A catheter includes a shaft having a proximal end, a distal end, and a central lumen extending continuously from the proximal end to the distal end. A hypotube forms a proximal region of the shaft, and a polymer tube forms a distal region of the shaft. A periphery of the hypotube is cut in a pattern which provides a decreasing stiffness in a proximal-to-distal direction, and in some embodiments the polymer tube is reinforced by a wire embedded over at least a portion of the polymer tube's length. A guidewire lumen is disposed at or near the distal end of the catheter and extends for a portion of the catheter's length. The catheter may be used for aspiration, device delivery, or other purposes in a patient's vasculature.