Stent retriever having an expandable fragment guard

A stent retriever assembly having a proximal end and a distal end, and including a mesh tube having a distal and proximal end, and being connected to a first wire. Also, a blood-porous fragment guard is at the distal end of the mesh tube, the fragment guard including spokes joined at a central hub and extending radially and proximally from the central hub, and wherein a second wire is connected to the central hub so that when the second wire is pulled proximally relative to the first wire, the hub is pulled proximally, causing the spokes to spread out and causing the fragment guard to widen.

BACKGROUND

The medical arts have advanced rapidly in the area of stroke treatment. Until recently, only medicinal treatment could be offered. Then, stents capable of retrieving the clot material blocking a blood vessel in an ischemic stroke were developed. Now, if a patient is seen quickly after onset the clot material can be swiftly removed, thereby saving a great deal of brain function, that would otherwise be lost.

Still, many challenges remain, in the removal of a clot that blocks a cerebral artery. One of these challenges is the tendency of fragments of material to break off of the clot as it is being removed, flow in the direction of blood flow, and lodge anew in some narrow cerebral artery, causing a secondary stroke, which can be damaging.

SUMMARY

In a first separate aspect, the present invention may take the form of a stent retriever assembly having a proximal end and a distal end, and including a mesh tube having a distal and proximal end, and being connected to a first wire. Also, a blood-porous fragment guard is at the distal end of the mesh tube, the fragment guard including spokes joined at a central hub and extending radially and proximally from the central hub, and wherein a second wire is connected to the central hub so that when the second wire is pulled proximally relative to the first wire, the hub is pulled proximally, causing the spokes to spread out and causing the fragment guard to widen.

In a second separate aspect, the present invention may take the form of a method of removing a clot from an artery, utilizing a stent retriever assembly having a proximal end and a distal end. The stent retriever includes a mesh tube having a distal and proximal end, and being connected to a first wire. A blood-porous fragment guard at the distal end of the mesh tube, the fragment guard including spokes joined at a central hub and extending radially and proximally from the central hub, and wherein a second wire is connected to the central hub so that when the second wire is pulled proximally relative to the first wire, the hub is pulled proximally, causing the spokes to spread out and causing the fragment guard to widen. In the method, this stent retriever is deployed to a proximal side of the clot and pushed through the clot. Then the second wire is pulled, relative to the first wire, thereby widening the fragment guard, and the stent retriever is pulled proximally to pull material from the clot proximally.

In a third separate aspect, the present invention may take the form of a stent retriever catheter assembly having a proximal end and a distal end, and including a catheter, including a flexible tube sized to fit through the arterial system of a person, and to reach a blood clot in an artery. A first and a second wire extend through the tube, and a handle is connected to the first and second wires, permitting the first and second wires to be advanced and retracted with at least 1 cm of independence relative to each other. Also, a mesh tube having a distal and proximal end, is connected to the first wire and a blood-porous fragment guard is positioned at the distal end of the mesh tube. This fragment guard includes spokes joined at a central hub and extending radially and proximally from the central hub, and wherein the second wire is connected to the central hub so that when the second wire is pulled proximally relative to the first wire, the hub is pulled proximally, causing the spokes to spread out and causing the fragment guard to widen.

Exemplary embodiments are illustrated in referenced drawings. It is intended that the embodiments and figures disclosed herein are to be considered illustrative rather than restrictive.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring toFIGS. 1 and 2, In a preferred embodiment, a stent retriever10includes a wire mesh12and a woven fragment guard14. it is controlled by a pair of wires18A and18B, which must be separately advanceable for the stent retriever10to work correctly. The stent retriever10is positioned in an artery20, near a clot22by introduction of a catheter16. After a distal end of catheter16is positioned near clot22, the stent retriever10is deployed by pushing wires18A and18B forward. A system for permitting this action is shown and described in U.S. Pat. No. 8,876,863. After or during deployment the stent retriever10is pushed through clot22, so that at least the fragment guard14is pushed all the way through.

Referring also toFIG. 3, wire18B is advanced relative to wire18A. Fragment guard14is made of a set of spokes24that meet in an apex26, and are all covered by a fabric28. When wire18B is advanced, or wire18A is retracted, then spokes24are spread apart (much as the spokes of an umbrella). The stent retriever is now pulled proximally, bringing the clot22with it, and with fragment guard14protecting the artery20further on in the direction of blood flow, from fragments that could break off from clot22. Referring toFIG. 4, as the stent retriever10is pulled toward the incision where catheter16was introduced, artery20will typically widen. Wire18A may be pulled further back relative to wire18B, thereby widening out fragment guard14. Wires18B and18A each support a radiopaque marker40and42, respectively, to aid a surgeon in locating the stent retriever during a procedure. The two markers40and42are spaced apart and mutually distinguishable, to aid a surgeon in determining the orientation of stent retriever10. In an alternative preferred embodiment, marker42is closer to the distal tip of retriever10.

In one preferred embodiment, wire mesh12and spokes24are made of nitinol. In another preferred embodiment mesh12and spokes24are made of a titanium alloy. In one embodiment, fabric28is made of woven strands of expanded polytetrafluoroethylene (ePTFE). In one embodiment, the weave is loose, to permit blood to flow through the interstices of the threads. In still another embodiment, the fabric28is made of threads arranged in a circular manner about said spokes, to form a pattern similar to that of a spider web.

Referring toFIG. 5, catheter16is connected to a handle44, having separately positionable positioners46A and46B, for wires18A and18B. Handle44permits a user to separately move wire18A and18B, for deployment and control of the fragment guard14.