Monophasic action potential of right human atrium during atrial flutter and after conversion to sinus rhythm. Argument for re-entry theory.

In I2 patients right atrial monophasic action potential recordings were obtained during atrial flutter and after conversion to sinus rhythm. Monophasic action potential duration is a valuable index of refractoriness of the atrial muscle; it ranges from 136 to 155 msec for the flutter waves and from 290 to 390 msec for the regular sinus complexes. If the duration of the monophasic action potential of the flutter waves lengthens to about 200 msec sinus rhythm occurs; inversely, if sinus complexes present a monophasic action potential duration about 260-270 msec, flutter is impending. The results allow one to assume that the re-entry mechanism is one of the most important in the maintenance of atrialflutter. DC shock may be effective through depolarization of the atrial muscle, but it may have an additional effect on the refractoriness of the myocardium, allowing the slow depolarization of the re-entry pathway.