A medical device system comprising: a structure (218; 308; 313) comprising a plurality of elongate members, each of the elongate members comprising a proximal end, a distal end, and an intermediate portion between the proximal and distal ends (307, 305); and a plurality of electrodes (315; 415) positionable in a bodily cavity and supported by the structure (218; 308; 313), wherein a group of electrodes (336a, 336a-b, 338a-d) of the plurality of electrodes (315; 415) is located on each of a set of one or more elongate members (304a, 304b) of the plurality of elongate members; wherein the structure (218; 308; 313) is selectively moveable between: a delivery configuration in which the structure (218; 308; 313) is sized to be percutaneously deliverable to the bodily cavity, and a deployed configuration in which the structure (218; 308; 313) is sized too large to be percutaneously deliverable to the bodily cavity, wherein at least some of the plurality of electrodes (315; 415) are arranged in a plurality of concentric ringed arrangements about an axis of the structure (218; 308; 313) when the structure (218; 308; 313) is in the deployed configuration, a first concentric ringed arrangement of the plurality of concentric ringed arrangements having a fewer number of electrodes than a second concentric ringed arrangement of the plurality of concentric ringed arrangements, wherein the intermediate portions of the elongate members are angularly arranged with respect to one another about the axis when the structure (218; 308; 313) is in the deployed configuration, wherein, in accordance with their proximity to the axis of the structure (218; 308; 313), at least one of a shape, dimension and size of surfaces of various electrodes varies, and wherein a distribution of the plurality of electrodes (315; 415) on the structure (218; 308; 313) has an increased spatial density in regions proximate the axis of the structure (218; 308; 313). a structure (218; 308; 313) comprising a plurality of elongate members, each of the elongate members comprising a proximal end, a distal end, and an intermediate portion between the proximal and distal ends (307, 305); and a plurality of electrodes (315; 415) positionable in a bodily cavity and supported by the structure (218; 308; 313), wherein a group of electrodes (336a, 336a-b, 338a-d) of the plurality of electrodes (315; 415) is located on each of a set of one or more elongate members (304a, 304b) of the plurality of elongate members; wherein the structure (218; 308; 313) is selectively moveable between: a delivery configuration in which the structure (218; 308; 313) is sized to be percutaneously deliverable to the bodily cavity, and a deployed configuration in which the structure (218; 308; 313) is sized too large to be percutaneously deliverable to the bodily cavity, a delivery configuration in which the structure (218; 308; 313) is sized to be percutaneously deliverable to the bodily cavity, and a deployed configuration in which the structure (218; 308; 313) is sized too large to be percutaneously deliverable to the bodily cavity, wherein at least some of the plurality of electrodes (315; 415) are arranged in a plurality of concentric ringed arrangements about an axis of the structure (218; 308; 313) when the structure (218; 308; 313) is in the deployed configuration, a first concentric ringed arrangement of the plurality of concentric ringed arrangements having a fewer number of electrodes than a second concentric ringed arrangement of the plurality of concentric ringed arrangements, wherein the intermediate portions of the elongate members are angularly arranged with respect to one another about the axis when the structure (218; 308; 313) is in the deployed configuration, wherein, in accordance with their proximity to the axis of the structure (218; 308; 313), at least one of a shape, dimension and size of surfaces of various electrodes varies, and wherein a distribution of the plurality of electrodes (315; 415) on the structure (218; 308; 313) has an increased spatial density in regions proximate the axis of the structure (218; 308; 313).