Welcome to the second installment in our ECG Mixtape series! It looks like this will be an irregular publication while we streamline our process of picking cases and getting permission to reproduce them. Enjoy!
Pick of the Week
This weeks top pick comes from cardiologist Dr. Gianni Manzo in São Paulo, Brazil, who shared this case on the Figure 1 app [note: the app and site require free registration to view cases].
A 78 year old male presented with a chief complaint of “oppressive” chest pain. The patient’s past cardiac history was significant for coronary artery bypass graft (CABG) surgery and pacemaker. The following ECG was obtained on arrival.
It shows an AV-sequential paced rhythm at approximately 70 bpm (probably a DDDR pacemaker). Most folks would just end their interpretation there (and the machine certainly will), but there’s a lot more to see on this tracing… like an infero-posterior STEMI!
Somehow the myth persists that you can’t identify ischemia in the setting of a paced rhythm. I don’t know it survives—I’ve got texts that Marriott wrote decades ago demonstrating STEMI’s with pacemakers—yet at least once a week I hear someone say, “He’s got a pacemaker; we can’t tell if there’s ischemia.”
The key is Sgarbossa’s criteria (and Smith’s modification), used to identify ischemia in the setting of left bundle branch block (LBBB); they can also be applied to paced rhythms! For an overview of how to understand and apply these simple criteria I recommend Tom Bouthillet’s three-part tutorial:
- Making Sense of Sgarboss’a Criteria (Part 1)
- Making Sense of Sgarboss’a Criteria (Part 2)
- Making Sense of Sgarboss’a Criteria (Part 3)
In this case we have excessively discordant (> 25%) ST-elevation in III and aVF in the distribution of an inferior STEMI. Even more impressive is the excessively discordant ST-depression in I and aVL—reciprocal changes just like we’d see in a non-paced inferior STEMI.
Sealing the diagnosis, we also see in appropriate concordant ST-depression in V1–V3. This is reciprocal to posterior ST-elevation, confirming that this is an infero-posterior STEMI. V5 and V6 show normal discordant ST-elevation (< 25%), while V4 is mixed between the findings in V3 and V5, showing an abnormal lack of the discordant ST-elevation we would expect not not meeting the criteria for frank ST-depression.
Angiography showed a 100% occlusion of the mid-right coronary artery (mid-RCA), confirming the diagnosis.
I have to add some caveats. First, Sgarbossa’s criteria hasn’t been as well-studied in pacemakers as it has in typical LBBB’s. This isn’t a big deal since: 1) It’s performed pretty well in the studies that have been done, and 2) people could still identify LBBB and paced-STEMI’s before Dr. Sgarbossa’s seminal paper; her work just gave concrete proof and objective measures to the concepts that experts has known for decades. You’re gonna miss a lot of STEMI’s if you wait until there is large-scale, definitive proof of this pretty intuitive translation to pacemakers.
Second, and this is purely anecdote, but based on my experience, Sgarbossa’s criteria and Smith’s modification seem to be slightly less specific in the setting of paced rhythms. I can’t give you any real data (though Smith is currently studying this topic), but that’s my two cents on the matter. I still use the criteria routinely, I’m just slightly more careful when I apply the results.
Dr. Smith’s ECG Blog has a number of posts examining ischemia in the setting of paced rhythms:          
Our Favorite Blogs
Dr. Smith’s EGG Blog has been posting some fascinating cases the past few weeks so we’re actually going to highlight two of them here. The first concerns a 58 year old male patient who had been experiencing intermittent chest pain for two weeks and presented with the following 12-lead. The catch? Serial troponin levels were not only normal but undetectable! Make sure you click the image to see the full case description.
Our second case from Dr. Smith concerns another middle-age man presenting with chest pain and the following ECG. Is is a STEMI or just LVH? Follow the link for the answer and discussion.
I’m always looking for good examples of arrhythmias and their effects on invasive hemodynamic monitoring, and Mike over at Float Nurse shared a nice run of VT in a patient with an arterial line.
Next up are a pair of ECG’s obtained 15 min apart over at Dr. John Larkin’s ECG of the Week. What’s the cause of the T-wave inversions?
The Best of Social Media
In the Facebook group 12 Lead ECG – I’ve Got the Rhythm, Tomasz Adamski shared a great example of an antero-lateral STEMI visible through a LBBB—similar to our Pick of the Week showing a paced STEMI. Interestingly, the computerized interpretation managed to pick up the infarction.
From that same Facebook group we got another great LBBB anterior STEMI via Paul Halsey.
Heading over to the Twitter-verse, emergency physician Patricia van den Berg shared this awesome subtle “high lateral” STEMI—a diagnosis she made alone, in the middle of the night, when you really don’t want a false-positive activation. If you’re interested in more info on high lateral STEMI’s and why they look the way they do, I might suggest my own approach to the topic, located here.
Sticking to Twitter, cardiac electrophysiologist Janet K. Han, MD shared not one, but two cases of atrial flutter recently referred to her as “persistent sinus tachycardia.” Remember: sinus tachycardia will vary by at least a few bpm depending on the patient’s activity, positioning, treatment, mood, etc… If the monitor is stuck at one particular rate for 10+ minutes, strongly consider a non-sinus arrhythmia (usually flutter). I’ve collected more tips for spotting subtle flutter over here.
We’re not done with Twitter! Interventional cardiologist Dr. Eitan Friedman shared this uncommon rhythm. If you know the pattern it’ll take you 10 seconds to spot the diagnosis…
Well if you got the last one you’ll get this one too. Rajagopal Ramaswami shared another manifestation of that same rhythm over in the EKG Club on Facebook.
I’m a sucker for dynamic acute coronary syndrome (ACS) so I love this case from Blake Bradley, NRP over on Twitter. Over 17 minutes his patient’s ECG evolved from subtle hyperacute T-waves in the inferior leads (superimposed on some diffuse subendocardial ischemia) to a full-blown obvious infero-posterior STEMI.
Shane Long was taking care of a patient with chest pain and a subtle anterior STEMI (check out that computerized interpretation)…
…when suddenly the patient went unresponsive. Whoops, that’s VF! One shock get him out of it. Don’t forget, even STEMI’s with only mild ST-elevation still carry a significant risk of sudden cardiac arrest.
Our last case was shared by Dr. Iliyas Sheikh in the EKG Club on Facebook. A routine EKG was performed on a 60 year old male:
If this patient had presented with acute chest pain our first thought would by hyperacute T-waves from an anterior STEMI, but it turns out this is just a normal variant in a patient with no acute symptoms.
For a similar ECG with more discussion check out this tracing from Dr. Smith’s ECG Blog. Thank you to EKG Club member Bartosz Kuczyński for finding this similar case!
I hope you find the cases interesting and take the time to check out the links to their original posts. Look forward to our next installment of the ECG Mixtape series returning… sometime soon!