Precordial ST depression. What is the diagnosis?

A middle aged male with no h/o CAD presented with one week of crescendo exertional angina, and had chest pain at the time of the first ECG:Here is the patient's previous ECG:NormalHere is the patient's presenting ED ECG:What do you think?There is isolated ST depression in precordial leads, deeper in V2 - V4 than in V5 or V6.  There is no ST elevation.  Precordial ST depression may be subendocardial ischemia or posterior STEMI.  How can we tell the difference?  See the list below.If you thought it might be a posterior STEMI, then you might have ordered a posterior ECG [change leads V4-V6 around to the back (V7-V9)].  This was indeed done: Notice the limb leads have been reversed (axes of every lead are inverted!).  But we are now concerned with the precordial leads.  V7-V9 (labelled V4-V6) have no ST elevation.  Notice there is tachycardia.  I have warned in the past that one must think of other etiologies of ischemia when there is tachycardia.  In this case, the patient had failed to take his atenolol in the AM and was having reflex tachycardia in addition to ACS.  BP was 160/100.  He was given metoprolol IV which succuessfully brought his heart rate and BP down.  His chest pain resolved completely, but his ECG continued to show profound ST depression.  We performed a bedside echo and found a posterior wall motion abnormality.The cath lab was activated and the pat...
Source: Dr. Smith's ECG Blog - Category: Cardiology Authors: Source Type: blogs