Your patient is a 38 yo man who presents with palpitations.
So, is it VT or SVT with aberrant conduction due to bundle branch block vs SVT with aberrant conduction due to an accessory pathway (i.e. WPW)?
If the patient is unstable always treat as VT.
If in doubt, treat as VT.
If you have time to think, you can use the Brugada criteria – features that increase the likelihood of VT are:
– Absence of typical RBBB or LBBB morphology
– Extreme axis deviation (“northwest axis”) – QRS is positive in aVR and negative in I + aVF
– Very broad complexes (>160ms)
– AV dissociation (P and QRS complexes at different rates)
– Capture beats — when the sinoatrial node transiently ‘captures’ the ventricles, in the midst of AV dissociation, to produce a QRS complex of normal duration
– Fusion beats — when a sinus and ventricular beat coincides to produce a hybrid complex
– Positive or negative concordance throughout the chest leads, i.e. leads V1-6 show entirely positive (R) or entirely negative (QS) complexes, with no RS complexes seen
– RSR’ complexes with a taller left rabbit ear – this is the most specific finding in favour of VT. This is in contrast to RBBB, where the right rabbit ear is taller
Also very useful is the Vereckei sign – look at the QRS complex in lead aVR:
– a dominant initial R wave in aVR is indicative of VT
– a dominant terminal R’ wave in aVR (i.e. following a Q/S wave) is more likely SVT with aberrancy (also commonly seen in TCA poisoning)
I attach a copy of the Vereckei algorithm which I find pretty straightforward.