The Differential Morphology of Anomalous Ventricular Complexes of RBBB-Type in Lead V 1

Abstract

The distinction between ectopic ventricular beats and aberrant ventricular conduction (AVC) is of practical diagnostic and therapeutic importance; but the differentiation can be difficult or impossible, especially in the presence of tachycardia or atrial fibrillation. Since the great majority of aberrant beats show a right bundle-branch block (RBBB) pattern, this study is restricted to anomalous complexes showing or simulating RBBB in lead VI. The morphology of 3 groups of anomalous ventricular complexes has been analyzed for empirical differences: 1) 50 early supraventricular beats showing AVC of RBBB form, 2) 100 examples of fixed RBBB 3) 100 ectopic ventricular beats showing a "RBBB" contour 70% of the aberrant beats and 67% of the RBBB records showed a triphasic (rsR[image], rSR[image], or rsr[image]) pattern, whereas only 6% of the ectopic ventricular beats were triphasic. Most of the remaining complexes in each group were monophasic (R) or diphasic (qR, QR, qu, or RS). Of the aberrant beats 44% showed aninitial 0.02 vector identical with that of the associated normally conducted beats, whereas only 4% of the ectopic ventricular beats showed an apparently unchanged initial vector. One may therefore conclude that (1) triphasic patterns in VI favor the diagnosis of aberration, whereas monophasic or diphasic patterns to a lesser extent favor the diagnosis of ventricular ectopy; and (2) although a changed initial vector is of little value in distinguishing between ectopy and aberration, an identical initial vector provides strong evidence in favor of aberrant conduction.