On the effect of preceding atrial- atrial and His-atrial intervals on the atrioventricular nodal conduction time in rabbit heart.

The study of conduction in the atrioventricular node is often associated with two characteristic time intervals. The first of these intervals reflects the time between two successive atrial excitatory complexes. The second interval reflects the time from the moment of the appearance of the excitation at the output of the atrioventricular node to the next atrial complex. In different publications the value of the conduction time is associated predominantly either with one (atrial-atrial) or with the other (His-atrial) preceding intervals. The present paper makes an attempt at comparative estimation of the effect of preceding atrial-atrial and His-atrial intervals on current conduction time. The experiments are carried out on rabbit heart preparation, using micro- and macroelectrode technique. Stimulation programmes guaranteeing the imposition of rhythm with fixed atrial-atrial and His-atrial intervals are used. It is concluded that there is no strictly determined connection between the value of any of the above intervals and atrioventricular conduction time.