JP2010512224A - Apparatus and method for minimizing flow obstruction in a stented region of a lumen - Google Patents

Abstract

The stent according to the present invention incorporates an intravascular scaffold for the initial relief of stenosis or to provide support in pediatric and adult body lumens such as blood vessels. The scaffold minimizes flow obstruction in the stented region of the body lumen through the use of struts with a transitional luminal surface, thereby developing neointimal growth and subsequent reinfusion. Limit the possibility of stenosis and reduce the possibility of the formation and removal of early and late thrombosis. Any stent for use in any application can be initially manufactured in the form of a strut of the present invention. As an alternative, the shape of the existing stent struts can be modified during post-processing post-processing steps, thereby making the present invention adaptable to all currently available stent designs. To do.

Description

(Related application)
This application claims the benefit of US Provisional Patent Application No. 60 / 874,428, filed December 12, 2006, under the name “Sent with Specialized Strut Shape”.

(Background of the present invention)
Stent implantation is an accepted clinical method of restoring patency and fluid flow distal to luminal stenosis. Unfortunately, excessive restenosis, often initiated by neointimal proliferation, limits the success of vascular stents to approximately 30% of the patient population. The number of patients experiencing restenosis can be higher for certain patient populations, such as diabetics, for example, as high as 42% has been reported. Drug-eluting stents are now being used with increasing frequency as they have been shown to reduce the rate of restenosis in the years following stent implantation. However, recent rumors indicate that drug-eluting stents can only delay restenosis and, as previously thought, do not promote healing of intima damaged by previous vascular disease or stent implantation procedures It suggests that there is something. As a result, the rate of restenosis for a drug eluting stent may ultimately be similar to a bare metal stent, even with a time lag. Furthermore, drug eluting techniques may not be applicable to all patient populations, such as diabetic patients and locations within the vasculature such as branches. Stent geometry can be an important indicator of neointimal proliferation, and the rate of restenosis tends to change with stent design. The placement of a stent typically results in damage to the lumen in which it is placed. After such damage, the frictional force acting on the lumen wall as a result of the flowing fluid, also known as wall shear, mediates cell proliferation that can lead to neointimal proliferation.

  Inadequate healing associated with drug eluting stents can be attributed to incomplete coverage of the stent struts by endothelial cells, thereby making the vessel more susceptible to early and late thrombosis. This slow thrombosis is defined as the presence of a platelet-rich thrombus that encompasses more than 25% of the lumen beyond 30 days after stent implantation. A recent clinical finding has shown that 50% of patients experiencing slow thrombosis have had myocardium if the blood flow through the stented region results in the thrombus exiting and embolizing in the downstream vasculature. Shows death from infarction.

  Thus, the technique of stenting into a body lumen inherently improves the rate of restenosis and the potential for thrombosis by minimizing blockage of flow through the stented region of the lumen. You can benefit from the way you reduce.

(Summary of Invention)
The stent according to the present invention minimizes the rate of restenosis and thrombus by optimizing the local flow pattern created by the stent, thereby minimizing the blockage of flow through the stented region of the lumen. The possibility is essentially reduced. Such optimization, along with the possibility of thrombus formation and removal, minimizes hydrodynamic indicators related to neointimal growth and subsequent restenosis. The stent according to the present invention optimizes the scaffold but, when optimally placed, may have a configuration and stent-to-vessel ratio that minimizes vessel damage and flow alteration through the stented region. preferable.

