A medical apparatus, including a probe having a distal endconfigured for insertion into a body cavity and containing alumen that opens through the distal end, and an inflatableballoon deployable through the lumen into the body cavity suchthat when the balloon is deployed through the lumen andinflated, a distal pole on a distal side of the balloon islocated opposite the lumen.In embodiments of the presentinvention, the medical apparatus also includes an electrodeattached to the distal side of the inflatable balloon andextending over at least 50% of an area of the distal side of theballoon that is within 30° of arc from the distal pole.
