JP4015204B2 - Intravascular stent - Google Patents

Description

Background of the Invention
Field of Invention
The present invention relates to an intravascular stent, and more particularly to an intravascular stent that is easy to introduce into a tortuous portion of a blood vessel.
Explanation of related technology
Angioplasty (coronary or general angioplasty) has advanced in the art and has become the most effective means of regenerating stenotic blood vessels. In the early 1980s, angioplasty was first used for coronary clinical methods and has since proven to be an effective alternative to conventional bypass tissue transplantation procedures. Angioplasty using balloon catheters remains the most reliable and most practical interventional procedure. Other ancillary techniques, such as laser treatment or directional or rotational arthrotomy, have limited effectiveness, or angioplasty using a balloon to complete the intended procedure Has been found to be either one that uses Restenosis after angioplasty using a balloon is the most serious drawback and is particularly prominent in the coronary artery system.
Many regimens have been devised to control stenosis, but the degree of success has been limited. Such regimens include laser-based treatment and directional or rotational arthrotomy. However, it is noteworthy that the rate of restenosis after angioplasty is reduced by intravascular stent implantation. Intravascular stent implantation procedures typically use balloon angioplasty to pre-expand the target vessel, then deploy the stent and expand the stent to support the expanded vessel wall from within To be.
Intravascular stents provide splint scaffolding for the vessel lumen. The splint support of the vessel wall by the stent (a) prevents elastic return of the expanded vessel wall, and (b) prevents residual stenosis of the vessel (typically occurring during balloon angioplasty). (C) keep the diameter of the stented vessel segment slightly larger than the native non-occluded vessel located proximal and distal to the vessel segment, and (d) modern clinical Helps reduce the incidence of restenosis as shown in the data. Following the performance of angioplasty, the rate of restenosis of stent-retained blood vessels is determined by restenosis of blood vessels that have not undergone stent support or have been treated with another method (including drug treatment and other methods described above). It has been found that it is significantly lower than the incidence.
Another advantage of vascular stent support is the expected reduction in emergency bypass surgery due to angioplasty. Stent support has proven to be effective in some cases in treating impending blood vessels during angioplasty. Stent support can also control and stabilize unstable local intima tears caused by normal actions during angioplasty. In some cases, balloon angioplasty can be successfully patented by stent implantation, even if the vascular lesions are not sufficiently expanded or less than optimal.
There have been serious anticoagulant problems with stent implantation methods, especially in the coronary arteries early in the development phase. However, anticoagulant technology has evolved since then and has become easier and more effective. Good and easy-to-use regimens (including simple outpatient anticoagulant treatments as such regimens) are constantly being introduced, resulting in shorter hospital stays for patients treated with stents It was.
An example of a patent related to a conventional stent is US Pat. No. 5,102,417 (hereinafter referred to as “Palmaz patent”). The stent described in the Palmaz patent consists of a series of elongate tubular members that have a plurality of slots disposed substantially parallel to their longitudinal axes. The tubular members are connected to each other by at least one flexible connector member.
The unexpanded tubular member of the Palmaz patent is too stiff, so its practical application is limited to short lengths. In an embodiment of a multi-link design with a flexible connector that connects a series of tubular members together, a long stent cannot travel along a tortuous vessel. Furthermore, the stiffness of the unexpanded stent increases the possibility of damaging the blood vessel during insertion. The shrinkage of the stent during insertion complicates the correct placement of the stent and reduces the area that the expanded stent can cover. Furthermore, there is no way to program the stent diameter along its longitudinal axis to obtain a tapered expanded stent, and no method is provided for reinforcing the end or other region of the stent.
Another example of a patent related to a conventional stent is WO96 / 03092 (hereinafter referred to as “Bran patent”). The stent described in the Blanc patent is formed of patterned shaped tubes, which have first and second serpentine patterns. The even-numbered and odd-numbered winding patterns are 180 ° out of phase, and the odd-numbered pattern occurs between every second even-numbered pattern. The second winding pattern extends perpendicular to the first winding pattern along the axis of the tube.
Adjacent first serpentine patterns are connected to each other by a second serpentine pattern to form a uniform distribution pattern as a whole. Due to the symmetrical configuration with the first and second tortuous patterns with steep right-angle bends, the vessel wall is trapped during delivery. In addition, large turns in the second tortuous pattern are not completely straightened during expansion, reducing the stiffness and structural strength of the expanded stent. Further, there is no way to program the stent diameter along its longitudinal axis to obtain a tapered design stent, and no method is provided to reinforce the end or other region of the stent.
Conventional and other designs of these and other designs have various disadvantages to some degree. As such disadvantages, (a) the non-expanded stent has a high columnar rigidity and cannot adapt to the bent portion of the blood vessel, and (b) the structural strength of the non-expanded stent in the radial and axial directions. (C) the stent shrinks significantly during expansion, (d) the length of the stent is limited, (e) the expansion stent has a constant diameter, and (f) the crimping characteristics. (G) the change in the surface of the unexpanded stent is rough.
There is a need for a stent with sufficient longitudinal flexibility to be able to travel through a tortuous vessel in an unexpanded state. Further, there is a need for a stent that is structurally strong in an unexpanded state so that the risk of damage or distortion during delivery is minimized. There is a further need for a stent that maintains substantially the same longitudinal length during expansion so that the coverage at the target site can be increased and proper placement of the stent can be easily performed. There is a further need for stents that are designed with longitudinal flexibility to allow long stents up to 100 mm to be safely delivered into tortuous vessels. There is a need for a stent shaped to expand to a variable diameter along the length of the stent so that a taper can be applied to the expanded stent, thereby matching the native taper of the target vessel. (I) Can be firmly crimped onto the dilatation balloon in a thin (low profile) state and in a flexible state, and (ii) crimped onto the delivery catheter to prevent catching on the vessel wall during delivery And (iii) at the end or middle, or both, so as to maintain the end of the stent in fixed contact with the vessel wall of the target vessel. There is a need for a stent with a reinforcing ring.
