Lown-Ganong-Levine Syndrome

His bundle recordings were obtained in three patients with histories of recurrent supraventricular tachycardias and electrocardiograms demonstrating a short P-R interval with a normal QRS (the Lown-Ganong-Levine syndrome). The His bundle electrograms obtained during sinus rhythm demonstrated a normal A-H (atrium-to-His bundle) time in one patient and a low normal A-H time in two patients. The H-V (His bundle-to-ventricle) time was short in all three patients. Atrial pacing in two patients produced an attenuated degree of prolongation of the A-H time without a change in conduction distal to the proximal His bundle. The probable mechanisms of accelerated conduction in these three patients include: (1) partial A-V nodal bypass via (a) the posterior intenodal tract or (b) functional bypass fibers within the A-V node; and (2) accelerated conduction within the A-V conduction system distal to the A-V node.