The early repolarization experiment

Any paramedic who has studied the STEMI mimics has heard of the classic benign early repolarization pattern of a "fish-hooked" J-point with upwardly concave (smiley-faced) ST-segment, often best appreciated in lead V4.

But, as the excellent work of Stephen Smith, M.D. demonstrates, not all cases of early repolarization present this way, and it can often be very difficult to differentiate between early repolarization and LAD occlusion.

So, we took a run-of-the-mill "male pattern" early repolarization pattern, removed the computerized interpretation, and posted the ECG to our Facebook fan page.

The variety of interpretations was shocking! 

Some of the common interpretations included Wolff-Parkinsons-White syndrome, pericarditis, hyperkalemia, and (less commonly) acute anterior STEMI. Very few mentioned early repolarization.

This just goes to show how important and valuable Stephen Smith's work on this topic really is!

Here's the same ECG with the computerized interpretation.

I have a sneaking suspicion that some of the very same paramedics who rail against computerized interpretive algorithms are unconsciously influenced by the computerized interpretation whether they realize it or not.

That may not be a bad thing.

A baseline reading of "normal ECG" creates a comfort level for this normal variant. Keep in mind, ST-elevation in leads V2 and V3 for a young male is not a normal variant. It's a normal finding! But these T-waves are a little more impressive than we might expect, so I'm calling it a variant.

So what gives away that it's not hyperacute anterior STEMI?

Dr. Smith has an abstruse formula (he probably doesn't think it's abstruse but then again the man's a physicist as well as a physician) that was recently published in the Annals of Emergency Medicine.

(1.196 x STE at 60 ms after the J-point in V3 in mm) + (0.059 x computerized QTc) – (0.326 x R-wave Amplitude in V4 in mm)

A value greater than 23.4 is quite sensitive and specific for LAD occlusion.

Dr. Smith adds these qualifiers:

"It is critical to use it only when the differential is subtle LAD occlusion vs. early repol. If there is LVH, it may not apply. If there are features that make LAD occlusion obvious (inferior or anterior ST depression, convexity, terminal QRS distortion, Q-waves), then the equation MAY NOT apply. These kinds of cases were excluded from the study as obvious anterior STEMI. ST elevation (STE) is measured at 60 milliseconds after the J-point, relative to the PR segment, in millimeters." 

What does this mean for the field provider? I'm a firm believer in keeping it simple.

The bottom line (in my opinion) is that we should suspect the possibility of benign early repolarization when: 

  • R-wave progression is intact (this is big)
  • There is a tall R-wave in lead V4
  • The QTc is on the low end of normal (in this case < 400 ms)
  • There is an absence of reciprocal changes
  • ST-elevation is upwardly concave
  • U-waves are easily identifiable (additional tip shared by Dr. Smith in private conversation)
  • There are no changes on serially obtained ECGs

None of these rules of thumb are 100% but we're trying to make a logical game-time decision and knowledge is power.

Simply knowing that the differential diagnosis is early repolarization vs. LAD occlusion would be an important improvement when faced with an ECG like this (which frankly isn't anywhere near as difficult as some others we've seen).

For example:

Here's another:


  • Early repolarization is a common and underappreciated STEMI mimic
  • It does not always present with "fish-hooked" J-points
  • The ST-elevation and T-waves can often be scary with early repolarization
  • The key here is knowing that the differential is LAD occlusion vs. early repolarization

I encourage everyone to read the archived early repolarization cases at Dr. Smith's ECG Blog by clicking here.


  • Gene says:

    Tom et al,
    On the first "for example" ECG I have 4/392/16 rendering a value of  22.67, making it Early Repol, albeit just barely.
    Is this correct? Can you elaborate on this ECG?
    Because I've got to say, I'm not sure I would have the confidence to NOT activate this one from the field. Assuming we have the appropriate presentation, if it did end up being a STEMI because I had one of the numbers slightly off, or it was one of the 10%, or what have you, I'm certain the doc would feel it necessary to yank me by the balls to the side and point out the obvious STE I apparently should have recognized. He would walk away thinking me an arrogant, shitty paramedic and I would go home one set of testicles less than I started with.

  • Dr. Smith manually calculated the QTc at 387 but the computer came up with 416. There are features about this ECG that are very concerning. We don't have the results of diagnostic testing. We just know that the patient was discharged from the ED with "early repol". I wouldn't blame you for calling a Code STEMI based on this ECG. On the other hand, in a perfect world, any false positive or false negative would be handled in a collegial manner.

Leave a Reply

Your email address will not be published. Required fields are marked *

EMS 12-Lead

Cardiac Rhythm Analysis, 12-Lead ECG Interpretation, Resuscitation

JEMS Talk: Google Hangout

How to be successful at IV therapy – some advice for paramedic students
I learned from one of my field instructors to squeeze the arm on the opposite side of the insertion site rather than using your thumb to hold the vein straight/still. When you use your thumb you are more prone to not being able to drop the catheter to a proper angle, after flash, in order…
2015-09-03 20:10:24
Masters Case #01: 50 Year Old Male – Severe Chest Pain
Short runs of V.T LAD LAHB Widespread st depression with St elevation in avr Lf msin / three vessle disease Not sure about rhythm
2015-08-26 06:34:44
Darren Earley
Masters Case #01: 50 Year Old Male – Severe Chest Pain
1. L.A.D 2. De Winters (ST Elevation aVR, ST abnormality V2-3). 3. Non sustained VT 4.Poor quality ECG so cannot say about p waves or whether A.fib. Pre alert for ppci = evolving occlusion of LAD artery. Aspirin. Pain relief. Diesel
2015-08-25 17:26:50
Masters Case #01: 50 Year Old Male – Severe Chest Pain
first pt. sat's are to low at 94% for just room air pt. needs hi-flow o2 at 15 lt. min. i see a-fib. with runs of 3. st depression. there is also a chance of pheumonia. after o2 administer fluids, a chest x-ray, monitor the heart and ekg especially where bp is low.
2015-08-25 16:57:39
Ivan Rios
Understanding Adenosine (Adenocard)
Correct, even for stress test, with the same purpose.
2015-08-18 17:07:24

ECG Medical Training

12-Lead ECG Challenge Smartphone App


12-Lead ECG Challenge Smartphone App - $5.99

  • Apple iOS
  • Android
  • Amazon
  • Web Based

  • FRN-TV video review
  • review
  • Interested in Resuscitation?

    Interested in Advanced Cardiac Life Support?

    FireEMS Blogs eNewsletter

    Sign-up to receive our free monthly eNewsletter

    Visitor Map / Stats

    Locations of visitors to this page