The last classical symptom of the acid flux is the heartburn. It is also known as a pyrosis among the health care professionals. It can be described as the burning feeling in the chest in the upper abdomen. Most often, this sign is associated with the acid flux. Most of the people suffer from this feeling at least once in their lives. When it happens, laying down becomes horrible procedure. Also, the heartburn can be supported by the acidic gurgling sensation in the throat.