JP2005501651A - Longitudinal flexible stent [Related application] This application is a continuation-in-part of application No. 09 / 864,389, filed on May 25, 2001, and is filed on February 28, 2001. No. 09 / 795,794, a continuation-in-part application, which is an application of application No. 09 / 516,753 filed on Mar. 1, 2000. Claims priority of provisional application 60 / 202,723 of monthly application. - Google Patents

Abstract

An endovascular stent that is particularly suitable for implantation into arterial bends. This stent retains longitudinal flexibility after expansion. The stent is composed of meander patterns that are intertwined with each other to form triangular cells. The triangular cells are tuned to provide radial support and to provide longitudinal flexibility after expansion. The vessel wall is more fully covered by the triangular cells. Stents can be partially optimized for radial support or longitudinal flexibility, respectively. The loop in the stent is expanded after the stent is expanded in the curved lumen, the stent bends, the cells outside the curve open in the length direction, the width decreases, and the cells inside the curve have a length. It is shortened, widened and installed and adjusted to cooperate between the inside and outside of the bend to keep the density of the stent element region much more constant than in other cases. As a result, when drug is applied to the stent, the density of the stent elements is more constant, so a uniform amount of drug is applied to the inner wall of the lumen, providing a harmful amount in one location, The possibility that only an amount that does not reach the effective amount is supplied elsewhere is avoided.

Description

【Technical field】
[0001]
The present invention generally relates to a stent which is a stent tube that is implanted in a body vessel, such as a blood vessel, to support the blood vessel and keep it open, or to fix and support other stent tubes in the blood vessel. .
[Background]
[0002]
Various stents are known in the art. Generally, stents are typically tubular and can expand from a relatively small, unexpanded diameter to a large, expanded diameter. In order to implant a stent, the stent is usually attached to the tip of a catheter, and at this time, the stent is attached to the catheter in a relatively small diameter state before expansion. The catheter guides the unexpanded stent through the lumen to the desired implantation site. When a stent reaches a desired implantation site, generally, for example, an internal force such as inflating a balloon inside the stent, or a sleeve around a self-expanding stent is removed and the stent is expanded outward. The stent is expanded by the self-expansion of the stent itself. In either case, the expanded stent counters the tendency for blood vessels to narrow and maintains the patency of the blood vessels.
[0003]
Israel et al., US Pat. No. 5,733,303 (hereinafter “the '303 patent”), incorporated herein by reference, is a first and second meander pattern having axes extending in first and second directions. A unique stent formed of a tube having a patterned shape with The second meander pattern is intertwined with the first meander pattern to form a flexible cell. Such stents are very flexible when unexpanded and can easily pass through tortuous lumens. When the stent is expanded, it provides excellent radial support, stability, and vessel wall covering. This stent is also consistent and conforms to the shape of the vessel wall during implantation. Naturally, for example, when the stent shown in FIG. 8 is expanded in a curved lumen, the cells outside the curved portion open in the length direction and become narrower, while the cells inside the curved portion are in the length direction. Obviously, the density of the elemental area of the stent remains much more constant between the inside and outside of the bend than in other cases.
[0004]
However, a feature of such a cellular mesh stent is that it has limited longitudinal flexibility after expansion, which is disadvantageous for certain applications. This longitudinal flexibility limitation creates stress points at the end of the stent and along the length of the stent. A conventional mesh stent, such as that shown in US Pat. No. 4,733,665, lacks longitudinal flexibility and is shown in FIG. 1, which is a schematic illustration of a conventional stent 202 in a curved vessel 204.
[0005]
When implanting a stent, the stent is delivered to the desired site by a balloon catheter in an unexpanded state. The balloon catheter is then inflated to expand the stent and secure the stent in place. The balloon's high inflation pressure, up to 20 atmospheres, straightens the curved vessel 204 and the longitudinally flexible stent when the balloon is inflated. When the stent is relatively rigid or rigid after expansion due to its network configuration, the stent tends to keep or keep the same or substantially the same shape when the balloon is deflated. However, as shown in FIG. 1 for a conventional mesh stent, the artery attempts to return to its natural curve (shown as a dotted line). A mismatch between the natural curve of the artery and the linear portion of the artery containing the stent can cause stress concentration points 206 at the end of the stent and stress throughout the length of the stent. Because the cardiovascular structure moves relatively large with each heartbeat, it can further stress the stent. For illustration purposes, the difference between the vascular curve and the linear stent is exaggerated in FIG.
[0006]
Richter, US Pat. No. 5,807,404, which is expressly incorporated herein by this reference, discloses another stent that is particularly suitable for implantation in arterial bends or bone-affected portions. The stent can be provided with a portion having a greater flexibility in bending than the remaining portion of the stent in the axial direction near the end of the stent. By making such changes at the end of the stent, the stress at the end is reduced, but stress throughout the length of the stent cannot be excluded.
[0007]
Various stents are known that can maintain longitudinal flexibility after expansion. For example, the various stents disclosed by Wiktor U.S. Pat. Nos. 4,886,062 and 5,133,732 (hereinafter referred to as "Wiktor '062 and' 732 patents") are comprised of wires, which first form a serpentine zigzag pattern. It is formed into a band, and then a zigzag band is wound into a spiral stent. These stents are expanded by internal forces, such as by inflating a balloon.
[0008]
The helical zigzag stent shown in Figures 1 to 6 of the Wiktor '062 and' 732 patents is flexible in the longitudinal direction in both expanded and unexpanded forms, making it easier to twist tortuous lumens. After passing through and installing, the shape becomes relatively close to the shape in the blood vessel. Although these stents are flexible, the support force after expansion is also relatively unstable. Furthermore, in the case of these stents, a large portion of the vessel wall remains uncovered, and tissue and plaque hang down into the lumen of the vessel.
[0009]
Therefore, it has longitudinal flexibility that allows it to easily pass through tortuous lumens before dilatation and, after dilation, keeps the vessel continuous to minimize tissue drooping into the lumen. It is preferable to achieve a stent with longitudinal flexibility that can be adapted to the natural flexibility and curvature of the vessel while providing stable and stable coverage.
[0010]
[Patent Document 1]
U.S. Pat.No. 5,733,303
[Patent Document 2]
U.S. Pat.No. 4,733,665
[Patent Document 3]
U.S. Pat.No. 5,807,404
[Patent Document 4]
U.S. Pat.No. 4,886,062
[Patent Document 5]
U.S. Patent No. 5,133,732
DISCLOSURE OF THE INVENTION
[0011]
Therefore, an object of the present invention is to have a longitudinal flexibility that can easily pass through a tortuous lumen before dilatation, and the longitudinal flexibility is maintained even after dilation, and the vascular flexibility To provide a stent that is consistent with sex and substantially eliminates stress points by following the natural curve of the vessel.
