Wednesday, October 9, 2013

Terminal QRS Distortion due to LAD Occlusion

A male in his 30's presented with chest pain. Here is his initial ECG:
  • There is sinus rhythm, with a normal QRS and precordial ST elevation. 
  • There is upward concavity in all of V2-V5.  
  • There is no lead with massive ST elevation [there is 2mm of STE in V2 and 3 mm in V3, as measured at the J-point; in males under 40, recommended STE cutoffs are 2.5 mm in 2 consecutive leads, so this does not meet that "critierion"].   
  • There is no reciprocal ST depression in inferior or anterior leads, no T-wave inversion.  
  • There are very narrow Q-waves in V3 and V4, and though these may be (rarely) normal, especially in subjects under 40 years of age, one should  suspect they are pathologic and are not  normally seen in early repolarization.  
  • Finally, there is terminal QRS distortion (see below) 
So, the only plausible reasons for ST elevation are anterior STEMI or Early Repolarization.  One might be tempted to apply the formula that helps to differentiate the two.  However, when we studied these ECGs, we excluded patients with features that made STEMI "obvious," or at least not subtle.  These features included Q-waves and Terminal QRS distortion.  In this case, the Q-waves do not make it an obvious MI, but the QRS distortion does:
 
QRS Distortion is defined as: "Emergence of the J point ≥50% of the R wave in leads with qR configuration, or disappearance of the S wave in leads with an Rs configuration)"  (from this paper by Birnbaum).    I would add to this: if there are distinct J-waves in these leads, then early repolarization is still a likely possibility.  In this case, there are no distinct J-waves in V2 or V3 (although there is a small one in V4)

Thus, this should be thought of as diagnostic of anterior STEMI.  If the formula had been used, then the value would have been [1.196 x 3.5]+[0.059 x 402]–[0.326 x 17] = 22.362 (which is less than 23.4 and thus consistent with early repolarization).  The formula would have given a false negative, because this was an LAD occlusion. 

Learning Point:

When there is Terminal QRS distortion (absence of BOTH an S-wave and a J-wave in EITHER of leads V2 or V3, it is not early repolarization.  When the differential diagnosis only includes early repol and LAD occlusion, then LAD occlusion is strongly favored.

10 comments:

  1. Welcome back Dr. Smith.
     Very interesting post.
    The lack of reciprocal ST segment depression can be attributed to the precocity of ECG recording or other mechanism?
    Thank you.

    Vittorio Masciulli

    ReplyDelete
    Replies
    1. Vittorio,

      Thanks. (I was vacationing in Vittorio Veneto, biking!)

      About 50% of anterior STEMI have no reciprocal ST depression, in particular, mid-LAD occlusion. Proximal LAD occlusion, because it affects the first diagonal to the high lateral wall, usually results in ST depression in inferior leads. Septal STEMI often has ST depression in reciprocal leads V5 and V6.

      Thanks,

      Steve Smith

      Delete
  2. My way of seeing it - V2 has relatively low QRS voltage, this coupled with excesive ST elevation and T wave ( in my opinion ) should make u suspect LAD occlusion ( an anterior MI )

    ReplyDelete
    Replies
    1. More than suspect: it is all but diagnostic.

      Delete
  3. I'm sorry, where is the QRS distortion? Aren't the S waves preserved for RS complexes and the j points < 50 % for qR? I may be making a silly mistake.

    ReplyDelete
    Replies
    1. "Emergence of the J point ≥50% of the R wave in leads with qR configuration, or disappearance of the S wave in leads with an Rs configuration)"

      V2: STE is greater than 50% of height of R-wave
      V3: There is no S-wave and this is a lead where it would be expected.

      Meets the definition.

      No?

      Steve Smith

      Delete
    2. But V2 doesn't have a qR comfiguration, right?

      Delete
    3. I understand now. The Rs configuration is what the lead *should* be - as it had a small q I presumed it was a qR lead. Steve, I've learnt more about the ischaemic ECG from this blog than any other source. Many thanks. As it turns out, just today I was shown an ECG by one of my residents – staff weren't sure if it was early repolarization or a STEMI. No reciprocal ST depression. But there were small q waves in V2-V4 like this ECG, and very clearly in V3, a loss of the S wave. This lady recannalized her vessel spontaneously so we were able to see the difference. I'll send it on to you. At the cath, and without ST elevation, there was a 30% in the mid LAD. The importance for me was in feeling confident that she really had a ruptured plaque with thrombus that ultimately dissolved and therefore guiding more aggressive treatment despite the 'minor CAD'. MP

      Delete
    4. Sebastien, you're absolutely right. My mistake. So the distortion is, by Birnbaum's definition, only in V3.

      Then proportions alone are what make V2 look so abnormal and distorted. when there is that much ST elevation, it is only normal when there is a lot of QRS amplitude, either large R-wave or S-wave.

      thanks for your comment!

      Steve Smith

      Delete
    5. MP - fantastic! Please send the ECGs! dr.smiths.ecg.blog@gmail.com

      Steve

      Delete

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