COMPARISON OF ELECTROCARDIOGRAMS AND VECTORCARDIOGRAMS IN CONGENITAL AORTIC STENOSIS*†

In a previous study (Hugenholtz, Lees, and Nadas, 1962) correlations between the resting hemodynamic state in congenital aortic stenosis (AS) and the cube vectorcardiogram showed great accuracy in predicting the presence of left ventricular hypertension. Results were better than those obtained by the standard electrocardiogram in a study of a larger group of similar patients (Braunwald et al., 1963). Furthermore, alterations in the direction and magnitude of specific QRS vectors, as projected on the horizontal plane, correlated to some degree with left ventricular peak pressure and aortic gradient. However, the wide variation in these measurements often made proper assessment of the individual case impossible. Thus, while distinctly better than the standard electrocardiogram in the recognition of left ventricular hypertension, this type of uncorrected vectorcardiographic recording still proved to be inferior to the assessment of severity obtained by means of cardiac catheterization. The lead system proposed by Frank (1956) possesses characteristics which, on theoretical grounds, would make it a more desirable system for registration of the " equivalent dipole " (Langner et al., 1958). In practical terms it has confirmed these expectations in sharper delineation of the normal (Hugenholtz and Liebman, 1962), in improved accuracy in the necropsy confirmed diagnosis of various myocardial disorders (Hugenholtz, Forkner, and Levine, 1961), and in the assessment of left and right ventricular hypertension in patients with congenital aortic and pulmonic stenosis (Hugenholtz and Gamboa, 1964). It appeared timely therefore to compare its usefulness to that of the standard electrocardiogram and the cube vectorcardiogram obtained simultaneously in the same patient. The availability of detailed hmmodynamic data such as left ventricular peak systolic pressure, aortic valve gradient, stroke work, and valve area, suggested the study of these factors and their relation to electrical depolarization. The age-groups studied (5 to 21j years) appeared particularly useful since complicating factors such as conduction defects or coronary artery disease were absent. Heart weight or wall thickness at necropsy, the traditional yard-sticks, which in previous studies had shown a less than satisfactory correlation with the cardiogram (Griep, 1959; Scott, 1960; Selzer et al., 1958), were not analysed.