November 11, 2013

REBEL ECG of the Week #2

58 year old female with chief complaint of chest pain x2hours with PMH of type 2 diabetes mellitus, Hyperlipidemia, and hypertension.    She is brought in via EMS still having active chest pain.

BP: 102/88  HR: 82  RR: 24  O2 Sat on 2L: 99%  Temp 99.0

ECG obtained at arrival is shown…

Before reading on, try to come up with your own interpretation of this ECG before moving on to the final impression

Proximal RCA STEMI

  • Rate: Ventricular rate 82
  • Rhythm: Normal sinus rhythm
  • Axis: normal axis
  • QRS: narrow complex
  • ST/T Waves: ST elevation in leads II, III, and aVF (inferior leads) and V3R – V6R (right sided leads);  ST depression in leads I and aVL (high lateral leads)
  • Final ECG Interpretation: Right Sided STEMI

There are several points to discuss on this ECG.  First, lets focus on the inferior ST elevation and the reciprocal changes in the high lateral leads.  Lead aVL is the closest thing on the ECG to a mirror image of the inferior leads.  As a matter of fact it is exactly 150 degrees away from lead III (Reciprocal Changes in Lead aVL).  If you take lead aVL and flip it upside down (shown below) it has a similar morphology as lead III (mirror images).  Reciprocal changes in lead aVL and ST elevations in the inferior leads are typically seen in 70 – 97.2% of patients with a true inferior wall MI. [1][2]

Flipped Lead aVL

Lead aVL Turned Upside Down (mirror image of inferior leads)

Next lets talk about the ST elevation in the inferior leads and anterolateral leads. In general, the right coronary artery is the culprit vessel in about 80 – 90% of inferior wall MIs.  The left circumflex can also be the culprit vessel in some cases.  There are a few clues that can help determine which vessel is involved in inferior myocardial infarction:

  1. If ST elevation in lead III > lead II and ST depression in leads I and aVL (> 1 mm), then RCA is the culprit artery with a sensitivity of 90%, specificity of 71%, and PPV of 94%. [3]
  2. If ST elevation in leads V3R and V4R, then RCA is the culprit artery with sensitivity of 100% and specificity of 87% [1]
  3. No ST depression in lead aVL, then LCx is the culprit vessel with sensitivity of  80% and specificity of 93%. [1]

In this ECG, ST elevation is greater in lead III vs lead II and there is > 1mm ST depression in lead aVL.  Also, there is ST elevation in leads V3R and V4R pointing to an RCA occlusion.  3 options to consider with inferior STEMI are:

  1. Dominant RCA = ST elevation in leads II, III, & aVF + ST elevation < 2mm in V5 & V6 [4]
  2. Dominant LCx
  3. “Mega-artery” = ST elevation in leads II, III, & aVF + ST elevation > 2mm in V5 & V6 [4]
  • Mega-artery = Large posterolateral branches (originating from the RCA or LCx arteries) and a small or medium LAD artery [5]

Case Conclusion: Cath showed a 100% proximal RCA occlusion with a “mega-RCA”


  1. Birnbaum Y et al. the Electrocardiogram in ST Elevation Acute Myocardial Infarction: Correlation with Coronary Anatomy and Prognosis. Postgrad Med J 2003. PMID: 13679544
  2. Barrabes JA et al. Prognostic Significance of ST Segment Depression in Lateral Leads I, aVL, V5 and V6 on the Admission Electrocardiogram in Patients with a First Acute Myocardial Infarction Without ST Segment Elevation. JACC 2000. PMID: 10841229
  3. Zimetbaum PJ et al. Use of the Electrocardiogram in Acute Myocardial Infarction. NEJM 2003. PMID: 12621138
  4. Eskola MJ et al. How to Use ECG for Decision Support in the Catheterization laboratory. Cases with Inferior ST Elevation Myocardial Infarction. J Electrocardiol 2004. PMID: 15484153
  5. Assali AR et al. Comparison of Patients with Inferior Wall Acute Myocardial Infarction with Versus without ST-Segment Elevation in Leads V5 and V6. Am J Cardiol 1998. PMID: 9462612
Cite this article as: Salim Rezaie, "REBEL ECG of the Week #2", REBEL EM blog, November 11, 2013. Available at:
The following two tabs change content below.

