A 33-year-old man presents with constant, dull retrosternal pain for 6 hours, which radiates to the left shoulder, is worsened by exertion, and is associated with dyspnea. He has had watery diarrhea since today. The week before, he returned from a family holiday in Brazil. His father developed diarrhea 5 days ago, and is being treated for typhoid infection. A chest x-ray is found to be normal, but serial ECGs show upwardly convex ST elevations in the leads V1-V6, I and aVL.