a 56-year-old man has been brought to the emergency department by emergency medical services (ems) and has been diagnosed with a myocardial infarction (mi) based on his presentation and electrocardiogram (ecg). the patient has been identified as a candidate for percutaneous transluminal coronary angioplasty (ptca). the nurse who is providing care for this patient should recognize that the extent of cardiac damage will primarily depend on: