A mapping catheter adapted for use in a heart chamber, has a distal mapping assembly with a spiral ribbon that is radially expandable and contractable by means of an expander so that electrodes on the ribbon can contact heart wall at a plurality of locations simultaneously. The expander extends the length of the catheter between a control handle and a distal end of the spiral ribbon. The expander can be controlled directly at its proximal end by a user or the expander can be responsive to a puller wire controlled by a user interface on the control handle.