A catheter with ablation and potential sensing capabilities is adapted for outer circumferential contact with an opening of a tubular region and inner circumferential contact within the tubular region. The catheter has a proximal electrode assembly and a distal electrode assembly for ablation of an ostium and potential sensing inside the pulmonary vein so that it is possible to obtain ECG signals inside a pulmonary vein when ablating around the ostium. The distal electrode assembly has an elongated member defining a longitudinal axis and a plurality of spines surrounding the member and converging at their proximal and distal ends, where each spine has at least one electrode and a curvature so that the spine bows radially outwardly from the member. The proximal electrode assembly has a proximal electrode assembly has an elongated member configured with a generally radial portion and a generally circular portion generally transverse to the catheter axis, where the generally circular portion comprising a plurality of electrodes. The control handle advantageously allows a user to manipulate a tensile member for changing the curvature of the spine.