Expansible shearing catheters for thrombus removal

A thrombectomy catheter comprising:

• a flexible tubular body having a proximal end and a distal end;
• a flexible drive shaft rotatably disposed within the tubular body;
• an outer shearing member attached near the distal end of the tubular body, the outer member having a circumferential series of independent outer struts, the outer struts having inner surfaces;
• and
• an inner shearing member rotationally driven by the drive shaft within the outer member, the inner member having a proximal portion, a distal portion, and a circumferential series of independent inner struts, the inner struts having outer surfaces which slide across the inner surfaces of the outer struts so as to shear clot material when the inner shearing member rotates, at least one member of the group comprising the inner struts and the outer struts being helically oriented and having a local pitch that increases toward the proximal and distal portions sufficiently to inhibit excessive separation between adjacent struts when the outer shearing member flexes axially,
• wherein at least one member of the group comprising the inner struts and the outer struts have protrusions which inhibit sliding of clot material axially between cooperating edges of the inner and outer shearing members.