A QUANTITATIVE ELECTROCARDIOGRAPHIC METHOD BY

The sum of the numerous electromotive forces generated during the spread of the ventri-cular impulse can be regarded as a vector quantity and represented by a straight line of certain length and direction. The angle made with the horizontal by the projection of this vector on to the frontal plane is kniown as the electrical axis of the heart and can be calculated, by the method of Einthoven et al. (1913), from the magnitude of the initial ventricular deflections in two of the limb leads of the standard electrocardiogram. It is possible to apply this method to an electrocardiogram derived from three points in the sagittal plane of the body, thus identifying in a similar way the sagittal projection of the same vector. From these two projections on to planes at right angles to each other, both the direction and magnitude of the vector itself can readily be calculated. The present investigation is concerned only with the magnitude evaluated in this way, and was undertaken to explore the possibility of obtaining quantitative information on the state of the ventricular muscle. The values obtained are empirical, as only a small and unknown proportion of the total electromotive force generated by the heart is induced at the periphery and becomes available for measurement. It is not, however, unreasonable t