[0012]
Another object of the present invention is to provide a stent that has longitudinal flexibility after being brought into place, flexes during the heartbeat cycle, and reduces periodic stress along the stent end and stent.
[0013]
Yet another object of the present invention is to provide a stent with a closed cell pattern that can successfully cover and support the vessel wall after expansion.
[0014]
Other advantages of the present invention will be apparent to those skilled in the art.
[0015]
In accordance with these objectives, the stent of the present invention is a patterned shape having first and second meander patterns having axes extending in first and second directions, wherein the second meander pattern is first. It is formed as a tube intertwined with the meander pattern.
[0016]
According to one embodiment of the present invention, the meander pattern entangled with each other has three points where the first and second meander patterns meet each other, forming a cell called a triangular cell in this sense. These three cornered or triangular cells are flexible about the longitudinal axis of the stent after expansion. This triangular cell has four points where the first and second patterns meet, and in this sense is called a square cell, and has a radial supporting force comparable to a cell formed by an intertwined meander pattern .
[0017]
In another embodiment of the invention, a band of cells is provided throughout the length of the stent. The cell band at the end (square cell) is mainly adjusted to improve the radial bearing capacity in the center cell (triangular cell), which is mainly adjusted to improve the longitudinal flexibility after expansion. ing.
[0018]
In another embodiment of the present invention, the first meander pattern is tailored to prevent “spreading” of the first meander pan loop during delivery of the stent to the desired site.
[0019]
The stent according to the present invention retains longitudinal flexibility in the unexpanded state of the '303 patent cellular stent and improves longitudinal flexibility in the expanded state. This is achieved without sacrificing the support force, ie the vascular wall covering or radial support.
[0020]
Further, in some embodiments, the structure of the cell with three corners is such that it compensates for shortening.
BEST MODE FOR CARRYING OUT THE INVENTION
[0021]
FIG. 2 is a schematic illustration of a longitudinally flexible stent 208 of the present invention. The stent 208 is carried by the balloon catheter to the curved vessel 210 and implanted into the artery by inflating the balloon. As described above, the balloon causes the artery to straighten when the balloon is inflated. However, when the balloon is deflated, the stent 208 conforms to the natural curve of the vessel 210 because it is longitudinally flexible and retains it after expansion. This reduces stress points that can occur along the length of the stent end and the stent. Furthermore, because the stent is flexible in the longitudinal direction even after expansion, it contracts longitudinally with the vessel during the period generated by the heartbeat. This also mitigates periodic stresses along the stent end and the length of the stent.
[0022]
FIG. 3 shows a pattern of a stent according to the present invention. This pattern can be made of a known material such as stainless steel, but is particularly suitable for being made of NiTi. The pattern can be formed by etching a flat sheet of NiTi into the pattern shown. A flat sheet is formed into a tubular stent by rolling the etched sheet into a tubular shape and welding the edges of the sheet. Details of how to form such a stent with certain advantages are disclosed in US Pat. Nos. 5,836,964 and 5,997,973, hereby expressly incorporated by reference. Other methods known to those skilled in the art, such as laser cutting or tube formation by etching, may be used to construct a stent utilizing the present invention. After being formed into a tubular shape, the NiTi stent is subjected to a heat treatment known to those skilled in the art to utilize the shape memory characteristics of NiTi and its superelasticity.
[0023]
The pattern 300 is formed by collecting a plurality of two orthogonal meander patterns that are intertwined with each other. The term “meander pattern” here refers to a periodic pattern with respect to the center line, and “orthogonal meander pattern” means a pattern in which the center lines are orthogonal to each other.
[0024]
The meander pattern 301 is a vertical sine curve having a vertical centerline 302. It will be appreciated that this is not a perfect sinusoid but an approximation thereof. Thus, as used herein, the term sinusoid refers to a periodic pattern that varies positively and negatively about an axis and need not be an exact sine function. The meander pattern 301 has two loops 304 and 306 in one cycle. The loop 304 opens on the right side and the loop 306 opens on the left side. The loops 304, 306 share a common component 308, 310, the component 308 is coupled to one loop 304 and is connected to the subsequent loop 306, and the component 308 is coupled to one loop 306 and then the loop 304 Connect with. The vertical sinusoid of the meander pattern 301 has a first amplitude.
[0025]
The meander pattern 312 (two of which are shaded for reference) is a horizontal pattern with a horizontal centerline 314. The horizontal meander pattern 312 also has loops 316, 318, 320, 322, and there is a section 324 between the loops of one period. In other words, these loops are part of a vertical sine curve 303 with more amplitude than the meander pattern 301. The vertical sine curve 301 alternates with the vertical sine curve 303. The vertical sinusoid 303 has a second amplitude that is greater than the first amplitude of the vertical meander pattern, ie the sinusoid 301.
[0026]
The vertical meander patterns 301 are provided in odd and even (o and e) versions that are 180 ° out of phase with each other. Thus, the loop 306 with the left side of the meander pattern 301o open is opposite to the loop 304 with the right side of the meander pattern 301e open, and the loop 304 with the right side of the meander pattern 310o open is the left side of the meander pattern 301e. Opposite the open loop 306.
[0027]
Horizontal meander patterns 312 are also provided in odd and even configurations. The straight section 324 of the horizontal meander pattern 312e intersects the third common component 310 of the even number of vertical meander patterns 301e. The straight section 324 of the horizontal meander pattern 312o also intersects every third common component 310 of the odd number of vertical meander patterns 301. If the vertical sine is viewed as 303, the alternating sine curve 303 is completely connected to the meander pattern 301. For example, between the points 315 and 317, the vertical pattern 303 is connected to the vertical pattern 301e, and two loops 306 and one loop 304 of the vertical pattern 301e and three loops 319 and two loops 321 of the vertical pattern 303 are included. is there.
[0028]
This corresponds to two periods of the pattern 301 and three periods of the pattern 303. Similarly, there are two loops 304 and one loop 306 between two connection points between the vertical pattern 301o and the vertical pattern 303, and here, two cycles are formed. Three loops 321 and two loops 319 are created, which is also equal to three periods of pattern 303.
