Characterization of atrial flutter. Studies in man after open heart surgery using fixed atrial electrodes.

Abstract

Studies were performed using bipolar atrial wire electrodes to record atrial electrograms and to pace the atria in 27 patients who developed atrial flutter after open heart surgery.Two types of atrial flutter, classic or type I atrial flutter, and type II atrial flutter, were identified.Both types of atrial flutter were characterized by uniformity of the beat-to-beat atrial cycle length, morphology, polarity, and amplitude of the recorded bipolar atrial electrogram.Both types sometimes manifested a beat-to-beat electrical alternans, which in turn was sometimes associated with an alternans in beat-to-beat cycle length.The initial basis of separation of types I and II atrial flutter was that type I atrial flutter was always influenced by rapid atrial pac- ing from the high right atrium, and type II atrial flutter was not.Two additional observations suggested that types I and II atrial flutter were different, although related, rhythms: 1) In four patients, type II atrial flutter was present after termination of rapid atrial pacing used to treat type I atrial flutter; 2) in two patients, type II atrial flutter changed to type I atrial flutter in a one-step fashion.The range of rates of the two types of atrial flutter were also different type I atrial flutter was slower (range 240-338 beats/min) than type II (range 340-433 beats/min).We concluded that type II atrial flutter is a distinct rhythm which may be intermediate between classic, or type I, atrial flutter and atrial fibrillation.ATRIAL FLUTTER is a supraventricular arrhyth- mia which has long been recognized in man,' al- though its underlying mechanism has not been ex- plained.Based on the ECG, it has been characterized as a regular, rapid atrial rhythm, most often with an atrial rate close to 300 beats/min, with the upper and lower limits of its range uncertain and variously stated.2-8At our institution, at the time of open heart surgery, bipolar wire electrodes are routinely placed on the right atrial epicardium for possible diagnostic or therapeutic use in the immediate postoperative period.9-12Since many patients develop atrial flutter spontaneously during this latter period, this was an opportunity to use these electrodes to characterize and define this rhythm better while providing patient care.Methods Twenty-seven patients who developed atrial flutter in the immediate period after open heart surgery were studied.The atrial flutter was identified initially from a standard or monitored ECG, or from bipolar atrial electrograms recorded from a pair of atrial wire elec- trodes placed routinely 0.5-1.0cm apart on the epicar- dial surface of the superior portion of the right From the Department of Medicine and the Cardiovascular Research and Training Center,