PHYSIOLOGIC DETERMINANTS OF THE ELECTROCARDIOGRAPHIC DIAGNOSIS OF LEFT-VENTRICULAR HYPERTROPHY

The relative importance of left ventricular (LV) geometry, wall thickness, and mass on the inscription of left ventricular hypertrophy (LVH) on the ECG was examined in 93 patients; 36 had no LVH on the ECG, 10 had borderline voltage for LVH, and 47 had LVH on the ECG. LV cineangiograms in the right anterior oblique projection were analyzed for LV end-diastolic volume, free wall thickness (h), semiminor radius (R), LV mass index (LVMI), and the geometric relations described by h/R, mass/volume, and h-R. Although mean LVMI was greater in patients whose ECG voltage was either borderline or diagnostic of LVH, increased LVMI also occurred without LVH on the ECG. None of the variables (h, R, h/R or mass/volume) reliably indicated when LVH would be inscribed on the ECG. The product of h-R. however, defined three electrocardiographic groups; all patients with LVH on their ECG had h-R >2.6 cm2. Wall thickening sufficient to result in an increased LV mass did not result in LVH on the ECG unless sufficient concurrent chamber dilatation was present. Thus, a critical geometric relationship resulting from the interplay of wall thickness and chamber dilatation is necessary for LVH to appear on the ECG. This finding is consistent with the solid-angle theory of electrocardiography as it relates to ventricular hypertrophy.