[The antegrade GAPs (author's transl)].

GAP in a-v conduction is defined as a zone within the cardiac cycle where premature atrial impulses fail to evoke ventricular responses whereas atrial beats of greater and lesser prematurity do. This phenomenon occurs when the effective refractory period (ERP) of a distal site is greater than the functional refractory period (FRP) of a proximal site of the conduction system. To date, Damato and Co. classify antegrade gaps into six types on the basis of blocks location and proximal delay that permits conduction recovery: type I: HPS and AVN; type II: HPS (distal) and HPS (proximal); type III: HPS and His-bundle; type IV: AVN (distal) and AVN (proximal); type V: AVN or HPS and atrium; type pseudo-V: AVN or HPS and antrial miocardium proximal to stimulation site; type VI: HPS and supernormality (no proximal delay). The Authors propose, on the basis of 37 cases of GAP phenomenon observed in 185 electrophysiological studies, a new classification of antegrade gaps, which complete and partially modifies Damato's one. Tyes I-II-II-IV and V are divided into A and B forms according to the type and the site of the distal block. GAP type VI is replaced by Damato's pseudo-V. Two new types are proposed: in the first (type VII) the distal block is in the atrium and the proximal delay is in atrial miocardium proximal to stimulation site; in the second (type VIII), in subjects with pre-excitation, the block is in the accessory pathway and the proximal delay is in atrium.