[0029]
Since this stent embodiment is made of NiTi and is recoilable, it is generally self-expanding. As the stent expands, the loop of vertical meander pattern 301 opens in the vertical direction. As a result, the loop is shortened in the horizontal direction. The loop of the horizontal meander pattern 312 opens in both the vertical and horizontal directions to compensate for the shortening of the vertical meander pan loop.
[0030]
The loop of the horizontal meander pattern 312 is the loop of the vertical pattern 303 of the present invention and avoids shortening of the self-expanding stent in a particularly effective manner. Self-expanding stents made of shape memory alloys must be compressed from an expanded position to a compressed position in order to be carried. As shown in FIG. 7, the configuration of the loops 319 and 312 of the horizontal meander pattern 312 is such that when the stent is compressed from the expanded position 602 to the compressed position 604, the length of the horizontal meander pattern 606 (of the vertical pattern 330). Width) contracts naturally. As a result, when the stent expands, the loops 319 and 321 become longer, compensating for the shortening of the vertical meander patterns 301e and 301o when the vertical meander patterns 301e and 301o expand. On the other hand, as shown in FIG. 14, for example, an N-shaped horizontal meander pattern does not naturally contract in the length direction when compressed from the expanded position 608 to the compressed position 610.
[0031]
The ability to compensate for such shrinkage is further illustrated in FIG. FIG. 16 shows how a loop that is part of the horizontal meander pattern and includes a section 901 with a higher amplitude compensates for the shortening of the section 903 with a lower amplitude when the stent is expanded. In the upper part of the figure, both a high amplitude loop including section 901 and a low amplitude loop including section 903 are shown compressed. The width of the section 903 is from the line 905 to the line 907. The low amplitude interval width is from line 907 to line 909. In the lower part of the figure, an expanded stent is shown. The width of the low amplitude section 903 is shortened so that the width is only the line 905 to the line 911. However, when expanding, the high amplitude section 901 compensates for this shortening. The width of the high-amplitude section 901 is from line 911 to line 909, and shortening can be compensated without causing friction. As mentioned above, this is particularly advantageous for self-expanding stents known under the name Nitinol, including those made of, for example, austenitic NiTi, that expand to a memorized shape.
[0032]
For example, referring to FIG. 4, the high amplitude loop is coupled to the low amplitude loop, such as at the coupling point 540 also shown in FIG. This is also happening at join points 538 and 542. The thickness of these points is greater than the other parts, which limits the ability of the loop to open. On the other hand, the loop extending from the curved components 548 and 549 is not limited. As a result, the corner between component parts 513 and 516 opens, for example, larger than the corner between component parts 519 and 522. The combined effect of these corners increases the width of the high amplitude section, which compensates for the shortening of the low amplitude section.
[0033]
A stent formed from the pattern of FIG. 3 and made of NiTi is particularly suitable for use in the carotid artery or other lumen subjected to external pressure. One reason for this is that the stent is made of recoilable NiTi, which is a desirable property for stents placed in the carotid artery. Another reason is that the stent of FIG. 3 provides excellent support, which is particularly important in the carotid artery. Support is particularly important in the carotid artery because particles that move in the artery may close the vessel and cause pulsations.
[0034]
FIG. 4 is an enlarged view of one flexible cell 500 of the pattern of FIG. Each flexible cell 500 includes a first component 501 having a first end 502 and a second end 503, a second component 504 having a first end 505 and a second end 506, A third component 507 having a first end 508 and a second end 509, and a fourth component 510 having a first end 511 and a second end 512. The first end 502 of the first component 501 is coupled with the first end 505 of the second component 504 by the first curved component 535 to form a first loop 550 and a second Second end 506 of component 504 is coupled to second end 509 of third component 508 by second curved component 536, and first end 508 of third component 507 is third. Is coupled to the first end 511 of the fourth component 510 by a curved component 537 to form a second loop 531. The first loop 530 defines a first corner 543. The second loop 531 defines a second corner 544. Each cell 500 also includes a fifth component 513 having a first termination 514 and a second termination 515, a sixth component 516 having a first termination 517 and a second termination 518, and a first A seventh component 519 having a first end 520 and a second end 521, an eighth component 522 having a first end 523 and a second end 524, a first end 526 and a second end A ninth component 525 having a 527 and a tenth component 528 having a first end 529 and a second end 530. The first end 514 of the fifth component 513 is coupled to the second end 503 of the first component 501 at the second coupling point 542, and the second end 515 of the fifth component 513 is A curved component 539 is coupled to the second end 518 of the sixth component to form a third loop 532, and the first end 517 of the sixth component 516 is formed by the fifth curved component 548. Coupled to the first end 520 of the seventh component 519, the second end 521 of the seventh component 519 is coupled to the second end 524 of the eighth component 522 at the third coupling point 540. The fourth end 523 of the eighth component 522 is coupled to the first end 526 of the ninth component 525 by the ninth curved component 549, The second end 526 of the second component 525 is coupled to the second end 530 of the tenth component 528 by the seventh curved component 541 to form a fifth loop 534; First end 529 of the ten components 528 is coupled to the second end 512 of the fourth component 510. The third loop 532 defines a third corner 545. The fourth loop 533 defines a fourth corner 546. The fifth loop 534 defines a fifth corner 547.
[0035]
In the embodiment shown in FIG. 4, the first component 501, the third component 507, the sixth component 516, the eighth component 522, and the tenth component 528 are relative to the longitudinal axis of the stent. Having substantially the same angular orientation, the second component 504, the fourth component 510, the fifth component 513, the seventh component 519, and the ninth component 512 are relative to the horizontal axis of the stent. Have approximately the same angular orientation. In the embodiment shown in FIG. 4, the lengths of the first, second, third and fourth components 501, 504, 507 and 510 are substantially equal. The lengths of the fifth, sixth, seventh, eighth, ninth, and tenth components 513, 516, 519, 522, 525, and 528 are substantially equal. Other embodiments in which individual component lengths are determined for a particular application, component material, or delivery method are possible and would be preferred for them. It can be seen that each cell includes two periods of a low amplitude vertical pattern and three periods of a high amplitude vertical pattern.
