2) A 67-year-old woman presented with an episode of chest pain. There were no obvious ischemic changes in her ECG. Five hours later, she experienced more pain; this time the pain was accompanied with ST elevation in leads II, III, and aVF, and was diagnosed to be acute inferior wall myocardial infarction. Six days after admission, she developed hypotension with increased pressure in the jugular vein. Reinfarction was suspected. Which test is most useful in diagnosing recurrent MI developing within a week?