[Functional block in the His-Purkinje system (author's transl)].

In nine patients without clinical or laboratory evidence of heart disease, premature atrial depolarization (PAB) induced a complete block of conduction in the intraventricular conducting system. In these patients the functional refractory period AV (FRPav)) gave short and very similar results to the effective refractory period of the His-Purkinje system (ERPhp), and the effective refractory period AV (ERPAV) was found to be shorter than the ERPhp in all cases. A linear correlation between the ERPhp and the basic cycle length (BCL) was also observed. These special functional properties of the AV node justify the occurrence of intraventricular block after PAB. In fact, the stimulus, rapidly conducted through the AV node, finds a complete or incomplete refractoriness in the ventricular conducting system, and therefore bundle branch or complete intraventricular block occurs. The linear correlation between the ERPHP and the BCL explains why the atrial pacing is not always useful for pointing out intraventricular conducting defects.