Central and local arterial stiffness in White Europeans compared to age-, sex-, and BMI-matched South Asians

Background Ethnicity impacts cardiovascular disease (CVD) risk, and South Asians demonstrate a higher risk than White Europeans. Arterial stiffness is known to contribute to CVD, and differences in arterial stiffness between ethnicities could explain the disparity in CVD risk. We compared central and local arterial stiffness between White Europeans and South Asians and investigated which factors are associated with arterial stiffness. Methods Data were collected from cohorts of White Europeans (the Netherlands) and South Asians (India). We matched cohorts on individual level using age, sex, and body mass index (BMI). Arterial stiffness was measured with ARTSENS® Plus. Central stiffness was expressed as carotid-femoral pulse wave velocity (cf-PWV, m/s), and local carotid stiffness was quantified using the carotid stiffness index (Beta) and pressure-strain elastic modulus (Epsilon, kPa). We compared arterial stiffness between cohorts and used multivariable linear regression to identify factors related to stiffness. Results We included n = 121 participants per cohort (age 53±10 years, 55% male, BMI 24 kg/m2). Cf-PWV was lower in White Europeans compared to South Asians (6.8±1.9 vs. 8.2±1.8 m/s, p0.05 for interaction). Systolic blood pressure was associated with carotid stiffness in both cohorts, whereas age was associated to carotid stiffness only in South Asians and BMI only in White Europeans. Conclusion Ethnicity is associated with central but not local arterial stiffness. Conversely, ethnicity seems to modify associations between CVD risk factors and local but not central arterial stiffness. This suggests that ethnicity interacts with arterial stiffness measures and the association of these measures with CVD risk factors

Coronary–aortic interaction during ventricular isovolumic contraction

In earlier work, we suggested that the start of the isovolumic contraction period could be detected in arterial pressure waveforms as the start of a temporary pre-systolic pressure perturbation (AICstart, start of the Arterially detected Isovolumic Contraction), and proposed the retrograde coronary blood volume flow in combination with a backwards traveling pressure wave as its most likely origin. In this study, we tested this hypothesis by means of a coronary artery occlusion protocol. In six Yorkshire × Landrace swine, we simultaneously occluded the left anterior descending (LAD) and left circumflex (LCx) artery for 5 s followed by a 20-s reperfusion period and repeated this sequence at least two more times. A similar procedure was used to occlude only the right coronary artery (RCA) and finally all three main coronary arteries simultaneously. None of the occlusion protocols caused a decrease in the arterial pressure perturbation in the aorta during occlusion (P > 0.20) nor an increase during reactive hyperemia (P > 0.22), despite a higher deceleration of coronary blood volume flow (P = 0.03) or increased coronary conductance (P = 0.04) during hyperemia. These results show that the pre-systolic aortic pressure perturbation does not originate from the coronary arteries

The Ultrasound Window Into Vascular Ageing: A Technology Review by the VascAgeNet COST Action

Non-invasive ultrasound (US) imaging enables the assessment of the properties of superficial blood vessels. Various modes can be used for vascular characteristics analysis, ranging from radiofrequency (RF) data, Doppler- and standard B/M-mode imaging, to more recent ultra-high frequency and ultrafast techniques. The aim of the present work was to provide an overview of the current state-of-the-art non-invasive US technologies and corresponding vascular ageing characteristics from a technological perspective. Following an introduction about the basic concepts of the US technique, the characteristics considered in this review are clustered into: 1) vessel wall structure; 2) dynamic elastic properties, and 3) reactive vessel properties. The overview shows that ultrasound is a versatile, non-invasive, and safe imaging technique that can be adopted for obtaining information about function, structure, and reactivity in superficial arteries. The most suitable setting for a specific application must be selected according to spatial and temporal resolution requirements. The usefulness of standardization in the validation process and performance metric adoption emerges. Computer-based techniques should always be preferred to manual measures, as long as the algorithms and learning procedures are transparent and well described, and the performance leads to better results. Identification of a minimal clinically important difference is a crucial point for drawing conclusions regarding robustness of the techniques and for the translation into practice of any biomarker

Augmentation index is not a proxy for wave reflection magnitude: mechanistic analysis using a computational model

