Ventricular Activation and the Vectorcardiogram in Bundle-Branch Blocks

Abstract

The relationship between the ventricular activation and the vectorcarcliogram was studied in clinical aucl experimental cases of bundle-branch blocks. The observations were limited to the methods of Frank ancl Grishman, taken as representatives of the two mail1 groups of vectorcardiographic methods in use. 111 clinical cases of right or left bundle-braticll block, the curves obtained with the method of Grisli~nan showed a better correlation with the electrocarcliographic trwit~gs and with our knowledge of the sequence of the ventriv-6l ular ;wtiratioil process. I11 clogs. after the production of either right or left bundle-branch blocli, the vectorcarcliogram~s accordiilg to the methods of Frank aucl Grishman did not reveal iniportant ventricular forces which were presrn t in the vectorcardiograms calculateci from the installtaneons apparent masiinn~u potential graclients. The concept of equivalent or single clipole as representing the electrical actirity of the heart was cliscussecl. The limitations of its application to rectorcarcliogral)l~y were pointed out. Comparing the diagnostic valuc of clcctrocardiography versus vectorcarcliograpliy, the conclusion was reachecl that a distant exploration ("moving away " from the heart) will never give as much information is a. proximal esploratioil (LL~novii~g close" to the heart). The apparent superiority of Grisliman's over Frank's method was attributed to the fact that Grishmm's methocl does not adjust to the clipole concept, which is closely aclhered to in Frank's method. By adhering to the clipole concept as closely as possil,le, the ~nowments of the many activation fronts of carcliac activity are lost, ;and a situation is created which is entirely artificial according to the understanding of the activation process of the heart. A possible solution to the problem of vectorcardiograph may lie in the development of lead tensors.