Is it heartburn or heart attack?

Heartburn is an uncomfortable but common feeling of burning or warmth in the chest. Although the pain of heartburn is felt in the chest, heartburn has nothing to do with your heart. Instead, heartburn is caused by regurgitated stomach acid A heart attack occurs when the blood supply to part of the heart muscle itself - the myocardium - is severely reduced or stopped. The reduction or stoppage happens when one or more of the coronary arteries supplying blood to the heart muscle is blocked by atherosclerosis.

Note: It is not necessarily atherosclerosis. AMI can be caused by an embolism or a host of other things.