Ventricular rhythms have wide QRS complexes (>120 ms) that arise from ectopic impulses outside of the normal conduction system. Ventricular rhythm exists if 3 or more consecutive beats are of ventricular origin. Look closely in all leads (especially V1) for atrial activity. There should be no P waves or any P-QRS association.
Ventricular rhythms by ventricular rate:
If the ventricular rate is < 120, don't treat as VT and consider the following mimics: AIVR, hyperkalemia, & sodium channel blocker toxicity