Showing papers by "Luc M. Van Bortel published in 2007"

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

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 (P<0.001) 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 (P<0.001). Reflection coefficient and reflection magnitude increased with age (P<0.001) 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.

Noninvasive (input) impedance, pulse wave velocity, and wave reflection in healthy middle-aged men and women. Editorial Commentary

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 (P<0.001) 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 (P<0.001). Reflection coefficient and reflection magnitude increased with age (P<0.001) 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.

Altered arterial function in migraine of recent onset

Abstract: Objective: Migraine is associated with cardiovascular disorders but the underlying mechanisms are unknown. Arterial structure and function are important determinants of cardiovascular morbidity and mortality. The aim of the present study was to assess arterial properties in patients with migraine of recent onset. Methods: In a cross-sectional study, structural and functional arterial properties were assessed using ultrasound and applanation tonometry in 50 patients with a history of migraine >1 and Results: Brachial artery diameter (4.82 ± 0.93 mm vs 5.39 ± 0.89 mm, p = 0.01) and compliance (0.30 ± 0.17 mm 2 /kPa vs 0.37 ± 0.19 mm 2 /kPa, p = 0.02) were decreased in migraine patients compared with controls. Femoral artery compliance was decreased in migraine patients (1.19 ± 0.55 mm 2 /kPa vs 1.42 ± 0.59 mm 2 /kPa, p = 0.04). Carotid arterial wall properties were similar between groups. Aortic augmentation index was increased in migraine patients (4 ± 10% vs −1 ± 10%, adjusted p = 0.04). Flow-mediated vasodilation of the brachial artery (normalized to peak shear rate) was decreased in patients with migraine (29 ± 15 vs 37 ± 15 10 −3 %. sec, p = 0.006). Conclusion: Functional arterial properties are altered in patients with migraine of recent onset.

Assessment of pressure wave reflection: getting the timing right!

Abstract: Assessment of timing and magnitude of wave reflection is ideally based on wave separation analysis (WSA). In clinical practice, however, waveform analysis (WFA) is often used to study wave reflection, with different coexisting approaches to assess 'landmarks' on the waveform which are indicative for return of the reflected wave. The aim of this work was to compare WSA and WFA. Data were obtained from 2132 subjects (1093 women) aged between 35 and 56 and free from overt cardiovascular disease. Carotid pressure and aortic flow waveforms, and carotid-femoral pulse wave velocity were measured non-invasively. WSA yielded the timing of return of reflected wave (Tf-b), the ratio of forward and backward pressure wave (Pb/Pf), and the effective length of the arterial tree (Leff). WFA resulted in identification of the shoulder (Tsho) or inflection point (Tinf) as landmark points, with subsequently derived augmentation index and Leff (AIxsho and Leff,sho, AIxinf and Leff,inf, respectively). (i) Neither Tinf nor Tsho corresponded with the timing obtained from WSA. (ii) Measurements of Leff were found to decrease with age (conforming with current physiological insights) whilst Leff,inf was found to increase with age in women, and mixed results were obtained for Leff,sho. (iii) Both AIxinf and AIxsho showed a persistent gender difference which was not present in Pb/Pf. Using the pressure at Tf-b to calculate AIx, the systematic gender difference in AIxf-b was greatly reduced. Analysis of pressure wave reflection is optimally based on measurement of pressure and flow, rather than on waveform analysis alone.

Arterial stiffness and wave reflections in renal transplant recipients

Abstract: BACKGROUND Arterial stiffness predicts cardiovascular disease (CVD) events and has been well documented in haemodialysis patients. Information in renal transplant recipients (RTR), however, remains limited despite their higher CVD risk compared to the general population. We aimed to assess arterial stiffening and wave reflections in RTR and healthy controls and to evaluate which factors could explain potential differences. METHODS Carotid augmentation index (AI) and carotid-femoral pulse wave velocity (PWV) were measured in 200 RTR and 44 controls using applanation tonometry. The impact of traditional and non-traditional CVD risk factors was assessed using linear regression analysis. Glomerular filtration rate (GFR) was measured by (51)Cr-EDTA (RTR) and estimated using the abbreviated Modification of Diet in Renal Disease formula (RTR and controls). RESULTS After correction for age, blood pressure and anthropometry, AI and PWV remained 7.4 +/- 3.6% (P = 0.04) and 0.7 +/- 0.3 m/s (P = 0.01) higher in RTR than controls, corresponding to a difference in vascular age of >10 years. In multivariate analysis, additional independent factors related to AI and PWV were GFR (-1.8% and -0.19 m/s per 10 ml/min) and C-reactive protein (3.2% and 0.21 m/s per logarithm increase). CONCLUSIONS Increased arterial stiffness and wave reflections in RTR are attributable to incomplete restoration of GFR and the presence of subclinical inflammation.

The use of a generalized transfer function: different processing, different results!

Abstract: It has become common knowledge that, on its path from the central aorta towards the periphery, the amplitude of the pressure pulse is amplified [1,2]. As a result, systolic blood pressure is substantially higher in peripheral vessels, such as the brachial and radial arteries, than in the central aorta. Although there is mixed evidence available indicating that a knowledge of central blood pressure improves diagnosis and is more predictive than peripheral blood pressure in terms of outcome [3–5], it is certainly defendable to assess these central blood pressures from a physiological point of view. After all, it is the central pressure that the heart is facing, and this forms the true afterload. The question is how to assess these central blood pressures in a non-invasive way. One option is to use applanation tonometry at a vessel as close to the heart as possible, where the carotid artery is an obvious choice [6]. Another option is to assess peripheral blood pressure waveforms at the radial artery, where applanation tonometry is somewhat easier to perform, and to use a so-called transfer function (TF) to generate ‘synthesized’ central pressure waveforms from the radial ones [7,8].