Dyspnea, Right Bundle Branch block, and ST elevation

An elderly male called 911 for acute onset of shortness of breath and vomiting.  EMS found him with a heart rate as high as 180 and hypoxic with O2 saturations in the 80's. A prehospital 12-lead was obtained:There is atrial fibrillation (irregularly irregular, no P-waves) with a rapid ventricular response.There is right bundle branch block (RBBB).There is ST elevation in V2-V5.Is this acute STEMI??On arrival in the ED, the patient had this ECG recorded:Atrial fibrillation with RVR.ST Elevation in V2-V5.Is this acute STEMI?Note the well-formed Q-waves in the leads with ST elevation!  This suggests old MI. Comment: Old MI with persistent ST elevation, otherwise known as "LV aneurysm" morphology, usually has QS-waves (deep S-wave without a subsequent R-wave).  But RBBB alters the sequence of ventricular activation such that the wave of depolarization ends by going to the right.  Thus, an R-wave which would otherwise be absent is present in right precordial leads.Normally, RBBB has rSR'.  But with old infarction, the initial r-wave is obliterated and one is left with a QR.  This can occur in acute STEMI with RBBB, but should raise the suspicion for LV aneurysm.Let's look at a second instructive case in which the patient alternated between RBBB and normal conduction:Note classic anterior LV aneurysm morphology (QS-waves in V1-V3 with ST elevation).  There is ST elevation, but the T/QRS ratio is less than 0.36 in all of leads V1-V4, indicatin...
Source: Dr. Smith's ECG Blog - Category: Cardiology Authors: Source Type: blogs