Abstract: A device for internal circumferential ablation of a tubular vascular structure includes an expandable structure having a central opening extending therethrough to allow a relatively unobstructed flow of body fluid through the tubular vascular structure. The expandable structure is expandable from a collapsed configuration to an expanded configuration, with the expandable structure being configured to be secured in a desired location on the tubular vascular structure. The expandable structure further is configured to emit or absorb energy to ablate tissue. A method of circumferential ablation of a terminal segment of a coronary sinus or other vascular structure using a catheter system in order to treat heart rhythm disorders and performing ablation without significant obstruction of blood flow is further disclosed.