Interaction between atrial excitation waves and conduction in the atrioventricular node. II. Differences in the...

During in vitro experiments on the right atrium of rabbit heart microelectrodes were used to record simultaneously action potentials from different cells in the atrioventricular node (AVN) under stationary basic rhythms, imposed separately or jointly at the posterior and anterior inputs. A comparison was made of the pattern of conduction in the three different phase correlations between the input excitatory waves. Causal relation is found between the changes in the phase correlation and the conduction pattern with unchanged duration of the basic cycle. The formation of more than one excitatory front in AVN has no priority connection with the anterior input. Although stimulation at the posterior input is connected with more homogeneous conduction, even then the formation and interaction of two excitatory fronts is possible; on the other hand, during independent stimulation of the anterior input the formation of a second excitatory wave is possible, which, upon entering the node posteriorly, may have a dominating influence on conduction. A special case is the differentiation of an excitatory front which enters AVN only through one of the inputs. For example, upon anterior stimulation it is possible to induce one direct excitatory front to the N-zone and a second one which first activates the posterior AN-zone and then turns antegradely. The interaction of these two fronts creates different patterns concerning the characteristics of the action potentials and the organization of conduction, being related to the complex spatial inhomogeneous structure of excitable elements in different refractory phases.(ABSTRACT TRUNCATED AT 250 WORDS)