Comparison of Frank-vectorcardiograms of normal conduction and right bundle branch block in patients with...

For the purpose of obtaining fundamental data to make the diagnostic criteria for coexisting electrocardiographic abnormalities in right bundle branch block (RBBB), the Frank-vectorcardiographic and electrocardiographic parameters were studied in both normal and RBBB conductions in 25 patients (16 males and 9 females, aged 6 to 78 years) with intermittent or transient RBBB. There were no statistically significant differences in the corresponding instantaneous QRS vectors between normal and RBBB conductions during the first 10.4 (+/- 3.2) msec of the QRS duration on the average. No statistically significant differences existed in the mean Q amplitudes of the Frank leads between normal and RBBB conductions. After the development of RBBB, voltages of Rx and Ry, and the planar maximum QRS vectors decreased approximately by 10% on the average, and Rz decreased significantly by 63.9% on the average, and S amplitudes of the 3 Frank leads increased significantly. We observed 3 patients showing a complete reversal of the sense of inscription of the horizontal QRS loop from counterclockwise to clockwise after the development of RBBB. Two of these patients showed no clinical evidence of cardiac or pulmonary diseases except for RBBB. After the appearance of RBBB, maximum T vectors deviated significantly posteriorly in the horizontal and left sagittal planes. Twenty-three patients showed counterclockwise inscription of the T loop both in the horizontal and left sagittal planes, and 9 patients in the frontal plane. After the development of RBBB, we observed a complete reversal in the sense of inscription of the T loop from counterclockwise to clockwise in 13 cases (56.5%) in the horizontal plane, in 15 cases (65.2%) in the left sagittal plane, and in 8 cases (88.9%) in the frontal plane.