Heart attacks occur when a coronary artery is blocked, almost always from cholesterol build-up and a superimposed blood clot. About two-thirds of people have warning symptoms before their heart attack. These are often chest pains, shortness of breath, decreased exercise tolerance, or fatigue. These prodromal symptoms may be classic (central or left chest pressure, constriction, burning with exertion) or they can be atypical. Women may be more likely than men to have atypical warning signs.
If you are having symptoms that may be a warning of coronary artery disease, see your doctor right away. There are many non-invasive tests that can be done to define whether your symptoms are likely from coronary artery disease and whether you are at risk for a heart attack. There is much we can do to prevent complications of coronary artery disease, and there is much we can do to reverse the process.
If you are having continuous symptoms for more that 15 minutes, call 911 and have them take you right to the Emergency Department. It could be a heart attack, and minutes count to prevent permanent heart damage. Better to be seen for a "false alarm" than to have a heart attack be completed at home.
Some people can have a heart attack be the first manifestation of coronary artery disease. Most people having a heart attack do not die immediately, but some do. This is usually from a too-fast heart rhythm (ventricular tachycardia or fibrillation), but can also be from a heart attack-induced very slow heart rhythm, or from the heart just not being able to pump because too much of it is being damaged.
Dying immediately with the onset of symptoms (called Sudden Cardiac Death) in people over 35 is most often from coronary artery disease and heart attack. In people younger that 35, it is usually from a primary heart rhythm problem caused by cardiomyopathies. These are abnormalities of the heart muscle such as hypertrophic cardiomyopathy (too thick heart muscle), right ventricular cardiomyopathy (parts of the right ventricle are replaced with fibro-fatty tissue), or a primary heart rhythm disturbance which is an abnormality of the heart's electrical system. These causes in the young generally have a genetic component.
There is, of course, overlap, with some young people having heart attacks (I have cared for several men in their 20's with heart attacks) and some middle-aged and older adults having the genetic predisposition to sudden cardiac death. Sudden cardiac death from the causes that are not coronary artery disease is often preceded by fainting. Sudden cardiac death can often be aborted by getting immediate CPR and reversing the abnormal rhythm with a shock.