Summary of the Invention
Accordingly, it is an object of the present invention to provide a splint support means for the lumen of a blood vessel.
Another object of the present invention is to provide a stent that prevents vascular rebound after angioplasty.
Another object of the present invention is to provide a stent that keeps the vessel lumen large compared to results obtained using only balloon angioplasty.
Another object of the present invention is to provide a stent that reduces the shrinkage of the stent length when expanded.
Another object of the present invention is to provide a stent with increased flexibility when delivered to a selected site within a blood vessel.
Another object of the present invention is to provide a low profile stent when crimped onto the delivery balloon of the stent assembly.
It is another object of the present invention to provide a stent that reduces vessel wall damage.
It is another object of the present invention to provide a chain mesh stent that reduces “trapping” to blood vessels in tortuous or curved blood vessels.
The above and other objects of the present invention are achieved by providing a stent in an unexpanded state. The first expansion strut pair has first and second expansion struts located adjacent to each other. A joining strut of the first expansion strut pair joins the first expansion strut and the second expansion strut to each other at the end of the first expansion strut pair. The plurality of first expansion strut pairs form a first expansion column. A second expansion strut pair has first and second expansion struts located adjacent to each other. A joining strut of the second expansion strut pair couples the first expansion strut and the second expansion strut of the second expansion strut pair to each other at the proximal end of the second expansion strut pair. The plurality of second expansion strut pairs form a second expansion column. The first connecting strut has a proximal head and a distal tail. The proximal head is coupled to the distal end of the first expansion strut pair in the first expansion column, and the distal tail is at the proximal end of the second expansion strut pair in the second expansion column. Are combined. The plurality of first connection struts form a first connection strut column that connects the first extension column and the second extension column to each other. The distal tail extends in a first lateral direction relative to the longitudinal axis of the proximal head to form a first tilt angle. The stent has first and second expansion struts in which a third expansion strut pair is located adjacent to each other. A third joint strut of the third expansion strut joins the first expansion strut and the second expansion strut at the proximal end of the third expansion strut pair. The plurality of third extension strut pairs form a third extension column. The first expansion strut of the first expansion strut pair in the first expansion column is parallel to and offset from the longitudinal axis of the first expansion strut of the second expansion strut pair in the second expansion column. Having a longitudinal axis. The second expansion strut of the third expansion strut pair in the third expansion column is parallel to and offset from the longitudinal axis of the first expansion strut of the second expansion strut pair in the second expansion column. Having a longitudinal axis. The second connecting strut includes a proximal head and a distal tail. The proximal head of the second connecting strut is coupled to the distal end of the second expansion strut pair in the second expansion column. The distal tail of the second connecting strut is coupled to the proximal end of the third expansion strut pair of the third expansion column. The plurality of second connection struts form a second connection strut column that couples the second extension column and the third extension column to each other. The distal tail of the second connecting strut is in a direction opposite to the first lateral direction with respect to the longitudinal axis of the proximal head of the second connecting strut so as to form a second tilt angle. It extends in a second lateral direction. The ratio of the number of expansion struts in the expansion strut column to the number of connection struts in the connection strut column is 2: 1. The first tilt angle reduces the degree of contraction of the stent between the first expansion column and the second expansion column when the stent is in the expanded state.
In another embodiment, the stent assembly has a balloon and an expandable stent disposed on the exterior of the balloon. The stent has a first expansion strut. The plurality of first expansion struts form a first expansion column. A plurality of second expansion struts form a second expansion column. A plurality of first connecting struts form a first connecting strut column. Each first expansion strut of the first expansion column is coupled to a second expansion strut of the second expansion column. The first connecting strut has a proximal end coupled to the distal end, and at least a portion of the first connecting strut has a first straight portion and a first tilt angle.
[Brief description of the drawings]
FIG. 1A is a side view of a pre-expansion mode of a stent embodiment of the present invention.
FIG. 1B is a cross-sectional view of an embodiment of the stent of the present invention.
FIG. 1C is a longitudinal cross-sectional view of an embodiment of the stent of the present invention.
FIG. 2A is a schematic illustration of a strut pattern of an embodiment of the stent of the present invention.
FIG. 2B is a development view of a part of the pattern of FIG. 2A.
FIG. 3A is a schematic representation of the pre-expansion mode of the stent embodiment of the present invention.
FIG. 3B is a schematic view after expansion of an embodiment of the stent of the present invention.
FIG. 4A is a schematic diagram with dimensions of an embodiment of the stent of the present invention.
FIG. 4B is a partially enlarged view of the schematic of FIG. 4A.
FIG. 5 is a schematic illustration of an embodiment of a stent of the present invention with a tapered diameter in the expanded mode.
FIG. 6A is a schematic illustration of an embodiment of a stent of the present invention with a reinforced expansion column.
FIG. 6B is a perspective view of the embodiment of FIG. 6A.
FIG. 7A is a schematic illustration of an embodiment of a stent of the present invention with a relief cut at the strut joint to increase the flexibility of the strut joint.
FIG. 7B is a partially enlarged view of the embodiment of FIG. 7A.
