A medical device is disclosed for delivering energy to a body lumen. The device includes an elongate member including a proximal portion and a distal portion adapted for insertion into a body lumen； and an energy delivery device disposed adjacent the distal portion of the elongate member, the energy delivery device including at least one elongate electrode arm, wherein the elongate electrode arm is configured to transition between a first configuration and a second configuration different than the first configuration. The at least one elongate electrode arm includes an active region configured to contact and deliver energy to the body lumen. When the elongate electrode arm is in the first configuration, at least a portion of the active region of the elongate electrode arm extends radially inward toward a longitudinal axis of the energy delivery device.
