The esophageal electrocardiogram in the study of atrial activity and cardiac arrhythmias

Abstract

In clinical electrocardiography the atrial complex is often so small in conventional leads that it does not permit of careful study. Inconspicuousness of the P wave may render impossible the exact diagnosis of cardiac arrhythmias. It is perhaps no exaggeration to say that a precise knowledge of atrial activity is the key to the diagnosis of many arrhythmias. In efforts to improve the recording of atrial activity, various exploratory methods have been advocated. These include certain precordial and esophageal leads. The exploratory precordial leads comprise many combinations of placement of the chest and distant electrodes, the former usually located at, or to the right of the sternum in more or less anatomic relation to the right atrium. 1–16 While such leads frequently reveal atrial deflections better than limb leads, cases of arrhythmias are often seen in which the mechanism cannot be elucidated even with these methods. In such cases recourse to esophageal electrocardiography may be advisable. The earliest reports on clinical esophageal electrocardiography were scanty and empirical. 17–21 Brown, in 1936, established it as a sound and rational procedure. 22,23 His classical studies proved the validity of regarding the rapid intrinsicoid deflection of the P wave at certain esophageal levels as being truly comparable with the intrinsic deflection obtainable directly from the left atrium. As a result of using the polarity prevailing at the time, however, all his illustrations are reversed by present standards. A recent study confirmed the belief that true intrinsicoid deflections are obtainable by esophageal leads, and that these leads are the only true semidirect ones for the atrial muscle in man. 24 There have been several important contributions to the study of esophageal electrocardiography, but most of them deal with the form of the ventricular complex 25–29 or with myocardial infarction. 30–34 No study of a large series of arrhythmias by this method has been reported since Brown's publications. It is the purpose of this paper to describe the appearance of the esophageal electrocardiogram in a variety of arrhythmias and to evaluate the aid which this method may offer toward their diagnosis.