FIG. 7C is an enlarged view of a single connecting strut joining two expansion strut pairs together according to the embodiment of FIG. 7A.
FIG. 8A is a schematic diagram showing another geometry of the connecting struts and joint struts of the present invention.
FIG. 8B is a schematic diagram illustrating another geometric shape of the connecting struts and joint struts of the present invention.
FIG. 8C is a schematic diagram illustrating another geometry of the connecting struts and joint struts of the present invention.
FIG. 8D is a schematic diagram illustrating another geometry of the connecting struts and joint struts of the present invention.
FIG. 8E is a schematic diagram illustrating another geometric shape of the connecting struts and joint struts of the present invention.
FIG. 9 is a schematic view of a delivery balloon catheter illustrating the stent delivery method of the present invention.
Detailed description
A first embodiment of the present invention is shown in FIGS. 1A, 1B, 1C, 2A and 2B. Referring to FIG. 1A, an unexpanded elongated hollow tubular stent 10 is shown. The proximal end 12 and the distal end 14 define a longitudinal length 16 of the stent 10. The longitudinal length 16 of the stent 10 may be as long as 100 mm or more. The proximal opening 18 and the distal opening 20 communicate with the lumen 22 of the stent 10. The stent 10 may be a single piece without seams or weld joints, or it may consist of multiple pieces.
The stent 10 is comprised of 2-50 or more expansion columns or rings 24 connected to each other by interspersed connecting strut columns 26. The first column of the proximal end 12 of the strut 10 and the last column of the distal end 14 are expansion columns 24.
The expansion column 24 is formed by a series of expansion struts 28 and joint struts 30. The expansion strut 28 is a thin and elongated member configured to extend at least partially in the direction of the longitudinal axis of the stent 10. When an outward external force is exerted on the stent 10 from the inside by a dilatation balloon or other means, the dilatation struts 28 become more circumferential, ie along the surface of the cylindrical stent 10 and its longitudinal axis. The direction changes so as to extend perpendicularly to. By changing the orientation of the expansion struts 28, the stent 10 has an expanded circumferential length and diameter. In FIG. 1A, the expansion struts 28 of the unexpanded stent 10 appear to extend substantially parallel to the longitudinal axis of the stent 10.
The expansion struts 28 are joined together by joint struts 30 to form a plurality of expansion strut pairs 32. The expansion strut pair has a closed end 34 and an open end 36. Additional joining struts 30 join the expansion struts 28 of adjacent expansion strut pairs 32 to each other, and the expansion struts 28 are alternately joined to the adjacent expansion struts 28 at their proximal and distal ends to expand the expansion column. 24 is formed. Each expansion column 24 has a plurality, typically 8-20, 20-60 or more expansion struts 28.
Connecting struts 38 connect adjacent expansion columns 24 together to form a series of scattered connecting strut columns 26 that each extend around the circumference of the stent 10. Each connecting strut 38 joins a pair of expansion struts 28 in the expansion column 24 to a pair of adjacent expansion struts 28 in the adjacent expansion column 24. For the stent 10 of FIG. 1A, the ratio of the number of expansion struts 28 in the expansion column 24 to the number of connection struts 38 in the connection strut column 26 is 2: 1, but this ratio is typically x: 1. , Where x is greater than or less than 2. Furthermore, the stent 10 of FIG. 1A begins with an expansion column 24 at the proximal end 12 and ends with an expansion column 24 at the distal end 14, so that there are n expansion columns 24 present per column. If the number of struts 28 is m, the number of connected strut columns 26 will be (m−1) and the number of connected struts 38 will be n (m−1) / 2.
By reducing the number of connection struts 38 in each connection strut column 26 compared to the expansion struts 28 in each expansion column 24, the stent 10 can be flexible in the longitudinal direction. To further increase longitudinal flexibility, use narrow connecting struts and additional flexibility and flexibility to the stent as it moves around the bend in the native vessel give.
At least part of the open space between the struts of the stent 10 forms an asymmetric cell space 40. The cell space is an empty area on the surface of the stent 10 that is completely surrounded by one or a combination of stent struts including expansion struts 28, connecting struts 38 or joint struts 30. The asymmetric cell space 40 has no geometric symmetry, that is, rotationally symmetric, linearly symmetric, rotationally and linearly symmetric, or other symmetric. That's not true.
The asymmetric cell space 40 of FIG. 1A includes a first expansion strut pair 32 of a first expansion column 24, a first connecting strut 38, a second expansion strut pair 32 of an adjacent expansion column 24, a first joint strut. 30, a second connecting strut 38 and a second joint strut 30. In addition, the expansion strut pairs 32 of the asymmetric cell space 40 may be circumferentially offset, i.e. having a longitudinal axis that is not collinear and opposite open ends 36. The space between the two expansion struts of the expansion strut pair 32 is called the loop slot 42.
FIG. 1B shows the lumen 22, radius 44 and stent wall 46 of the stent 10. The stent wall 46 comprises a stent strut including an expansion strut 28, a connecting strut 38 and a joint strut 30.
FIG. 1C shows the proximal end 12, distal end 14, longitudinal length 16, lumen 22 and stent wall 46 of the stent 10. The lumen 22 is surrounded by a stent wall 46 that forms the cylindrical surface of the stent 10.
2A and 2B, the joint strut 30 of the stent 10 appears to extend at an angle with respect to the expansion strut 28 and is at a small angle with one expansion strut 28 in the expansion strut pair 32. 48 and a large angle 50 with the other expansion struts 28 of the expansion strut pair 32. The small angle 48 is less than 90 ° and the large angle 50 is greater than 90 °. The joining struts 30 extend longitudinally along the longitudinal axis of the stent 10 and circumferentially along its surface perpendicular to the longitudinal axis of the stent 10.
