ROLE OF LEFT-VENTRICULAR GEOMETRY IN THE ALTERATION OF INITIAL QRS VECTORS DUE TO CONCENTRIC VENTRICULAR HYPERTROPHY

The relation between serial magnitudes of instantaneous spatial vectors, obtained throughout ventricular depolarization, and echocardiographically estimated left ventricular (LV) mass was investigated in 64 patients with congenital aortic stenosis and in 16 patients with coarctation of the aorta. While the correlation was positive between LV mass and vector magnitudes at 50 and 60 ms after QRS onset (r = .530 and .557, P < .01), it was found to be negative with regard to the magnitude of the initial 10 and 20 ms vectors (r = -.285 and -.355, P < .01). Computer simulation of activation propagation in different models of LV enlargement has shown that the decrease of the spatial magnitude of initial vectors, as well as a marked decrease of the area of the anterior portion of the horizontal plane QRS loop and of the Q amplitude of the orthogonal z lead, are characteristic of concentric LV hypertrophy with decreased diastolic volume and were not observed with unchanged or dilated chamber size. Repeated assessment of the magnitude of initial QRS vectors may indicate changes of LV remodeling in patients with LV pressure overload.