A basket style electrical mapping catheter includes an elongated body with a proximal end and a distal end, where the proximal end has a user interface for controlling a basket-shaped electrode assembly that extends from the distal end of the elongated body. The basket-shaped electrode assembly includes a plurality of flexible splines supporting measurement electrodes configured to contact an electrically active substrate, and an expander spline disposed along a central axis of the basket-shaped catheter assembly supported a reference electrode. The orientation of the measurement electrodes relative to the reference electrode allows for electrical mapping to be conducted with greater sensitivity and specificity in order to more accurately detected diseased or damaged substrate.