[0036]
The first, second, third and fourth components 501, 504, 507 and 510 are the fifth, sixth, seventh, eighth, ninth and tenth components 513, 516, It has a width greater than the width of 519, 522, 525, 528. The fact that the widths of the first, second, third and fourth components and the widths of the fifth, sixth, seventh, eighth, ninth and tenth components are different from each other is Contributes to flexibility and resists radial shrinkage of the cell. The widths of the various components can be adjusted for specific applications. For example, the width ratio can be about 50-70%. The fifth, sixth, seventh, eighth, ninth, and tenth components are mainly optimized to ensure vertical flexibility both before and after expansion. The fourth component may be optimized so that primarily the radial compression generates sufficient resistance to keep the vessel open. The individual components are primarily optimized to achieve the desired properties, but all parts of the cell cooperate with each other and contribute to the properties of the stent.
[0037]
FIGS. 5 and 6 show a pattern of an embodiment according to the present invention and an enlarged view of one cell, specifically tailored for a stent made of stainless steel. This pattern is similar to that of FIGS. 3 and 4, and the same reference numerals are used for almost corresponding parts. The stent of the embodiment of FIGS. 5 and 6 is typically expanded by a balloon in a conventional manner.
[0038]
3 and 5 are also viewed as being composed of high- and low-amplitude vertical sinusoidal patterns or vertical loop inclusion sections, arranged approximately circumferentially and interconnected periodically. Can do. Accordingly, a first loop inclusion section extending along the line 301 and generating a loop with a first amplitude, and a second loop inclusion section extending along the line 302 and generating a loop with the first amplitude are provided. is there. A third loop inclusion section 303 extending along line 305 has a loop that occurs at a second amplitude higher than the first amplitude. This is installed between the first and second loop inclusion sections and is alternately coupled to the first and second loop inclusion sections. In the illustrated embodiment, the high amplitude is 3/2 of the low amplitude. As described above, the high amplitude loop inclusion element is narrow. The relative width can be selected so that the high amplitude elements can be crimped to the same diameter as the low amplitude elements.
[0039]
Further, the small width of the high amplitude vertical pattern provides an element with a low maximum strain. In particular, the low maximum strain is less than the maximum strain in the absence of inelastic deformation of the stent material. In this embodiment where the stent is composed of stainless steel, the low maximum strain is less than about 0.4% even when bent 150 °, which has been confirmed by finite element analysis. In contrast, the stent of the type of the '303 patent has a maximum strain of 8% when bent to the same extent. Thus, the high flexibility of the stent of the present invention means that it bends with each heartbeat, in addition to better fitting with a curved lumen. Strain during the heartbeat occurs 8,000,000 times each year, and the stent breaks when the elastic limit is greatly exceeded. Therefore, keeping the strain below the limit of the embodiments of the present invention means that the stent of the present invention can bend to the lumen each time the heart beats without breaking for many years.
[0040]
Also in this embodiment of the invention, the second loop 531 is strengthened by shortening the third and fourth components 507, 510. This helps to ensure that the second loop does not “spread” while the stent is advanced into the tortuous anatomy. This “spread” is not a problem for NiTi stents that are coated during transport.
[0041]
Furthermore, the length of the constituent parts in this embodiment can be made shorter than the length of the corresponding constituent parts in the embodiments shown in FIGS. Typically, the amount of strain allowed in a self-expanding NiTi stent is about 10%. For stainless steel stents, for example, the amount of strain that is tolerated in the case of plastic deformation that occurs during expansion, for example, is typically 20% or more. Thus, the NiTi component can be longer than the stainless steel stent component so that the NiTi stent and the stainless steel stent can be expanded to an equivalent diameter.
[0042]
When the stent is expanded in a curved lumen, it bends as shown in FIG. The results of such bending are shown in FIG. 15 for one cell 500. Although the cell outside the curved portion opens in the length direction, the width is narrowed, and the cell inside the curved portion is shortened in length and widened. As a result, the density of the components per unit surface area expands and remains close to that of the uncurved state, both inside and outside the curved portion. Similarly, as can be seen from FIG. 15, the cell area is more constant than without compensation. For this reason, the density of the stent element in contact with the lumen is kept more constant regardless of whether it is inside or outside the curved portion. As a result, when a drug is applied to the stent, a more constant amount of drug is applied to the inner wall of the lumen, a large amount of the drug is supplied to one place, and an effective amount is applied to another place. The possibility of supplying only an amount of drug that does not reach the limit is eliminated. In some cases, the ratio of harmful to effective amounts is less than 10: 1.
[0043]
In particular, it can be seen that in the cells outside the curve at the connection points 542, 538, the cells open larger along the length of the cell. Furthermore, at the joining points 535, 536, 537, 539, 540, 542, the joining struts approach each other, and the cell becomes smaller in width, ie in the circumferential direction, to compensate for the increase in length. Inside the bend, the vertical distance must be reduced. Again, compression occurring inside causes the struts inside or outside the joining points 542, 538 to contract, reducing the cell width. At the same time, at the coupling points 535, 536, 537, 539, 540, 542, the struts are further away from each other, the cells are narrow in length and wide, and compensation is also provided here. Thus, in either case, the increase in one direction is compensated in the opposite direction and the area is more constant than without compensation.
[0044]
FIG. 7 illustrates another aspect of the present invention. The stent shown in FIG. 7 is also composed of orthogonal meander patterns 301 and 302. This meander pattern forms a series of two types of interlocking cells 50, 700. A first type of cell 50 is taught in US Pat. No. 5,733,303. These cells are arranged such that they form alternating bands 704 of the first cell 50 and bands 706 of the second type cell 700.
[0045]
As can be seen from FIG. 8, each cell 50 of the '303 patent includes a first longitudinal apex 100 and a second apex 100, particularly for cells numbered for ease of explanation. It has a longitudinal end 78. Each cell 50 also has a first longitudinal end 77 and a second longitudinal apex 104 located at the second longitudinal end 78. Each cell 50 also includes a first component 51 having a longitudinal component having a first end 52 and a second end 53, a longitudinal end having a first end 55 and a second end 56. A second component 54 having a component, a third component 57 having a longitudinal component having a first end 58 and a second end 59, a first end 61 and a second end 62 A fourth component 60 having a longitudinal component is included. The stent also includes a first loop or curved configuration that defines a first corner 64 provided between the first end 52 of the first component 51 and the first end 55 of the second component 54. It has a portion 63. A second loop or curved component 65 defining a second corner 66 is provided between the second end 59 of the third component 57 and the second end 62 of the fourth component 60. It is installed almost opposite to the first loop 63. The first flexible compensation component (ie, part of the longitudinal meander pattern) 67 having two legs with a bend and a first end 68 and a second end 69 is the first component 51 and the third component 57, the first end 68 of the first flexible compensation component 67 is coupled to and communicates with the second end 53 of the first component 51 The second end 69 of the flexible compensation component 67 is coupled and in communication with the first end 58 of the third component 57. The first end 68 and the second end 69 are placed away from each other by different distances in the length direction. A second flexible compensation component (i.e. part of the longitudinal meander pattern) 71 having a first end 72 and a second end 73 comprises a second component 54 and a fourth component 60. Between. The first end 72 of the second flexible compensation component 71 is coupled and in communication with the second end 56 of the second component 54, and the second end 73 of the second flexible compensation component 71 is the fourth end The first end 61 of the component 60 is coupled and communicated. The first end 72 and the second end 73 are installed apart from each other by a different distance in the length direction. In this embodiment, the first and second flexible compensation components, and in particular their curved portions 67, 71, are arcuate.
