What are the sure symptoms of heart attack? how long does it last for??????

Heart attack: Typically some form of chest discomfort often accompanied by breathlessness,sweat,nausea,palpitations,a sense of impending doom ,anxiety,with radiation of discomfort to various areas in the SVC distribution;BUT some or all of these may or may not be present in the majority of presentations. A large minority up to 20=40% present with very atypical symptoms inc. painless