Experimental Production of Auricular Fibrillation by Several Stimuli Applied to the Auricle.

Abstract

Auricular fibrillation has hitherto been produced experimentally only by faradization of the auricle, and under these conditions the period of fibrillation rarely outlasts the period of stimulation. Moreover, though it is usually possible to cause spontaneous auricular fibrillation in the dog to cease abruptly after the injection of quinidine it is, as Alfred Cohn has reported, 1 only rarely possible to stop the fibrillation during faradization of the auricle. This practically prevents a satisfactory experimental study of the drugs that might be used to influence auricular fibrillation.

In this investigation we have produced auricular fibrillation in dogs by throwing into the auricle a cycle of 3 independent make and break induction shocks, about one-eighth of a second apart, each shock being applied to a different part of the auricle. The fibrillary contractions were easily visible in the wall of the auricle and in the electrocardiogram, and were accompanied by the usual absolute arrhythmia in the carotid pulse tracing recorded with a membrane manometer.

In these experiments we used the make and break secondary shocks from 3 independent Harvard induction coils, the secondary-circuits of which led to a cylindrical electrode containing 4 insulated wires whose bare ends were about 2 mm. apart. One of these wires was connected with all 3 induction coils in order to complete the 3 circuits. The poles of the 3 primary circuits were connected with a dry cell and then with the base of a Harvard kymograph, the drum of which was covered with a piece of glazed paper bearing 3 perforations made in an oblique descending line, each perforation about 5 mm. in front and above the next one. As the drum was rotated rapidly, a contact was made whenever one of these perforations moved past a spring brass wire set upon a ring stand (from which it was insulated) and this brass wire passed to the second electrode in the primary circuit of one of the induction coils. As the drum rotated once in 6 seconds, this gave a cycle of 3 independent stimuli to different parts of the auricle with an interval of about one-eighth of a second between them. This is about equal to the A-V conduction time.

A single cycle of these stimuli sufficed to set up a “circus movement” in the auricle and in every experiment but one resulted in the development of fibrillation. In almost every experiment we were able to obtain periods of fibrillation which greatly outlasted the periods of stimulation. The fibrillation sometimes lasted from one-half to 2 hours, and we were able to obtain lasting fibrillation by this method in a number of dogs when fibrillation produced by faradization ceased within a few seconds after cessation of the stimulation.