Evaluation of the Cardiac Conduction System by his Bundle Recordings

Abstract

Intracardiac catheter recordings of the specialized conducting tissue have greatly enhanced diagnostic acumen in A-V conduction disorders and disturbances of cardiac rhythm (1–9). His bundle (BH) recordings in conjunction with stimulation studies are now a clinical diagnostic tool available in an increasing number of cardiac catheterization laboratories. Such recordings of the specialized conduction system in man have both diagnostic value and are of clinical therapeutic and prognostic significance (10, 11). His bundle recordings permit a breakdown of the P-R interval into its three component conduction intervals, i.e., intra-atrial (P-A), A-V nodal (A-H), and His-Purkinje system (H-V) (12). The therapy and prognosis of A-V conduction defects may depend on the site of the lesion which cannot always be localized on the basis of the standard surface electrocardiogram. The range of a normal P-R interval is very wide (0.12–0.20 sec.) as compared to the narrow range of conduction time through the His-Purkinje system (H-V = 0.035 to 0.045 sec.) or the BH (0.015 to 0.020 sec.). The P-R interval or the QRS complex may remain within normal limits despite significant delays in the BH (even up to 200%).