EKG Challenge No. 12: Once Upon a Time in Triage

You are working as the "triage physician" in a busy city emergency department when a 34 yo female presents with chest pain.   The pain is retrosternal and burning in nature and has been persistent for 3 hrs.  It is associated with some nausea, but no shortness of breath or diaphoresis.  You order a GI cocktail and get an EKG:

 What is your differential diagnosis?  What would you do next?
 Read the case conclusion here