The apparatus includes a catheter having a combined infusion/aspiration lumen, a three lumen proximal portion and a two lumen distal portion. An infusion/aspiration valve located at the distal end of the catheter facilitates performing infusion and aspiration through the same lumen, which in turn reduces the number of lumens, and enables the combined infusion/aspiration lumen to be made larger without the need to increase the diameter of the catheter. Differing material properties in the proximal and distal portions of the catheter enable the proximal portion to be made stiffer for pushability, while the distal portion is more flexible to navigate tortuous vasculature and enable a greater amplitude agitator to be received within the catheter.