The electrocardiogram and the position of the heart.

0 NE of the troublesome problems in the field of electrocardiography is to decide whether certain peculiarities in the tracings are due to abnormalities of the myocardium or to nothing more than an unusual position of the heart. Difficulties of this kind occur in connection with the interpretation of both limb and precordial leads and may limit the value of the records considerably. This paper is not a review of the extensive literature on the subject, but it is an attempt to point out some basic relationships between electrocardiograms and the anatomical position of the heart, to discuss some recent studies which have a bearing on the problem, and to emphasize some difficulties and unanswered questions arising from this work. Einthoven, Fahr, and de Waart ls2 showed that the form of the standard electrocardiogram varies with respiration or change of posture and attributed this to a change in the position of the heart. Some years later, Meek and Wilson,” working with dogs, reported consistent changes in the limb leads when the heart was rotated about the anteroposterior or the longitudinal axis alone and pointed out that, unless care is exercised, movement about the former axis is usually accompanied by rotation about the latter. Since the two types of rotation, so induced, act to shift the electrical axis in opposite directions, erratic and unpredicatable changes in the axis found in their early experiments were satisfactorily explained. These workers emphasized the importance of rotation of the heart on its long axis as a factor which determines the direction of the electrical axis and amply confirmed earlier studies by Groedel and MBnckeberg.4 It has been known for many years that standard electrocardiograms taken on normal subjects and on many patients with heart disease, often show changes if tracings are taken with the body in different positions. Thus, with the subject lying on the left side, a shift of the electrical axis to the right is usually seen, and a shift to the left may occur when the subject is lying on the right side. Alterations of this kind are particularly apt to be found in subjects with relatively