The invention relates to methods and devices for treating and/or preventing atrial fibrillation. In an embodiment, the invention includes a method of treating and/or preventing atrial fibrillation including applying an oscillating electrical stimulus to a tissue of a patient, the oscillating electrical stimulus sufficient to block transmission of electrical signals through the tissue. In an embodiment, the invention includes an implantable medical device including a stimulator configured to generate an oscillating electrical stimulus at a frequency and amplitude sufficient to block transmission of electrical signals through a tissue, a stimulation electrode in communication with the stimulator, the stimulation electrode configured to deliver the oscillating electrical stimulus to the tissue, and control circuitry in communication with the stimulator, the control circuitry configured to selectively deliver the oscillating electrical stimulus to treat and/or prevent atrial fibrillation. Other embodiments are also described herein.