Thursday, May 27, 2021

Why is there ST Elevation in lead V2? Think Lead Placement.

 I was shown this ECG of a 40-something intoxicated male with altered mental status.  The provider was very worried about LAD occlusion.

What do you think?














There is ST Elevation in lead V2, but there is also an RSR' wave which creates a kind of saddle ("saddleback pattern").  This is rarely due to anterior MI.  

There is also tachycardia, which unless a patient has cardiogenic shock, is also uncommonly due to ACS.  

And, of course, without chest pain, the pretest probability is very low.

RSR' and saddleback can be due to leads being placed too high, but since the P-wave is upright in lead V2, I did not think that was the problem.

I said it was unlikely to be ischemic.  I recommended IV fluids and to measure a troponin.  A cardiac POCUS would be useful to be certain there is good LV function.  One would expect it to be hyperdynamic.

Then record another ECG after that.  And measure troponins.

3 hours later I went to see if another ECG was recorded.  As I walked into the patient's room, this ECG was being printed out from the ECG machine:

There is still an RSR' and STE in V2.
I looked at the lead placement.
Leads V1 and V2 were far too high on the chest.
I placed them correctly and instructed the tech to record again.


Here is what came out:
Correcting the lead placement resulted in a more normal ECG


All trops were negative.

Learning Points:

1. Pretest probability is crucial
2. Saddleback (which is almost always lead V2) is unusual as a manifestation of OMI
3. Lead placement is crucial.  V1 and V2 are often placed too high.  They should be in the 4th intercostal space.  V4-V6 in the 5th intercostal space.  4th and 5th spaces are not that far apart; thus, the leads should ALMOST be horizontal across the chest.  See images below.
4. Tachycardia should make you suspicious of another etiology than ACS
5. Placing leads V1 and V2 too high can result in:
   a. Q-waves mimicking septal MI
   b. RSR' mimicking Brugada
   c. ST Elevation mimicking Acute MI (OMI)
   d. Saddleback mimicking Type 2 Brugada
   e.  Intentional placement too high may uncover Brugada.
   f.  Usually if placed too high, P-wave in V2 is inverted (it should always be upright if leads are correctly placed)


Correct lead placement, from LITFL:


Incorrect lead placement, seen in similar images all over the internet:


 
Article 1: Great article by Brooks Walsh:

The precordial electrocardiogram (ECG) leads V1 and V2 are often misplaced. Such misplacement usually involves placing these leads too high on the chest. The resulting ECG may generate erroneous ECG patterns: e.g. incomplete right bundle branch block, anterior T wave inversion, septal Q waves, ST-segment elevation. These features may falsely suggest acute or old cardiac ischemiapulmonary embolism, or a type-2 Brugada pattern. On rare occasion, conversely, high placement of V1 and V2 may reveal a true type-1 Brugada pattern. The emergency clinician needs to be aware of the possibility of lead misplacement, and should know how to suspect it based on unusual P wave morphology in V1 and V2.



Article 2:  Walsh B, Watford C, DeGiulio V, Oto B, Sifford D, Grauer K, Smith SW.  google Image is a bad way to learn ECG lead placement: we all agree.  SMACC-Dub. June 2016.

















4 comments:

  1. Isnt there a delta wave in chest leads.

    ReplyDelete
  2. Thank you steve
    the dependance of V2 to VL is fantastically well described in Littman's last publication Littmann L. A new electrocardiographic concept: V1-V2-V3 are not only horizontal, but also frontal plane leads. J Electrocardiol. 2021 Mar 4;66:62-68. doi: 10.1016/j.jelectrocard.2021.02.014. Epub ahead of print. PMID: 33774422.

    ReplyDelete

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