Initial vectors of ventricular premature beats and anterior fascicular conduction defects

Vectorcardiographic studies on ventricular premature beats (VPBs), occurring in records wherein the sinus beats were associated with an intraventricular conduction defect attributed to anterior fascicular delay or block, did not identify the exact site of a presumed reentry mechanism. The hypothesis that the orientation of the initial vectors of the VPB might reveal either anterograde or retrograde emergence from the anterior fasciculus with a reentry PVB was not strongly supported, although one or the other mechanism was compatible with the early vectors of certain VPBs. The VPBs revealed greater angular change on the spatial orientation of sequential early vectors (5-10-15 milliseconds) than occurred in sinus beats. Recurring VPBs, which appeared to casual visual inspection stereotyped in form, showed considerable variation in the orientation of the early vectors, indicating, in the cases studied, that VPBs, in the strictest sense, may be associated with difering initial entrance pathways to the myocardium and thus may be 'multiform'.