Apparatus and method for occluding a vessel

An ablation system (10) includes an electrical ablation element (12) of elongate form with an electrically conductive element including a resistive part (22). A control unit (40) includes a processing unit (42), a power unit (44) and, optionally, a temperature sensor (46). The control unit (40) in one embodiment carries out ablation in at least two phases, the first phase at a higher energy level and a second phase, after at least partial retraction of the resistive part (22), at a second lower phase in order to close any remaining lumen within a blood flow obstruction formed within the vessel (18) during the first phase. Other embodiments provide for sensing retraction of the resistive part (22) and effecting ablation during and/or after the retraction process in order to create a more effective occlusion barrier.