The Maze procedure is a surgical treatment for atrial fibrillation, which can often be done using minimally invasive techniques. To perform the surgery, the surgeons use radiofrequency energy, or freezing, to create an intricate "maze" pattern of scar on the upper chamber of the heart muscle. Because scars do not carry electrical signals, they interrupt the conduction of abnormal impulses and allow the heart to return to a regular, coordinated beat. At the same time, a natural outpouching of an upper chamber of the heart, called the atrial appendage, is closed. This procedure has an overall success rate of approximately 90 percent, and post-procedure freedom from stroke has been estimated at 99 percent. It may also allow the patient to avoid taking blood thinners, which most patients with cardiac arrhythmias are required to take.