Construction of body-surface isoharmonic maps from Frank XYZ leads

Signal-averaged Frank leads obtained during sinus rhythm from 11 patients with sustained ventricular tachycardia (VT), 10 without VT, and 9 normal controls are analyzed. Magnitudes of the 13-56 Hz and 70-128 Hz bands in the Fourier transform over the cardiac cycle, found previously to distinguish patients with from those without VT, were plotted as isoharmonic maps over the body surface described by cylindrical coordinates. The contours of 13-56 Hz maps and 70-128 Hz isoharmonic maps differed markedly between patient groups. Moreover, the average value of 13-56 Hz maps was less (p < .01) in patients with VT compared to the maps of those without VT. This approach enables the spatial distributions of distinguishing electrocardiogram features to be estimated from Frank leads.