Use of the Dipole Moment in the Assessment of Left Ventricular Hypertrophy

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Abstract
A multi-electrode grid lead system, suited for the measurement of the total outward electromotive force of the heart expressed as a dipole moment, was tested in 64 subjects without heart disease and in 44 patients with left ventricular overload. The normal group showed the maximum dipole moment to the left (L-MDM) to be proportional to body weight, and by inference to left ventricular weight. For the patients with heart disease, the degree of hypertrophy was assessed in terms of LV weight derived from biplane angiocardiograms; for these patients, L-MDM was found to be proportional to LV weight (r = 0.85). The grid allowed for a more accurate assessment of LV weight than parameters obtained from the Frank lead system in the same patients. A substantially improved estimation of LV weight was achieved with both systems when body weight was considered in addition to the electrocardiographic measurements. Among the reasons for the better performance of the grid system are surface potential integration instead of sampling, consideration of individual torso dimensions, and as a result of distributed multiple electrodes, absence of distortion in the local field.