[0046]
When the curved stent expands within the lumen, again in cell 50, the cells outside the curve open in the length direction, the width narrows, the cells outside the curve decrease in length, and widen, Thereby, the density of the component per unit surface area is kept more constant inside and outside the curved portion.
[0047]
In particular, it can be seen that in the cells outside the curved portion, the flexible connecting components 67, 71 open as the distances 70, 74 increase. Furthermore, the component parts 57 and 60 approach each other in the same manner as the component parts 51 and 54. This makes the cell even longer. At the same time, however, it narrows in width, ie in the circumferential direction, to compensate for the opening of the flexible connection components 67, 71. Inside the bend, the distance in the length direction must decrease. Again, the internal compression causes the loops 67, 71 to contract and the distances 70, 74 to decrease. At the same time, the component parts 57, 60 and the component parts 51, 54 are further away from each other, and the longitudinal components of the component parts 57, 60, 51, 54 are reduced. Thus, the cell is shortened but widened. Thus, in either case, the increase in one direction is compensated in the opposite direction, and the area is more constant than without compensation.
[0048]
A second type of cell 700 is shown in FIG. 9, and the same reference numerals are used to indicate generally corresponding portions of the cell. The foretop 100, 104 of the second type cell 700 is offset in the circumferential direction. Each of the flexible compensation components 67, 71 also includes a first portion or leg 79 having a first end 80 and a second end 81, a second end having a first end 83 and a second end 84. A portion or leg 82, a third portion or leg 85 having a first end 86 and a second end 87, the first end 81 and the second end 84 being joined by a curved component, The end 83 and the first end 86 are joined by a curved component. The first end of the flexible compensation component 67, 71 is the same as the first end 80 of the first portion 79, and the second end of the flexible compensation component 67, 71 is the second end of the third portion 85. Same as second end 87. A first inflection region 88 is provided between the second end 81 of the first portion 79 and the second end 84 of the second portion 82, where there is a curved portion connecting them. A second inflection region 89 is provided between the first end 83 of the second portion 82 and the first end 86 of the third portion 85, where there is a curved portion connecting them.
[0049]
Although FIG. 7 shows a pattern of alternating cell bands, the stent can be optimized for a particular application by adjusting the shape of the bands. For example, the central band of the second type cell 700 may be formed by the cell 50, or vice versa. The second type of cell shown in FIG. 7 can also use the cell configuration described in FIGS. According to the cell configuration of FIGS. 4 and 6, there is an advantage that no torque is generated with respect to another part of the cell in one part of the cell with respect to the longitudinal axis of the stent to be expanded. This torque may occur when the second type of cell 700 expands, causing the stent to deform and protrude.
[0050]
As shown in FIG. 7, all of the flexible compensation components are arranged such that the path from the left to the right of the flexible compensation component passes in a substantially downward direction. Cell 700 can also be arranged so that the flexible compensation components of one band are substantially upward, and the flexible compensation components of adjacent bands are arranged in a generally downward direction. Those skilled in the art can easily make these changes.
[0051]
FIG. 10 shows that the first and second meander patterns, which are intertwined with each other, meet at three points. A schematic diagram comparing a stent cell 802 according to the '303 patent, in which two meander patterns meet at four points and have four corners in this sense, namely a square cell. More specifically, on the left side of FIG. 10, a pair of vertical meander patterns 806, 826 are joined by components 808, 810, 812 (which are part of the longitudinal meander pattern) to form a plurality of triangles A cell 804 is formed. Triangular cells mean that there are three sections 810, 812, 814 that each have a loop portion and three associated points 816, 818, 820 connecting each, and forming each cell.
[0052]
On the right side of FIG. 10, a pair of vertical meander patterns 822, 824 are combined with compensation components 828, 830, 832, 834 (these are part of the longitudinal meander) to form a plurality of square cells 804. To do. A square cell means that there are four sections forming each cell, each having a loop portion and four related points connecting them. For example, a shaded cell 802 is formed from four sections 832, 836, 830, 838 having 840, 842, 844, 846 connecting each.
[0053]
Both square cells and triangular cells have two types of sections with loops. The first type of loop inclusion section is formed from a vertical meander pattern and is primarily optimized to allow radial support. The second type of loop inclusion section is optimized primarily to achieve flexibility along the longitudinal axis of the stent. Each loop inclusion section is optimized primarily to achieve the desired characteristics of the stent, but the sections are interconnected and cooperate to define the characteristics of the stent. Thus, the first type of loop inclusion section contributes to the longitudinal flexibility of the stent and the second type of loop inclusion section contributes to the radial support of the stent.
[0054]
In the square cell 802, it can be seen that the second type of loop inclusion sections 830 and 832 have one inflection point 848 and 850, respectively. In the triangular cell, the loop inclusion sections 810 and 812 each have two inflection points 852, 854, 856, and 858. If the number of inflection points is large, the degree of freedom of deformation after expansion of the stent is increased, and the deformation is distributed over longer sections, so that the maximum strain along these loop inclusion sections is reduced.
[0055]
Further, the square cells 802 are typically longer along the longitudinal axis of the stent than the triangular cells 804, and the triangular cells 804 are typically longer along the circumference of the stent. This also contributes to high flexibility after expansion.
[0056]
If the first meander patterns 806, 822, 824, 826 of both types of cells are identically configured and spaced by the same amount, the area of the triangular cell 804 is the same as the square cell 802. . This can be easily understood by referring to the band of cells around the circumference of the stent. Each band encloses the same area, and each band has the same number of cells. Therefore, the area of one cell in each band formed by square cells is the same as the area of another band formed by triangular cells.
[0057]
Although the cell area is equal, the periphery of the triangular cell is longer than the periphery of the square cell. Therefore, when compared with a square cell, the triangular cell covers the vessel wall more fully.