The expansion strut spacing 52 between adjacent expansion struts 28 in a given expansion column 24 is constant for the stent 10 of FIGS. 2A and 2B, but non-constant spacing may be used. The expansion strut separation distance 52 may vary, and for example, the separation distance 52 between adjacent expansion struts 28 in the expansion column 24 may alternate between a small separation distance and a large separation distance. Further, the separation distance 52 within a single expansion column 24 may be different from other separation distances 52 of other columns 24.
It is noted that changing the expansion strut separation distance 52 that forms the loop slot 42 results in a change in the width of the loop slot. Further, the longitudinal axis of the loop slot 42 need not be collinear with or parallel to the longitudinal axis of the loop slot 42 of the adjacent expansion column 24. 2A and 2B show the arrangement of the expansion struts 28 such that the loop slots 42 located on the same straight line and the adjacent loop slots 42 parallel to each other are formed. A loop slot 42 which is not parallel and is not parallel can also be used.
Further, the shape of the loop slot 42 need not be the same throughout the loop slot of the single or multiple expansion columns 24. Changing the shape of the loop slot 42 involves changing the orientation or physical dimensions of the expansion strut 28 and / or the joining strut 30 that interconnects the expansion struts 28 of the expansion strut pair 32 that define the boundary of the loop slot 42. Good.
The connecting struts 38 connect adjacent extension columns 24 to each other by connecting the distal ends of the extension strut pairs in one extension column 24 to the proximal ends of adjacent extension strut pairs 32 in the second extension column 24. is doing. The connecting strut 38 of FIGS. 2A and 2B is formed of two straight portions, the distal end of the first straight portion 54 is joined to the proximal end of the second straight portion 56, and the first inclined angle 58 is formed. Is formed.
The first straight portion 54 of the connecting strut 38 is joined to the expansion strut 28 where the joining strut 30 makes a small angle 48 with the expansion strut 28. The first straight portion 54 extends substantially collinearly to the joining strut 30 and continues the line of joining strut 30 into the space between the expansion columns 24. The distal end portion of the first straight portion 54 is joined to the proximal end portion of the second straight portion 56 to form an inclination angle 58. The second straight portion 56 extends substantially parallel to the expansion strut 28 and its distal end is connected to the joining strut 30 in the adjacent expansion column 24. The distal end of the second straight portion 56 is attached to the expansion strut 28 at a point where the joining strut 30 makes a small angle 48 with the expansion strut 28. Further, the joint strut 30 may have the same width as the first tilt angle or may have a different width and second tilt angle.
2A and 2B show the connecting struts 38 and the joining struts 30 tilted with respect to the longitudinal axis of the stent 10, and the circumferential orientation of these tilted struts is from one column to the next. Alternating. The circumferential direction is the winding direction of the inclined struts around the surface of the stent 10. The direction of inclination of the first straight portion 54 of the connecting strut in the connecting strut column 26 in the circumferential direction is determined by the inclination of the first straight portion 54 of the connecting strut in the adjacent connecting strut column 26 in the circumferential direction. It is the opposite of direction. Similarly, the direction of inclination of the joining strut 30 in the extension column 24 in the circumferential direction is opposite to the direction of inclination of the joining strut 30 in the adjacent extension column 24 in the circumferential direction. By alternating the direction of inclination of the connecting struts 38 in the circumferential direction and the direction of inclination of the connecting struts 30 in the circumferential direction, axial warping of the stent 10 during delivery and expansion is prevented. Other inclined orientation patterns that are not alternating for the connecting struts 38 or the joining struts 30 or both may be used.
3A and 3B are schematic diagrams showing the stent of the present invention in an unexpanded state and an expanded state, respectively. The stent is shown by design as a flat projection image as if the stent 10 had been cut longitudinally parallel to its longitudinal axis and flattened. The connecting strut 38 consists of a first straight portion 54 and a second straight portion 56 that form an inclination angle 58 at the pivot point 60. An asymmetric cell space 40 is formed by the expansion strut pair 32, the connecting strut 38 and the joint strut 30. A large number of entangled asymmetric cell spaces 40 constitute a design pattern.
When the stent is expanded (see FIG. 3B), the expansion strut pairs 32 expand at their open ends 36, and the length of the expansion struts 28 decreases along the longitudinal axis of the cylindrical stent. In contrast to the longitudinal shortening of the expansion strut 28 during expansion, the connecting strut 38 extends in the longitudinal direction. When the inclination angle 58 increases during expansion, the connecting struts 38 become straight and the distance between the coupled expansion strut pairs 32 increases. As the distance between the coupled expansion strut pairs 32 increases, the longitudinal shortening of the expansion struts 28 is substantially compensated. Thus, the stent has a substantially constant longitudinal length in the unexpanded and expanded states.
As the stent expands, each expansion column 24 is stretched circumferentially, increasing the space between the struts. The stent 10 is provided with high radial support strength by connecting the expansion columns 24 to each other by connecting struts 38 that are straightened during the expansion phase. As the entire stent 10 expands, it is coupled to a continuous chain mesh consisting of stretched expansion columns 24 and connecting strut columns 26, which are asymmetric interlaced cells that resist both axial and radial collapse. A geometric shape is formed. As the stent expands, the stiffness and fatigue tolerance of the stent increases.
