A medical treatment system, including a catheter body defining a fluid flow path therethrough an expandable element disposed on the catheter body, the expandable element defining a cooling chamber therein in fluid communication with the fluid flow path a plurality of electrodes disposed on the expandable element a cryogenic fluid source in fluid communication with the fluid flow path and a radiofrequency energy source in electrical communication with the plurality of electrodes. A method of treating a cardiac tissue site proximate an orifice, including substantially occluding the orifice with an expandable element powering a plurality of electrodes coupled to the expandable element to reach a predetermined target temperature circulating a coolant through the expandable element to freeze portions of the cardiac tissue site located between the plurality of electrodes and ablating the non-frozen portions of the tissue site with the plurality of electrodes.
