Synchronization effects in the pacemaker during high-frequency atrial stimulation

The succession of intra-impulse intervals in venous sinus of isolated frog heart was studied during suprathreshold atrial stimulation at a frequency exceeding the initial pacemaker rate by l5-200%. Near to the initial and multiple frequency pacemaker synchronization takes place with the stimulator rhythm. With the stimulation of frequency increase atrial impulses begin to conduct retrogradely and regular ectopic rhythm is established. A unilateral pacemaker acceleration with the unilateral frequency drawing together is revealed in intermediate areas. Different effects appear to accompany it including asymptotic and cyclic synchronization proving in the form of arrhythmias.