MXPA99011173A - Controlled detachment stents - Google Patents

Abstract

A stent is provided with specific"designated detachment"points or zones, such that after the stent is deployed, the stress applied on the stent will cause the stent to detach at these designated detachment points or zones. When the detachment occurs completely around the circumference of the stent, the stent separates into stent segments, each able to move with the vessel independently of the other stent segments. The components at the designated detachment zones may have a cross-sectional area sufficiently low so that the components will detach under the stress placed on the stent after implantation. Alternatively or additionally, the components at the designated detachment zones may be made of a material that is sufficiently weaker so that the components will detach under the stress placed on the stent after implantation. The stent may have a lower number of components at the designated detachment zones than in the stent segments.

Description

STENTS DEPRESS DIMI ENTO CONTROLLED The invention relates generally to stents, which are endoprostheses implanted in vessels within the body such as blood vessels, to support and maintain vessels open, or to secure and support other vessels endoprostheses.

BACKGROUND OF THE INVENTION Several stents are known in the art. Typically the stents are generally tubular in shape, and are expandable from a relatively small unexpanded diameter to a larger expanded diameter. For implantation, the stent is typically mounted at the end of a catheter, with the stent being held in the catheter at its relatively small unexpanded diameter. Through the catheter, the unexpanded stent is directed through the lumen to the intended implantation site. Once the stent is at the intended site of implantation, it expands, typically either by an internal force, for example inflating a balloon inside the stent, or allowing the stent to self-expand, allowing the stent to be stented. expand out. In any case, the expanded stent resists the tendency of the vessel to narrow, so that the opening of the vessel is maintained. Some examples of patents related to stents include the Patent of E. U. , No. 4,733,665 of Palmaz; U.S. Patent No. 4,800,882 and 5,282,824 to Gianturco; U. Patent Nos. 4,856,516 and 5,136,365 Hillstead; Patents of E. U., Nos. 4,886,062 and 4,969,458 to Wiktor; U.S. Patent No. 5,019,090 to Pinchuck; The Patent of E. U. , No. 5, 102,417 of Palmaz and Schatz; U.S. Patent No. 5,104,404 to Wolff; the Patent of E. U. , No. 5, 161, 547 of Tower; the Patent of E. U. , No. 5,383,892 of Cardón et al; U. U. Patent No. 5,449,373 to Pinchasik et al. and U. U. Patent No. 5,733,303 to Israel et al. An objective of the above stent designs has been to ensure that the stent has sufficient radial strength when it is expanded so that it can sufficiently support the lumen. Stents with high radial strength, however, also tend to have a greater longitudinal rigidity than the vessel in which they are implanted. When the stent has a longitudinal rigidity greater than the vessel in which it is implanted, increased trauma to the vessel at the ends of the stent may occur, due to stress concentrations due to the unevenness in resistance between the stented sections and without stent. glass.

BRIEF DESCRIPTION OF THE INVENTION An object of the invention is to provide a stent that more closely matches the strength of the vessel in which it is implanted, with relatively little or no sacrifice in radial resistance, even when the stent is made too long. In accordance with one embodiment of the invention, a stent with specific "detachment points" is provided, such that after the stent is deployed, and during vessel movement, the effort applied to the stent will cause the stent to be segmented into these designated detachment points. When the designated detachment points are arranged around the entire circumference of the stent, creating a circumferential "designated detachment" area, detachment at designated detachment points separates the stent into two or more separate stent segments, each capable of move with the vessel independently of the other stent segments. Because each stent segment can be moved with the vessel independently of the other stent segments, the series of stent segments attains great strength between the stented and stent-free sections of the vessel than the unitary stent, which is longer and that the stress on the vessel wall is reduced. The stent is preferably designed such that after detachment, the ends of the stent segments created by the detachment are relatively smooth, so they do not damage the wall of the glass. Also, the stent is preferably configured such that the individual stent segments have sufficient radial strength after detachment, such that detachment results in little or no significant reduction in compression stent resistance. The stent may be designed such that detachment occurs only after a period of time after implantation, such that the stent will already be buried under the neointima at the time of detachment. Thus, the stent segments that remain after detachment will be maintained in place by the neointima and will not move relative to the lumen, that is, they will not "telescope" one into another, and will not move away from each other, creating unsupported spaces. A variety of mechanisms can be used to perform the detachment. For example, the stent may be provided at certain points or zones along its length with components that have a sufficiently low cross-sectional area such that the stent segments will be detached preferably under the stress placed on the stent after implantation . Alternatively or additionally, the stent may be provided at certain points or zones along its length with components made of a material that is sufficiently weaker than another point on the stent such that the stent segments will be preferably peeled off under the stress placed on the stent after implantation. Alternatively or additionally, the stent may be designed such that it has a smaller number of components, or struts, in the designated areas of detachment, so that each such component bears more load than components elsewhere in the stent. These components are configured to separate under the increased loads they support when the stent is stressed repeatedly after implantation. The factors that contribute to the detachment can be applied individually or in combination. For example, the designated stripping struts may have sectional areas low transverse and may also be formed of weaker material, or the designated areas of detachment may have a reduced number of components, with or without the components having low cross-sectional areas and / or being formed of weaker material.

