Rapid Prehospital Evolution of STEMI

82 year old male, in good physical shape, stops at a cafe for lunch after cycling for an hour. Witnesses report a syncopal episode lasting approximately 30 seconds. Patient history significant for prior MI requiring 3 stents. No other significant history.

Patient denies any CP, SOB, N/V, lightheadedness. In fact, he denies any complaints at this time, and questions whether or not he should just go home. You do ask whether his cool, soaked shirt was the result of his workout, and he says no.

 

Here is the ECG1 acquired on scene (T-0):

ECG2 acquired enroute (T+9):

 

ECG3 enroute (T+16):

 

 

ECG4 Hospital arrival (T+21):

 

At no time during ECGs 1-3 was the patient symptomatic. Unsurprisingly, at the time of ECG4 at the hospital, he was feeling markedly worse.

What changes do you see between ECGs 1 and 2?

In the span of only 21 minutes, the ECG evolved very subtly from non-specific to full blown STEMI.

Perform serial ECGs, especially on high risk patients, and scrutinize the 12 lead for subtle changes. In the field, we have ample opportunities to obtain them. They are not costly or invasive, and may greatly improve the outcome of our patients. 

See more on this case at DrSmithsECGBlog

 

Triaging Triage ECGs

I’ve spent nine years working in an emergency department, which means I’ve also spent nine years performing electrocardiograms at triage. With a couple thousand waiting-room ECGs under my belt, I’ve noticed a few things:

  • A lot of ECGs are ordered at triage.
  • Many of them are performed on low-risk patients.
  • Very few of those ECGs lead to a change in initial management.

Oh, and one more thing:

  • Most physicians hate signing triage ECGs.

I can’t say I blame them. Triage ECGs interrupt their workflow and, worse than just slowing them down, that distraction can lead to errors. As an additional frustration, these patients often end up being seen by a different doctor in the department, and no one likes making diagnostic or treatment decisions that another provider will have to deal with. Plus, if the signing physician does happen to find something wrong, there’s always a nagging concern that the patient will end up being added to their already full group and need to be seen immediately—further interrupting flow.

Triage ECGs bring work and distraction.

So it’s understandable why many emergency physicians are rejoicing at the publication of a new study by Hughes, Lewis, Katz, and Jones: “Safety of Computer Interpretation of Normal Triage Electrocardiograms” [1].

Below are some great opinions on the article from the target demographic: emergency physicians.

They’re all well thought-out posts with perfectly reasonable conclusions. Dr. Salim Rezaie and Dr. Anand Swaminathan from R.E.B.E.L. EM also make it clear that they wouldn’t want to eliminate physician over-reads of “normal” triage ECGs, just delay them to reduce interruption.

My only issue with that approach is that the emergency physicians I’ve work with are always busy. Whether they read a triage ECG now or in fifteen minutes, they’re going to be doing something when I try to slide that paper in front of their screen.

As the only tech at triage, I’ve also got somewhere between one and thirty patients out in the waiting room, so if I don’t get that ECG signed right after it’s performed, I’ll get distracted myself and occasionally forget. It’s a lose-lose situation.

Maybe it’s just the practice at the hospital I worked at, but I think we’d make more progress at reducing interruptions by investigating a stricter triage protocol for ECGs. Though the rate of “normal” ECGs in this study was 26%, in my experience it’s somewhat uncommon to see a tracing with the words “Normal ECG” printed at the top in the ED (I’m just making this up, but I’d guess something < 10% at triage).

It’s not the “normal” ECGs that are weighing on my physicians.

I believe a bigger burden comes from ECGs that are read as “abnormal” in some way by the computer but were not indicated in the first place and do not change the patient’s management in the waiting room. If we could cut back on the number of triage ECGs that are performed on low-risk patients with non-cardiac complaints, I think that would make a bigger dent in reducing interruptions.

But I digress…

While seeing the computer spit out “Normal ECG” certainly stratifies a patient as lower risk, it’s not the same as “no risk.” That’s a problem, because triage ECGs are (or should be) performed in a moderate-to-high risk population with complaints suggestive of an acute cardiac process. In that cohort, the negative LR suggested by this study won’t “rule-out” concerns as well as it would in a general ED population getting ECGs as part of their routine workup.

As Dr. Steve Smith summarizes in his post on the topic, “Computer algorithms that make the diagnosis of ‘normal’ are usually correct, but is usually good enough?”

We don’t have an answer, and I don’t expect to make any headway on that issue with this blog post, but I thought it would be interesting to share a few subtle STEMIs from my collection that were read as normal by the computer.

It’s not data, and certainly not scientific, but it’s interesting (to the folks who like ECGs, at least).

Enjoy!

 

References

  1. Hughes KE, Lewis SM, Katz L, Jones J. Safety of Computer Interpretation of Normal Triage Electrocardiograms. Acad Emerg Med. 2017;24(1):120-124. doi: 10.1111/acem.13067

ECG Mixtape: Vol. 2

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:

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: [1] [2] [3] [4] [5] [6] [7] [8] [9] [10]

 

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!