An electrode support structure comprises a guide body having at its distal end a flexible spline leg. The spline leg is flexed to define an arcuate shape to facilitate intimate contact against tissue. An electrode element is carried by the spline leg for movement along its axis. The structure includes a control element coupled to the electrode element. The control element remotely imparts force to move the electrode element along the axis of the spline leg. Therefore, in use, the physician can cause the electrode element to travel along a path that the spline leg defines, without otherwise changing the location of the guide body.