[0058]
In the particular embodiment described above, the stent is substantially uniform throughout its length. However, other cases where the stent is tailored to provide partially different properties are possible. For example, as shown in FIG. 11, a cell band 850 may have different flexibility characteristics or different radial compression characteristics than the rest of the cell bands by changing the width and length of the components that make up the band. Can be designed to provide. Alternatively, the stent may enter the lateral branch lumen by providing at least one cell 852 that is larger than the remaining cells, or by providing an entire band 854 of cells that is larger than the other bands of cells. You may adjust to increase access. Alternatively, the stent can be treated by applying a drug to the stent, plating the stent with a protective material, plating the stent with a radiopaque material, or coating the stent with a material after formation of the stent. it can.
[0059]
12 and 13 show alternating patterns for a stent constructed in accordance with the principles of the present invention. The stent shown in FIG. 12 has two cell bands 856 placed at a proximal end 860 and a distal end 862, respectively. The cells forming the cell band 856 located at the end of the stent are of the type according to the '303 patent. The remaining cells in the stent are the same as described for cell 500 shown in FIG. Two bands of cells of the '303 patent type are drawn at each end, but this is not a requirement and can be more or less, and the number of bands is the same at both ends. There is no need. Further, although eleven strips of the cell 500 are drawn, the number may not be eleven.
[0060]
A particularly useful embodiment as a ureteral stent has, for example, one band of cells 856 and four bands of cells 500 at each end. The geometry of the cell 500 is very soft in the longitudinal direction, and the nature of many renal artery lesions is that they are the entrance. In the case of an entrance lesion, the structure composed only of the cell 500 is pushed and extended, and the escape portion of the lesion passes through a longer (expanded) cell. In normal lesions, the stent cannot be pushed open due to friction of the stent on both sides, but at the entrance of the renal artery it is possible because there is no support for a single ring on the aortic side.
[0061]
Thus, to remedy this problem, a stent with two cell strips 856 at the end is used whose basic geometry is that of cell 500 but with the '303 patent type geometry. Is done. This results in a stent having a rigid, unexpanded cell band positioned at each of the proximal and distal ends 860 and 862, but flexible before and after installation.
[0062]
The stent shown in FIG. 13 has alternating cell bands 864, 866, 868. The first type of cell band 864 comprises cells of the type of the '303 patent. The second and third types of cell bands 866, 868 are formed of the cells described with respect to the cell 500 shown in FIG. Of course, various cell combinations can be used in the present invention.
[0063]
Thus, a longitudinally flexible stent utilizing a closed cell structure that satisfactorily covers a vessel wall has been described. It is possible to form stents of configurations other than the specific examples described herein using the general concepts described herein. For example, a bifurcated stent can be formed using the general concept. Those skilled in the art will appreciate that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the invention is defined in the following claims.
[Brief description of the drawings]
[0064]
FIG. 1 is a schematic illustration of a conventional rigid stent placed in a curved lumen.
FIG. 2 is a schematic illustration of a stent of the present invention installed in a curved lumen.
FIG. 3 shows a pattern for a stent constructed in accordance with the present invention.
FIG. 4 is an enlarged view of one cell in the pattern of FIG.
FIG. 5 shows a pattern for a stent constructed in accordance with the present invention.
FIG. 6 is an enlarged view of one cell of the pattern of FIG.
FIG. 7 shows a pattern for a stent constructed in accordance with the present invention.
FIG. 8 is an enlarged view of one cell used in the pattern of FIG.
FIG. 9 is an enlarged view of another cell used in FIG.
FIG. 10 is a schematic diagram showing a comparison of a four-corner or “square cell” with a three-corner or “triangular” cell according to the present invention.
FIG. 11 illustrates a pattern for a stent constructed according to the principles of the present invention that varies in geometry along its length.
FIG. 12 is a diagram illustrating another pattern for a stent constructed in accordance with the principles of the present invention.
FIG. 13 illustrates another pattern for a stent constructed in accordance with the principles of the present invention.
FIG. 14 is an enlarged view of a portion of a horizontal meander pattern constructed in accordance with the principles of the present invention.
FIG. 15 is a diagram in which one cell installed outside the bending portion is overlapped with the same cell inside the bending portion.
FIG. 16 shows compensation for shortening that occurs when the stent of the present invention is expanded.

Claims (41)

A stent for holding a blood vessel in an expanded state,
a. A first loop inclusion section that is arranged generally circumferentially and the inner loop occurs at a first amplitude;
b. A second loop inclusion section that is arranged substantially circumferentially, wherein a loop inside occurs at said first amplitude;
c. The inner loop is installed in a substantially circumferential space between the first and second loop inclusion sections, including sections that occur at a second amplitude higher than the first amplitude, and alternately A third loop inclusion section connecting the first and second loop inclusion sections;
d. The loops in the first, second and third loop inclusion sections are such that when the expanded stent is in a curved lumen, the cells outside the curved portion open in the length direction and in the circumferential direction. The cells inside the bends are narrowed and installed and adjusted to cooperate in such a way that the length is shortened and spreads in the circumferential direction e. The third loop inclusion interval becomes smaller when the width of the first and second loop inclusion intervals is expanded than when the width is compressed, and the width of the third loop inclusion interval becomes smaller than when the width is compressed. A stent that compensates for the shortening of the first and second loop inclusion sections when the stent is expanded to become larger when expanded. The outer cell of the curved part opens in the length direction, narrows in the circumferential direction, the inner cell of the curved part shortens in the length direction, and the outer cell becomes longer due to the compensation that occurs when it widens in the circumferential direction. The stent according to claim 1, wherein the density of the stent element region is more constant between the inside and outside of the curved portion than when the inside cell is merely shortened. The stent according to claim 2, wherein a drug is applied to the stent, and a more uniform amount of drug is applied to the inner wall of the lumen by the compensation. The outer cell of the curved part opens in the length direction, narrows in the circumferential direction, the inner cell of the curved part shortens in the length direction, and the outer cell becomes longer due to compensation that occurs when it widens in the circumferential direction. The stent according to claim 1, wherein the area of the cell of the stent is more constant between the inside and outside of the curved portion than when the inside cell is merely shortened. The stent according to claim 4, wherein a drug is applied to the stent, and a more uniform amount of drug is applied to the inner wall of the lumen by the compensation. A stent for expanding the blood vessels of the human body,
a. A plurality of first circumferential bands including a loop pattern of a first amplitude;
b. Including a loop pattern of a second amplitude higher than the first amplitude, alternating with the first circumferential band, and a plurality of second loops periodically connected to form a cell With a circumferential belt,
c. When the expanded stent is in a curved lumen, the outer loop of the band opens in the longitudinal direction and narrows in the circumferential direction, and the inner cell of the curved section extends in the length direction. Shortened and arranged and coordinated to work together to spread in the circumferential direction,
d. The second circumferential band is smaller when the width of the first circumferential band is expanded than when it is compressed, and when the second circumferential band is compressed A stent that compensates for shortening of the first circumferential band when the stent is expanded to become larger when expanded. The outer cell of the curved part opens in the length direction, narrows in the circumferential direction, the inner cell of the curved part shortens in the length direction, and the outer cell becomes longer due to compensation that occurs when it widens in the circumferential direction. The stent according to claim 6, wherein the density of the stent element region is more constant on the inside and outside of the curved portion than when the inside cell is merely shortened. The stent according to claim 7, wherein a drug is applied to the stent, and the compensation applies a more uniform amount of drug to the inner wall of the lumen. The outer cell of the curved part opens in the length direction, narrows in the circumferential direction, the inner cell of the curved part shortens in the length direction, and the outer cell becomes longer due to compensation that occurs when it widens in the circumferential direction. The stent according to claim 4, wherein the area of the cell of the stent is more constant on the inside and outside of the curved portion than when the inside cell is merely shortened. The stent according to claim 9, wherein a drug is applied to the stent, and the compensation applies a more uniform amount of drug to the inner wall of the lumen. A stent formed of a plurality of triangular cells for holding a blood vessel in an open state.
