The role of the phase relation between the atrial excitatory waves in determining the functional refractory...

Through programme stimulation of the two basic inputs of the atrioventricular node (AVN)--crista terminalis and interatrial septum--different spatial and temporal relations between the excitatory waves passing from the atrium into the node were modelled in intact rabbit heart preparation. The essential role of the spatial-temporal organization for the determination of the refractory properties is demonstrated. The functional refractory curves depend not only on the basic rhythm, but also on the direction of the atrial excitation front. It is shown that interaction of the input waves is possible in intact preparation as well. At optimum phase regimes combined stimulation of the two inputs leads to prolongation or shortening of the initial H1H2 interval. The qualitative characteristic of the observed effects is very varied. It is defined predominantly by the stimulation programme, but it does not depend on which of the two inputs the basic rhythm is applied. The view is expressed that in order to obtain a more accurate characterization of the AVN-conduction, it is necessary to consider the interaction of the atrial excitatory waves arriving at the posterior and anterior inputs of AVN and the reflection of this interaction on its refractory properties.