SINGLE FIBER RECORDING DURING THE PRODUCTION AND CONTROL OF FLUTTER IN THE ISOLATED ATRIUM OF THE RABBIT

¹ Department of Pharmacology, University of Washington School of Medicine, Seattle, Washington

Isolated right atria, or segments thereof, from rabbits were prepared for dual intracellular recording. Recordings were made in spontaneously beating preparations from one electrode in the sinoatrial node arid the other in the body of the right atrium. In other experiments the sinoatrial node was excised and both microelectrodes were inserted into atrial cells. Data for the recovery of excitability were obtained under control conditions, in the presence of acetyicholine or methacholine and in the presence of quinidine. In the presence of a cholinergic drug, arrhythmias were produced by a pair of electrical stimuli in which the interval closely approached the absolutely refractory period. The onset and the course of the arrhythmia were observed from the dual microelectrode recording both in the spontaneously beating preparation and in the driven preparation. Diminution of the tissue size finally resulted in a preparation in which the arrhythmia could not be induced. In preparations in which arrhythmias could be induced repeatedly, quinidine antagonized the perpetuation or the initiation of the arrhythmia. On the basis of the evidence presented, it is proposed that a re-entry mechanism is responsible for the arrhythmia.