In addition, the effective bending and straightening of the connecting struts 38 at the pivot point 60 can increase the longitudinal flexibility of the stent. In order to bend the stent longitudinally, at least some of the connecting struts 38 bend in their tangential plane. The tangent plane of a particular connecting strut 38 refers to the plane that substantially contacts the cylindrical surface of the stent at that connecting strut 38. The width of the connecting struts 38 is typically 2-4 times greater than the thickness, which makes the connecting struts 38 relatively inflexible when bent in their tangential plane. However, the pivot point 60 of the connecting strut 38 provides a flexible joint to the connecting strut 38 that is more flexible and increases the longitudinal flexibility of the stent.
4A and 4B, a first embodiment of the stent 10 of the present invention is shown. In this variation, the stent 10 has a length 16 of 33.25 mm and a perimeter length 88 of 5.26 mm when not crimped and unexpanded. Interstitial strut columns 26 are interspersed between the 15 expansion columns 24. Each expansion column 24 consists of 12 expansion struts 28 joined alternately at the proximal and distal ends by joint struts 30 forming six expansion strut pairs 32. The expansion struts 28 are aligned parallel to the longitudinal axis of the cylindrical stent 10. The joint strut 30 forms a small angle 48 and a large angle 50 with each expansion strut 28 of the expansion strut pair 32. Adjacent expansion columns 24 employ joint struts 30 in which the inclination directions in the circumferential direction are alternated.
In this variation of the first embodiment, the expansion strut width 62 is 0.20 mm, the expansion strut length 64 is 1.51 mm, and the connecting strut width 66 is 0.13 mm. The distance 68 from the outer edge of the first expansion strut 28 in the same expansion column 24 to the outer edge of the second adjacent expansion strut 28 is 0.64 mm, leaving a loop slot width 70 of 0.24 mm. ing.
In this modification of the first embodiment, the connecting strut 38 is obtained by joining the first inclined linear portion 54 to the second linear portion 56 at an inclination angle 58. The first straight portion 54 is slightly longer than the second straight portion 54, and its proximal end is attached to the expansion strut 28 in the expansion column 54. The proximal end of the first straight portion 54 is attached to the expansion strut 28 at a point where the joint strut 30 forms a small corner 48 with the expansion strut 28. The first straight portion 54 extends substantially collinearly with the joining strut 50, and its distal end is attached to the proximal end of the second straight portion 56 to form an inclined angle 58. The second straight portion 56 extends substantially collinearly with respect to the expansion strut 28 and its distal end is attached to the expansion strut 28 of the adjacent expansion column 24. Such attachment is performed where the expansion strut 28 forms a small corner 48 with the joining strut 30. The first straight portions 54 imitating the joint struts 30 are inclined with alternating circumferential directions between adjacent columns.
The joining of the connecting strut 38 and the expansion strut 28 at the point where the small angle 48 is formed makes the surface of the non-expanded stent streamlined and minimizes the points where it can be trapped. Helps 10 smooth delivery. Thus, as a result of the bare delivery of the stent 10 to the target site in the blood vessel, snags are minimized when the stent 10 is advanced through the bends and bends in the blood vessel. become. The stent 10 behaves like a flexible tubular sledge when moving back and forth in a blood vessel while attached to a delivery catheter, with a tortuous blood vessel and vessel lumen. It slides over the bumps of irregular size caused by plaques due to internal atherosclerosis.
The stent 10 of FIGS. 4A and 4B, when fully expanded, has an inner diameter of up to 5.0 mm while maintaining an acceptable level of radial support strength and fatigue tolerance. The outer diameter of the crimped stent should be as small as 1.0 mm or less depending on the conditions of the delivery balloon profile located below it. It is particularly important that the outer diameter in the crimped state is small if stent delivery is attempted without pre-expansion of the target site. When the stent is optimally crimped onto the delivery balloon, the surface of the crimped stent is smooth, and the stent does not become caught during advancement or retraction in the blood vessel.
FIG. 5 shows a second embodiment of the present invention in which the expanded stent 10 has a taper from the proximal end 12 to the distal end 14. The shaded segments 72, 74, 76, 78, 80, 82, 84 of the expansion strut 28 represent the area of the expansion strut 28 to be removed. Removal of the shaded segments 72, 74, 76, 78, 80, 82, 84 causes the stent 10 to exhibit a gentle taper when expanded, with the distal end 14 being smaller than the proximal end 12. Has an expanded diameter. The degree of contraction of the expanded diameter of the stent 10 at a given expansion column 24 is proportional to the length of the removed segment 72, 74, 76, 78, 80, 82 or 84 at that expansion column 24. I will. In the expansion stent 10, the shortened expansion strut 28 has a shortened component along the circumference of the stent, resulting in a decrease in circumferential length and diameter. The tapered diameter portion may be positioned somewhere along the length of the stent 10, and moderately large or small expansion struts 28 in a given expansion column 24 to make the taper somewhat loose. The part should be removed. Taper is particularly important for long stents longer than 12 mm. This is because blood vessel tapers are more prominent over longer lengths. Long stents with a constant stent diameter can only match the diameter of the target vessel over a short area. If the proximal vessel size matches the stent diameter, the expanded end of the stent will be too large for the native vessel, and stent expansion may cause intimal dissection of the distal vessel. On the other hand, if the size of the distal vessel matches the stent diameter, the proximal end of the expanded stent will be too small to be set inside the vessel lumen. Accordingly, it is desirable to provide a stent with a tapered expanded diameter.
Another way to achieve a tapered expansion stent is to change the stiffness of the stent strut, expansion strut, connection strut or joint strut so that the stiffness of the strut varies along the length of the stent. To change the stiffness of the struts, change the length, width or thickness, add stiffening material, change the physical properties of the stent material using chemical or mechanical means, or around the stent One or a series of elastic elements.
