Very. Ami is acute myocardial infarction is a result of coronary artery disease and by far the most common cause of death in this country. This is an emergency and must be treated in the hospital. If you have symptoms and diagnoses that put you at high risk for coronary artery disease, you must seek treatment immediately.
Heart attack. Heart is a pump. Poor blood flow and/or blockage of blood flow leads to poor oxygen flow to muscle downstream from the blockage, causes cell death (infarction), scarring of the area-muscle can't pump right if scarred, can cause electrical disturbances (some benign, some can be fatal), can lead to pump failure (congestive heart failure). Varies with size, location. A big deal. See your doc.