FIG. 1 shows an elevational view of a prior art endoluminal stent placed in a lumen, two cross sections at two longitudinal positions, normalized wall shear stress and neointimal growth. And related graphs to compare. 2A is an axial cross-sectional view of the strut of the stent of FIG. 1 positioned against the lumen wall. 2B is a radial cross-sectional view of the strut of FIG. 2A positioned against the lumen wall. FIG. 3 is a perspective view of an embodiment of a stent according to the present invention. FIG. 4A is an axial cross-sectional view of a first embodiment of a stent strut according to the present invention positioned against a lumen wall. 4B is a radial cross-sectional view of the strut of FIG. 4A positioned against the lumen wall. FIG. 5A is an axial cross-sectional view of a second embodiment of a stent strut according to the present invention positioned against a lumen wall. FIG. 5B is a radial cross-sectional view of the strut of FIG. 5A positioned against the lumen wall. FIG. 6A is an axial cross-sectional view of a third embodiment of a stent strut according to the present invention positioned against a lumen wall. 6B is a radial cross-sectional view of the strut of FIG. 6A positioned against the lumen wall. FIG. 7A is an axial cross-sectional view of a fourth embodiment of a stent strut according to the present invention positioned against a lumen wall. FIG. 7B is a radial cross-sectional view of the strut of FIG. 7A positioned against the lumen wall. FIG. 8 provides two axial cross-sectional views of the lumenal stented area.

(Description of Preferred Embodiment)
While the disclosure herein is detailed and accurate to enable those skilled in the art to practice the invention, the physical embodiments disclosed herein may be implemented in other specific structures. It merely illustrates the invention that can be made. While preferred embodiments have been described, the details may be changed without departing from the invention, which is defined by the claims.

  The distribution of low wall shear stress constructed after stent implantation appears to alter the development of neointimal proliferation in the rabbit intestinal artery. When this neointimal growth occurs within the stented region, the lumen geometry and associated wall shear stress distribution is transient in a manner that gradually terminates the wall shear stress imbalance. Changed to The geometric characteristics of the implanted stent are made by the extent of stent shortening, the local scaffold, and the stent, including the number, width, and thickness of the stent supports (ie, the binder within the stent). Along with the degree of lumen curvature, it can contribute to changes in the wall shear stress index associated with neointimal proliferation.

  The number, width, and thickness of stent struts associated with implanted stents can introduce potentially deleterious distribution of wall shear stress that leads to the development of neointimal proliferation and subsequent restenosis. Of these design parameters, the number and thickness of stent struts associated with a stent can have a greater impact on the development of neointimal growth and subsequent restenosis than the width of the stent struts. The thickness of the stent strut generally determines the extent of protrusion into the region of fluid flow through the body lumen, which in turn leads to fluid flow disturbances. Similarly, by increasing the number of stent struts, a larger lumen scaffold is achieved by limiting the protrusion of the vessel wall through the stent struts, axially and circumferentially within the stented region. Leads to increased uniformity in direction. Conversely, increasing the width of the strut adds material to the stent strut that is primarily in the direction of fluid flow and is therefore not associated with flow obstruction to the same extent as other design considerations.

  Post-implantation The geometry of the implanted region affects the pattern of blood flow through the stent that will play an integral role in this process. In a recent study, five of these included bifurcation lesions, weak strut adhesion, placement of overlapping stents, use of longer stents, and stent struts that infiltrated the necrotic core. Factors were listed as particularly affecting the likelihood of stent thrombosis after drug-eluting stent implantation. These factors can also be detrimental to the success of bare metal stents. Of these five factors, the first four adversely affect fluid flow through the stented region of the vasculature. Collectively, these findings indicate that it is potentially desirable to minimize the distribution of WSS in the vicinity of the altered blood flow and the implanted stent in order to reduce the likelihood of subsequent thrombosis. ing.

