There are two kinds of heart pain. The first, angina, is a pain in the chest due to a temporary shortage of oxygen being carried in the blood to the heart muscle. Angina should be suspected if the chest pain is brought on by exercise and relieved by rest. The second is the more severe and prolonged pain of a heart attack. Potentially dangerous confusion can arise when someone neglects their heart pain believing it to be heartburn.
Acid is present in the stomach to digest food.
This is called reflux. The gullet, unlike the stomach, does not have a protective lining. So when it is exposed to the acid, it can become inflamed and painful. At the bottom of the gullet there is a muscle which, by its contraction, acts as a barrier to keep the acid in the stomach. If this doesn't work properly, reflux occurs.