Tuesday, February 11, 2020

ST Elevation in aVL with reciprocal ST Depression in inferior leads and DIffuse ST depression

An elderly male had volume depletion and anemia, and complained of chest pain.

We recorded this ECG:
Q-waves and ST Elevation in I and aVL
ST Depression in inferior (reciprocal to aVL) and precordial leads.   
Is it posterolateral OMI?
What do you think?

Notice that not only are there Q-waves in I and aVL, they are QS-waves (there are no R-waves).

However, there are very well-formed R-waves in the other "lateral" leads, V5 and V6.

These 4 lateral leads do not always look identical, as V5 and V6 are more inferior that I and aVL, but they should never look this different EXCEPT if you are recording a right sided ECG in someone with Dextrocardia.

Notice also that, in spite of STD in V5, there is STD in aVR.  These leads are effectively opposite each other and should be reciprocal to each other.

So this is lead reversal.  The computer did NOT see this.

Here is what it looked like after we placed the leads correctly:
This is also after blood and fluid resuscitation, so that there is less ischemia evident.

This is supply/demand subendocardial ischemia, and it finally resolved with full resuscitation.

Learning Points:

1. R-waves in I/aVL should not be opposite to V5, V6
2. STD in V5 should be accompanied by STE in aVR

These points should be major clues to lead reversal.

MY Comment by KEN GRAUER, MD (2/11/2020):
ECG Courses and textbooks often pay little attention to recognition of lead misplacement. As a result — in those uncommon situations in which lead misplacement occurs — it all-too-often goes unrecognized.
  • Today’s post by Dr. Smith highlights a number of points to keep in mind to facilitate recognition of lead misplacement. I’ll add to his comments with a slightly different perspective.

PEARL  My favorite on-line Quick GO-TO” reference for the most common types of lead misplacement comes from LITFL ( = Life-In-The-Fast-Lane). I have used the superb web page they post in their web site on this subject for years. It’s EASY to find — Simply put in, LITFL Lead Reversal in the Search bar — and the link comes up instantly.
  • This LITFL web page describes the 7 most common lead reversals. There are other possibilities (ie, in which there may be misplacement of multiple leads) — but these are less common and more difficult to predict.
  • By far (!) — the most common lead reversal is mix-up of the LA (Left Arm) and RA (Right ArmelectrodesThis is the mix-up that occurred in todays case. For clarity — I’ve reproduced the illustration from LITFL on LA-RA reversal in Figure-1.

Figure-1: LA-RA Lead Reversal — adapted from LITFL (See text).

MAPPROACH  What has helped me over the years to rapidly recognize most cases of lead misplacement is attention to the following parameters:
  • Lead I — usually manifests a predominantly positive QRS complex, because this left-sided lead normally sees the heart’s electrical activity as traveling toward lead I. It is of course possible to have right axis deviation — but you will virtually never see an all-negative (ie, QS) complex in lead I unless there is: i) lead reversal; or iidextrocardia.
  • It is also extremely uncommon for there to be a very deep and wide Q wave in lead I in the presence of a QR complex in this lead. Of course, there are exceptions (ie, a large lateral MI) — but I always consider the possibility of lead misplacement whenever there is a predominant initial negative deflection (ie, a large and wide Q wave in the presence of a QR complex) in lead I.
  • IF there is global negativity” (ie, negative P wave, QRS complex and T wave) in lead I — then the diagnosis of either lead reversal or dextrocardia is virtually assured! (ie, IF lead I looks like you expect aVR to look — and aVR looks like you expect lead I to look — then suspect LA-RA lead reversal!)
  • Lead aVR — usually manifests a predominantly negative QRS complex, because this right-sided lead normally views the heart’s electrical activity as traveling away from the remote (looking down from the right shoulder) viewpoint of lead aVR. Clearly, there are instances in which the QRS manifests positive activity in lead aVR — but the finding of an all negative QRS in lead I with an all positive QRS in lead aVR is virtually diagnostic of either lead reversal or dextrocardia!
  • The P wave should always be upright in lead II when there is sinus rhythm. The only 2 exceptions (ie, when there may be sinus rhythm without the P in lead II being upright) — is when there is either lead reversal or dextrocardia.
  • Finally — the way to distinguish between lead reversal vs dextrocardia on ECG is to look at R wave progression. When there is dextrocardia — there will be reverse R wave progression (ie, a modest R wave in lead V1 will quickly become smaller and disappear as you move across left-sided chest leads). Repeating the ECG with right-sided leads when the patient has dextrocardia will normalize R wave progression.

