The ECG shown here is from a 65 year old woman who came to the Emergency Department because of chest pain and shortness of breath of rather sudden onset. 24 hours earlier she had returned to the United States by plane following a holiday in Europe. Her physical examination was unremarkable except for tachypnea and hypotension (95/62). Which diagnosis would you favor: 1) an acute inferior wall myocardial infarction? 2) a pulmonary embolus? 3) a panic attack with hyperventilation?