BRIEF DESCRIPTION OF THE DIAMETERS Figure 1 shows a schematic diagram of a stent, generally in the form of a cylinder, having designated areas of detachment between stent segments; Figure 2 shows a schematic diagram of the stent of Figure 1 after detachment, in which the stent has been separated into a series of shorter stent segments; Figure 3 shows a piano design of a stent pattern in which the components in the designated areas of detachment have a cross-sectional area that is sufficiently low such that the stent segments will come off under the tension placed on the stent after the implantation; Figure 4 shows a flat design of the stent pattern of Figure 3, after detachment has occurred in the designated areas of detachment; and Figure 5 shows a flat design of a stent pattern in which the stent has a smaller number of components in the designated areas of detachment, such that each such component bears an increased load and separates under such an increased load.

DETAILED DESCRIPTION OF THE DRAWINGS Figure 1 shows a schematic diagram of a stent 1, generally in the form of a cylinder. The stent 1 comprises a series of stent segments 2 separated by designated areas of detachment. The designated stripping zones 3 comprise one or more designated stripping components or struts (see Figures 3 to 5). The designated stripping zones 3 are designed such that the designated stripping components or struts are separated under repeated tension placed on the stent 1 after implantation. When all the struts designated to detach around the circumference of the stent in a designated area of separate detachment in particular, the stent separates itself into a series of independent stent segments 2, as shown in Figure 2. Designated release zones 3 may be designed such that detachment does not occur until some time after implantation, such that stent segments 2 will already be buried under the neointima at the time of detachment and therefore will not move in relation to the lumen. Persons of ordinary skill in the art will appreciate that the basic geometry of the stent segments 2 can take any suitable form, and that the stent segments 2 can be formed of any suitable material. Examples of suitable structures for stent segments 2 include those shown in U.S. Patent No. 5,733,303 to Israel et al. whose description is expressly incorporated herein by reference in this application. Figure 3 shows a flat design of a stent pattern comprising stent segments 2 separated by designated stripping zones 3. In the finished stent, each stent segment 2 in this embodiment has a configuration that generally corresponds to a stent configuration described in U.S. Patent No. 5,733,303. The stent segments 2 are joined to one another by the components or struts 4 designated for detachment in the designated areas of detachment. In this embodiment, each of the designated stripping brackets 4 has a reduced cross-sectional area that is sufficiently low to allow separation of the strut-designated struts 4 under tension placed on the stent after implantation. The amount of reduction of the cross section of the detachment struts 4 compared with, for example, the components labeled by the reference numeral 5 in the stent segments 2, can be, for example, of the order of tens of percent. For example, the release struts 4 may be 25% to 75% thinner or narrower than the components 5. These designated release struts 4 may additionally or alternatively be made of a weaker material, in order to ensure proper separation . The weaker material can be provided either in the supply material used to form the designated stripping struts 4, or by treating the struts 4. designated release (or designated release zones 3) after the stent has been produced, such that the treatment weakens the material of the so-called release struts 4. In addition to the reduction in cross section, the remaining geometry of the designated stripping struts can be selected to achieve the desired results. As shown in Figure 3, the width A of the row of struts 4 designated for shedding may be narrower than the width of a row of corresponding components in the stent segment 2, for example the width B of the row of components marked by the reference numeral 5. This reduced width in the designated areas of detachment helps to ensure detachment in the designated areas 3 of detachment under repeated longitudinal bending. Also, the struts 4 of detachment designations can be made sufficiently short to reduce the length of the free ends after separation, so as not to leave long, hanging ends after detachment. For example, the length of the detached struts 4 is shorter than the length of the components 5. Figure 4 shows a flat design of the stent pattern of Figure 3 after detachment has occurred in the designated areas 3. of detachment. As shown in Figure 4, the stent after detachment comprises a series of separate and independent stent segments 2. As it is also seen in the Figure 4, because the struts 4 designated for detachment were short, the length of free ends 6 after separation is kept to a minimum. Figure 5 shows an alternative design in which, in the designated areas of detachment, the stent is provided with a smaller number of components 7 around the circumference of the stent. In the embodiment shown in Figure 5, each designated stripping zone 3 has five struts 7 designated for stripping around the circumference of the stent. By comparison, the stent has nine of the components marked as components 5 in a band of such components within the stent segments 2. Of course, different numbers of designated stripping struts and stent segment components can be used, without departing from the general concept of the invention. The so-called detachment struts 7 are configured such that they detach under the loads they bear on account of the attention placed on the stent after implantation. As shown in Figure 5, the designated stripping struts 7 may also have a reduced cross-sectional area. Also, as with the designated strut struts in other embodiments, the stripped struts 7 may be additionally formed from weaker material, or the struts 7 or designated stripping zones 3 may be treated to make the material weaker after stripping. stent production.

