Differentiating aberrantly conducted SVT from VT

It's VT if see:
- sinus capture
- fusion
- wiiiide QRS
- V-A conduction (aka AV dissociation)

Also, if the pre-tachycardia QRS complex is narrow then you can use the following criteria, depending upon whether you see a RBBB or LBBB:

RBBB: "ladders"
- LAD
- R>S in V1,
- S>R in V6

...this kind of VT is the one that occurs in structurally normal hearts and is precipitated by exercise.

LBBB: "Q6R1"
- Q6, R1>40msec duration and 70msec from onset of R wave to nadir of S wave (partially because there has to be notching of the downstroke of this S1)


There is also the Brugada way of doing things: "Brugada's absent RS and long RS rule"
1. Is there any praecordial lead that does not have an RS complex?
If they all have RS complexes, go on to:
2. Measuring the distance from the onset of that R to the nadir of the S - if it is >100msec, it's VT.