In an electrode assembly for a catheter system, a plurality of struts each extend from a proximal end to a distal end of the electrode assembly. Each strut spirals about the longitudinal axis of the electrode assembly and has a corresponding electrode disposed thereon. The electrode assembly is configurable between a collapsed configuration and an expanded configuration, with the electrodes being transversely spaced from the longitudinal axis of the electrode assembly a greater distance in the expanded configuration than in the collapsed configuration. In the expanded configuration the electrodes are transversely equally spaced from the longitudinal axis of the electrode assembly. In other aspects, at least one asymmetric element is provided on the electrode assembly to facilitate symmetric expansion about the longitudinal axis of the assembly. In another aspect, the electrode assembly is a single coil that winds about the longitudinal axis of the assembly.
