The mechanism of supraventricular tachycardia induced by a single premature beat in the isolated left atrium of the rabbit. II. The termination of the tachycardia.

Tachycardias induced by a single stimulus in the left atrium of the rabbit, are based on a circus movement of the impulse through the atrial myocardium. Circus movement often stopped spontaneously after only one beat ("coupled extrasystole") or after a small number of beats. This frequent early cessation of circus movement is explained by the relatively high conduction velocity and relatively long refractory period in the early stage of tachycardia. As an exception tachycardia lasted for a longer period. The circulating impulse then could always be interrupted by the application of a properly timed stimulus. In this case the circulating impulse will encounter the activation wave elicited by the stimulus. This resulted either in termination or resetting of the tachycardia.