The vectorcardiogram in incomplete left bundle branch block

Abstract

Twenty-one cases with electrocardiographic findings of incomplete left bundle branch block unaccompanied by findings suggestive of anteroseptal infarction were studied vectorcardiographically. The vectorcardiographic findings correlated closely with the electrocardiographic abnormalities in these cases in that the QRSsÊ loop was invariably written to the left and usually anteriorly and inferiorly, and there was often conduction delay in the initial deflection of the loop or, on occasions, in other portions of the loop. These findings would be the vectorcardiographic counterpart of the slurred initial upstroke of the R wave in leads i, aVL and V 6 of the electrocardiogram. The characteristic figure of eight configuration and posterior rotation of the QRSsÊ loop in the horizontal projection were also of diagnostic value in the recognition of the pattern of incomplete left bundle branch block.