This is not an easy thing to do. The source of the wct is from outside the normal Sa- avn - his purkinje system. In both VT and wpw avrt anti d, the source is from a nidus outside this system and in the ventricle.
The following rules were developed knowing that it is an imperfect science. Wpw avrt ant d occurs in 6% of wct. It should be considered in patients without structural
Heart disease or the common risk factors for VT ie ischemia and cmo.
Look at V4-V6
If all qrs complexes r negative = VT likely
If positive , look for qR in V2-6 , if present = likely VT
If not - look for av dissociation - If present = likely VT
If none of above is present, consider wpw avrt antidromic circuitry
Do not give adenosine or any drug that could block the av node.
DC cardio version synchronized in a well patient 100J or unsychronised in a ALOC patient is the treatment option if wpw antidromic avrt is considered.