A deflectable tip cardiac electrophysiology/ablation lumen catheter includes first and second passages, one of which communicates with an inflatable member or balloon. The second passage terminates in an opening or port downstream of the inflatable member. The second passage is adapted to introduce a liquid during an electrophysiology study while the inflatable member prevents backflow of an injected liquid or dye and blood, or is adapted to alternatively receive a guide wire therethrough.