stent elements configured to be implanted within said vessel as a multi-element stent, said stent elements being spaced apart such that said stent elements do not contact each other;
said stent element being formed from a bioabsorbable polymeric material, said stent element comprising closed cells;
the radial stiffness of the stent element is configured to decrease after implantation in a vessel as the polymer is resorbed;
The thickness of the stent elements, the shape of the closed cells, the cell pattern of the stent elements, and the polymeric material are configured to provide an initial radial stiffness to the vessel upon implantation of greater than or equal to about 15 N/cm. cage,
wherein the stent element is configured to provide a reduction in the radial stiffness of the vessel to a radial stiffness of less than 1 N/cm over a period of about two years, the thickness of the stent element, the The device, wherein the shape of the closed cells, the cell pattern of the stent elements, the polymeric material, and treatment of the polymeric material are configured to provide a decrease in radial stiffness of the vessel over time. 2. The device of claim 1, wherein the closed cells are diamond-shaped closed cells. 2. The device of claim 1, wherein the closed cells comprise a first set of closed cells and a second set of closed cells. The first set of closed cells has a repeating adjacent longitudinally aligned pattern and a repeating adjacent circumferentially aligned pattern, and the second set of closed cells has a repeating adjacent longitudinally aligned pattern. having a directionally aligned pattern and a repeating adjacent circumferentially aligned pattern, wherein the first set of closed cells and the second set of closed cells are circumferentially offset; 4. The device of claim 3, wherein the first set of cells and the second set of closed cells have a spirally aligned repeating adjacent alternating pattern. 5. The device of claim 4, wherein the first set of closed cells and the second set of closed cells have the same shape and size. 6. The device of claim 5, wherein the first set of closed cells and the second set of closed cells are diamond-shaped closed cells. 5. The device of claim 4, wherein the first set of closed cells and the second set of closed cells have different shapes and/or sizes. 2. The device of claim 1, wherein the stent elements have a thickness of about 115-145 microns. 9. The device of claim 8, wherein the stent elements are formed by struts having widths of about 95-125 microns. The radial stiffness of the stent element slowly decays as its structural polymer is debonded and metabolized, so that the stent element slowly becomes more flexible and adapts and remodels the vessel. and causing restoration of elasticity of the blood vessel. 2. The method of Claim 1, further comprising a therapeutic agent, wherein said therapeutic agent prevents or attenuates inflammation, cell dysfunction, cell activation, cell proliferation, neointima formation, hypertrophy, late atherosclerotic changes, or thrombosis. Devices listed. The bioabsorbable polymeric material is poly(L-lactic acid) (PLLA), poly(D-lactic acid) (PDLA), poly(D,L-lactic acid) (PDLLA), semi-crystalline polylactide, polyglycolic acid (PGA). ), poly(lactic-co-glycolic acid) (PLGA), poly(desaminotyrosyl iodide-tyrosine ethyl ester) carbonate, polycaprolactone (PCL), salicylate-based polymer, polydioxanone (PDS), poly(hydroxybutyrate ), poly(hydroxybutyrate-co-valerate), polyorthoester, polyanhydride, poly(glycolic acid-co-trimethylene carbonate), poly(iodinated desaminotyrosyl-tyrosine ethyl ester) carbonate, polyphosphoester , polyphosphoester urethanes, poly(amino acids), cyanoacrylates, poly(trimethylene carbonates), poly(iminocarbonates), polyalkyleneoxalates, polyphosphazenes, polyiminocarbonates, and aliphatic polycarbonates, fibrin, fibrinogen, cellulose, Polyurethanes, including starch, collagen, polycarbonate urethanes, polyethylene, polyethylene terephthalate, ethylene vinyl acetate, ethylene vinyl alcohol, silicones, including polysiloxanes and substituted polysiloxanes, polyethylene oxides, polybutylene terephthalate-co-PEG, PCL-co-PEG, 2. The method of claim 1, comprising PLA-co-PEG, PLLA-co-PCL, polyacrylate, polyvinylpyrrolidone, polyacrylamide, or combinations thereof. A method for maintaining or enhancing blood flow through a blood vessel comprising:
advancing a balloon catheter into the vessel;
expanding a balloon on the balloon catheter to expand a plurality of bioabsorbable vascular stent elements disposed on the balloon to contact an inner wall of the vessel, the stent elements comprising the expanding, wherein the stent elements are spaced apart from contacting each other;
deflating the balloon while leaving the vascular stent element in place within the vessel;
removing the balloon catheter from the blood vessel;
wherein the stent element comprises closed cells, the radial stiffness of the stent element is configured to decrease after implantation within a vessel as the polymer is absorbed, the thickness of the stent element, the occlusion The shape of the cells, the cell pattern of the stent elements, and the polymeric material are configured to provide an initial radial stiffness to the vessel upon implantation of greater than or equal to about 15 N/cm, and the stent elements configured to provide a decrease in the radial stiffness of the vessel to a radial stiffness of less than 1 N/cm over a period of years; The method, wherein the cell pattern of stent elements, the polymeric material, and the treatment of the polymeric material are configured to provide a decrease in radial stiffness of the vessel over time. 13. The method of claim 12, wherein the closed cells are diamond-shaped closed cells. 13. The method of claim 12, wherein the closed cells comprise a first set of closed cells and a second set of closed cells. The first set of closed cells has a repeating adjacent longitudinally aligned pattern and a repeating adjacent circumferentially aligned pattern, and the second set of closed cells has a repeating adjacent longitudinally aligned pattern. having a directionally aligned pattern and a repeating adjacent circumferentially aligned pattern, wherein the first set of closed cells and the second set of closed cells are circumferentially offset; 15. The method of claim 14, wherein the first set of cells and the second set of closed cells have a spirally aligned repeating adjacent alternating pattern. 16. The method of claim 15, wherein the first set of closed cells and the second set of closed cells have the same shape and size. 17. The method of claim 16, wherein the first set of closed cells and the second set of closed cells are diamond-shaped closed cells. 16. The method of claim 15, wherein the first set of closed cells and the second set of closed docells have different shapes and/or sizes. 13. The method of claim 12, wherein the stent element has a thickness of approximately 115-145 microns. 20. The method of claim 19, wherein the stent elements are formed by struts having widths of about 95-125 microns.

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