  Turning now to the drawings, FIG. 1 depicts an implanted prior art stent 10 incorporating a strut configuration that includes a strut 12 having a generally rectangular cross-section. In general, as can be seen, the distribution of wall shear stress that results after implantation is related to the spatial development of neointimal proliferation. Neointimal proliferation is most pronounced in the region of low wall shear stress brought in by the stent after implantation. FIGS. 2A and 2B each show an axis of a strut 12 of a prior art stent 10 that has been placed against a lumen wall 2 having an inner surface 4 surrounding a flow region 6 such as a lumen, for example. It is sectional drawing of the part of a radial direction. The axes associated with FIGS. 2A and 2B are for reference only and fluid flow through a flow region 6 such as blood flowing through a blood vessel can be assumed in the x-direction as an example. In FIGS. 2A and 2B, once the stent 10 is deployed, implantation into the vessel wall 2 begins, and the shape of the lumen 6 is affected, at least in part, by the geometry of the stent strut 12. Please note that. The implantation of the prior art stent 10 provides a scaffold that supports the blood vessel 2, but the steep transition 7 from the strut 12 to the wall 2 generally creates a steep slope of wall shear stress, thereby creating a lumen. The two inner surfaces 4 protrude into the flow region 6 and result in disturbing the axial and circumferential uniformity of the inner surface 4.

  FIG. 3 provides a perspective view of one embodiment 100 of a stent according to the present invention. Embodiment 100 includes a plurality of interconnected struts 112, which are designed to limit protrusion into the flow region. The struts 112 may be axially aligned and malleable, thereby facilitating flexibility and conformity to a variety of profiles during positioning and placement and after initial implantation. The stent 100 is provided in a desired length 102 and is expandable to at least a predetermined diameter 104. FIGS. 4A and 4B each show a first embodiment of a stent strut according to the invention arranged against a lumen wall 2 having an inner surface 4 surrounding a region of flow 6 such as a lumen, for example. A cross-sectional view of the 112 axis and radial portion is shown. A stent strut is generally one of a plurality of interconnected support members that make up a stent. Each strut 112 further includes a flow surface 114 having a length provided along a longitudinal axis 113 and extending between flow surface edges 115. The flow surface edges 115 are preferably substantially or completely parallel to one another. The flow surface 114 has a circumferential width 116 of the flow surface and an axial width 118 of the flow surface. Nearly opposite the flow surface 114 is a scaffold surface 120 having a circumferential width 122 of the scaffold surface and an axial width 124 of the scaffold surface. The strut 112 also has a transitional side portion 126 that connects the flow surface 114 and the scaffold surface 120 via a radial thickness 128, where the radial thickness 128 is Measured at right angles to 114. The side portion 126 preferably leads to the flow surface 114 along the flow surface edge 115. The radial shape thickness 128 of the strut 112 can be, for example, a maximum of 0.1 millimeters, or the radial strut thickness associated with other commonly available stents. May be based on order.

  A stent strut 112 having at least a portion formed in accordance with the present invention includes a transitional side portion 126 that provides a more gentle transition at the interface between the strut 112 and the lumen wall 2 such as a vessel wall, The result is a smoother fluid flow surface in that portion of the flow region 6. Generally, such transitional side portions 126 provide a desired ratio between the flow surface width 116, 118 and the scaffold surface width 122, 124, respectively, and the flow surface width. It can be formed by inclining a side 126 from the edge 115 towards the surface 120 of the scaffold. The specific ratio between each of the flow surface widths 116, 118 and the scaffold surface widths 122, 124 is influenced at least in part by the characteristics of the lumen wall 2, but the flow surface width 116 may preferably be, for example, two to three times wider than the corresponding scaffold surface width 122. The circumferential width 116, 122 of at least a portion of the stent strut 112 may be related to the number of struts 112 provided around a given periphery of the stent 100. In addition, the axial width 118, 124 of at least a portion of the stent strut 112 is related to the relative axial proximity of the axially adjacent strut 112 within a given axial length of the stent 100. Can do. Both width 116, 122 and width 118, 124 may be selected or optimized according to the illustrated embodiment, but the actual dimensions will maintain lumen patency upon implantation and resist collapse Is selected to provide the appropriate radial strength needed for.

