Impact of arterial stiffening on left ventricular structure

Abstract

Aging of the vasculature results in arterial stiffening and an increase in systolic and pulse pressures. Although pressure load is a stimulus for left ventricular hypertrophy, the extent to which vascular stiffening per se, independent of blood pressure, influences left ventricular structure is uncertain. Two hundred seventy-six subjects (79 normotensive and 197 otherwise healthy hypertensive individuals) underwent echocardiography to assess left ventricular structure. Arterial stiffness was estimated by the pressure-independent stiffness index, beta, and the pressure-dependent elastic modulus derived from simultaneous carotid ultrasound and applanation tonometry. Systemic arterial compliance (the inverse of stiffness) was estimated by the arterial compliance index. In multivariate analysis, beta was related to age (P<0.001) and smoking history (P<0.01) but not mean pressure, whereas elastic modulus was related to age and mean pressure (both P<0.001). The arterial compliance index was only related to age. Whereas systolic and diastolic pressures and the elastic modulus were positively associated with left ventricular mass (all P<0.001), primarily because of increases in wall thicknesses, beta and the arterial compliance index bore no relation to left ventricular mass. beta was inversely related to chamber diameter and directly related to left ventricular relative wall thickness, the ratio of wall thickness to chamber radius. Younger and older hypertensive subjects had comparable left ventricular mass, despite higher systolic and pulse pressures in the older group, whereas older hypertensives had higher mean relative wall thickness, associated with a significant increase in arterial stiffness (beta, 7.06 versus 5.17; elastic modulus, 595 versus 437 dyne/cm(2) x10(-6)) and reduction in the arterial compliance index (0.87 versus 1.05 mL/mm Hg per square meter) (all P<0.001). Thus, the extent to which arterial stiffness relates to left ventricular hypertrophy is dependent on the method by which arterial stiffness is estimated. Pressure-dependent methods show an association with left ventricular hypertrophy, whereas the pressure-independent stiffness index, beta, and the arterial compliance index are most strongly associated with aging and left ventricular concentric remodeling but not hypertrophy.