“…Although typical ventricular pre-excitation occurred in 20 per cent of their patients, initial slurring of the QRS loop, which they observed much more frequently, was regarded as a lesser degree of ventricular preexcitation. Bilger et al (1961) compared the vectorcardiograms of 6 cases of Ebstein's anomaly with those of 47 cases of complete right bundle-branch block associated with other lesions, and noted only unimportant differences. The same group.…”