Methods and apparatus for flow restoration
Methods for restoring blood flow in occluded blood vessels using an apparatus having a self-expandable distal segment that is pre-formed to assume a superimposed structure in an unconstrained condition but can be made to take on a volume-reduced form making it possible to introduce it with a microcatheter and a push wire arranged at the proximal end, with the distal segment in its superimposed structure assuming the form of a longitudinally open tube and having a mesh structure of interconnected strings or filaments or struts. In a preferred embodiment, the distal segment has a tapering structure at its proximal end where the strings or filaments or struts converge at a connection point.
1. A method for mobilizing a thrombus in a cerebral blood vessel, comprising:
(a) delivering a thrombus-removal apparatus through a microcatheter to the cerebral blood vessel, the apparatus comprising a self-expandable tubular structure having a proximal end, a distal end, and a plurality of cells, the structure being configured to assume an expanded configuration at a site of the thrombus, and to be in a compressed configuration for delivery through the microcatheter, the compressed configuration having a smaller maximum cross-sectional dimension than the expanded configuration, the structure being configured to expand into the thrombus when transitioning from the compressed configuration to the expanded configuration;
(b) positioning the structure in the cerebral blood vessel such that the distal end is downstream of the thrombus, and the proximal end is upstream of the thrombus; and
(c) with the structure positioned as in (b), proximally withdrawing the microcatheter from over the structure such that the structure transitions to the expanded configuration and at least an outer portion of the structure engages and applies an outward radial force on the thrombus, whereby the structure interlocks with at least a portion of the thrombus, the portion of the thrombus extending both inside of the structure and outside of the structure; and
(d) retracting the apparatus, with the portion of the thrombus, toward a catheter while the portion of the thrombus extends both inside of the structure and outside of the structure.
2. The method of claim 1 , wherein the apparatus and the microcatheter are delivered with the catheter.
3. The method of claim 1 , further comprising positioning the apparatus and at least a portion of the thrombus in the catheter.
4. The method of claim 3 , further comprising removing the catheter.
5. The method of claim 1 , further comprising applying aspiration through at least one of the microcatheter and the catheter.
6. The method of claim 1 , wherein a distal end of the structure has a greater diameter than a proximal end of the structure.
7. The method of claim 1 , wherein expanding the apparatus improves the effectivity of natural lysing of the thrombus.
8. The method of claim 1 , further comprising retracting the apparatus and at least a portion of the thrombus into the microcatheter.
9. The method of claim 1 , wherein a distal end of the tubular structure is open in the expanded configuration.
10. The method of claim 1 , wherein the tubular structure is permanently attached to a distal end of an elongate member by a plurality of struts.
11. The method of claim 1 , wherein the structure penetrates the thrombus.
12. The method of claim 11 , wherein the structure integrates with the thrombus.
13. The method of claim 1 , wherein the structure is configured for attachment of the thrombus to the structure.
14. The method of claim 1 , wherein the plurality of cells is configured for attachment of the thrombus to the structure.
15. The method of claim 1 , wherein the cerebral blood vessel is in a patient, the method further comprising removing the portion of the thrombus and the apparatus from the patient.
16. A method for mobilizing a thrombus in a cerebral artery, comprising:
(a) delivering an apparatus with a microcatheter to the cerebral artery, the apparatus comprising a self-expandable distal segment and a proximal elongate member, the distal segment comprising a tubular structure, the proximal elongate member attached to the distal segment by a plurality of struts such that the proximal elongate member extends generally parallel to, and is offset from, a central longitudinal axis of the tubular structure, the structure having a proximal end and a distal end, the structure being configured to assume an expanded configuration at a site of the thrombus, and to be in a compressed configuration for delivery through the microcatheter, the compressed configuration having a smaller maximum cross-sectional dimension than the expanded configuration, the structure being configured to expand into the thrombus when transitioning from the compressed configuration to the expanded configuration; and
(b) positioning the structure in the cerebral blood vessel such that the distal end is distal to the thrombus, and the proximal end is proximal to the thrombus; and
(c) with the structure positioned as in (b), proximally withdrawing the microcatheter from over the structure such that the structure transitions to the expanded configuration and at least an outer portion of the structure engages and applies an outward radial force on the thrombus, whereby the structure interlocks with at least a portion of the thrombus, the portion of the thrombus extending both inside of the structure and outside of the structure; and
(d) retracting the apparatus, with the portion of the thrombus, toward a catheter while the portion of the thrombus extends both inside of the structure and outside of the structure.
17. The method of claim 1 , wherein the apparatus and the microcatheter are delivered with the catheter.
18. The method of claim 16 , further comprising positioning the apparatus and at least a portion of the thrombus in the catheter.
19. The method of claim 18 , further comprising removing the catheter.
20. The method of claim 16 , further comprising applying aspiration through at least one of the microcatheter and the catheter.
21. The method of claim 16 , wherein the structure penetrates the thrombus.
22. The method of claim 21 , wherein the structure integrates with the thrombus.
23. The method of claim 16 , further comprising retracting the apparatus and at least a portion of the thrombus into the microcatheter.
24. The method of claim 16 , wherein the self-expandable distal segment comprises cells of a first size at a first portion and cells of a second size at a second portion, the second size differing from the first size.
25. The method of claim 24 , wherein the second size is larger than the first size and the cells of the second size are proximal of the cells of the first size.
26. The method of claim 16 , wherein a distal end of the tubular structure is open in the expanded configuration.
27. The method of claim 16 , wherein the tubular structure is permanently attached to a distal end of the proximal elongate member by the plurality of struts.
28. The method of claim 16 , wherein the structure is configured for attachment of the thrombus to the structure.
29. The method of claim 16 , wherein the self-expandable distal segment comprises a plurality of cells configured for attachment of the thrombus to the structure.
30. The method of claim 16 , wherein the cerebral artery is in a patient, the method further comprising removing the portion of the thrombus and the apparatus from the patient.