Intraventricular Conduction Intervals during Orthograde Conduction in Patients with Complete Heart Block

¹ Cardiac Section, Bronx VA Hospital and Mount Sinai School of Medicine, New York City

His to ventricular activation (H-V) time intervals were evaluated during periods of orthograde conduction in five patients with electrocardiographic evidence of intraventicular conduction abnormalities who developed complete heart block (CHB). During CHB the site of block appeared to be in the intraventricular conduction system rather than in the A-V node. Normal H-V time intervals were found in four of the five patients during orthograde conduction. Three of these patients developed CHB within two-four days of their His bundle studies. These findings demonstrate that the presence of a normal intraventricular conduction time, as determined from the His bundle electrogram, does not preclude development of CHB within a relatively brief interval in patients with intraventricular conduction defects.