Implantable and lumen-supporting stents and related methods of manufacture and use

Abstract

An implantable stent includes multiple circumferential segments that surround a bore and are connected in series along a length to form a tubular wall. Multiple adjacent alternating opposite facing crowns arranged along each segment's circumference are bridged by struts. The struts include a series of staggered arcuate edges with limited flats to provide a limited region of maximum width between significantly extended reducing diameter tapers at either end where they transition into the crowns. Connections between adjacent segments are wider and stiffer than the struts and strut-crown transitions in the segments. The crowns include inner and outer radii with off-set centers along a common axis to provide medial crown peaks along the axis that are wider than the narrowed crown shoulders on either side of the axis and from which the tapered struts extend. Material strain and flexure along the stent during lateral bending is distributed mainly within the segments, e.g. along the struts or crowns, versus at the connections between segments. Material strain and deformation during radial expansion is principally concentrated at the crown shoulders and tapered transition region with the struts. Particular closed-open-closed arrangements along the stent length are disclosed, though with fewer stent connections in the relatively “closed” end-portions along the stent than are provided by other typically “open” cell stents in prior use. Enhanced combinations of performance characteristics are provided regarding visibility, trackability, expansion characteristics, fatigue failures, coating integrity, and local drug delivery from the stent.

1 . An implantable medical stent system, comprising:
 a radially expandable stent comprising a filamental structure in a pattern surrounding a bore to form a substantially tubular wall along a length relative to a longitudinal axis;   wherein the filamental structure comprises at least one arcuate crown with a crown peak having a radius of curvature located along a reference axis, and first and second arcuate crown shoulders on first and second sides, respectively, of the reference axis;   wherein the filamental structure also comprises at least one pair of adjacent first and second elongated struts extending from the first and second crown shoulders, respectively; and   wherein the arcuate crown peak comprises at least one of (a) a peak width that is greater than at least one of first and second shoulder widths along the first and second respective crown shoulders, (b) an outer radius of curvature about a first center that is offset from a second center of an inner radius of curvature, and (c) a radial expansion characteristic with a strain distribution that is substantially lower than along at least one of the first and second crown shoulders.   
     
     
         2 . An implantable medical stent system, comprising:
 a radially expandable stent comprising a plurality of adjacent circumferential segments that comprise patterned filamental structures that surround a bore and are arranged in series along a length relative to a longitudinal axis to thereby form a substantially tubular wall along the length;   wherein each pair of adjacent segments is connected by at least one of a plurality of connections between segments; and   wherein each connection comprises at least one of (a) a longitudinal bending stiffness that is greater than a longitudinal bending stiffness along either adjacent segment such that upon an applied force of deflection lateral to the longitudinal axis the stent exhibits more longitudinal flexure within the segments than at the connections, and (b) a minimum width that is greater than a minimum width along a patterned filamental structure comprised by at least one of the adjacent segments.   
     
     
         3 . An implantable medical stent system, comprising:
 a radially expandable stent comprising a filamental structure in a pattern forming a substantially tubular wall surrounding a bore along a length relative to a longitudinal axis, and with a plurality of adjacent alternating opposite facing arcuate crowns bridged by a plurality of elongated struts;   wherein each crown comprises an arcuate crown peak with a radius of curvature located along a reference axis, and first and second arcuate crown shoulders on first and second opposite sides, respectively, of the reference axis;   wherein each elongated strut extends over a length with an intermediate portion located between first and second end portions along the strut length, and also with inner and outer opposite edges relative to the reference axis;   wherein the first and second end portions of each strut are coupled to the first and second crown shoulders, respectively, of first and second adjacent opposite facing crowns, respectively; and   wherein each strut comprises at least one of (a) a maximum width along the intermediate portion that is greater than a width along the first and second end portions and that extends over less than one-half of the strut length, (b) a maximum width along the intermediate portion that is substantially greater than a radial thickness thereof; (c) a maximum width that is substantially greater than a width of the respectively adjacent crowns at either a crown shoulder or a crown peak thereof; (d) inner and outer radii along the inner and outer edges of the first end portion and that are substantially similar to outer and inner radii along the outer and inner edges of the second end portion, and (e) inner and outer substantially straight regions along the respective inner and outer opposite edges that are substantially offset such that a majority of each straight region does not overlap with the other straight region along the strut length and is associated with an arcuate region along the opposite edge.   
     
