Is it VT?

Absence of typical RBBB or LBBB morphology.

Extreme axis deviation (“northwest axis”) — QRS is positive in aVR and negative in I + aVF.

AV dissociation (P and QRS complexes at different rates).

Capture beats — occur when the sinoatrial node transiently ‘captures’ the ventricles, in the midst of AV dissociation, to produce a QRS complex of normal duration.

Fusion beats — occur when a sinus and ventricular beat coincide to produce a hybrid complex of intermediate morphology.

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.

Brugada’s sign – The distance from the onset of the QRS complex to the nadir of the S-wave is > 100ms.

Josephson’s sign – Notching near the nadir of the S-wave.

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.

 Very broad complexes (>160ms).