"Diagnostic Quality" of a 12 Lead compared to a 3

[AZCEP]

I would say no, you can't make that diagnosis base only on 2 leads. Personally I would but more stock in your clinical assessment of the patient's presentation, in particular the history to help you make a decision. If you see ST changes in lead II or III it would highly elevate your suspicion but I don't think you can definitively diagnose STEMI.

Why would you not be able to diagnose an inferior MI with these changes?

Two contiguous leads--check

Diagnostic spectrum--check

MI identified

Would it be good to have the other 10 leads, 9 if you discount aVR as you should? Yes, but you could still use the information you have.

[Stretchermonkey]

Over here in Blighty (specifically in the East of England Amb Service) we use Zoll 'M' series ECG machines, to diagnose and thrombolyse in the pre-hospital arena.

Because a 12 lead ECG gives a more comprehensive view of different aspects of the heart, one can look for and assess reciprocal changes in the leads opposite to those with the S-T elevation. Having the 12 lead view is also essential to diagnose LBBB. With LBBB being present, is it almost impossible to certainly diagnose an STEMI, due to the corruption of the ECG caused.

However, even with a 12 lead ECG it will not show a posterior MI. I place the chest leads posteriorly to obtain the view differently to look for a posterior MI, if I suspect one is present from what I see in the standard 12 ECG. I spend time doing this on scene, as I can thrombolyse there and then, if an MI is present.

What I would question is why would one want to spend time on scene using equipment that can not definitively diagnose an STEMI, rather than get the pt to a place that can. Studies have shown that for every minute the MI progresses, 11 days of life expecantcy is lost. Our aim is to resolve the MI asap. Before the introduction of pre-hosp thrombolysis, all pt's presenting with chest pain, believed to be of a cardiac origin, were transported to hosp with lights and sirens and a pre-alert to the receiving hospital given.

If it looks like an MI, smells like an MI & sounds like an MI...it is an MI until proved otherwise. If one can't disprove it on scene without delay, go to somewhere that can.

[Asysin2leads]

Here's what I know about doing a 12 lead, besides put the leads here, here, and here and push the button. In 12 lead mode, the monitor (for sake of arguement I use a Lifepak 12), uses more sensitive filters than in a 3 lead, that's why often it bitches at you that there is "noisy data", because artifacts it doesn't pick up in 3 lead mode it does pick up in 12 lead mode. So, the 12 lead mode not only gives you more views of the heart but it also gives you a more accurate, and some would call "diagnostic" views of the electrical activity of the heart. To be perfectly frank, however, no cardiologist in his right mind would use a field 12 lead to make a positive diagnosis. I guess you could call the 12 lead mode a "presumptive diagnostic mode."

I can say, from a couple of experiences, there is a notable difference between the 3 and 12 lead mode. If you have the 12 lead hooked up, on a lifepak 12, you can still look at V1,V2,V3,V4 etc. by adjusting the lead setting in 3 lead mode, which is useful if you want to track a change in anyone of those leads. However, because it is not using the filters of the 12 lead mode, it does not give you a fully accurate depiction of the lead it is displaying. A couple of cardiac patients I have had hooked up to the monitor showed 'ugly' ST elevations in various leads in 3 lead mode that would not appear when a proper 12 lead was done. I've saved a couple of them and I'm going to see if I can harrass a cardiologist or other 12 lead know it all about the nuts and bolts of why this is, I'll give you an update when I get one. Hope this helps.

[Stretchermonkey]

however, no cardiologist in his right mind would use a field 12 lead to make a positive diagnosis. I guess you could call the 12 lead mode a "presumptive diagnostic mode."

Our local recieving hosp uses the same ECG machine as we do on our ambulances...hence why we thrombolyse on scene.

[MrSpykes]

I was taught that a three lead has a built in filter so that the QRS is in better focus and the P wave, T wave, U wave, ST elevation and artifact is filtered. So certain things may or may not show up in a three lead. Conversely in a twelve lead there is not a filter like that so you get a true P wave, T wave, U wave, ST elevation or depression, and artifact. Hence, when obtaining a twelve lead it is suggested to not have the truck in motion. So if you see ST elevation in leads II, III, and AVF in your three lead you then do a twelve lead you may find absolutely no elevation in any of the leads. Three lead is great for monitoring a pts rhythm. A twelve lead is gonna give you a better picture of the heart to look for ischemia and infarction.

[mobey]

The real question is should you be diagnosing an MI on a III lead as a basic? If pt is presenting an MI treat an MI. From what I have been taught ST elevation can be an indication of myocardial ischemia, but not a for sure thing (it could be old infarct for all you know). For the most part you should not need a monitor to tell you if your pt. is ischemic anyway.

[JPINFV]

The real question is should you be diagnosing an MI on a III lead as a basic?

Occupation: nearly PCP'd

Patrick

EMT-B

Paramedic Student

Pot meet kettle. Kettle meet pot. :roll:

[buddha]

Sorry mobey, but you need to attend a few more classes. According to accepted standards, ST elevation greater than 1 mm in two or more contiguous leads = STEMI, pure and simple. The ST elevation will normalize within 24 hours post MI, and often you are left with a pathologic Q wave that indicates an old infarct. Our regional chest pain protocol relies on this criteria to determine patient destination. In short, a 12 lead is performed on all chest pain patients (or any other patient suspicious for AMI). The 12 lead gets sent to the hospital for MD review. Patients without ST elevation or presumed new onset LBBB go to the local facility. Protocol dictates that those patients with ST elevation greater than 1 mm (in 2 contiguous leads) or new LBBB go directly to the nearest cath lab. Our 12 leads must be good enough for the cardiologists, because we often wheel these patients right into a lab.

ST Depression = ischemia.

[canuckEMT]

K I may have missed it in the thread, but I didn't see anyone mention checking MCL 1 for reciprocal changes which would also heighten your suspicion for infarct with a 3 lead monitor. Although it can't confirm like in a 12 lead, still would be evidence enough to start on the CP protocol and administer 160mg ASA. As well as being able to make an ALS rendevous (if applicable to transport time) or give to the recieving physician.

[mobey]

Accepted standards??

This must be a US/Canada thing.

I double checked with a few instructors and they said (in canada at least) we do not definitively diagnose an MI in a ambulance on a 3 lead. especially when the person asking is a basic. It is a tool for diagnosis but that is all. And really do we want basics to start treating an MI without other symptoms just based on a 3 lead?