     
         4 . An implantable medical stent system, comprising:
 a radially expandable stent comprising a filamental structure in a pattern surrounding a bore to form a substantially tubular wall along a length relative to a longitudinal axis;   wherein the filamental structure comprises at least one high strain region and at least one low strain region along the pattern;   wherein the filamental structure comprises a material strain distribution under deflection force of lateral bending or radial expansion relative to the longitudinal axis that is principally locally concentrated along the high strain region; and   wherein the low strain region comprises at least one of (a) a width in a circumferential plane around the longitudinal axis that is substantially greater than a width of the high strain region along the longitudinal axis, (b) a width that is substantially greater than a radial thickness at the respective low strain region, and (c) a substantially increased radiopacity versus the high strain region.   
     
     
         5 . A method of deflecting a stent for at least one of radial expansion and lateral bending of the stent, comprising:
 applying a deflection force onto the stent for at least one of radial expansion and lateral bending of the stent;   wherein in response to the deflection force the stent undergoes a material strain that is principally locally distributed along at least one of (a) a plurality of adjacent circumferential segments that surround a bore and are connected in series to form a substantially tubular wall along a longitudinal axis, and (b) a patterned filamental structure of the stent at a plurality of transition regions where a plurality of struts of the filamental structure extend between a plurality of crown shoulders of a plurality of opposite facing crowns of the filamental structure.   
     
     
         6 . The system of  claim 1 , wherein:
 the filamental structure pattern further comprises a plurality of adjacent circumferential segments surrounding the bore and that are provided in series along the length;   the filamental structure pattern of each segment comprises a plurality of said arcuate crowns in alternating opposite facing orientations along a circumference of the segment surrounding the bore, and a plurality of said pairs of struts, such that each pair of adjacent struts bridge the shoulders of one crown with a shoulder of each next adjacent opposite facing crown, respectively; and   each adjacent pair of segments is connected by at least one connection.   
     
     
         7 . The system of  claim 4 , wherein:
 the filamental structure pattern further comprises a plurality of adjacent circumferential segments surrounding the bore and that are provided in series along the length;   the filamental structure pattern of each segment comprises a plurality of arcuate crowns with each crown having an arcuate crown peak with a radius of curvature located along a reference axis and first and second arcuate crown shoulders on first and second opposite sides, respectively, of the reference axis, said crowns being in alternating opposite facing orientations along a circumference of the segment surrounding the bore, and comprising a plurality of pairs of adjacent struts bridging between opposite facing adjacent the crowns in the respective segment, such that each pair of adjacent struts bridge the shoulders of one crown with a shoulder of each next adjacent opposite facing crown, respectively; and   each adjacent pair of segments is connected by at least one connection.   
     
     
         8 . The system of  claim 6 , wherein each arcuate crown peak comprises a peak width, the first and second shoulders comprise first and second shoulder widths, and the peak width is greater than each of the first and second shoulder widths. 
     
     
         9 . The system of  claim 6 , wherein each arcuate crown peak comprises an outer radius of curvature about a first center located along the reference axis, and an inner radius of curvature about a second center that is offset from the first center along the reference axis. 
     
     
         10 . The system of  claim 9 , wherein the first center of the inner radius of curvature of the crown peak is offset away from the crown peak on the reference axis relative to the second center of the outer radii of curvature of the crown peak, such that the second center is closer to the crown peak than the first center. 
     
     
         11 . The system of  claim 6 , wherein the strain distribution relative to each crown during radial expansion of the stent comprises substantially higher strain along the first and second crown shoulders than along the crown peak. 
     
     
         12 . The system of  claim 6 , wherein each arcuate crown peak comprises a peak width that is greater than first and second shoulder widths along the first and second respective crown shoulders, an outer radius of curvature about a first center that is offset from a second center of an inner radius of curvature along the reference axis, and a radial expansion characteristic with a strain distribution that is substantially lower than along each of the first and second crown shoulders. 
     
     
         13 . The system of  claim 6 , wherein each connection comprises a lateral bending stiffness that is greater than a lateral bending stiffness along at least one respectively adjacent segment, such that upon an applied force of deflection lateral to the longitudinal axis the stent undergoes more flexure within the segments than at the connections. 
     
     
         14 . The system of  claim 2 , wherein each connection comprises a minimum width that is greater than a minimum width along each adjacent segment. 
     
     
         15 . The system of  claim 14 , wherein the minimum width of each connection is greater than a maximum width along each respectively adjacent segment. 
     
