Blocking of acetylcholine-induced fibrillation by use of norepinephrine into the AV node artery.

The arterial blood supply to the canine AV (atrioventricular) node mainly through the posterior septal artery has been confirmed by LUMB et al.1) and later by JAMES2), while a considerable part of the interventricular septum is supplied by the anterior septal artery.WEST at al.8 described a technique for the catheterization of individual branches of the coronary artery in intact dogs which permits the intra-coronary injection of pharmacological agents.They demonstrated nodal tachycardia from an injection of norepinephrine into the left circumflex artery.NADEAU and AMIR-JAHED4) cannulated the posterior septal artery in order to perfuse the myocardium including the AV node with the animal's own blood led from the femoral artery. They obtained AV block by the selective administration of acetylcholine. In a previous report, the authors5) described an arrangement for perfusion of the sinus node artery at a constant pressure.In the present study the sinus node artery and the posterior septal artery (AV node artery) were simultaneously cannulated and both perfused at a constant pressure of 100 mm Hg.The authors6) reported briefly a new finding, that of AV node activity in blocking acetylcholine-induced fibrillation when nodal tachycardia was induced by the selective administration of norepinephrine into the AV node artery.In this paper the mode of the blocking effect when the pacemaker was shifted to the AV node is analyzed in detail.