A method of treatment of a patient diagnosed with atrial arrhythmia by forming a circumferential conduction block in a region of tissue at a location where a pulmonary vein extends from an atrium. The method includes either forming one such circumferential conduction block around one of the pulmonary vein ostia, forming multiple such circumferential conduction blocks around each one of the pulmonary vein ostia or in subset combinations thereof. The circumferential conduction block may also surround a pulmonary vein in order to bridge the adjacent ends of two linear lesions also extending along the left posterior atrial wall and between the pulmonary vein and another adjacent pulmonary vein in a less-invasive "maze"-type procedure. The circumferential conduction block may also be formed to intersect with another similar circumferential conduction block around an adjacent pulmonary vein ostium in a modified and improved version of the "maze"-type procedure. A circumferential ablation device is provided which is adapted for forming the circumferential conduction block and includes a pear-shaped expendable member with a circumferential ablation element located along a contoured, tapered surface of the pear shape such that the circumferential ablation element is adapted to engage the circumferential path of tissue along the atrial wall when at least a portion of the expendable member is engaged within the pulmonary vein ostium. Another device is also provided for use according to the inventive method and includes a "loop"-shaped ablation member which is adapted to form the circumferential lesion by advancing the looped ablation member against the tissue to be ablated.