a 54-year-old man presents with chest pain. he has a past medical history of hypertension and diabetes mellitus. the pain is located in the middle of his chest and radiates to his jaw. the pain began about 20 minutes ago, and he rates the pain as a 10 on a 0-10 point scale, with 10 being the worst pain he has ever felt. he has had 3 similar episodes, but they have always resolved after 5 minutes or so of rest. he has smoked 1 pack of cigarettes a day for the past 36 years. he drinks 2 or 3 beers on friday nights. review of systems (ros) is positive for diaphoresis, acute dyspnea, and impending doom. ros is negative for fever, chills, and malaise. physical exam shows an obese, middle-aged man in moderate distress. bp is 148/80; pulse is 100; and respirations are 26. heart and lung exams are normal, except for tachycardia and tachypnea. he has no pedal edema. electrocardiogram (ecg) shows st elevation in leads ii, iii, and avf; this is a new finding when compared to ecg from 3 months ago. question: what is the diagnosis?