Ideally, a tapered diameter stent should be fabricated using a tapered diameter stent and matched to deliver and deploy a tapered diameter stent. Methods using matched tapered balloon catheters used with tapered diameter stents are within the scope of the present invention.
Also, expanding a non-tapered stent using a tapered balloon will result in a tapered expanded stent, but since the metal is not removed from the stent, the stent will taper as a result of incomplete expansion. Therefore, the stent has many metal fractions at the tapered end, resulting in a high risk of acute thrombosis. Metal fraction is the percentage of the surface of the expanded stent that is covered with stent strut material. By shortening the expansion strut as shown in FIG. 5, a taper expansion stent with a substantially constant metal fraction along its length is obtained.
The third embodiment of the present invention shown in FIGS. 6A and 6B has a number of reinforced expansion columns 86 disposed along the length of the stent 10. Reinforcing column 86 is positioned along the length of the stent and provides additional local radial support strength and stiffness to the suntet 10. Additional strength and stiffness are particularly important at both ends of the stent in preventing stent deformation both during delivery and after deployment. During delivery, the stent end can be caught on the vessel wall, possibly deforming the unexpanded stent and changing its expansion characteristics. After placement of the stent, it is important that the ends of the stent be rigid so that they remain firmly in contact with the vessel wall, otherwise, during subsequent catheter manipulation procedures, Alternatively, a guide wire may be caught at the end of the suntet and pull the stent away from the vessel wall, possibly damaging or occluding the vessel.
A particular variation of the third embodiment of the stent 10 shown in FIGS. 6A and 6B has a length 16 of 20.70 mm and a non-crimp and non-expanded peripheral length 88 of 5.26 mm. The stent 10 consists of six expansion columns 24 and three reinforcing expansion columns 86, each of which consists of twelve expansion struts 28 or reinforcing expansion struts 90, respectively. One reinforcing expansion column 86 is disposed at each end and one along the length of the stent 10. The expansion strut width 62 is 0.15 mm, the reinforced expansion strut width 92 is 0.20 mm, and the connecting strut width 66 is 0.10 mm. The small angle 48 formed by the joint strut 30 and the expansion strut 28 is 75 °, and the small angle 94 formed by the reinforcement joint strut 96 and the reinforcement expansion strut 90 is 60 °.
Other arrangements of reinforced expansion struts 86, such as reinforced expansion columns 86, may be provided only at both ends of the stent, only at one end, or at multiple locations throughout the length of the stent, and this is within the scope of the present invention. . The taper may also be programmed into the reinforced stent 10 by shortening the expansion struts 28 and reinforced expansion struts 90 in the appropriate expansion columns 24,86.
The fourth embodiment of the present invention shown in FIGS. 7A, 7B and 7C is similar to the third embodiment, but has another feature of relief cuts 98,100. A relief cut is a cut after the metal is removed from the struts, usually at a junction where a number of struts are connected. Providing the relief cuts increases the flexibility of the strut or joint because a thin and narrow area is formed along the strut or joint. A relief cut 98 is formed at the junction formed between the first straight portion 54 of the connecting strut 38 and the expansion strut 28. A relief cut 100 is formed at the junction between the second straight portion 56 of the connecting strut 38 and the expansion strut 28. Placing a relief cut provides additional flexibility to the unexpanded stent. A relief cut may be placed at the other joint and may be incorporated into any of the embodiments described above.
8A, 8B, 8C, 8D and 8E show several variations of connecting struts that can be used in any of the above-described embodiments. FIG. 8A shows a round loop connection strut 38 joining two circumferentially offset expansion strut pairs 32 in the adjacent expansion column. The expansion struts 28 of each expansion strut pair 32 are joined to each other by joint struts 30. The joint struts 30 are inclined to form a small angle 48 and a large angle 50 with the expansion struts 28 to which they are connected. A round loop connecting strut 38 is connected to the expansion strut 28 where a small angle is formed between the expansion strut 28 and the joint strut 30. The slope of the round connecting strut 38 at the proximal end 102 and the distal end 104 substantially matches the slope of the joining strut 30 that connects the pair of expansion struts 28. Thus, the round loop connecting strut 38 is smoothly joined to the joint strut 30. Further, the round loop connecting strut 38 has a first radius of curvature 106 and a second radius of curvature 108.
In the design of FIG. 8B, round loop connecting struts 38 join two circumferentially offset expansion strut pairs 32 in adjacent expansion columns. The expansion struts 28 of each expansion strut pair 32 are joined to each other by joint struts 30. The joining struts 30 are perpendicular to the expansion struts 28 to which they are connected. The round loop connection strut 38 is connected to the expansion strut 28 at the same location as the joint strut 30. The round connecting strut 38 has a first radius of curvature 106 and a second radius of curvature 108 to connect the circumferentially offset expansion strut pairs 32 to each other.
In the design of FIG. 8C, connecting struts 38 join two circumferentially offset expansion strut pairs 32 in adjacent expansion columns. The expansion struts 28 of each expansion strut pair 32 are joined to each other by joint struts 30. The joint struts 30 are inclined to form a small angle 48 and a large angle 50 with the expansion struts 28 to which they are connected. The connecting struts 38 connect the expansion struts 28 to each other where a small angle 48 is formed between the expansion strut 28 and the joint strut 30.