a. A first loop inclusion section arranged approximately circumferentially;
b. A second loop inclusion section joined to the first loop inclusion section at a first joining point;
c. A third loop inclusion section that is coupled to the first loop inclusion section at a second coupling point and is coupled to the second loop inclusion section at a third coupling point;
d. The loop in the cell is such that when the expanded stent is in a curved vessel, the cells outside the bend open in the length direction, narrow in the circumferential direction, and the cells outside the bend in the length direction. Shortened and arranged and coordinated to work together to spread in the circumferential direction,
e. The third loop inclusion section becomes smaller when the first and second loop inclusion sections are expanded than when compressed, and the width of the third loop inclusion section is expanded when compressed. A stent that compensates for the shortening of the first and second loop inclusion sections when the stent is expanded so that it becomes larger at a later time. The outer cell of the curved part opens in the length direction, narrows in the circumferential direction, the inner cell of the curved part shortens in the length direction, and the outer cell becomes longer due to the compensation that occurs when it widens in the circumferential direction. 12. The stent according to claim 11, wherein the density of the area of the stent element is more constant on the inside and outside of the bend than when the inner cell is merely shortened. The stent according to claim 12, wherein a drug is applied to the stent, and the compensation applies a more uniform amount of drug to the inner wall of the lumen. The outer cell of the curved part opens in the length direction, narrows in the circumferential direction, the inner cell of the curved part shortens in the length direction, and the outer cell becomes longer due to the compensation that occurs when it widens in the circumferential direction. 12. The stent according to claim 11, wherein the area of the cell of the stent is more constant between the inside and outside of the curved portion than when the inside cell is merely shortened. 15. The stent of claim 14, wherein a drug is applied to the stent, and the compensation applies a more uniform amount of drug to the inner wall of the lumen. A stent for expanding the blood vessels of the human body,
a. A plurality of first meander patterns;
b. A plurality of second meander patterns that are intertwined with the first meander pattern to form triangular cells, the first meander pattern and the second meander pattern being expanded by the stent. When the stent is in a curved vessel, the cells outside the curved portion open in the length direction and narrow in the circumferential direction, the cells inside the curved portion shorten in the length direction, and the circumference Arranged and coordinated to work together to spread in the direction,
c. The second meander pattern is smaller when the width of the first meander pattern is expanded than when it is compressed, and the width of the second meander pattern is expanded when it is compressed. A stent that compensates for shortening of the first meander pattern when the stent is expanded to be larger. The outer cell of the curved part opens in the length direction, narrows in the circumferential direction, the inner cell of the curved part shortens in the length direction, and the outer cell becomes longer due to the compensation that occurs when it widens in the circumferential direction. 17. The stent according to claim 16, wherein the density of the stent element region is more constant on the inner side and the outer side of the curved portion than when the inner cell is merely shortened. 18. The stent of claim 17, wherein a drug is applied to the stent, and the compensation applies a more uniform amount of drug to the inner wall of the lumen. The outer cell of the curved part opens in the length direction, narrows in the circumferential direction, the inner cell of the curved part shortens in the length direction, and the outer cell becomes longer due to compensation that occurs when it widens in the circumferential direction. The stent according to claim 16, wherein the area of the cell of the stent is more constant between the inside and outside of the curved portion than when the inside cell is merely shortened. 20. The stent of claim 19, wherein a drug is applied to the stent, and the compensation applies a more uniform amount of drug to the inner wall of the lumen. A stent for holding the lumen open,
a. A plurality of even and odd vertical meander patterns and the odd number of vertical meander patterns are placed between every other even number of vertical meander patterns, and are out of phase with the even number of vertical meander patterns. ,
b. A plurality of even and odd horizontal meander patterns, wherein the odd horizontal meander patterns are installed between every other even number of horizontal meander patterns;
c. The vertical meander pattern is intertwined with the horizontal meander pattern to form a plurality of triangular cells;
d. The horizontal meander pattern and the vertical meander pattern are arranged such that, after the stent is expanded, when the stent is installed in a curved lumen, the cells outside the curved portion open in the length direction, and the circumferential direction. The cells inside the curved portion are arranged and adjusted so as to cooperate in a shortened and longitudinal direction,
e. The horizontal meander pattern and the vertical meander pattern form a high and low amplitude loop section, and the high amplitude loop section is smaller when the width of the low amplitude loop section is expanded than when compressed, A stent that compensates for shortening of the low-amplitude loop section when the stent is expanded such that the width of the high-amplitude loop section becomes larger when expanded than when compressed. The outer cell of the curved part opens in the length direction, narrows in the circumferential direction, the inner cell of the curved part shortens in the length direction, and the outer cell becomes longer due to the compensation that occurs when it widens in the circumferential direction. 23. The stent according to claim 21, wherein the density of the stent element region is more constant on the inside and outside of the bend than if the inner cell is merely shortened. 23. The stent of claim 22, wherein a drug is applied to the stent, and the compensation applies a more uniform amount of drug to the inner wall of the lumen. The outer cell of the curved part opens in the length direction, narrows in the circumferential direction, the inner cell of the curved part shortens in the length direction, and the outer cell becomes longer due to the compensation that occurs when it widens in the circumferential direction. The stent according to claim 21, wherein the area of the cell of the stent is more constant on the inside and outside of the curved portion than when the inside cell is merely shortened. 25. The stent of claim 24, wherein a drug is applied to the stent, and the compensation applies a more uniform amount of drug to the inner wall of the lumen. An expandable stent comprising a plurality of enclosed flexible spaces,
Each of the plurality of enclosed flexible spaces is
a) a first component having a first end and a second end;
b) a second component having a first end and a second end;
c) a third component having a first end and a second end;