  The general purpose of the transitional side portion 126 provides a gentler transition from the stent 112 to the wall 2 by allowing the wall 2 to capture the stent 112 more securely, thereby providing It is at least to reduce the inhibition of axial and circumferential uniformity of the inner surface 4 of the lumen wall 2 caused by the steep slope of wall shear stress experienced with previous stents 10. As a result, flow disturbances and associated neointimal proliferation, restenosis, and the potential for thrombus formation and removal are reduced. The shape of the stent strut 112, including but not limited to the circumferential and axial width and thickness of the strut 112, is not necessarily the same structure throughout the stent 100 or along any particular strut 112.

  5A and 5B provide views of the shaft and peripheral portion, respectively, of a second embodiment of a stent strut 212 according to the present invention, with like reference numerals being similar to those of the first embodiment 112. Browse the structure. This embodiment 212 includes a relatively flat flow surface 214 as in the first embodiment 112, but with a scalloped transitional side portion 226 that slopes toward a rounded scaffold surface 220. Also includes.

  6A and 6B provide views of the shaft and peripheral portion of a third embodiment of a stent strut 312 according to the present invention, respectively, with like reference numerals being similar to those of the first embodiment 112. Browse the structure. In this embodiment 312, the flow surface 314 is scalloped to further limit flow obstruction between the stent strut 312 and the vessel wall 2 and facilitate a smooth transition. The radius or shape of this scalloped surface 314 may be related to the desired final deployment diameter of the stent and / or the total number of surrounding stent supports 312 at locations about a given axis of the stent. For example, a stent having four peripheral struts at a position about a given axis may have its struts 312 scalloped to a larger extent, as depicted in FIG. That is, it has a smaller radius than a stent with twice as many struts 312 at a position about a given axis. In addition, the transitional side portion 326 is scalloped and the scaffold surface 320 is smoothed to a radius. Details of these designs may relate to the elasticity of the lumen wall 2.

  7A and 7B provide views of the shaft and peripheral portion, respectively, of a fourth embodiment of a stent strut 412 according to the present invention, with like reference numerals being similar to those of the first embodiment 112. Browse the structure. This embodiment 412 includes a relatively flat flow surface 414 as in the first embodiment 112 but with a relatively flat transitional side portion that slopes toward a rounded scaffold surface 420. 426.

  A stent according to the invention can initially be produced using at least one strut according to the invention. Alternatively, a pre-manufactured stent with a pre-existing form of support is preferably, but not limited to, a post according to the present invention by subsequent process operations on the surface of at least one support scaffold. Can be modified to include at least a portion thereof. Such post-process operations may include, but are not limited to, laser cutting, grinding, microblasting, overblasting or electrical discharge machining. Further process operations can include, but are not limited to, electropolishing, harmful tissue growth, cell proliferation, neointimal proliferation, etching or charge to inhibit neoplastic growth and restenosis. Not.

  Stents according to the present invention include a group consisting of plastic (eg, polymer), shape memory metal (eg, nickel-titanium) or deformable metal (eg, 316L stainless steel or cobalt chrome) that promotes design characteristics, It can be assembled purely with, or not limited to, biocompatible materials. The material can be chosen so that the stent is sufficiently radiopaque, thereby facilitating its visualization during conventional angiography or other imaging procedures. As an alternative or in addition, the material can be chosen to provide sufficient compatibility of the stent with magnetic resonance imaging (MRI).

  The stent according to the present invention also elutes the drug to prevent deleterious development of cell proliferation, neointimal proliferation, neoplastic growth, restenosis, thrombus formation and removal, or for any other reason Biocompatible therapy agents or special process procedures can be provided. Biocompatible agents that elute potential drugs that can be added to the stents discussed in this invention include anticoagulants, immunosuppressive agents, antitumor agents, antithrombolytic agents, microtubule agents, growth It may consist of, but is not limited to, a factor target substance, a fibrinolytic agent, a glycoprotein IIb / IIIa inhibitor, an antiplatelet substance, an antiproliferative agent, a chimeric monoclonal antibody, an antiproinflammatory cytokine and an allograft rejection agent. A biocompatible therapeutic agent that elutes any drug associated with a stent according to the present invention may be implanted as part of the bioabsorbable portion of such a stent. As a result, the drug can be released over the bioabsorption period. The drug can also be contained within the stent coating and released over time without any degradation of the stent.

