There is no definitive way to differentiate between cardiac and non-cardiac chest pain without further evaluation. Severe chest pain should always be taken seriously and evaluated in an emergency department. Cardiac chest pain is caused by reduced blood flow and oxygen to the heart, which can lead to a heart attack without treatment. Non-cardiac chest pain can be due to structures in the chest like the esophagus or lungs. A medical history and physical exam can provide clues but further testing is often needed to determine the underlying cause of chest pain.