Salim Rezaie

Emergency Physician at Greater San Antonio Emergency Physicians (GSEP)
Creator & Founder of REBEL EM
  • Vince D
    Posted at 09:40h, 11 November Reply

    Nice review, but it is essential to point out that the above ECG is a right-sided tracing utilizing V3R-V6R. Also, all of the instances in the text where you mention ST-elevation in the precordial leads should be in reference to right-sided precordial leads, not the standard leads, otherwise it makes no sense. There’s no reason for there to be ST-elevation in V4 with a RCA occlusion, but an injury pattern in “V4R” certainly fits the picture.

    • Salim Rezaie
      Posted at 09:54h, 11 November Reply

      Hello Vince,
      Yes great catch. It is actually a rt sided ECG (V3R – V6R). Post updated. TY


  • Stephen Smith
    Posted at 09:44h, 11 November Reply

    Yes, it is an RCA, but this is a right ventricular (RV) STEMI, not “anterior” STEMI.

    This is a right sided ECG, not a left-sided. If this were a left-sided ECG, then there would be an R-wave in V5 and V6, which there is not. You can see that this is not because of lateral Q-waves, because there is an R-wave in lead I.

    In a left sided ECG with inferior MI, you may see “anterior” ST elevation in 2 cases: 1 simultaneous inferior and anterior STEMI due to wraparound LAD or 2) “pseudoanteroseptal MI” due to large RV infarct.

    Steve Smith

    • Salim Rezaie
      Posted at 10:01h, 11 November Reply

      Hello Steve,
      Welcome to the new site. A work in progress. Glad to have you commenting on here. Yes it is a right sided ECG (V3R – V6R). Great point the Q waves in leads V4R – V6R are a give away because of the R wave seen in lead I.
      Also fantastic point of “Anterior” ST elevation in inferior MI. thank you again. I have corrected the post to show right sided ECG, completely my mistake. Thank you.


  • Stephen Smith
    Posted at 12:11h, 11 November Reply

    Also, any ST depression in aVL is extremely sensitive for inferior MI. Here is one article:

    We are submitting a manuscript in which we found that 99% of 155 inferior MI had some (at least .25 mm) ST depression in aVL.


    • Salim Rezaie
      Posted at 12:14h, 11 November Reply

      As always TY Steve. I will have to add this to my growing library of ECG articles.


  • Ken Grauer, MD
    Posted at 01:06h, 12 November Reply

    Hi Salim. I’ll add 2 points to excellent comments by Vince D and Steve Smith.

    #1) Even before one places right-sided leads, you can get a hint of likely acute RV infarction by looking at lead V1. Note that the ST segment is flat in V1 and not depressed as it is in V2. There is obvious acute posterior MI here (given V2’s appearance). Normally you would also see significant ST depress in lead V1 with posterior MI – unless this was countered by ST elevation from acute RV MI (with net effect ST flattening in V1). Acute RV STEMI of course becomes obvious once you place V3R-thru-V6R ….

    #2) You need to flip horizontally your blow-up of lead aVL to get the true “mirror-image” of lead III (you flipped it over AND also flipped it horizontally – when you should not have flipped it horizontally, because it is now backwards … ). For the true “mirror-image” of lead aVL – GO TO my Dropbox AT: – Feel free to download that image and replace it with the one you currently show.

    That said – this IS an important post – and I appreciate the pearls about large posterolateral branches being a cause of ST elevation in V5,V6.

    • Salim Rezaie
      Posted at 06:48h, 12 November Reply

      As always Ken TY for the insightful comments. It is great to have you and Steve Smith commenting on the blog. I will flip the image horizontally as well, to get the exact mirror image, which you are correct needs to be flipped both vertically and horizontally. TY again. And please keep the comments coming. 🙂


  • The LITFL Review 116 - LITFL
    Posted at 01:42h, 20 November Reply

    […] by frequent ALiEM contributor Salim Rezaie, it started with a couple ECG of the week posts here and here. I anticipate there will be more good stuff on its way! […]

Post A Comment

Time limit is exhausted. Please reload CAPTCHA.