A system is disclosed for removing gas bubbles from blood during circulatory assist procedures. Such bubbles are generated, along with particulate matter, in an extracorporeal circulatory bypass system by the pump, oxygenator and other components. Current filters are inefficient at removing small bubbles that can cause neurological defects and renal and other organ failures in the patient. An active filter apparatus and method is disclosed that forces the bubbles to the center of the system where they are removed from the blood before the blood exits the filter. The filter comprises an axially elongate cylindrical shell with a blood inlet, a blood outlet and a gas outlet. A motor driven impeller spins the blood within the shell and forces the gas toward the center by centripetal force, utilizing the buoyancy effects of the bubbles in blood, whereby the bubbles can be bled off at the center of the filter.