Heartburn is an uncomfortable feeling of burning and warmth behind the breastbone (sternum) but sometimes rising as high as the neck. It usually occurs after meals, when lying down, or at night while sleeping. Heartburn usually is due to gastroesophageal reflux disease (GERD), the rise of stomach acid back up into the esophagus. Heartburn has nothing whatsoever to do with the heart though the discomfort of heartburn may be confused with heart pain and vice versa. Heartburn is a popular nonmedical term that often is referred to medically as pyrosis. Heartburn is a common cause of burning sensation in the chest and chest pain. Heartburn can be associated with sour taste in the mouth, dry cough, hoarseness, sore throat, and difficulty swallowing.