Studies on the Spatial Ventricular Gradient in Essential Hypertension

Abstract

Spatial ventricular gradients in essential hyper-tension were investigated by means of three com-ponent leads of the Frank system, with the purpose of clarifying changes characteristic of the left ventricular overloading. Three component leads (X, Y and Z leads) of the Frank system were recorded simultaneously with a paper speed of 100mm per second for 100 cases of essential hypertension. Based on these records, spatial ventricular gradients and their analytical values were calculated by means of a digital computer, OKITAC 5090-H type. Kyushu University Computation Center. The methods of measurement of the spatial ventricular gradients and the items of analysis were the same as the previous reports. Hypertensive subjects were classified into four groups by mean blood pressures (Table I): Group A (110 mmHg, 31 cases), Group B (110-119 mmHg, 29 cases), Group C (120-139 mmHg, 21 cases), and Group D (140 mmHg, 19 cases). Spatial ventricular gradients (SA^^^VG) and their analytical values are shown in Tables IIIV. Spatial ventricular gradients and their analytical values in the above-mentioned four groups are given in Table V. Statistical comparisons of the observed and analytical values of the ventricular gradients among the young and middle-aged indi-viduals with normo-and hypertension are given in Table VI. Changes in the spatial ventricular gradients characteristic of the left ventricular overloading were decrease in the spatial magnitude and increase in azimuth and elevation, which tended to appear in the above order with an advance of the left ventricular overloading. These changes of SA^^^VG were resulted from decreases in magnitude of X as well as Y components in the same degrees without accompanying any significant change of Z component. The characteristic changes of the spatial ventricular gradients projected on the three perpendicular planes were decrease in right sagittal angle. Spatial QRS area vectors (SA^^^QRS) and spatial T area vectors (SA^^^T) which constitute the spatial ventricular gradients were also investigated concerning the spatial magnitude, azimuth, elevation, magnitudes and directions projected on the three perpendicular planes, and X, Y and Z components of these vectors. The spatial magnitude and elevation of SA^^^QRS increased, and azimuth angle decreased in the left ventricular overloading. As for the X, Y, and Z components of SA^^^QRS, increase in magnitude of X component and decrease in magnitude of Z-component were as certained, but there was no significant change in Y component. As for SA^^^T, the spatial magnitude decreased, and azimuth and elevation increased in the state of left ventricular overload-ing. X and Y components of SA^^^T decreased, but the anterior elements of Z components increased. SA^^^QRS-SA^^^T angles (dA), SA^^^QRS-SA^^^VG angles (dB), and SA^^^VG-SA^^^T angles (dC) enlarged with an advance of the left ventricular overloading. The ratio of dA, dB, and dC were 1 : 0.52 : 0.48 in hypertensive subjects, indicating relatively narrow dB and wide dC as compared to the ratio (1 : 0.7 : 0.3) in normal middle-aged individuals. The enlargement of dC angle was observed even in hypertension of slight degree (Group A). Accordingly, enlargement of this angle may be taken into account as an early sign of the left ventricular overloading. The progress of the left ventricular overloading resulted in increase in magnitude of dB angle, because the displacement of SA^^^VG-H were developed forward to the opposite direction against the displacement of SA^^^QRS-H, which were usually moved backward for the hypertension. However, dC angle has not significantly changed, because the displacement of SA^^^VG-V and SA^^^T-V developed in the same directions. SA^^^VG-Mag/SA^^^QRS-Mag ratio and SA^^^T-Mag/ SA^^^QRS-Mag ratio decreased in the left ventricular overloading because of the diminutions in SA^^^VG-Mag and SA^^^T-Mag and the increases in SA^^^QRS-Mag. [the rest omitted]