Heartburn is a symptom that rarely has anything to do with your heart. It occurs when you feel a burning sensation in your chest that is often accompanied by a bitter taste in your throat or mouth. Symptoms of heartburn may get worse after you eat a large meal or when you are lying down. In general, the symptoms of heartburn can be treated successfully at home. However, if frequent heartburn makes it difficult to eat or swallow, your symptoms may be a sign of a more serious medical condition.