The connecting strut 38 is composed of three straight portions 110, 112, 114 that form two inclination angles 116, 118. The proximal end of the straight portion 110 is attached to the expansion strut 28 at a location where the joint strut 30 forms a small angle 48 with the expansion strut 28. The straight portion 110 extends substantially collinearly with respect to the joining strut 30, and its distal end is attached to the straight portion 112 to form an inclined angle 116. The straight portion 112 extends at an angle relative to the straight portion 110 such that the straight portion 112 is substantially parallel to the expansion strut 28, the straight portion 112 having a straight portion at its distal end. An inclination angle 118 is formed by being connected to the base end portion of 114. The straight portion 114 extends at an angle so that it is substantially collinear with the joining strut 30 of the adjacent expansion strut pair 32. The straight portion 114 is attached at its distal end to the expansion strut 28 of the adjacent expansion strut pair 32 at a point where the joint strut 30 forms a small angle 48 with the expansion strut 28.
In the designs of FIGS. 8D and 8E, the connecting struts 38 join together two circumferentially offset expansion strut pairs 32 in adjacent expansion columns. The expansion struts 28 in each imposed pair 32 are joined together by a joining strut 30. The joint struts 30 are perpendicular to the expansion struts 28 to which they are connected. The connection strut 38 is connected to the expansion strut 28 at the same location as the joint strut 30.
The connecting struts 38 of FIGS. 8D and 8E are composed of a number of connecting strut portions, which have a number of tilt angles that couple the expansion strut pair 32 to the adjacent expansion strut pair 32. The ends are connected to form a jagged connecting strut 38. The connecting strut of FIG. 8D is composed of three connecting strut portions 120, 122, 124 formed with two inclined angles 126, 128, whereas the connecting strut of FIG. 8E has three inclined angles 138, 140. , 142 are formed of four connecting strut portions 130, 132, 134, 136. In addition, the connecting strut portion 134 has been redesigned by using a connecting strut portion 144 shown in dotted lines in place of the connecting strut portion 136, thereby providing another possible geometric configuration for the connecting strut 38. The shape is obtained.
One skilled in the art will recognize that many examples of arrangements that fall within the scope of the present invention for connecting struts and splicing struts are possible, and that the above examples are not exclusive.
The stent of the present invention can be used for non-coronary, aortic, and avascular tubular internal organs due to the flexibility of the stent design, but is ideal for coronary applications.
A typical coronary stent has an expanded diameter of 2.5 mm to 5.0 mm. However, stents that have large radial strength and fatigue tolerance and expand to a diameter of 5.0 mm may have a stent metal fraction that is high enough to exceed acceptable limits when used on small diameter vessels. . If the stent metal fraction is high, the risk of thrombosis and restenosis will increase. Even with the same metal fraction, blood vessels with small luminal diameters tend to have a higher incidence of thrombosis than those with large diameters. Therefore, for coronary applications, it is used for at least two different types of stents, ie small diameter stents used for blood vessels with a diameter of 2.5 mm to 3.0 mm and blood vessels with a diameter of 3.0 mm to 5.0 mm. It is preferred to provide a large diameter vascular stent. Thus, both small and large vessels will receive ideal metal fraction stents similar to each other when treated with an appropriately sized stent.
The stent of the present invention can be manufactured by cutting a stent pattern from a stainless steel tube using a CAM-driven laser cutting system. The coarsely cut stent is preferably electropolished to remove surface defects and sharp edges. Other methods of manufacturing the stent, such as EDM, photoelectric etching or other methods can also be used. Any suitable material can be used as the constituent material of the stent, such materials including other metals and polymers. Provided that these materials have the necessary structural strength, flexibility, biocompatibility and expandability.
The stent is typically plated at least in part with a radiopaque metal such as gold, platinum, tantalum or other suitable metal. Although it is preferable to plate only both ends of the stent by the local plating method, the entire stent or other regions may be plated. When plating both ends, 1 to 3 or more expansion columns at each end of the stent are plated to mark both ends of the stent so that they can be identified by fluoroscopy during the stent loading procedure To. By plating the stent only at both ends, interference of the radiopac plating material of the stent frame with performance or surface conditioning properties is minimized. Furthermore, the required amount of plating material is reduced and the material cost of the stent is reduced.
After plating, the stent is usually cleaned using detergents, saline and ultrasonic means well known in the art. The stent is then inspected for quality control, assembled into a delivery balloon catheter, properly packaged, labeled and sterilized.
The stent may be sold alone or as a pre-attached delivery balloon catheter assembly as shown in FIG. Referring to FIG. 9, the stent 10 is crimped or crimped onto a folded balloon 146 located at the distal end 148 of the delivery balloon catheter assembly 150. The assembly 150 includes a proximal adapter 152, a catheter shaft 154, a balloon channel 156, a guide wire channel 158, a balloon 146 and a guide wire 160. The balloon 146 may be tapered or curved from the proximal end to the distal end in the expanded state, or may be tapered and curved. Furthermore, the stent 10 may be not tapered or tapered in the expanded state.
Typically, a guide wire 160 is inserted into a vein or artery and advanced to the target site. The catheter shaft 154 is then advanced along the guide wire to position the stent 10 and catheter 146 in place at the target site. Once in place, balloon 146 is inflated through balloon channel 156 to expand stent 10 from a crimped state to an expanded state. In the expanded state, the stent 10 provides the desired splint support for the blood vessel. Once the stent 10 is expanded, the balloon 146 is deflated and the catheter shaft 154, balloon 146 and guidewire 160 are removed from the patient.
