Intraluminal device with improved flexibility and durability
In accordance with the present invention, there is provided a stent for insertion into a vessel of a patient. The stent is a tubular member having front and back open ends and a longitudinal axis extending there between. The tubular member has a first smaller diameter for insertion into a patient and navigation through the vessels, and a second larger diameter for deployment into the target area of a vessel. The tubular member is made from a plurality of adjacent hoops extending between the front and back ends. The hoops include a plurality of longitudinal struts and a plurality of loops connecting adjacent struts. The stent further includes a plurality of bridges having loop to bridge connections which connect adjacent hoops to one another. The bridge to loop connection points are separated angularly with respect to the longitudinal axis. The bridges have one end attached to a loop, another end attached to a loop on an adjacent hoop. The connection point between the bridge and the hoops will have a repeating pattern over a plurality of strut apices such that the benefits of a decreased number of bridges is realized while simultaneously avoiding the creation of overly unconstrained hoops. It is preferred that the ratio of total number of circumferentially aligned loops to the number of loops spanned by a particular bridge be a whole number.
1. A stent for insertion into a vessel of a patient, said stent comprising:
a tubular member with front and back open ends and a longitudinal axis extending there between, said member having a first smaller diameter for insertion into said vessel, and a second larger diameter for deployment into said vessel, said tubular member comprising a plurality of at least three adjacent hoops each having proximal and distal open ends relative to the longitudinal axis, said adjacent hoops comprising a plurality of longitudinal struts and a plurality of loops connecting circumferentially adjacent struts so as to form a series of peaks and valleys in a substantially S or Z shaped pattern; and
a plurality of bridges connected between loops on said adjacent hoops in a repeating pattern, wherein each bridge comprises an elongated linear strut member having an arcuate first end and an arcuate second end with a no curve portion along a majority of bridge length between the first and second arcuate ends, the linear strut member extending perpendicularly to the longitudinal axis and directly connected to a first connection region on a first curved bridge loop member of a first hoop and to a second connection region on a radially offset second curved bridge loop member of an adjacent hoop, such that a first bridge of the plurality of bridges connects a first adjacent hoop to an adjacent second hoop and is parallel to a second bridge of the plurality of bridges that connects the adjacent second hoop to an adjacent third hoop so as to approximate the mechanical behavior of a helical spring coil, wherein the ratio of the circumference of the tubular member to the length of the elongated linear strut member is less than 5.
2. The stent according to claim 1 wherein the repeating pattern is a ratio of the total number of loops for a given end of one of the adjacent hoops to the number of connection regions for the same end of the same hoop, and wherein the ratio is a whole number.
3. The stent according to claim 2 wherein the ratio is 4:1.
4. The stent according to claim 2 wherein the ratio is 8:1.
5. The stent according to claim 2 wherein the ratio is 2:1.
6. The stent according to claim 1 wherein the loops on adjacent hoops are longitudinally aligned but oppositely oriented relative to the longitudinal axis.
7. The stent according to claim 1 wherein the immediately opposite loops on adjacent hoops are rotationally off-set relative to the longitudinal axis.
8. The stent according to claim 5 wherein the whole number is an even number.
9. The stent according to claim 1 wherein the bridges are evenly spaced along the circumference of the tubular member.
10. The stent according to claim 1 wherein the ratio of the circumference of the tube to the distance between the adjacent hoops is between 20:1 and 50:1.
11. The stent according to claim 1 wherein said stent is made from a superelastic alloy.
12. The stent according to claim 11 wherein said alloy comprises from about 50.5 percent to about 60 percent Nickel and the remainder comprising Titanium.
13. The stent according to claim 5 wherein said elongated linear strut member is tapered with the narrowest point at the center point along its length.