Figure-2: The initial ECG in the ED — with features of LA-RA lead reversal written below the tracing (See text).

Let’s now take another look at the initial ED ECG ( = ECG #1A) in this case (Figure-2):
  • For clarity — I’ve added the effects listed in Figure-1 that LA-RA lead reversal manifests under the initial ECG.
  • CHALLENGE  In your “mind’s eye” — TRY TO ENVISION what this initial ECG would have looked like IF the limb leads were correctly placed.
  • Applying MAPPROACH to ECG #1A — The most striking finding in this tracing is the all negative QRS complex in lead I. This immediately tells you something is wrong! Coupled with the all positive QRS in lead aVR tells you in less than 5 seconds that there is either lead reversal or dextrocardia. Looking at the chest leads reveals good R wave progression (with transition occurring between leads V2-to-V3) — so this can not be dextrocardia. It has to be LA-RLead Reversal.
  • NOTE #1  The P wave in lead II of ECG #1A is tiny but positive. Sometimes the P wave in lead II may still be positive even when there is lead reversal.
  • NOTE #2  While it is common for there to be “global negativity” (ie, of P wave, QRS complex and T wave) in lead I when there is LA-RA Lead Reversal — the T wave in lead I may be upright IF there is significant ischemia (ie, lots of ST depression elsewhere) — and this is what we see in ECG #1A.

Let’s finish this case with Figure-3 — in which I have: i) inverted lead I from ECG #1A; ii) switched positions for leads II and III; andiii) switched positions for leads aVL and aVR.
  • ECG #1B shows what the initial ECG would have looked like IF all leads had been correctly placed! Note that the normal expected relationships have all been restored (ie, the QRS in lead I is positive — and, the QRS in lead aVR is negative).
  • As per Dr. Smith — ECG #1B suggests the picture of diffuse subendocardial ischemia (with marked ST depression in multiple leads + ST elevation in lead aVR).
  • For another case of limb lead reversal on Dr. Smith’s blog — CLICK HERE.

Figure-3: Comparison of the initial ECG in the ED ( = ECG #1A) — with what this ECG would look like (as shown in ECG #1B) IF: i) Lead I was inverted; ii) Leads II and III switched places; and, iii) Leads aVR and aVL switched places (See text).


  1. Replies
    1. I completely agree Jerry that the negative P in lead I is another tip-off to lead reversal. The finding of “global negativity” (ie, of P wave, QRS complex and T wave) in lead I virtually guarantees you are dealing with either lead reversal or dextrocardia (and the normal R wave progression here rules out dextrocardia). The reason the T wave upright (instead of negative) in lead I of ECG #1A in this case, is because of the subendocardial ischemia … but there is still the QS complex and negative P in lead I that immediately virtually gives us “the answer” — :)

  2. Educational post, there are a lot of tips! Are there broad and notched P waves in inferior leads?

    1. Thanks for your positive feedback! As to your question — I don’t think the P waes in the inferior leads of ECG #1A are helpful. It’s hard to tell if there truly is notching vs baseline undulations from artifact in these inferior leads. As we’ve already noted — the finding of a negative P wave in lead I (as we see in ECG #1A) is another clue to the lead misplacement. And, there ARE times when the finding of a P wave in lead II that is much smaller than the P wave in lead I or lead III suggests that if the rhythm is sinus, that there is some form of lead misplacement — BUT — in this case (ie, in ECG #1A) — I don’t think any conclusions regarding lead misplacement can be drawn from P wave appearance in the inferior leads.


DEAR READER: I have loved receiving your comments, but I am no longer able to moderate them. Since the vast majority are SPAM, I need to moderate them all. Therefore, comments will rarely be published any more. So Sorry.

Recommended Resources