Abstract
Aconitine was administered to the isolated right atrium of the rabbit, and atrial flutter and fibrillation were induced. The action potentials of unipolar lead electrogram regularly appeared in atrial flutter, and their configuration was different from that in sinus rhythm. In the initial stage of atrial fibrillation, both appearances of the action potentials of unipolar lead and intracellular lead electro-grams were regular and synchronous in some degree. In atrial flutter and fibrillation, the membrane resting and action potentials decreased to various degree. The rising velocity of upstroke of action potential decreased, and the duration of action potential shortened. The steepness of diastolic slow depolarization increased. It may be concluded that atrial flutter results from rapid impulse formation in a single focus. Atrial fibrillation would be caused by rapid impulse formation in multiple ectopic foci.
