Noninvasive (Input) Impedance, Pulse Wave Velocity, and Wave Reflection in Healthy Middle-Aged Men and Women

Abstract

Abstract-The relation between arterial function indices, such as pulse wave velocity and augmentation index with parameters derived from input impedance analysis, is still incompletely understood. Carotid pressure, central flow waveforms, and pulse wave velocity were noninvasively acquired in 2026 apparently healthy, middle-aged subjects (1052 women and 974 men) 35 to 55 years old at inclusion. Input and characteristic impedance, reflection coefficient, the ratio of backward-to-forward pressure amplitude (reflection magnitude), and augmentation index were derived. Pulse wave velocity increased by 15% (from 6.1 to 7.0 m/s) both in men and women. In qualitative terms, input impedance evolved from a pattern indicative of wave transmission and reflection to a pattern more compatible with a windkessel-like system. In women, a decrease in total arterial compliance led to an increased input impedance in the low frequency range, whereas few changes were observed in men. Characteristic impedance did not change with age in women and even decreased in men (PϽ0.001) and could not be identified as the primary determinant of central pulse pressure. Augmentation index increased with age, as was expected, and was systematically higher in women (PϽ0.001).Reflection coefficient and reflection magnitude increased with age (PϽ0.001) without gender differences. We conclude that, in healthy middle-aged subjects, the age-related increase in arterial stiffness (pulse wave velocity) is not fully paralleled by an increase in arterial impedance, suggesting a role for age-dependent modulation of aortic cross-sectional area. Wave reflection increases with age and is not higher in women than in men. Key Words: cardiovascular physiology Ⅲ blood pressure Ⅲ vascular capacitance Ⅲ arteries Ⅲ biomechanics T he analysis of arterial stiffness and function and of pressure wave reflection received increasing attention for the past 3 decades. Several methods to describe arterial stiffness in a clinical setting emerged, 1 the most investigated being pulse wave velocity (PWV) and augmentation index (AIx). Some aspects related to AIx still need further investigation, such as the systematically higher AIx in women even after adjustment for body size and heart rate, and the observation that AIx tends to levels off to a plateau value above the age of 60 years. 2 Although PWV and AIx are related, they seem to reflect different aspects of arterial function. 2,3 A more global view on the arterial system can be obtained from impedance analysis, 4 -6 requiring measurement of central pressure and flow waveforms. In addition, pressure waveforms (P wf ) can be separated into their forward and backward components. 7 In a recent study in hypertensive patients, Mitchell et al 8 applied impedance analysis and found an increased aortic characteristic impedance (Z c ) to play an important role in the elevated pulse pressure in patients with systolic hypertension. There are no integrated large-scale studies where both impedance analysis and newer indices like PWV and A...

Model-based assessment of dynamic arterial blood volume flow from ultrasound measurements

“…Furthermore, the bias in the BVF dynamics parameters influences significantly cardiovascular research studies involving better modeling and understanding of the cardiovascular biomechanics. For instance, models like windkessel, lumped parameters, wave propagation or 3D fluid dynamics models are based on dynamical BVF waveforms [3,24,32,35].…”

“…Hence, the relation between arterial properties, BP and BVF waveforms has been subject of extensive analysis, using Windkessel as well as lumped parameter and wave propagation models for the arterial system (e.g. [3,24,32,35]). Wave reflections have been, furthermore, investigated with several other methods such as decomposition of forward and backward traveling waves (e.g.…”

Ventricular–vascular coupling in hypertension

“…59 The complex interplay between hypertension-induced aortic distension, which reduces characteristic impedance, and passive stiffening due to recruitment of collagen fibres could thus provide contrasting results when aortic stiffness and ventricular load are assessed with different parameters. 109,110 Elasticity of large arteries is influenced by polymorphisms of genes coding for elastin, 111 collagen, 112,113 fibrillin 114 and the renin-angiotensin system. 115,116 All these genetic variants can affect the structural and functional characteristics of the arterial tree and have significant impact on arterial load.…”

Oxidized Low-Density Lipoprotein Cholesterol Is Associated With Decreases in Cardiac Function Independent of Vascular Alterations

“…14 Further measurements included the following (methodology described in the online supplement): wall thickness (interventricular septal [IVS] and posterior wall [PW]), LV mass, ejection fraction (EF), systolic (SЈ), and early (EЈ) and late (AЈ) diastolic mitral annulus pulsed wave tissue Doppler (TDI) velocities, PW Doppler early (E) and late (A) diastolic transmitral flow velocities, and carotid-femoral pulse wave velocity. 13,15 Intima-media thickness was measured in the bilateral carotid and femoral arteries, which were also were carefully scanned for the presence of plaque. Atheroscle- Data are meansϮSDs or median (interquartile range) unless otherwise specified.…”