Studies in human atrial flutter with the use of proximity electrodes.

SUMMARY Ten patients with the electrocardiographic diagnosis of atrial flutter were investigated by exploration with electrodes within the esophagus and the right atrium. The records obtained were studied in regard to the timing of the intrinsic deflection and the contour of the atrial waves, as recorded at various sites. In four patients, atrial activation progressed in sequence cephalad in the left atrial wall and caudad in the right atrium. This process continued through two thirds of the total atrial cycle, favoring "circus movement" as the underlying mechanism. In six other patients, activation was believed to originate low in the left atrium, with simultaneous spread of excitation of both atrial walls in a general cephalad direction and terminating within the first half (usually the first third) of the atrial cycle. This pattern is compatible with, but not conclusive of, an ectopic focal mechanism. Serial records in one patient are presented in which transformation of one type into a second type of atrial flutter is suggested. It is likely that at least two mechanisms are present in human atrial flutter. Additional Indexing Words: Circus-movement hypothesis Right intra-atrial electrocardiogram Right intra-atrial esophageal potential-differen A LTHOUGH SEVERAL hypotheses have been proposed for the underlying mechanism in human atrial flutter, they can be grouped broadly into three basic models: (1) the continuous circulating movement of the excitation wave;1-3 (2) the unifocal or multi-focal impulse formation4 5; and (3) the theory of the multiple re-entry.68 In spite of extensive studies and the vast amount of information accumulated during the past half century, the gaps between the proponents of each hypothesis are far from being bridged. This study is an attempt to elucidate the excitation pattern in atrial flutter with the use of electrodes placed within the esophagus and the right atrium. Ectopic unifocal impulse formation Esophageal electrocardiogram ce curve investigated by means of vectorial analysis.9' 10 Using standard limb leads, Sir Thomas Lewis and associates9 in 1921 suggested that circus movement is present around the two cavae, probably directed upward in the left atrial wall and downward in the taenia terminalis of the right atrium. Later, this mechanism was experimentally demonstrated in animals by extensive crushing of tissue between the venae cavae to form an obstacle to the wave progression. With this procedure, circus movement of the wave of excitation could be maintained.3' 6, 11-13 In some studies, interfering with the integrity of the circular pathway …