[The atrial stimulation programmed for the research of dual A-V nodal conduction pathways (author's transl)]

Several techniques of premature atrial stimulation were used in a group of 28 not selected patients admitted to electrophysiological investigations of different rhythm troubles. The purpose of this study was the demonstration of dual A-V nodal pathways. The method consisted in the delivery of one or two atrial extrastimuli at every sixth beat, with or without atrial pacing at increasing rate, up to the either atrail or nodal refractory period. Then a curve of intranodal conduction was plotted. The different techniques led us to a curve reproducible in the 89% of the cases. Its main features are the steady increase of the A-H interval, the subsequent sudden "jump" of the same at critical shortening of the coupling stimulation interval and finally a third segment of steady increase until the atrial or nodal refractory period is reached. We believe that this behaviour is common in the man. The significance of the "jump", of the morphology of the curve and their possible relationship with the existence of dual A-V nodal pathways is discussed. Finally the different stimulation techniques are compared.