Embodiments of a guide and flexible sleeve for use with catheters for ablation or other medical procedures are disclosed. An exemplary catheter comprises a guide element having a proximal end and a distal end, the distal end configurable in a desired shape. A flexible sleeve is conformable to the guide element so that the flexible sleeve slides over the guide element, the flexible sleeve has a proximal end and a distal end. A controller couples to the flexible sleeve. The controller operates to move the flexible sleeve at least part way between the distal end of the guide element and the proximal end of the guide element. At least one ablation element disposed at the distal end of the flexible sleeve operates to form a substantially continuous ablative lesion when the flexible sleeve is in contact with a contiguous volume of target tissue.
