Embodiments of the invention provide apparatus and methods for the detection and treatment of atrial fibrillation (AF). An embodiment of an apparatus for the detection and treatment of AF comprises an electrical lead having proximal and distal portions. The distal portion is positionable in an atrial chamber with a proximal portion end coupled to a pacemaker. The lead includes a plurality of conductive wires clad with an insulative coating and has sufficient flexibility to be positioned in the atria from a percutaneous or other introductory site. The conductive wires are coupled to a plurality of pairs of bipolar electrodes positioned on a membrane attachable to the heart wall. The electrode pairs are distributed in a pattern defining an area for detecting the location of a foci of aberrant electrical activity and sending a pacing signal to that location to prevent or stop an AF occurrence caused by the foci.
