A circumferential ablation device assembly which is adapted to forming a circumferential conduction block in a pulmonary vein is described. The assembly includes a circumferential oblation clement which is adapted to ablate a circumferential region of tissue along a pulmonary vein wall which circumscribes the pulmonary vein lumen, thereby transecting the electrical conductivity of the pulmonary vein against conduction along its longitudinal axis and into the left atrium. The circumferential ablation element includes an expandable member with a working length that is adjustable from a radially collapsed position to a radially expanded position. An equatorial band circumscribes the outer surface of the working length and is adapted to ablate tissue adjacent thereto when actuated by an ablation actuator. A pattern of insulators may be included over an ablation element which otherwise spans the working length in order to form the equatorial band described.