Cardiac Ultrasound may be a surprisingly easy way to help make the diagnosis

Dr Smith's ECG Blog, 2012

100).  The QRS was measured by the computer at 117 ms (but to my eye is normal)  There is an rSr' in V1, and if the QRS really is long, this is an incomplete RBBB (I don't think it is long).  Computerized QTc is 435 ms.  There is abnormal T-wave inversion in leads V2-V5, suggestive of ischemia.  There is another finding which suggests the diagnosis.
There is sinus rhythm at a normal rate (75).  There is abnormal T-wave inversion in lead V2 only now, but the S1Q3T3 (the finding which suggests PE) is here also. 
So is this just baseline T-wave inversion?  Wellens'?  Pulmonary embolism?  First, the increased heart rate should always sway you towards PE.  Wellens' syndrome implies open arteries, perfusion of the myocardium, and the patient uncommonly has tachycardia.  Baseline T-wave inversion is an unlikely explanation because there is extension out to V5.  PE is very likely with this ECG.  
The thick white arrow shows the right ventricle, which is dilated.  The thin red arrow shows the left ventricle, which should not be smaller than the RV, as it is here.
found normal angiograms in only 3 of 50 patients with massive PE, and 9 of 40 with submassive PE.  Today, however, that number would be lower because we diagnose more of the submassive PEs that have minimal symptoms.
Finally , they found that S1Q3T3, precordial T-wave inversions V1-V4, and tachycardia were independent predictors of PE. 
What is an S1Q3T3?  Very few studies define S1Q3T3.  What is it?   and both S1 and Q3 were defined as 1.5 mm (0.15 mV).  In the Marchik article, (assuming they defined it the same way, and the methods do not specify this), S1Q3T3 was found in 8.5% of patients with PE and 3.3% of patients without PE.
embolism is far more likely than ACS.  In this study, (quote) "negative T waves in leads III and V 1 were observed in only 1% of patients with ACS compared with 88% of patients with APE
In conclusion, the presence of negative T waves in both leads III and V 1 allows PE to be differentiated simply but accurately from ACS in patients with negative T waves in the precordial leads."
Strong work by the EMT! This case certainly highlights the impact that online education can have on patient outcomes.
Comments not appropriate for general posting, or interesting ECGs, may be sent here (do this judiciously!) : .