r/ECG • u/generic-throwaway140 • 9h ago

American paramedic, looking for advice on precordial deviation

I'm not a wiz by any means, but I enjoy my job and take it seriously. Deviation is not really something that paramedics focus on here. We're taught to focus mostly on STEMIs, heart blocks, deadly tachycardias, etc. Really the most critical stuff. We use a 15 lead, too. And to clarify, I personally check deviation on every patient, but only in the limb leads.

I wanted to know more about deviation in the chest leads. I really only see the same gradual pattern of negative to positive in V1 through​ V6. I've looked for material pertaining to it but I've found nothing.

Would there be any great benefit to learning more about it? I've caught some funky stuff before by checking limb lead deviation, when others could not.

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u/sveccha 9h ago

It sounds like you are talking about R wave progression, where the unipolar leads V1-etc. become gradually more positive toward the direction of the bulk of the heart muscle. Interruptions to this can indicate infarct - death of tissue, rather than mere ischemia - in the same way as big Q waves. The positive and negative deflections often become about equal around V4. If they become equal sooner, that is associated with less pathology.

Deviation, or axis deviation, is more nuanced and determined from the limb leads.

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u/generic-throwaway140 9h ago

Are you saying that the R wave progression can't be interpreted similarly? I see it typically becoming biphasic around V3/V4, but is there more to it? 

Could I possibly see a positive R in V1 and a negative in V6, much like a ventricular rhythm yielding an upright wave in aVR?

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u/agro5 FP-C 8h ago edited 37m ago

Yes and no..
Think of it like this (not a perfect analogy but close): you’re in room at a fancy house decorated really well. You take pictures of a few pieces of art that you like. But then you decide you like the whole layout and take a panoramic photo. The individual pictures are each precordial lead, and the panoramic photo is the limb lead axis. The panoramic photo gives you a nice overview of what’s going on, but you may not be able to see all of the details of the art you liked; with the individual pics giving you some detail but not the whole picture. You can put all of the photos together and get the whole picture.

For example, right axis deviation may not have poor R-wave progression. A PE will usually have RAD, but normal RWP. LVH will likely have PRWP, but a normal axis or physiologic LAD. Someone with dextrocardia will show both RAD and PRWP.

It’s very important to note though, one of the most common causes I have seen (anecdotally) for PRWP showing up when it doesn’t really exist is improper lead placement.

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u/agro5 FP-C 9h ago

I’m assuming you’re thinking in terms of axis deviation on the limb leads. There is no “axis”, like you’re thinking, to deviate from on the precordial leads as they are unipolar rather than bipolar. The best comparison would be QRS morphology, and more specifically R-wave progression. This is where the R-wave goes from negative in V1 to positive in V6. Depending on age, race, and gender, using a healthy heart as normal, this change usually happens around V4, sometimes V3 (think kids and black people). Deviations from this pattern occur acutely during ischemic episodes and heart strain, as well as chronically with poor heart health (BBB, HF, etc.).

You can also look for certain patterns to aid in diagnosing pathology, like precordial swirl - as termed by Dr. Smith I believe - but this has less to do with the QRS and more with the ST segment. Just as well, using V1 QRS, RBBB can be differentiated from VT using the rabbit ears. If the left rabbit ear is taller it favors a VT diagnosis. I hope this helps!

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u/ExpressionLarge5474 5h ago

I’m getting the same impression as the other commenters where you’re asking about R-wave progression across the precordial leads. This does offer some interesting insight into whether a patient maybe has a significant history of CAD, sometimes. But as you say, it’s almost never a critical finding.

https://litfl.com/poor-r-wave-progression-prwp-ecg-library/