66 yo M calls 911 for acute onset chest pain while at rest. 
Pain is described as sharp, 9/10 and non-radiating. There is also associated nausea and slight hypotension.
Medics capture a 12 Lead:

3 of the 4 Lateral Leads I, V5 and V6 all show minimal STE less than 1 mm with hyperacute T waves.
The undulating baseline in the Inferiors show a less than optimal view and should have been repeated – not available. The T waves in all 3 Inferiors do however appear hyperacute. Reciprocal to Lead II – AVR also has approx. 1 mm STD with an inverted hyperacute T wave making the Inferiors very suspicious. 

Most notable is the obvious ST Depression in the right precordials – V1-V3.
Remember that V2 and V3 normally have minimal ST Elevation based on age and gender.
There are other causes of STD in these leads however, STD maximal in V1-V3 should always be considered a Posterior Occlusion first! 
The T waves from V3- V6 all seem out of proportion to their respective QRS’. The ST-T segment in V3 has little concavity to it giving it a straight “takeoff” appearance. 

The medics astutely recognized these findings and called a “STEMI” alert. It’s worth mentioning that technically this does not meet standard “STEMI” criteria, but as it is so often – obvious occlusion does not meet these outdated criteria. So, this is OMI – not STEMI.

Fig. 2 is the repeat ECG on arrival at the ED:

Beats # 2,5 and 8 have a different morphology than the underlying rhythm. There is a P wave before each, the PR Interval is slightly shorter than the rest and a narrow QRS follows. My first thought was a PJC, however considering that each of these beats fall near perfectly “right on time” and does not interrupt the underlying cadence – I believe these to be Junctional escape beats. PJC’s can be “Interpolated” meaning they do not disrupt the cadence; however, I think this is unlikely here, but I could be wrong. Either way – the T wave that follows is also hyperacute. Even in ectopic beats – profound STE/STD/hyperacute T waves can indicate ischemia. These have both minimal STE and hyperacute T waves.

The STE in Leads I, V5 and V6 have increased, now there is also minimal STE in AVL. The S wave in V6 has been obliterated. Even the T waves appear to have increased. 
We now have a clear “view” of the Inferior Leads – no real STE/STD seen; however, the T waves here also seem hyperacute. 

The ST Depression in V1-V3 persist with the ST segment in V2 now appearing flat. 
This is near diagnostic of Posterolateral Occlusion. 
Cardiology accepts the patient for immediate PCI. 

 

The patient was found to have a 100% occlusion of OM2 – as you can see in Fig. 3 – this is a large branch supplying a great deal of blood flow to Lateral and Posterior walls. Drug eluding stent placed with good outcome. 

This is just another example of why the standard “STEMI” criteria is outdated and should be forgotten and never taught again. 
The REAL question should be – Is there an occluded artery? Not – Is it STEMI?

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