As a clot retrieval device, a dual-layer expandable aspiration catheter having a catheter with a distal slit and a flexible sheath surrounding the slit. The dual-layer expandable aspiration catheter maintains column strength (along the axis of the catheter) while the distal slit provide radial flexibility only to circumferential direction. This structure prevents the distal expandable segment from crumpling, thereby the stent retriever can be pulled into the expandable catheter smoothly.
