A method of forming a lesion at a predetermined heart location is provided. An
energy-delivering electrode is positioned proximal to the predetermined heart location;
a return electrode is positioned in contact with cardiac tissue. An electrosurgical
current, capable of delivering energy through the energy-delivering electrode to
the predetermined heart location at a magnitude and for a duration effective to
form a lesion is established. A system for treating atrial fibrillation by forming
transmural lesions and a heart-positioning device including a return electrode
are also provided. In one embodiment, one of the electrodes includes at least a
portion that is selectively movable between a first, retracted position in which
the electrode is adapted to be deployed through tissue, and a second, expanded
position in which the electrode is adapted to be placed within a chamber of a heart.
