Abstract: Cardiac sensing and/or stimulation devices and methods that adapt to implant location and positioning, and may employ automated vector selection from multiple electrodes. Devices include a housing having a first face opposing a second face, and an edge extending around the perimeter. A pulse generator and controller are coupled to three or more electrodes. Electrode arrangement facilitates selection of the particular electrodes that sense cardiac activity irrespective of one or more of positioning of the device, rotation of the housing, and which of the first and second faces of the housing is orientated toward the patient's skin. A first vector may be selected that provides for sensing cardiac activity, and a second vector may sense skeletal muscle activity. The vectors may be selected based on amplitude or signal-to-noise ratio exceeding a predetermined threshold. Methods may involve delivering defibrillation or cardioversion energy and/or determining cardiac rhythm states using selected vectors.