An irrigated balloon catheter, includes a balloon carrying contact electrodes, wherein a user can vary the balloon's configuration by manipulating an elongated expander that extends along the catheter and through the balloon's interior, with its distal end coupled to a distal end of the balloon. The expander may pass through an irrigation lumen to save on space within the catheter, and the expander itself may be hollow in providing a lumen for cables or lead wires. The expander may include flexure slits for increased flexibility. The distal end of the balloon includes a housing for components, e.g., a position sensor. The distal end of the balloon and the manner by which the balloon membrane is attached to the housing present a generally flat atraumatic surface suitable for direct head-on contact with tissue. Longitudinal spines extend along the outer surface of the balloon to provide support.
