THE USE OF HYPERTONIC SOLUTIONS TO PRODUCE ATRIAL FIBRILLATION IN THE DOG HEART-LUNG PREPARATION

¹ Department of Pharmacology, The University of Michigan Medical School, Ann Arbor, Michigan

The poststimulation atrial arrhythmia was studied in the dog heart-lung preparation. Induced by a 2-sec period of rapid electrical stimulation of the right atrium, the arrhythmia persisted after stimulation for variable but usually brief periods of time. Atropine decreased the persistence of the arrhythmia and abolished the initial rapid, fibrillation-like rhythm which otherwise might appear in the first second or two following stimulation. Physostigmine increased the persistence and the atrial rate of the poststimulation arrhythmia. After administration of hypertonic solutions of sodium chloride or mannitol, atrial stimulation initiated atrial fibrillation which persisted for well over 1 hr in most cases, and was not terminated by restimulation of the atrium. The atrial fibrillation seen after hypertonic solutions was slower and more regular than that seen after physostigmine, but more rapid and irregular than the atrial flutter seen in an occasional preparation which had received atropine but no hypertonic solution. Persistent atrial fibrillation was seen in preparations which had received sufficient sodium chloride or mannitol to raise the plasma osmolality to approximately 480 mOsmol/kg H₂O.