What are the signs of an impending heart attack?

Classically: Angina pectoris =substernal pressure, pain with radiation to the neck or left or right arm and shoulder. Some will have abdominal pain-and be confused with gallbladder or stomach symptoms. Ladies seem to have less classic// or tolerate pain better than men. Relief with Nitroglycerin is very suggestive. A feeling of impending doom, pallor, sweating suggest a bad day!