I have been studying various articles for 2 days now on this subject. I have not run across this issue in the field yet. It appears that ERAD with a positive R wave in V1 is very reliable. Also a axis of -91 to -180 as well. I have read a bit on Brugada criteria as well but need to do some more work on that one.
What method do you use?
Thanks for your help...
Axis is useful to
rule in VT,
but useless to rule out VT.
Concordance is useful to
rule in VT,
but useless to rule out VT.
Fusion and capture beats are very useful to
rule in VT...when or if you see them.
AV dissociation is relatively useful to
rule in VT. Whether or not it is easy to discern this in the field is what makes it only relatively useful.
Rate is horrible at ruling in or ruling out VT.
Although VT is much less likely >220-240.
Brugada's criteria is relatively useful to
rule in VT. The steps pose some practical concerns in the field, unless you're inhuman at memorizing the morphological criteria. It seems fine when used retrospectively, although the morphological criteria seems to get some intraobserver differences.
Vereckei's original aVR criteria (initial monomorphic R-wave; initial r- or q-wave >40ms; notching in the downstroke of negative QRS; Vi/Vt <=1.0) is relatively useful to
rule in VT. The final step is very impractical in the field, unless you're crazy inhuman. It is harder than Brugada's to use retrospectively.
Vereckei's updated aVR criteria (AV-dissociation; initial monomorphic R in aVR; strange BBB morphology; aVR Vi/Vt <=1.0) is relatively useful to
rule in VT. The updates are better than his original, for sure, but the final step is still very impractical in the field, unless you're crazy inhuman. It is harder than Brugada's to use retrospectively.
Sasaki's criteria (initial R in aVR; longest RS >100ms; initial r- or q-wave >40ms) is relatively useful to
rule in VT. It is the most practical of the "measuring" algorithms, but still less practical in the field.
R-wave Peak Time >50ms is relatively useful to
rule in VT...if you're mildly inhuman.
Ultimately, you really need to be concerned when you try to
rule out VT during a wide complex tachycardia. Dr. Ken Grauer enjoys preaching the following as the top 10 causes of a WCT:
- VT
- VT
- VT
- VT
- VT
- VT
- VT
- VT
- SVT with Aberrancy (of which for rates <160 is probably sinus tachycardia)
- Accessory Pathway (antidromic AVRT)
My personal algorithm in the field (wide and fast is VT until proven otherwise):
- If +aVR -> VT
- If QRSd >140ms and intrinsicoid deflection is grossly slurred -> VT
- If fusion/capture/AV dissociation/concordance -> VT
- If patient has Hx of MI/CHF/AICD -> VT (but for CHF go to sinus tachycardia search)
- Search for evidence of sinus tachycardia if rate <220-age, clinical picture fits, and textbook LBBB or RBBB is present
- If rate is ~150 consider atrial flutter
- If at this point, IVCD -> VT
Which translates to:
- If able to get a line and reasonably comfortable with patient's status, attempt adenosine if we didn't immediately think VT
- If QRSd <170ish procainamide, otherwise lidocaine (or if STEMI/ischemia suspected as cause, lidocaine first line)
- Otherwise cardiovert