The embodiments described herein are examples only, since other variations are within the scope of the invention as defined by the appended claims.

Claims (10)

1. REVIVAL DICATIONS 1. A stent for implantation in a vessel, wherein the stent comprises: (a) a plurality of stent segment; and (b) means for removably connecting stent segments adjacent said plurality of stent segments, to said detachable connector means adapted to allow said adjacent stent segments to separate from each other in response to physiological stress placed on said means. detachable connectors, wherein said separation occurs after a period of time after the implantation of the stent into the vessel, the period of time sufficient to allow the formation of neointima around the stent in an amount sufficient to ensure said plurality of segments of the stent. stent with respect to the vessel. A stent as claimed in claim 1, wherein said detachable connecting means comprises at least one designated stripping strut, wherein the cross-sectional area of the stripping designated strut is sufficiently low such that the stripping designated strut it will preferably be separated under tension placed on the stent after implantation. 3. A stent as claimed in claim 1, wherein said removable connecting means comprises at least one designated strut of detachment, wherein the stripping designated strut is made of a material that is sufficiently larger. Weaker than elsewhere in the stent such that the designated strut of detachment will preferably be separated under tension placed in the stent after implantation. A stent as claimed in claim 1, wherein said detachable connecting means comprises at least one designated strut of detachment, wherein the stripping designated strut has a cross-sectional area that is smaller than the cross-sectional area of a component within one of said stent segments. A stent as claimed in claim 4, wherein the designated detachment strut is also made of a material that is weaker than the material of a component within one of said stent segments. 6. A stent as claimed in claim 1, wherein said removable connecting means comprises at least one designated stripping strut, wherein the stripping designated strut is made of a material that is weaker than the one-component material. within one of said stent segments. A stent as claimed in claim 1, wherein said removable connecting means comprises at least one designated stripping strut, in a designated area of stent detachment, wherein the number of designated stripping strips in said designated area of detachment is less than the number of struts that traverse a plane that crosses one of said stent segments perpendicular to an axis of the stent segment. 8. A stent as claimed in claim 7, wherein at least one designated strut of detachment has a cross-sectional area that is smaller than the cross-sectional area of a component within one of said stent segments. 9. A stent as claimed in claim 8, wherein the designated detachment strut is also made of a material that is weaker than the material of a component within one of said stent segments. 10. A stent as claimed in claim 7, wherein at least one designated stripping strut is made of a material that is weaker than the material of a component within one of said stent segments. eleven . A stent comprising at least two stent segments and at least one designated strut of detachment; and wherein the designated strut of detachment has a cross-sectional area that is smaller than the cross-sectional area of a component within one of said stent segments. 12. A stent as claimed in claim 1, wherein the designated strut of detachment is also made of a material that is weaker than the material of a component within one of said stent segments. 13. A stent as claimed in claim 1, wherein the designated stripping strut is in a designated area of stent detachment, and wherein the number of designated strut stems in the designated stripping area is less than the number of struts traversing a plane crossing one of said stent segments perpendicular to an axis of the stent segment. 14. A stent as claimed in claim 13, wherein the designated detachment strut is also made of a material that is weaker than the material of a component within one of said stent segments. 15. A stent comprising at least two stent segments and at least one designated strut of shedding; and wherein the designated strut of detachment is made of a material that is weaker than the material of a component within one of said stent segments. A stent as claimed in claim 15, wherein the designated stripping strut is in a designated area of stent detachment, and wherein the number of stripping designated strips in the designated stripping area is less than the number of struts passing through a plane crossing one of said stent segments perpendicular to an axis of the stent segment.