Electrocardiograms of an unusual type in right bundle-branch block

There are certain cases of intraventricular block in which the ventricular complexes of the electrocardiograms show the following characteristics: In Lead I all the ventricular deflections are small. There is a conspicuous S deflection, and T is usually flat or upright. In Leads II and III the ventricular deflections are similar in all respects to those seen in bundle-branch block of the common variety.Precordial leads have been employed in three cases in which the standard electrocardiograms were of this kind. In these leads the ventricular complexes are like those that are recorded in dogs with right branch block and in patients with diphasic ventricular complexes of the rare type. It is thought that the curves referred to represent right branch block. Some additional factor that modifies the form of the electrocardiogram may be present.