Heartburn, also known as pyrosis, cardialgia, or acid indigestion is a burning sensation in the chest, just behind the breastbone or in the epigastrium, the upper central abdomen. The pain often rises in the chest and may radiate to the neck, throat, or angle of the jaw. Heartburn is usually associated with regurgitation of gastric acid (gastric reflux) which is the major symptom of gastroesophageal reflux disease (GERD). It may also be a symptom of ischemic heart disease, though this is true for only 0.6% of those experiencing heartburn.