The right atrial appendage is a small conical muscular pouch that is attached to the right atrium of the heart. Its margins have a dentated edge. The right atrial appendage projects from the upper and front part of the sinus forward and toward the left side, overlapping the root of the aorta. The right atrium, along with the right atrial body, is lined with pectinate muscles that form a network of hills and furrows that give it a trabeculated surface. It is believed that tachycardia to emerge from the right atrial appendage.