     
         16 . The system of  claim 3 , wherein each strut comprises a maximum width along an intermediate portion thereof that is greater than along first and second end portions thereof that couple to first and second opposite facing crowns, and which maximum length of the intermediate portion extends along less than about one-half of the length of the strut. 
     
     
         17 . The system of  claim 16 , wherein the maximum width of the intermediate portion is at a substantially discrete location along the strut and does not extend over a significant length of the strut. 
     
     
         18 . The system of  claim 2 , wherein each strut comprises a maximum width along an intermediate portion thereof that is substantially greater than a radial thickness thereof. 
     
     
         19 . The system of  claim 3 , wherein each strut comprises a maximum width that is substantially greater than a width of the respectively adjacent crowns at either a crown shoulder or a crown peak thereof. 
     
     
         20 . The system of  claim 3 , wherein each strut comprises a region of overlap between inner and outer opposite straight regions that is less than about one-half of the length of the strut. 
     
     
         21 . The system of  claim 3 , wherein each strut comprises each of:
 a maximum width along the intermediate portion that is greater than a width along the first and second end portions and that extends over less than one-half of the strut length, and that is also substantially greater than a radial thickness thereof the intermediate portion, and that is also greater than a width of the respectively adjacent crowns at the crown shoulders thereof;   inner and outer radii along the inner and outer edges of the first end portion and that are substantially similar to outer and inner radii along the outer and inner edges of the second end portion; and   inner and outer substantially straight regions along the respective inner and outer opposite edges that are substantially offset such that a majority of each straight region does not overlap with the other straight region along the strut length and is associated with an arcuate region along the opposite edge.   
     
     
         22 . The system of  claim 3 , wherein:
 first and second crowns of said adjacent opposite facing crowns are bridged by a strut;   the first and second crowns comprise respective arcuate peaks with respective radii of curvature centered along first and second reference axes, respectively, and with each respective arcuate crown also comprising first and second arcuate shoulders located on first and second opposite respective sides of the respective reference axis;   each elongated strut extends over a length between first and second end portions that are coupled to first and second respective shoulders of the first and second crowns, respectively;   each elongated strut comprises an inner edge and an outer edge along the length relative to the first reference axis;   the inner edge along the first end portion comprises a first arcuate region extending over a first length with a first radius of curvature away from the first reference axis and toward the second reference axis;   the inner edge along the second end portion comprises a second arcuate region extending over a second length with a second radius of curvature toward the first reference axis and away from the second reference axis;   the outer edge along the first end portion comprises a third arcuate region extending over a third length with a third radius of curvature away from the first reference axis and toward the second reference axis;   the outer edge along the second end portion comprises a fourth arcuate region extending over a fourth length with a fourth radius of curvature toward from the first reference axis and away from the second reference axis;   the first and third arcuate regions differ with respect to at least one of their respective radii of curvature and length;   the first and fourth arcuate regions are substantially similar with respect to at least one of their respective radii of curvature and length; and   the second and third arcuate regions are substantially similar with respect to at least one of their respective radii of curvature and length.   
     
     
         23 . The system of  claim 3 , wherein:
 each elongated strut extends over a length between first and second end portions that are coupled to and integral with first and second respective shoulders of first and second adjacent opposite facing crowns, respectively;   each elongated strut comprises an inner edge and an outer edge along the length relative to the reference axis of the first adjacent crown;   the inner edge along the first end portion comprises a first arcuate region with a first radius of curvature away from the reference axis and that extends from the first crown shoulder to a first location along the strut;   the outer edge along the first end portion comprises a second arcuate region with a second radius of curvature away from the reference axis and that extends from the first crown shoulder to a second location along the strut that is closer to the first crown shoulder than the first location; and   the outer edge further comprises a substantially straight edge region extending at least from the second location to the first location along the strut and that coincides at least in part with a portion of the first arcuate region along the inner edge.   
     
     
         24 . The system of  claim 1 , wherein:
 the stent comprises a substrate material with a surface;   a coating is located on the surface; and   the bioactive agent is stored by and elutes from the coating at the location.   
     
     
         25 . The system of  claim 1 , wherein:
 the stent comprises a plurality of discrete reservoirs within a metal scaffold filament; and   the bioactive agent is housed within and elutes from the reservoirs at the location.   
     
     
         26 . The system of  claim 2 , wherein a majority or all connections comprise each of characteristics (a)-(c) relative to the respectively adjacent segments.