Topographic diagnosis of atrio-ventricular conduction defects

Atrioventricular (A-V) conduction was evaluated in 51 patients who underwent electro-physiological study. Eighteen patients had nodal conduction delay (A-H greater than 150 ms), six of them were congenital, in two others it was associated to a His-Purkinje (H-V) delay. None of them had bundle branch block in the surface ECG. The conduction delay was located within the his bundle in 15 patients (29.4%). In three of them, a split His bundle electrogram was recorded; in the other 12 (80%), His bundle stimulation normalized QRS morphology; in all of these patients H-V interval was longer than 70 ms. His bundle delay was associated to infra H lesion in five patients. In one without ECG changes, atrial and His bundle stimulation demonstrated a left troncular delay with a distal block in the right bundle branch. Thirteen patients had infra His block represented by a long H-V interval (greater than 60 ms). We conclude that His bundle electrograms and stimulation is a low risk procedure very useful in the topographic diagnosis of A-V conduction disturbances.