The stent of the present invention may be as short as 10 mm or less, or as long as 100 mm or more. However, when using long stents, a matching length of delivery catheter balloon will generally be required to expand the stent to these deployed positions. Long stents depend on the target vessel, but this deployment may require a long curved balloon. A curved balloon that matches the natural curved state of the vessel reduces the stress on the vessel during stent deployment. This is particularly important for many coronary applications that require stenting within curved coronary vessels. The use of such curved balloons is within the scope of the present invention.
The foregoing description of the preferred embodiment of the present invention has been made for purposes of illustration. Such description is not exclusive and is not intended to limit the invention to the precise form disclosed. It will be apparent to those skilled in the art that many design changes and modifications can be made. The scope of the present invention is determined based on the description of the claims and the equivalent scope thereof.

Claims (11)

A stent, in an unexpanded state,
A first expansion strut pair comprising first and second expansion struts positioned adjacent to each other and a joint strut, the joint strut of the first expansion strut pair comprising a first expansion strut and a second expansion strut A plurality of the first expansion strut pairs forming a first expansion column; and a plurality of the first expansion strut pairs forming a first expansion column;
The stent further includes a second expansion strut pair comprising first and second expansion struts positioned adjacent to each other and a joint strut, and the joint strut of the second expansion strut pair includes a second strut A first expansion strut and a second expansion strut of the expansion strut pair are coupled to each other at the proximal end of the second expansion strut pair, and the plurality of second expansion strut pairs include a second expansion column. and forming,
The stent further includes a first connecting strut including a proximal head and a distal tail, the proximal head coupled to a distal end of a first expansion strut pair in a first expansion column. The distal tail is coupled to the proximal end of the second expansion strut pair of the second expansion column, and the plurality of first connecting struts couple the first expansion column and the second expansion column to each other first to form a connecting strut column, distal tail and Rukoto extending in a first direction transverse to the longitudinal axis of the proximal head portion to form a first inclination angle of,
The stent has a third expansion strut pair consisting of first and second expansion struts located adjacent to each other and a third joint strut, and the third joint strut of the third expansion strut pair . Joining a first expansion strut and a second expansion strut at a proximal end of a third expansion strut pair, wherein the plurality of third expansion strut pairs form a third expansion column; The first expansion struts of the second expansion strut pair in the second expansion column are circumferentially spaced relative to the first expansion struts of the first expansion strut pair in the first expansion column; And having a longitudinal axis parallel to the longitudinal axis of the first expansion strut of the first expansion strut pair in the first expansion column, the third expansion strut pair of the third expansion column in the third expansion column. Expansion of 2 Struts, spaced in the circumferential direction with respect to the first expansion strut of the second expansion strut pair in a second expansion column, and, in the second expansion strut pair in the second expansion column a first Having a longitudinal axis parallel to the longitudinal axis of the expansion struts ;
The stent further comprises a second connecting strut including a proximal side head and distal tail, the proximal head, coupled to the distal end of the second expansion strut pair in the second expansion column The distal tail is coupled to the proximal end of the third expansion strut pair of the third expansion column, and the plurality of second connecting struts couple the second expansion column and the third expansion column to each other Forming a second connecting strut column, the distal tail being in a direction opposite to the first transverse direction with respect to the longitudinal axis of the proximal head so as to form a second angle of inclination. and Rukoto extending in a second lateral direction,
At least a portion of the first connecting strut has a first straight portion joined to the joining strut of the first expansion strut pair and a second straight portion joined to the joining strut of the second expansion strut pair. The distal end of the first linear portion is joined to the proximal end of the second linear portion;
A first relief cut formed at the junction formed between the first straight portion of the connecting strut and the expansion strut, and formed at the junction between the second straight portion of the connecting strut and the expansion strut. Further having a second escape cut made ;
The ratio of the number of expansion struts in the expansion column to the number of connection struts in the connection strut column is 2 to 1, and the first angle of inclination is the first expansion column and the second expansion column when the stent is in the expanded state. stent, wherein the reducing the shrinkage of the stent between the second expansion column. The stent according to claim 1, wherein the first connecting strut has a plurality of inclination angles . The stent according to claim 1, wherein a width of a part of the first connecting strut is equal to or smaller than a width of a part of the first expansion strut. The stent according to claim 1, wherein a width of a part of the first connection strut is larger than a width of a part of the first expansion strut. 2. A reinforcing expansion column formed of a plurality of reinforcing expansion struts, wherein the width of each reinforcing expansion strut is larger than the width of the expansion strut in the first or second expansion column. The described stent. The stent according to claim 1, wherein the stent has a proximal end with a first reinforcing expansion column and a distal end with a second reinforcing expansion column. The stent according to claim 1, wherein at least a portion of the first connecting strut has a first radius of curvature. The stent of claim 1, wherein a portion of the first connecting strut having a first radius of curvature has a second radius of curvature. At least a portion of the first connecting strut has a first straight portion, a second straight portion, and a third straight portion, and a proximal end portion of the first straight portion is a joint of the first expansion strut pair. Joined to the struts, the ends of the second straight portions joined to the joined struts of the second pair of expansion struts, the first straight portion and the second straight portion being disposed between the straight portions The stent according to claim 1, wherein the stent is connected to each other by a third straight portion. At least a portion of the first connecting strut has a first straight portion, a second straight portion, a third straight portion, and a fourth straight portion, and the proximal end of the first straight portion is the first straight portion. Joined to the joining struts of the expansion strut pair, the end of the second straight section is joined to the joining strut of the second expansion strut pair, and the first straight section and the second straight section are connected to these straight sections. The stent according to claim 1, wherein the stent is connected to each other by a third linear portion and a fourth linear portion disposed therebetween. The stent according to claim 1, wherein the stent has a tapered diameter in an expanded state.

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