An interventional catheter assembly comprises an operating head for removing obstructive material from a target site in a body lumen or cavity and at least one aspiration port located proximal to the operating head and penetrating the catheter assembly, the aspiration port being in communication with a sealed lumen that communicates with a vacuum system for withdrawing aspirate fluid and obstructive material from the target site. The interventional catheter incorporates an elongated guidewire lumen bushing extending proximally from a distal region of the operating head to reduce the clearance between the guidewire and the internal surface of the guidewire lumen during operation of the interventional catheter. This feature restricts entry of fluid and debris into the guidewire lumen and promotes maintenance of consistent and high aspiration pressure and volume during operation of the aspiration system and interventional catheter assembly.