  The stent according to the present invention cuts stents that are similar in geometry but with different strut widths and then use a technique such as, but not limited to, full laser welding or spot welding. Can be made or manufactured by combining them or layering them. As an alternative or in addition, a stent according to the present invention may be coined into a cylinder configuration, sheet configuration or other configuration with a stent having a rectangular strut cross-section after it has been laser cut or electrodischarge processed from the sheet or cylinder. Or it can be made by forging or manufactured. As an alternative or in addition, a stent according to the present invention is made by coining or forging a sheet or cylinder stent and then laser cutting or electrical discharge machining the shape of the stent from the coined or forged material. Can be obtained or manufactured. Alternatively or additionally, the stent according to the present invention uses a conventional biaxial laser cutting system known to produce a cross-sectional orientation that is opposite to that shown in FIGS. 7A and 7B. Can be made or manufactured by cutting a stent pattern. After cutting the entire stent, the stent is then axially cut and rolled to produce the desired cross-sectional orientation. Stents can also be manufactured using thin film techniques such as photolithography. Stents can also be manufactured by laser cutting techniques, where the laser or its properties are adjusted to achieve the desired shape.

  The stent according to the invention can be placed to a predetermined diameter, whereby the creation of the scaffold is optimized and the flow disturbance is minimized. Such stents can be deployed using conventional stent delivery balloons or special delivery balloons that facilitate optimal coordination and optimal transition from the stent strut to the lumen wall. The stent can be preloaded on the delivery system or added to a pre-existing delivery catheter that is packaged separately. Alternatively, another special delivery device may be capable of determining when a placement pressure has been reached that optimizes the transition between the stent strut and the vessel wall. A stent can also be placed or implanted using a balloon catheter that includes a sensor, which can be implanted in the wall of the balloon, which determines when the optimal placement for a particular lumen has been obtained. To do so, measure the strain, pressure, or change in pressure inside the balloon (directly or as a function of voltage change or some other measurement) in addition to what is managed during inflation.

  The stent according to the present invention has a variety of uses. Such stents may be used in vascular and non-vascular areas corresponding to, but not limited to, the cardiovascular system, respiratory system, digestive system, endocrine system, gastrointestinal tract, renal system, and bile duct. Stents include coronary artery disease, peripheral vascular disease, aortic stenosis, peripheral pulmonary artery stenosis, allograft and conduit repair after tetralogy of Fallot, pulmonary vein stenosis, pyloric stenosis, intestinal closure and intestinal stenosis, esophageal stenosis, bile duct stenosis, imaginary Can be used to treat vascular and non-vascular abnormalities including, but not limited to, blood stroke, Takayasu arteritis, superior vena cava syndrome, retronasal obstruction closure, renal pelvic and ureteral junction obstruction, and airway stenosis . In addition, implantation of such stents can be a way to prevent restenosis and repeated blockage or occlusion after percutaneous transluminal coronary angioplasty. Stents can be used as a method of reconstructing fluid flow in a blood vessel or body lumen or repairing a blood vessel or body lumen.

  Stents according to the present invention are useful for interventional radiologists, endoscopists, interventional cardiologists, and adults of any sex, infants, children, adolescents, young adults, adults. And can be used by physicians including, but not limited to, general surgeons and vascular surgeons treating elderly patients.

  The foregoing is considered as describing only the principles of the invention. Furthermore, since many modifications and changes will readily occur to those skilled in the art, it is not desirable to limit the invention to the exact assembly and operation shown and described. While preferred embodiments have been described, the details may be changed without departing from the invention, which is defined by the claims.

