The present invention relates to an interventional catheter assembly comprising an operating head mounted at a distal end of the catheter assembly and comprising a system for removing obstructive material from a target site in a body lumen or a cavity, at least one aspiration port provided in proximity to the operating head and in communication with a sealed lumen for withdrawing aspirate fluids and obstructive material from the target site, at least one infusion port for supplying infusate fluid to a location in proximity to the target site, an aspiration system for applying vacuum to the aspiration port, and an infusion system for providing infusate fluid to the infusion port, wherein the infusion and aspiration systems are controlled during operation of the interventional catheter assembly to provide volume ratios of infusate to aspirate of greater than about 1:1 and less than about 2.5:1.
