Stent with variable stiffness
AssigneeSciMed Life Systems, Inc.
InventorPatrick Rivelli, Jr.
Life of this patent
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Abstract
A graftless prosthetic stent for treatment of vascular lesions such as aneurysms and arterio-venous fistulas, especially in neurovascular vessels, comprises a continuous helical ribbon formed of a shape-retaining metal having a transition temperature at which the stent expands from its contracted condition to a radially expanded condition, the stent remaining substantially cylindrical in its contracted and expanded conditions. The helical windings have variable width, thickness, number or size of openings, or combinations of these features, which affect the stiffness, rate of expansion at the transition temperature, and the area of vessel wall covered by the stent. A catheter device which includes the stent, and a method of treatment using the stent are also provided.
Claims27
A stent adapted for advancement through a catheter in an upstream to downstream direction to a target vessel site in a contracted stent condition, and with expulsion from the catheter, downstream end first, and radial expansion at the target site, for engaging the walls of the vessel, said stent comprising
- a continuous helical ribbon of a constant pitch formed of a shape-memory alloy;
- said stent having a downstream end and an upstream end and being substantially cylindrical, wherein the entirety of the stent forms a single conduit, the stent having a bending-stiffness gradient along its length due to one or more of the following:
- (i) a gradient of ribbon width, greater ribbon width at the upstream end of the stent, and lesser ribbon width at the downstream end of the stent, wherein the ribbon width progressively decreases from the upstream end in a downstream direction along the entire length of the stent, such that the width of the continuous helical ribbon at any point is greater or equal to the width of the continuous helical ribbon at any other point which is downstream;
- and
- (ii) a gradient of size or number of openings per unit length formed in the continuous helical ribbon, wherein the size or number of openings per unit length progressively increases from the upstream end in a downstream direction along the entire length of the continuous helical ribbon.
A stent having an upstream end and a downstream end adapted for advancement through a catheter in an upstream to downstream direction to a target vessel site in a contracted stent condition, and with expulsion from the catheter, downstream end first, and radial expansion at the target site, to engage the walls of the vessel, said stent comprising
- a continuous helical ribbon of a constant pitch formed of a shape-memory alloy having a ribbon thickness of 0.5 and 2 mils, and being effective to cover between 50% and 80% of the surface area of the vessel region containing the stent
- said stent having a bending-stiffness gradient along its length due to one or more of the following:
- (i) a gradient of ribbon width, greater ribbon width at the upstream end of the stent, and lesser ribbon width at the downstream end of the stent, wherein the ribbon width progressively decreases from the upstream end in a downstream direction along the entire length of the stent, such that the width of the continuous helical ribbon at any point is greater or equal to the width of the continuous helical ribbon at any other point which is downstream;
- and
- (ii) a gradient of size or number of openings per unit length formed in the continuous helical ribbon, wherein the size or number of openings per unit length progressively increases from the upstream end in a downstream direction along the entire length of the continuous helical ribbon, and
- being characterized by a contracted-condition diameter of between about 10 and 30 mils, and a diameter in a filly expanded condition of between 40 and 125 mils, said stent being substantially cylindrical in its contracted and expanded condition.
Dependencies are inferred from the claim text.