Vectorcardiographic diagnosis of right ventricular hypertrophy in the presence of right bundle branch block in young subjects.

Two groups of young patients, one with right bundle branch block complicated by right ventricular hypertrophy due to congenital heart disease, the other with right bundle branch block and no right ventricular hypertrophy, could be separated on the basis of a few quantitative vectorcardiographic and electrocardiographic criteria. Vectorcardiographic criteria proved better than electrocardiographic criteria in detecting right ventricular hypertropy in individual patients with complete right bundle branch block. Criteria based on the configuration of the QRS loop were also specific but much less sensitive for the diagnosis of this association. In a similar population, that is, young patients with postoperative right bundle branch block, the existence of a residual right ventricular overload would be strongly suggested by the presence of any one of the following criteria: (1) a clockwise rotation of the QRS loop in the horizontal plane, (2) a ratio of the magnitude of the R wave to that of the S wave (R/S ratio) in lead X at less than 2.0, (3) a mean QRS vector in lead X more negative than--10 mv.msec, or (4) a maximal QRS vector located between 90 degrees and 270 degrees in the horizontal plane. In contrast, an R/S ratio in lead X that was equal or superior to 2.0 or an azimuth angle of the mean spatial QRS vector that was not between 90 degrees and 180 degrees would indicate that the right ventricular conduction defect is probably uncomplicated.