A device for occlusion of a body lumen including an implantable occlusion apparatus (3) operably attached to an elongated catheter member (4) configured for transluminal delivery and deployment of the occlusion apparatus in the body lumen. The occlusion apparatus includes a radially expansible element (5) detachably attached to the elongated catheter member, and adjustable between a contracted orientation for transluminal delivery and a deployed orientation configured to occlude the body lumen, an energy delivery element (6, 14, 21) configured to deliver energy to surrounding tissue to heat the tissue, and a sensor (7) configured to detect a parameter of the wall of the body lumen. The energy delivery element (6, 14, 21) and sensor (7) are axially movable independently of the radially expansible element whereby, in use, the energy delivery element and sensor can be transluminally retracted leaving the radially expansible element in-situ occluding the body lumen.