Why capture a 12-lead ECG with the first set of vital signs?

If for no other reason, because MONA can “clean up” a 12 lead ECG, making it non-diagnostic by arrival at the hospital!

Before MONA

After MONA

If not for the prehospital 12 lead ECG, there’s no telling how long this patient would have lingered in the emergency department!

*** Update ***

Here’s another case (from several years ago) that helps illustrate the point.

This was from a chest pain patient who was transported to my jurisdiction from a neighboring EMS system by boat.

Image credit: Wikipedia (Jeff Morgan www.findparadise.com)

In other words, it was an EMS transfer. We met them at the dock and took the patient to the hospital.

Here is the ECG that was handed to me by the transferring paramedic (who recognized it was showing acute inferior STEMI).

I’m pretty sure it was recorded by a LP11.

You’ll notice that part of the computerized interpretation came off when I peeled back the scotch tape.

Here is the 12 lead ECG I captured en route to the hospital (using the exact same electrodes).

The ECG had become nondiagnostic.*

I’d love to tell you that the (first) prehospital 12 lead ECG saved the day. It didn’t. I personally showed it to the ED physician, but he was dismissive. No urgent action was taken.

I have no idea what ended up happening to the patient.

* Note: You can still identify acute inferior STEMI in the second ECG by the Q waves and non-concave ST segments in leads III and aVF, along with the downsloping ST segment in lead aVL. However, it’s the first prehospital 12 lead ECG that really tells the tale!


  • Second ECG could pass for BER. Very short and sweet post, but gets straight to the point. The point of pre-intervention 12-leads has been pressed pretty hard to my agency.

  • Interestingly, though, the Hospital 12-lead computer interpretation is still indicating an Anterior Infarct. Neither computer interpretation identified a STEMI. I would be very interested in seeing a repeat 12-lead from the Lifepak 12 (instead of the hospital EKG) to see how "cleaned up" it got by the end of the transport. (It just seems easier to compare 12-lead tracings from the same type of device…) Knowing hospitals they probably also used a slightly different electrode placement by ripping everything off and placing their alligator clips on — and some of the tech's I've worked aren't as careful as they probably should be with electrode placement.This particular topic of "no treatment (even O2) before 12-lead" is really interesting to me because I haven't found any studies suggesting that pre-intervention 12-leads can cause a STEMI to become non-diagnostic. (For the prehospital setting it's so new to be aggressive with 12-leads so I'm not surprised there are no studies…yet.) We've been teaching "Nitro can't unclog an artery" and "Nitro's vasodilation effects have yet to demonstrate survival"…but if Nitro can change a 12-lead these it sort of muddles my knowledge about the pathophysiology of STEMI.

  • Tom B says:

    Adam – You're right. It could pass for BER. Unless, of course, you're familiar with Dr. Smith's decision rule! :)The Q wave in lead V3 is also a disturbing finding, along with the upwardly convex ST segment in lead aVL.One thing I found particularly interesting (in addition to the resolution of the hyperacute T waves) is the disappearance of inferior reciprocal changes.The ST segments in II, III, and aVF went from flat and sagging to having a normal take-off.Tom

  • Tom B says:

    MIFL – I was also surprised the GE-Marquette 12SL interpretive algorithm did not give the ***ACUTE MI SUSPECTED*** message for the prehospital ECG in question.I've seen it call more subtle ECGs than that! This was the second prehospital 12 lead ECG in the series. Maybe one of them gave the ***ACUTE MI SUSPECTED*** message. I don't remember.Most of the time, the nurses (or techs) will utilize my precordial electrodes when I'm done with them, but I'm very meticulous with skin prep and lead placement. I can't speak for the other paramedics (although poor lead placement is certainly not limited to EMS).I have seen a study (from Hennepin County, MN) that shows several cases of resolved ST segment elevation by arrival at the hospital. I'll see if I can find it for you.Tom

  • You're right. It could pass for BER. Unless, of course, you're familiar with Dr. Smith's decision rule! 🙂But of coarse; I meant to the novice it could pass for BER. That is a great blog though. I hadn't known that rule prior to reading that post. Referencing to MIFL's comment. Will O2 alone possibly return the ST segment to isoelectric? Physiologically I can see that hypersaturating the cells may reduce the ischemia, but I have never heard of O2 reducing elevation, just nitrates.

  • Tom,I would love to read that study. Thanks for letting us know it's out there.Hey Adam,I've had some of the clinical educators inform us that a "12 lead should be done even before oxygen and aspirin", but honestly I don't believe that. I think they might be accidentally taking the extreme of the term, "Pre-intervention 12-lead" to mean absolutely nothing before the first 12-lead. I suppose I understand that nitro can reduce ST elevation, but I have two thoughts:- There is a patient population involving STEMI that has cases in which a STEMI resolves by itself. Knowing this, can we really say it was the NITRO that cause the ST elevation to return to normal…or would it have happened regardless? The only real way to test this properly is through a double-blind placebo study, but I doubt a study will be conducted for this. – While I can understand that Nitro can decrease the amplitude of ST Elevation, I'm still waiting on firm research that indicates that nitro can get rid of all the ST elevation together. I have always thought that Nitro is NOT reperfusion therapy (despite what some medics might thing) but if nitro did get rid of all ST elevation than perhaps my thinking is wrong…Love this discussion by the way!!!

  • Scott T says:

    As for the STEMI that resolves to nitrates i had one today. Elevation (tombstoning) V1 – V6. and after oxygen, two nitro spray and an aspirin the pt was pain free with no elevation -NONE. Cath lab activation, PCI, Cardiologist said this TSTEMI (transient STEMI) was probably caused by a clot or cornoary artery spasm (in an already heavily calcified area…it was proximal LAD)- hence resolved by vasodilation. Really interesting case.I had never heard of a TSTEMI before this case (and had never been in a cath lab!!).

  • Tom B says:

    @Adam – I don't know if oxygen alone could do it. I suppose that depends on a variety of factors, including the stage of the clot, coexisting coronary vasospasm, collateral circulation, SpO2 prior to oxygen, etc. I don't know if it's possible to hyperoxygenate cells. Sounds like possible narrative fallacy to me! :)@MIFL – No problem. It might have been an abstract at a conference. I think I have something about this study on my computer at work. A supervisor from Hennepin County EMS co-moderates the E2B listserv, so if I can't locate the study, I'll ask him where to get a copy! As far as I know, they still cath these patients, and they still find obstructive lesions in epicardial coronary arteries.@Scott T – Cath labs are cool, aren't they? That sounds like an awesome case! It would be a great opener for your blog! :)Tom

  • Brian T says:

    Tom-Might it make sense to record posterior leads when trying to distinguish between BER and Anterior STEMI? My thought is that posterior reciprocol changes might be evident in the setting of anterior STEMI while they won't be in the setting of BER.

  • Tom B says:

    Brian – That's a fascinating thought, and I'm going to try it next time I have an acute anterior STEMI! Tom

  • Brian T says:

    Sweet. I'll try it as well and let you know if I find anything interesting…..

  • Tom B says:

    MIFL – Please shoot me an email.ems12lead.blogspot.comTom

  • Protoman2050 says:

    This is really late, but ScottT, a condition called Prinzmetal's angina can cause ECG changes exactly like an AMI, included cardiac enzyme elevation, but resolves immediately with nitroglycerin. http://en.wikipedia.org/wiki/Prinzmetal%27s_angina

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