d) a fourth component having a first end and a second end; the first end of the first component in communication with the first end of the second component; The second end of the second component in communication with the second end of the third component and the third component of contact with the first end of the fourth component. The first termination;
e) the first component and the second component having a curved portion forming a first loop at its end;
f) the third and fourth components having a curved portion forming a second loop at their ends;
g) a fifth component having a first end and a second end;
h) a sixth component having a first end and a second end;
i) a seventh component having a first end and a second end;
j) an eighth component having a first end and a second end;
k) a ninth component having a first end and a second end;
l) a tenth component having a first end and a second end; the first end of the fifth component in communication with the second end of the first component; The second end of the fifth component in communication with the second end of the sixth component and the sixth component in communication with the first end of the seventh component. In communication with the first end of the seventh component and the second end of the seventh component in communication with the second end of the eighth component and the second end of the eighth component The first end of the eighth component, the second end of the ninth component in communication with the second end of the tenth component, and the fourth component The first end of the tenth component in communication with the second end of
m) the fifth component and the sixth component having a curved portion forming a third loop at the end;
n) the seventh component and the eighth component having a curved portion forming a fourth loop at the end;
o) the ninth component and the tenth component having curved portions forming a fifth loop at the ends, wherein the expanded stent is in a curved lumen, Regarding the cells outside the curved portion of the connection point of the fifth, fourth, and tenth components, the cells open as the cell length increases and are adjacent in each of the first to fifth loops The components approach each other, the cells narrow in the circumferential direction, compensate for the increase in length, and for the cells outside the bend at the point of contact of the first, fifth, fourth and tenth components, The cell closes as the cell length decreases, and in each of the first to fifth loops, adjacent components move away, the cell extends in the circumferential direction to compensate for the decrease in length,
The fifth to tenth components are smaller when the width of the first to fourth components is expanded than when compressed, and the width of the fifth to tenth components is compressed. A stent that compensates for shortening of the first through fourth components when the stent is expanded to be larger when expanded than when it is expanded. Due to the compensation that occurs outside the bend and inside the bend, the density of the elemental area of the stent between the inside and outside of the bend only increases the outer cell and shortens the inner cell. The stent according to claim 1, wherein the stent is more constant than the case where it is merely performed. 28. The stent according to claim 27, wherein a drug is applied to the stent, and the compensation applies a more uniform amount of drug to the inner wall of the lumen. Due to the compensation that occurs outside the curved portion and inside the curved portion, the inner area of the curved portion only increases the area of the stent and the inner cell only shortens the inner cell. 27. Stent according to claim 26, characterized in that it is more constant than the case. 30. The stent of claim 29, wherein a drug is applied to the stent and the compensation applies a more uniform amount of drug to the inner wall of the lumen. A stent having a plurality of cells,
A first loop, each of the square cells generally installed with its longitudinal direction reversed from the second loop, and a first pair of flexible compensation arrangements coupled to the legs of the first and second loops A plurality of square cell bands having portions; and
Each of the triangular cells generally includes a first loop inclusion section arranged in a circumferential direction, a second loop inclusion section connected to the first loop inclusion section, and the first loop inclusion section and the first loop inclusion section. A plurality of triangular cell bands with a third loop inclusion section connected to the second loop inclusion section;
The loops in both the square and triangular cells are such that when the expanded stent is in a curved vessel, the cells outside the bend open lengthwise, narrow in the circumferential direction, and the inside of the bend The cells are arranged and adjusted to work together to shorten in length and spread in the circumferential direction,
The third loop inclusion interval is smaller when the width of the first and second loop inclusion intervals is expanded than when compressed, and the width of the third loop inclusion interval is less than when compressed. A stent that compensates for shortening of the first and second loop inclusion sections when the stent is expanded to become larger when expanded. The stent having a plurality of cells according to claim 1, wherein each of the band of cells at the end of the stent is formed by a square cell. Each of the cells in the plurality of triangular cell bands is generally connected to a third loop arranged in the vertical direction opposite to the fourth loop, and a cell section including the third and fourth loops. A second pair of flexible components forming a cell, wherein the second cell band is incorporated into the first cell band, and the first loop and the second loop are formed on the stent. 32. The stent having a plurality of cells according to claim 31, wherein the stent is substantially aligned along a longitudinal axis, and the third loop and the fourth loop are in an offset relationship along the longitudinal axis. 32. The stent of claim 31, wherein the triangular cell band is incorporated into the square cell band to form a stent. Due to the compensation that occurs when the cells outside the curved portion open in the length direction and narrow in the circumferential direction, and the cells inside the curved portion shorten in length and widen in the circumferential direction, the curved portion 32. The stent according to claim 31, wherein the density of the stent element region is more constant between the inside and the outside than when only the outside cells are lengthened and the inside cells are only shortened. 36. The stent according to claim 35, wherein a drug is applied to the stent, and the compensation applies a more uniform amount of drug to the inner wall of the lumen. Due to the compensation that occurs when the cells outside the curved portion open in the length direction and narrow in the circumferential direction, and the cells inside the curved portion shorten in length and widen in the circumferential direction, the curved portion 32. The stent according to claim 31, wherein the area of the stent cell is more constant between the inside and the outside than when only the outside cell is lengthened and the inside cell is only shortened. 38. The stent according to claim 37, wherein a drug is applied to the stent, and the compensation applies a more uniform amount of drug to the inner wall of the lumen. 39. The stent of claim 38, wherein the more uniform amount of drug avoids the possibility of supplying a toxic amount to one portion and a less than effective amount to another portion. . 32. The stent according to claim 31, wherein the stent is a self-expanding stent. 32. The stent according to claim 31, wherein the stent is a balloon expandable stent.