The vectorcardiogram in left ventricular hypertrophy: A study using the Frank lead system

Abstract

In this report, we have presented the vectorcardiographic findings in a group of 24 adult patients with left ventricular systolic overload. The Frank lead system was used. The results indicate that left ventricular hypertrophy may be associated with significant changes in the initial, intermediate, and terminal forces of the QRS tracing. The magnitudes of the spatial Q and R vectors were increased. The terminal portion of the tracing was straight, without producing an S loop. The Q vector was directed inferiorly, in contrast to normal, and the R vector was displaced posteriorly. There was delay in inscription of the R loop, and QRS duration was prolonged. The above-noted alterations of the QRS loop in left ventricular hypertrophy have been discussed in relation to our present understanding of the anatomic and electrophysiologic sequelae of left ventricular enlargement. Twenty-nine per cent of the patients in this study demonstrated loop characteristics which suggested incomplete left bundle branch block. These changes consisted of (a) leftward initial forces, (b) extreme posterior displacement and delayed inscription of the R loop, (c) clockwise rotation of the R loop in the horizontal plane, (d) intermediate or terminal slowing, and (e) QRS prolongation. The frequent association of complete and incomplete left bundle branch block with left ventricular hypertrophy was discussed, and a possible mechanism to explain this association was proposed.