Systems and methods for catheter advancement

Abstract

A system can comprise a catheter and a device having an elongate member and an expandable member. The expandable member can be coupled to the elongate member. The elongate member can extend through the catheter. The expandable member can be positioned with a proximal member end proximal to a distal catheter end, a distal member end positioned distal to the distal catheter end, and at least a portion of the expandable member between the distal catheter end and the distal member end in an expanded state in which a maximum transverse dimension of the expandable member is larger than a maximum transverse dimension of the distal member end. The catheter can be advanced in a patient's body with the expandable structure, in the expanded state, at the distal end of the catheter.

What is claimed is: 
     
         1 . A system comprising:
 a catheter comprising a distal catheter end and having a catheter lumen;   a microcatheter comprising a distal microcatheter end and having a microcatheter lumen, the microcatheter being positioned at least partially within the catheter lumen with the distal microcatheter end positioned within the catheter lumen and proximal to the distal catheter end; and   a device comprising:
 an elongate member extending within the microcatheter lumen; and 
 an expandable member coupled to the elongate member and comprising a proximal member end and a distal member end, the proximal member end positioned proximal to the distal catheter end, the distal member end positioned distal to the distal catheter end, and at least a portion of the expandable member between the distal catheter end and the distal member end in an expanded state in which a maximum transverse dimension of the expandable member is larger than a maximum transverse dimension of the distal member end. 
   
     
     
         2 . The system of  claim 1 , wherein the portion of the expandable member is porous. 
     
     
         3 . The system of  claim 1 , wherein the portion of the expandable member comprises an outwardly concave section and an outwardly convex section, the outwardly convex section positioned between the outwardly concave section and the distal catheter end. 
     
     
         4 . The system of  claim 1 , wherein a longitudinal distance from the distal catheter end to the distal member end is greater than a maximum transverse dimension of the catheter lumen. 
     
     
         5 . The system of  claim 1 , wherein the maximum transverse dimension of the expandable member is approximately the same size as a characterizing transverse dimension of the catheter. 
     
     
         6 . The system of  claim 5 , wherein the maximum transverse dimension of the expandable member is at the location longitudinally aligned with the distal catheter. 
     
     
         7 . The system of  claim 5 , wherein the maximum transverse dimension of the expandable member is slightly smaller than a nominal inner diameter of the catheter to slightly larger than a nominal outer diameter of the catheter. 
     
     
         8 . The system of  claim 1 , wherein the expandable member comprises a braided plurality of strands. 
     
     
         9 . The system of  claim 1 , wherein a portion of the expandable member between the proximal member end and the distal catheter end is in an expanded state apposed to the inner catheter wall. 
     
     
         10 . The system of  claim 1 , wherein at least a portion of the expandable member is apposed against an inner wall of the microcatheter. 
     
     
         11 . The system of  claim 1 , wherein the expandable member is self-expanding. 
     
     
         12 . The system of  claim 1 , wherein the distal member end is slidably coupled to the elongate member. 
     
     
         13 . The system of  claim 1 , wherein the proximal member end is fixed to the elongate member. 
     
     
         14 . A method for advancing a catheter, the method comprising:
 (a) introducing a catheter into a vessel;   (b) positioning an expandable structure such that it extends distally from a distal end of the catheter;   (c) expanding at least a portion of the expandable structure distal to the distal end of the catheter to an expanded state;   (d), after (c), advancing the catheter while holding the expandable structure, in the expanded state, at the distal end of the catheter.   
     
     
         15 . The method of  claim 14 , wherein, in (b), a portion of the expandable structure is positioned within the catheter while the expandable structure extends distally from the distal end of the catheter. 
     
     
         16 . The method of  claim 14 , wherein the expandable member is configured for self-expansion, and (c) comprises allowing the portion of the expandable structure to expand. 
     
     
         17 . The method of  claim 14 , further comprising injecting a fluid through the expandable structure while holding the expandable structure, in the expanded state, at the distal end of the catheter. 
     
     
         18 . The method of  claim 17 , wherein the fluid is an intravascular contrast agent. 
     
     
         19 . The method of  claim 14 , wherein (d) comprises advancing the catheter from the vessel into a branch vessel while holding the expandable structure, in the expanded state, at the distal end of the catheter. 
     
     
         20 . The method of  claim 14 , wherein (d) comprises advancing the catheter from an aortic arch into a brachiocephalic branch while holding the expandable structure, in the expanded state, at the distal end of the catheter.