Friday, June 24, 2011

Chest pain, SOB, and tachycardia. What is the rhythm? Is it MI?

This was sent to me by a reader from India (Thank you, Rama Krishna).  The patient presented recently (age unknown).  He had a history of DM, HTN, COPD, and previous anterior wall MI.

Here is his presenting ECG:

 The answer is below:

It is ventricular tachycardia with 1:1 retrograde conduction to the atria and also with electrical alternans.  The small drawn circles, which appear to be p-waves, are not actually the p-waves.  Rather, the small negative deflection following these circles (narrow black arrows along the lead II rhythm strip at the bottom), are retrograde p-waves.  They are negative because of the retrograde conduction.  The alternate QRS has a negative p-wave that is buried in the negative T-wave (green arrow).  These p-waves are upright in aVR (see the blue arrows, and red arrow for the alternate QRS)  Also, the retrograde p-wave can be seen in V1 (purple arrow).

As for repolarization, there is ST elevation in V2-V4 (thick black arrow) diagnostic of MI.  It looks like it is old MI, not acute (see discussions of LV aneurysm on other posts).  Of course, these discussions apply to normal conduction, not normally to ventricular tachycardia.  But in this case it is fair to say that the ST segments are a result of MI [almost certainly old MI (which also fits the patient's history), possibly acute] rather than being due to the abnormal QRS.


  1. Thank you very much sir for your opinion on this ECG. I think i am very much satisfied with your version. Sir, can you kindly elaborate a little more on retrograde P waves and negative P waves ?

  2. If the impulse comes from the ventricle, then it will go up through the AV node rather than down. Therefore, the atrium will be depolarized from its lower pole to upper pole (normally upper to lower). Thus, the p-wave will have a polarity opposite of normal (inverted in lead II, upright in aVR).

  3. Looks more to me like SVT, more specifically AVNRT - QRS looks as you implied quite supra ventricular. Could even be antidromic AVRT - possible delta waves many leads. Alternans can certainly occur with SVT also. Steve, why so sure VT?

    Joe Esterson

  4. Joe,
    The QRS is wide, so it is either VT or SVT with aberrancy.
    There are three excellent rules that help to differentiate these two: Brugada's rule and 2 rules by Vereckei (I use his aVR rule).
    I will repost this ECG with a Vereckei and Brugada analysis when I get the time, but to make it short:

    Brugada: there is an LBBB-type morphology, and the descending limb in the right precordial leads is both prolonged and notched.
    Vereckei: there is a wide initial r-wave in aVR (this is NOT a p-wave, which is retrograde).

    There are no delta waves because these only come in sinus rhythm after an upright p-wave with a short PR interval, or in antidromic WPW. The p-wave is clearly after the QRS and inverted (which can be present in AVNRT), so it is not sinus. As for antidromic WPW, it is possible, but very much more unusual than VT.

  5. Thank you for this interesting case, sir.

    But could you explain a little about the electrical alternans in VT?

    1. I don't know why it happens, but it does and it does not represent effusion or tamponade as it does in sinus tachycardia.


DEAR READER: We welcome your Comments! Unfortunately — due to a recent marked increase in SPAM — we have had to restrict commenting to Users with a GOOGLE Account. If you do not yet have a Google account — it should not take long to register. Comments give US feedback on how well Dr. Smith’s ECG Blog is addressing your needs — and they help to clarify concepts of interest to all readers. THANK YOU for your continued support!

Recommended Resources