Yes but does RBBB with Left axis deviation mean anything and should under any circumstance you activate the cath lab?
Follow your protocols. If you protocols completely leaves it up to you, I would only activate the cath lab if it is a clear cut STEMI no questions asked. If it is not an obvious STEMI, do not activate the cath lab.
I feel like you are over thinking this. A STEMI can cause axis deviation, but axis deviation doesn't mean it is a STEMI. Normal axis doesn't rule out STEMI either. I do not use the axis to determine if it is a STEMI or not. I primarily look at ST and T wave changes in regard to STEMI. Is it elevated or depressed? What kind of morphology does it have? Are there reciprocal changes? I will consider the axis too, especially for anterior and posterior wall MIs. When I see late R-wave progression and subtle ST elevation in the anterior leads, red alarms will be going off for anterior wall MI. When I see early R-wave progression eg V1-2 already have decent size R-waves with ST depression in the anterior leads, I will seriously consider the possibility of a posterior wall MI. Look at the whole ECG and the patient.
Give away with STEMI mimics are the T-waves/ST changes are discordant with the terminal or mean of the QRS wave. I also apply the 0.2 rule I mentioned earlier. I know what STEMI-mimics look like too.
Left ventricular hypertrophy is the #1 mimic. Use sokolow voltage criteria or cornell's critieria. May have ST elevation without ST depression and T-wave changes. May have ST elevation and depression "strain patterns" throughout the ECG.
Left Bundle Branch Block. Look at I, V1, and V6 like I said. The ST changes and T-waves should be mostly discordant (exception of V5-6 like I said, which has caused confusion for me in the past).
Ventricular paced rhythm. Smith-sgarbossa criteria I think haven't been studied on this or something like that, but people apply it anyway. Pacer spikes may not be easily visible.
Pericarditis, although I think people over diagnosis this. ST elevation with no ST depression throughout the ST elevation. Pericarditis and wrap around type III LAD occlusion may look similar. Be careful!
I don't consider RBBB to be a STEMI-mimic even though Brandon's website listed it as one.
Ventricular aneurysm will get me sometimes... Apply the 0.2 rule. 0.36 may be better if you are willing to do the math. Morphology may look like a STEMI. I think this one can be hard to tell sometimes and easily look like a STEMI. In the heat the moment, I would probably activate these patients because at a glance they aren't that easy to tell in my opinion.
Benign Early Repolarization (BER) is another common STEMI-mimic. There should not be any reciprocal changes and consider the excessiveness of the ST elevation. The ST elevation is usually very very very little. I find this more common in young patients.
Anyhow... know what the STEMI mimics look like. Know what to look for. Axis isn't one of them. Axis can help support finding a STEMI (I find it most useful for anterior and posterior wall MI rather than the MIs you seen in the frontal axis), but does not rule in or out a STEMI. Look at the ST elevation/depression compared to the R and S wave of the QRS complex, morphology, concordance/discordance of ST/T changes, and look at the patient too when you get a chance.
Like I said, RBBB + LAD could be a bifascicular block. LAFB = pathological LAD. I would not worry about it unless the patient was symptomatic and as a paramedic there isn't anything you can really do for this patient other than treat the symptoms and transport. I would not activate that cath lab for a bifascicular or trifascicular block because those aren't STEMIs.
