When sinus rhythm is the underlying rhythm, identification of P waves and their relationship to the wide complex beat(s) is the single most important means of differentiating beats originating in the ventricles from those originating in the atria or AV node but conducting aberrantly. Examine these two simultaneously recorded leads from the same ECG and decide which of the wide complex beats are ventricular in origin and which are supraventricular but conducted aberrantly.