WCT - VT or Aberrancy?

Image 1-  ECG case

A 65 yo with history of HTN admitted due to aortic aneurysm.

Is this VT or aberrancy? Why?

Image 2 - ECG case marked

It is indeed difficult to tell with certaintly the difference from ventricular tachycardia (VT) and aberrant beats using rhythm strips. The famous Brugada algorithm used the 12lead ECG. It is wrong to use the ventricular rate to descriminate VT from aberrancy bec the rates overlap. 

V1 can be used on the assumption that V1 is on the right location (4th right ICS parasteral line). However, in reality most V1 are placed in the wrong spot.

Wide QRS tachycardia WCT) can be generally grouped into right bundle branch block (RBBB) or left bundle branch block (LBBB) morphology. This is based on the termial deflection of V1. A LBBB WCT is one with a terminal negative deflection in V1 and RBBB is then a positive

terminal deflection.

The presented case is a RBBB WCT. It has the "Rabbit ears" R>R' (blue arrow). This morphological criteria is part of the Wellen's criteria for RBBB VT. 

Another feature that can be seen here is a fusion beat (red arrow). This is highly diagnostic of VT. Those complexes are a blend of 2 sources.

Based on those findings (Rabbit ear RBBB and fusion beats), we can say that this WQRST is ventricular tachycardia.

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