An interventional catheter assembly comprises a catheter for insertion and guidance to a target site in a body and a rotational operating head (150) mounted in proximity to a distal end of the catheter, the operating head comprising a plurality of external cutter elements (152) for breaking down obstructive material into particles at the target site. The assembly also includes at least one aspiration port (156) which is located proximal to the external cutter elements (152) and extends over at least 20% of the circumference of the catheter and which is in communication with a first sealed lumen of the catheter for withdrawing fluids and obstructive material from the target site. The assembly also includes a plurality of infusion ports (154) located proximal to the at least one aspiration port and communicating with an infusion lumen in the catheter so as to supply fluid to a location in proximity to the target site.
