Advanced kink-resistant stent graft
Stent-grafts for treating thoracic aortic aneurysms and abdominal aortic aneurysms include graft portions having inflatable channels and graft extensions. The graft extensions include an undulating wire stent and porous, but substantially fluid impermeable, polytetrafluoroethylene (PTFE) graft materials.
1. An endovascular stent-graft comprising:
a graft; and
an undulating wire connected to the graft, the undulating wire helically wound in a longitudinal direction to form a plurality of undulating windings for a first portion, a second portion, and a third portion between the first and second portions in the longitudinal direction, each of the undulating windings having peaks and valleys,
wherein each of the undulating windings has a peak height defined as a longitudinal distance Y between a peak and an immediately adjacent valley of the undulating windings,
wherein each of the immediately adjacent undulating windings are separated from each other in the longitudinal direction by a valley-to-peak distance defined as a longitudinal distance X between a valley of one of the immediately adjacent undulating windings and a peak of the other immediately adjacent undulating windings,
wherein a ratio X/Y between the valley-to-peak distance X and the peak height Y of the undulating windings of the third portion is greater than the ratio X/Y of the undulating windings of each of the first and second portions, and
wherein the ratio X/Y of the undulating windings of the third portion is a positive value between 0.5 and 5, and the ratio X/Y of the undulating windings for at least one of the first or second portions is a negative value between −0.1 and −1 wherein when the undulating windings for at least one of first or the second portions comprise a first winding and a second winding, and a lowest valley of the first winding is lower than a highest peak of the second winding, the negative value results.
2. The endovascular stent-graft of claim 1 , wherein the ratio X/Y of the undulating windings of the first portion is greater than the ratio X/Y of the undulating windings of the second portion.
3. The endovascular stent-graft of claim 2 , wherein the ratio X/Y of the undulating windings of the first portion is from about −0.1 to about 0.3.
4. The endovascular stent-graft of claim 1 , wherein the graft comprises a crimped region between at least one adjacent pair of undulating windings.
5. The endovascular stent-graft of claim 4 , wherein the crimped region comprises a crimp that extends in a radial direction along a circumference of the graft.
6. The endovascular stent-graft of claim 5 , wherein the crimp extends entirely along the circumference of the graft.
7. The endovascular stent graft of claim 5 , wherein the crimp extends partially along the circumference of the graft.
8. The endovascular stent graft of claim 7 , wherein the crimp has a semi-circular shape.
9. The endovascular stent graft of claim 1 , wherein the graft comprises a plurality of layers, and the undulating wire is disposed between the layers of the graft.
10. The endovascular stent graft of claim 1 , wherein the second portion is configured to anchor the stent-graft in a main body graft, and the first portion is configured to anchor the stent-graft in an artery.
11. A method of making an endovascular stent-graft comprising:
providing a graft;
helically winding an undulating wire in a length direction to form a plurality of undulating windings for a first portion, a second portion, and a third portion between the first and second portions in the length direction, each of the undulating windings having peaks and valleys, wherein the forming of the undulating windings comprises:
disposing each of the undulating windings to have a peak height defined as a distance Y between a peak and an immediately adjacent valley of a corresponding undulating winding; and
separating each immediately adjacent undulating windings from each other by a valley-to-peak distance defined as a distance X between a valley of one of the immediately adjacent undulating windings and a peak of the other immediately adjacent undulating windings, wherein a ratio X/Y between the valley-to-peak distance X and the peak height Y of the undulating windings of the third portion is greater than the ratio X/Y of the undulating windings of each of the first and second portions, and wherein the ratio X/Y of the undulating windings of the third portion is a positive value between 0.5 and 5, and the ratio X/Y of the undulating windings for at least one of the first or second portions is a negative value between −0.1 and −1wherein when the undulating windings for at least one of first or the second portions comprise a first winding and a second winding, and a lowest valley of the first winding is lower than a highest peak of the second winding, the negative value results; and
connecting the undulating wire to the graft.
12. The method of claim 11 , wherein the ratio X/Y of the undulating windings of the first portion is greater than the ratio X/Y of the undulating windings of the second portion.
13. The method of claim 12 , wherein the ratio X/Y of the undulating windings of the first portion is from about −0.1 to about 0.3.
14. The method of claim 11 , further comprising forming a crimped region on the graft between at least one adjacent pair of undulating windings, wherein the crimped region comprises at least one crimp.
15. The method of claim 14 , wherein the forming of the crimped region comprises: stretching the undulating wire;
disposing one or more inner graft layers of the graft on an inner surface of the axially stretched undulating wire;
disposing one or more outer graft layers of the graft on an outer surface of the axially stretched undulating wire; and
relaxing the undulating wire to form the at least one crimp.
16. The method of claim 14 , wherein the forming of the crimped region comprises: arranging the graft and the helically wound undulating wire on a mandrel having at least one;
crimp shape on an outer surface of the mandrel; and
heating the graft and the helically wound undulating wire so that the at least one crimp is formed in the crimped region conforming to the at least one crimp shape of the mandrel.
17. The method of claim 14 , wherein the crimped region extends in a radial direction along a circumference of the graft.
18. The method of claim 11 , wherein the graft comprises a plurality of layers, and the undulating wire is disposed between the layers of the graft.