Thursday, November 3, 2011

Benign early repolarization


A few days ago I was just about to walk out of the pediatric ED, when the tech handed me an ECG: "I need you to look at this right now."


All caps = important.
All caps + asterisks = very important.


Ah. I see. 
The patient turned out to be a very healthy looking, comfortable, 28 y.o. African-American male, and he happened to have an odd chest discomfort, "like needles." He actually wasn't having the pain at the time the ECG was taken.

Despite the dire diagnosis on the EKG (Thanks Marquette!), he walked out of the ED a few hours later, after multiple negative cardiac enzymes, sequential ECGs, a bedside echo, as well as a turkey sandwich. However, his favorable course could have been predicted from the classic findings on the ECG, diagnostic for benign early repolarization (BER).
First off, before we review the criteria for BER, note that there are no reciprocal changes in the ECG, which would be extremely unlikely in a massive ***ACUTE MI***. Right off the bat, you know this is far more likely to represent a mimic of some ilk. 

So, widespread ST elevations without reciprocal depression, there are 2 possibilities in the differential. Pericarditis is one, but a few things mitigate against it. There doesn't appear to any PR depression (or any PR elevation in aVR), and the T waves are all upright. So, possible, but not not clear.

Now let's take a look at the criteria for BER.
This table comes out of the excellent review article by Brady and Chan (1999) (Download pdf). Looking at the ECG, we see ST elevation in leads I, II, aVL, and V2-V5 - certainly very widespread, with elevations in the precordial leads looking more prominent than the limb leads. 

Next, we note that in leads II and V5, where the ST elevation isn't that pronounced, there is nonetheless a notable elevation of the J-point, that place where the QRS "meets" the ST segment. 
Lead II, showing J-point elevation over 0.1 mV
Also note that none of the complexes with ST segment elevation show convex-upward segments, but instead concave-upwards morphology.

Note also that the J-point in the ECG doesn't show a clean transition from the R wave to the ST segment. Rather, there seems to be a messy transition, either a "slurring" or a notched junction. You can see the slurred J-point in the blow-up from lead II above, or take a look at lead V4:
Notched J-point
As noted before, the T-waves are all appropriately upright and quite prominent. As for the other criteria, they're difficult to judge on a single ECG!

Who has BER? Well, this patient was classic for the epidemiology of BER, being young, fit, male, and African-American.The pattern is found very often in male athletes, and appears to have no connection to HCM, or any other causes of sudden cardiac arrest.

My philosophy is that the emergency physician needs to be competent in many spheres, and across many disciplines. However, in a few areas we need to be the experts in the hospital, and reading ECGs for signs of acute ischemia, or its mimics, is such a skill. In training we study more ECGS than anybody in any other field. And when you're an attneding in the ED, it's just one after another... All that training and repition pays off - In one study, Turnipseed et al. showed that EPs could read BER versus AMI on the ECG just as well as cardiologists, if they corrected for years of experience. (download pdf)

See you in room 4!

4 comments:

  1. How did this patient's inverted T in III factor into your assessment? Is that why you got a second set? Would you ever not get enzymes with this (or a similar) presentation?

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  2. Inverted T's in III are seen so often in normal folks. I don't believe that anyone has found a use for them!

    Getting enzymes is fine, but it obligates follow-up with a cardiologist, potential for false positives, and consequent iatrogenic morbidity. If this guy had, say, a clear asthma attack, or a broken rib, I would argue against any cardiac enzymes. Just asking for trouble!

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  3. There's also a big upright T in V1 that is bigger than in V6, but is this not significant due to (pseudo?)-LVH?

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    1. As in a hyperacute T-wave? You always have to keep that in mind, I agree. By the patient's age and history, this wasn't very likely, though.

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