Mechanism of Atrial Flutter and Fibrillation Induced by Aconitine in the Dog, With Observations on the Role of Cholinergic Factors

The topical application of aconitine nitrate to the right atrial appendage in the "intact" anaesthetized dog produced atrial flutter. Premature systoles with fixed coupling preceded the development of flutter. In early stages of the arrhythmia, atrial rate was irregularly irregular. Also, the form of flutter beats was similar to that of preceding premature systoles. The fibrillatory activity of acetylcholine described by earlier workers has been confirmed. Transient atrial dissociation was seen after intravenous injection or topical application of acetylcholine. The occurrence of fibrillation in the left atrium after focal application of acetylcholine has been demonstrated, while the right atrial appendage containing the ectopic focus induced by aconitine continued to flutter. Aconitine produced slow-rate flutter in dogs treated with atropine or hemicholinium; this flutter was easily distinguishable from the sinus tachycardia produced by these drugs, by recording the electrocardiogram from a direct atrial lead from the area treated with aconitine, but not from limb lead II. The importance of these findings in the interpretation of the mechanism of atrial flutter and fibrillation is discussed.