In vivo validation of the origin of the esophageal electrocardiogram

Esophageal electrocardiography is a clinical and investigational technique that is useful for determining atrial conduction intervals, analyzing atrial rhythms and mapping conduction pathways. Although the left atrial origin of the esophageal electrocardiogram has long been implied, recently that origin has been questioned. In the present study, the origin of the esophageal deflection is defined by direct right and left atrial mapping studies performed with simultaneous esophageal electrograms obtained from three positions (high, mid and low). Seven patients with normal left atrial dimensions (group I) and five patients with left atrial enlargement (group II) underwent transseptal catheterization during the course of electrophysiologic study. In group I (normal left atrial dimensions), conduction time from the high right atrium to each of the three esophageal positions corresponded to conduction times to left atrial sites ranging from 1 to 3 em lateral to the left interatrial septum. The mid- and low esophageal conduction times were all significantly longer than conduction time to the left side of the septum (p < 0.05). In group II (enlarged left atrium), conduction times to each of the esophageal sites corresponded to conduction times to left atrial sites lying between the mid-left atrium and a point 1 em lateral to the left side of the septum. A significant trend toward longer conduction time to the mid-esophageal position than to the left septum was noted (p < 0.1). In both groups, conduction times measured with the esophageal catheter were significantly longer than conduction time to the right interatrial septum (p < 0.05). The esophageal electrogram corresponds to atrial deflections recorded within the left atrium distinct from the interatrial septum and right atrium. Esophageal electrocardiography is a valid technique for investigation of left atrial rhythms and interatrial conduction.