抄録
1. Both the sinus-and AV node arteries of the canine heart in vivo were simultaneously perfused at a constant pressure of 100 mmHg.
2. The selective administration of 0.1 to 0.3μg of norepinephrine into the AV node artery caused a shortening of the PQ interval, and the P wave eventually disappeared after a dose of 1 to 10μg. An inverted P wave was occasionally observed just before the disappearance of P wave. Thus the AV nodal tachycardia was induced when the pacemaker shifted from the sino-atrial node to the AV node. When the AV nodal rhythm reverted to the sinus rhythm in the course of recovery, the sinus rate decreased at first below control before being stabilized at the original value.
3. Atrial fibrillation resulting from the administration of acetylcholine into the sinus node artery did not occur when the pacemaker activity had been made to shift to the AV node.
4. The induction of atrial fibrillation to be induced by injection of acetylcholine into the sinus node artery was blocked even when the dominance of pacemaker activity in the right atrium was induced by electric pacing.
5. When the dominant pacemaker in the atrioventricular node was established successfully by injection of norepinephrine into the AV node artery, sustaining atrial fibrillation was blocked.
6. It was concluded that the dominant activity of sino-atrial pacemaker is necessary for induction and maintenance of atrial fibrillation by acetylcholine.
