Friday, March 7, 2014

Inferior STEMI? Read the ECG systematically.

Leads V1 and V2 appear to be reversed.  Otherwise, what is it?

This diagnosis may be obvious to some, but it is easy to let your eyes be drawn to the ST elevation in II, III, and aVF, with reciprocal ST depression in aVL.  Then one forgets to read the ECG systematically: rate, rhythm, intervals, axis, voltage, QRS abnormalities, ST segment, T-wave, U-wave.

If one is systematic, then before seeing the ST-T abnormalities, you will see the short PR interval and the long QRS, which is long because of a delta wave.

ST- and T-wave abnormalities must always be read in the context of the QRS.  An abnormal QRS (LVH, LBBB, RBBB, WPW, Brugada, Hyperkalemia, IVCD, etc.), or abnormal depolarization, leads to abnormal repolarization (abnormal ST-T).

In this case, all the ST-T abnormalities are due to the abnormal depolarization through an accessory pathway, producing a delta wave and abnormal depolarization.  Even without a delta wave and short PR interval, the voltage of this magnitude (LVH) could also produce such a pseudoSTEMI pattern.

The patient presented with chest pain and palpitations.  The ST-T abnormalities did indeed distract the treating physician, who felt embarassed at initially missing what to him/her in retrospect was obvious.

The mind plays tricks on us and so we have to read these systematically.

This is very important for radiographs as well.  In my experience, most misreads of radiographs are not from lack of knowledge, but from distraction, from missing the obvious because you are looking for something else or see something distracting.  This is frequently true of ECGs.

Here are some other examples of pseudoSTEMI due to WPW.


  1. Are there leads misplaced? The inconsistent r-wave progression through chest leads is odd.

    1. It appears so. I have mentioned that now. thanks!

  2. Is V2/V3 likely a lead placement error?

  3. Is the V2 lead mispositioned? If not then why is V2 positive when V1 and V3 are negative? I presume this is a right sided pathway? Many thanks for this interesting ECG

  4. Nice ECG, Steve. Speaking of systematic reading. No mention of the rhythm here.. Appear to be the same p-wave morphology before the QRSs, and w/the same PR Interval (short). I don't see much regularity at all...Also, the p-wave in V1 appears to be upright (whether V1 & V2 are reversed, or not).. thoughts?

    1. Good point. Looks like sinus "arrhythmia" with one PAC (2nd complex). Doesn't change the overall interpretation, though.


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