Heartburn or pyrosis is a painful and burning sensation in the esophagus, just behind the breastbone (Sternum) usually associated with regurgitation of gastric acid (gastric reflux). The pain often rises in the chest and may radiate to the neck, throat, or angle of the jaw. Heartburn is a major symptom of gastroesophageal reflux disease; acid reflux is also identified as one of the causes of chronic cough, and may even mimic asthma. Despite its name, heartburn actually has nothing to do with the heart; it is so called because of a burning sensation near to where the heart is located - although some heart problems may give rise to a similar burning sensation. Compounding the confusion is the fact that hydrochloric acid from the stomach comes back up the esophagus because of a problem with the cardiac sphincter, a valve which misleadingly contains the word "cardiac," referring to the cardia as part of the stomach and not, as might be thought, to the heart.