How do you know if you are having a heart attack or it's "angina" ?

EKG, Cardiac Markers: There is no foolproof way to tell the difference without er/hospital studies - generally if one has a history of angina and it isn't resolving with rest or nitrates or has a different character (more intense or with accomp. Pain elsewhere or nausea/sweating) -- it may be a heart attack and he/she should get to the er right away. New chest pain should always be eval'd right away. Time is tissue!