How do you know if you are having a heart attack?

Sometimes U don't: Heart attacks can cause no symptoms or atypical symptoms but the classic symptoms are: substernal discomfort, can become painful, described as a weight or vise-like tightening, with sweating, nausea, sometimes with breathlessness, sometimes radiating to the left arm or jaw. They are exceptionally rare in premenopausal women unless diabetic or on cocaine.