Claims (20)

A support structure disposed within a body lumen, the structure comprising:
Comprising a plurality of interconnected support members;
Each of the support members is a length provided along a longitudinal axis and an internal flow surface extending along the length and between the edges of the pair of flow surfaces;
The flow surface has an internal flow surface having a circumferential width of the flow surface measured perpendicular to the longitudinal axis;
An outer scaffold surface having a circumferential width of the scaffold surface measured perpendicular to the longitudinal axis, a thickness measured perpendicular to the inner flow surface, and the flow surface; A transitional side portion extending between the scaffold surface and
The circumferential width of the surface of the flow at a longitudinal position along the longitudinal axis of at least one support member is greater than the circumferential width of the surface of the scaffold at the longitudinal position Structure.   The structure of claim 1, wherein the structure is an intravascular stent.   The structure of claim 1, wherein edges of the flow surface of the at least one support member are substantially parallel.   The structure of claim 1, wherein the structure comprises a radiopaque material.   The structure of claim 1, wherein the structure is expandable to at least a predetermined diameter.   The structure of claim 1, wherein the structure comprises a material compatible with magnetic resonance imaging.   The structure of claim 1, wherein a thickness of the at least one support member adjacent an edge of the flow surface is less than 50% of the thickness at the longitudinal axis.   The structure of claim 1, wherein the at least one support member has a cross section at the longitudinal location, the cross section forming a collection of mathematically concave points.   The structure of claim 1, wherein the at least one support member has a cross section at the longitudinal position, the cross section forming a collection of mathematical convex points.   The structure of claim 1, wherein the longitudinal position has a circumferential width of the flow surface that is at least twice as large as a circumferential width of the scaffold surface.   11. The structure of any one of claims 1 to 10, wherein the structure further comprises a biocompatible therapeutic agent that elutes a drug bound to a portion of at least one support member.   The structure according to any one of claims 1 to 11, wherein the structure includes stainless steel.   The structure according to any one of claims 1 to 11, wherein a part of the support member is bioabsorbable to which the drug is bound. An improvement in a stent adapted for supporting a luminal wall of a living body, the stent comprising a plurality of interconnected support members, the support member comprising a longitudinal axis and the luminal wall A scaffold surface adapted to interface with a flow surface adapted to interface with a lumen;
The improvement comprises at least a portion along the length of the longitudinal axis of at least one of the plurality of interconnected support members having the flow surface wider than the support surface. The improvement department.   The portion further comprises the transitional side portion that slopes from an edge of the flow surface toward the scaffold surface and forms an acute angle between the flow surface and the transitional side portion. The improvement part of Claim 14.   The improvement part according to claim 14, wherein the improvement part is formed by laser cutting. A method of reducing flow blockage in a region of fluid flow within a body lumen, the method comprising:
Providing a support structure adapted for placement within a body lumen, comprising:
The support structure comprises a plurality of interconnected support members;
Each of the support members has a length provided along a longitudinal axis;
The internal flow surface extends along the length between the edges of the pair of flow surfaces,
The flow surface has a circumferential width of the flow surface measured perpendicular to the longitudinal axis;
The outer scaffold surface has a circumferential width of the scaffold surface measured perpendicular to the longitudinal axis;
The thickness is measured perpendicular to the internal flow surface,
A transitional side portion extends between the flow surface and the scaffold surface;
The circumferential width of the surface of the flow at a longitudinal position along the longitudinal axis of at least one support member is wider than the circumferential width of the surface of the scaffold at the longitudinal position; When,
Inserting the structure into a body lumen;
Expanding the structure to a desired diameter.   Further comprising placing the structure on an inflatable balloon prior to inserting the structure into the body lumen, wherein the expanding step is performed by the balloon acting on the structure; The method of claim 17.   18. The method of claim 17, further comprising: forming an opening in a patient's body prior to inserting the structure into the body lumen; and inserting the structure through the formed opening. The method described.   A support structure disposed in a body lumen, the structure comprising a plurality of interconnected support members, at least a portion of at least one support member of the plurality of support members being attached to the drawings. A support structure comprising a cross-section substantially as described herein with reference to.

Images