A catheter with ablation and potential sensing capabilities is adapted foroutercircumferential contact with an opening of a tubular region and innercircumferential contact withinthe tubular region. The catheter has a proximal electrode assembly and adistal electrode assemblyfor ablation of an ostium and potential sensing inside the pulmonary vein sothat it is possible toobtain ECG signals inside a pulmonary vein when ablating around the ostium.The distal electrodeassembly has an elongated member defining a longitudinal axis and a pluralityof spinessurrounding the member and converging at their proximal and distal ends, whereeach spine has atleast one electrode and a curvature so that the spine bows radially outwardlyfrom the member.The proximal electrode assembly has a proximal electrode assembly has anelongated memberconfigured with a generally radial portion and a generally circular portiongenerally transverse tothe catheter axis, where the generally circular portion comprising a pluralityof electrodes. Thecontrol handle advantageously allows a user to manipulate a tensile member forchanging thecurvature of the spine.
