抄録
The sinus node artery of 10 dog hearts was auto-perfused with blood led from the femoral artery under constant pressure at 100mmHg by the aid of a perfusion pump. Acetylcholine and carbachol given into the sinus node artery induced atrial fibrillation following sinus arrest. Electric pacing with a frequency from 1 to 5Hz was applied to the middle part of the free wall of the right atrium. Electric pacing at a rate below the sinus rate caused some extrasystoles, but pacing at a rate above the sinus rate did not cause any extrasystoles; by pacing at a higher rate than 4.5Hz, AV block was induced. The induction of atrial fibrillation by acetylcholine or carbachol was prevented by various frequencies of electric pacing at a rate either below or above the control sinus rate. But higher frequencies of pacing, 4 to 4.5Hz, occasionally could not prevent atrial fibrillation induced by acetylcholine or carbachol. The sustained atrial fibrillation induced by carbachol was not blocked by artificial pacing of the free wall of the right atrium at any rate of electric pacing.
