The relation of the position of the normal and the enlarged heart to the electrocardiogram

Abstract

It is well known that when the heart enlarges, it gives rise to alterations in the electrocardiogram; the curve takes on one form when the left ventricle is hypertrophic as in aortic insufficiency; it takes on an opposite form when the right ventricle is principally involved, as in mitral stenosis. These electrical signs have been useful in the clinic, but they have on occasion been misleading, for we have obtained curves resembling those found in enlarged hearts, in young soldiers and in civilians who, we were quite certain, were not the subjects of disease. It occurred to us that the position of the heart in the chest might be an important contributing factor in producing the abnormal electrocardiograms. It is well known that changes in the curves are possible as the result of respiratory movement; of the posture of the body. An exaggerated instance occurs in dextrocardia, as the result of which the electrocardiogram assumes the appearance of a mirrored image of the usual curve. Having these experiences to guide us we planned to ascertain in a systematic manner precisely what was the effect of the position of the heart in the chest. Obviously we could not rotate the heart in the chest, but we could rotate the chest about the heart Our method was as follows: Instead of taking the usual limb leads, we placed electrodes at the apices of the largest equilateral triangle which we could apply to the chest, the base of the triangle stretching between the shoulders, the apex below the sternum. We assured ourselves that the curves taken from these leads resembled closly those from the limb leads. We proceeded then to rotate this triangle through successive arcs of 40°, taking curves at each new positioll from those points of the chest wall to which the apices of the triangle pointed.