The augmentation index (AIx) is deemed to capture the deleterious effect on left ventricular (LV) work of increased wave reflection associated with stiffer arteries. However, its validity as a proxy for wave reflection magnitude has been questioned. We hypothesized that, in addition to increased wave reflection due to increased pulse wave velocity, LV myocardial shortening velocity influences AIx.Using a computational model of the circulation, we investigated the isolated and combined influences of myocardial shortening velocity vs,LV and arterial stiffness on AIx. Aortic blood pressure waveforms were characterized using AIx and the reflected wave pressure amplitude (pbw, obtained using wave separation analysis). Our reference simulation (normal vs,LV and arterial stiffness) was characterized by an AIx of 21%. A realistic reduction in vs,LV caused AIx to increase from 21 to 42%. An arterial stiffness increase, characterized by a relevant 1.0ms-1 increase in carotid-femoral pulse wave velocity, caused AIx to increase from 21 to 41%. Combining the reduced vs,LV and increased arterial stiffness resulted in an AIx of 54%. In a multi-step parametric analysis, both vs,LV and arterial stiffness were about equal determinants of AIx, whereas pbw was only determined by arterial stiffness. Furthermore, the relation between increased AIx and LV stroke work was only for about 50% explained by an increase in arterial stiffness, the other factor being vs,LV. The pbw, on the other hand, related less ambiguously to LV stroke work. We conclude that the AIx reflects both cardiac and vascular properties and should not be considered an exclusively vascular parameter

Large vessels as a tree of transmission lines incorporated in the CircAdapt whole-heart model:a computational tool to examine heart-vessel interaction

\u3cp\u3eWe developed a whole-circulation computational model by integrating a transmission line (TL) model describing vascular wave transmission into the established CircAdapt platform of whole-heart mechanics. In the present paper, we verify the numerical framework of our TL model by benchmark comparison to a previously validated pulse wave propagation (PWP) model. Additionally, we showcase the integrated CircAdapt–TL model, which now includes the heart as well as extensive arterial and venous trees with terminal impedances. We present CircAdapt–TL haemodynamics simulations of: 1) a systemic normotensive situation and 2) a systemic hypertensive situation. In the TL–PWP benchmark comparison we found good agreement regarding pressure and flow waveforms (relative errors ≤ 2.9% for pressure, and ≤ 5.6% for flow). CircAdapt–TL simulations reproduced the typically observed haemodynamic changes with hypertension, expressed by increases in mean and pulsatile blood pressures, and increased arterial pulse wave velocity. We observed a change in the timing of pressure augmentation (defined as a late-systolic boost in aortic pressure) from occurring after time of peak systolic pressure in the normotensive situation, to occurring prior to time of peak pressure in the hypertensive situation. The pressure augmentation could not be observed when the systemic circulation was lumped into a (non-linear) three-element windkessel model, instead of using our TL model. Wave intensity analysis at the carotid artery indicated earlier arrival of reflected waves with hypertension as compared to normotension, in good qualitative agreement with findings in patients. In conclusion, we successfully embedded a TL model as a vascular module into the CircAdapt platform. The integrated CircAdapt–TL model allows detailed studies on mechanistic studies on heart-vessel interaction.\u3c/p\u3

Monodisperse perfluorohexane emulsions for targeted ultrasound contrast imaging

Quantitative targeted ultrasound contrast imaging demands for contrast agents with a small monodisperse size and a high coverage of specific ligands for effective adhesion under physiological shear stress conditions. However, the particles should also be large enough to generate sufficient ultrasound reflection. Standard perfluorocarbon emulsions do not satisfy both requirements (adhesion and echogenicity). Therefore, we decided to develop a membrane emulsification technique to produce echogenic monodisperse perfluorohexane emulsions able to carry specific ligands for adhesion to the artery wall. In this work, we demonstrate that membrane emulsification is an excellent tool to create strictly monodisperse echogenic perfluorohexane emulsions with a preset droplet size. Perfluorohexane is emulsified in water using photolithographic microsieves. An ultrasound experiment demonstrates that the perfluorohexane emulsions clearly enhance echogenicity. The acoustic enhancement varies with droplet size and surface coverage. The emulsions, with a biotinylated fluoro-surfactant, are able to bind avidin coated SiO2 particles. This proves that these emulsions show a very promising potential to act as key species in the field of selective targeting, which can provide novel insights into the development and early detection of important vascular diseases, e.g. atherosclerosis

Noninvasive pulmonary transit time:a new parameter for general cardiac performance

\u3cp\u3eIntroduction: Pulmonary transit time (PTT) assessed with contrast-enhanced ultrasound (CEUS) is a novel tool to evaluate cardiac function. PTT represents the time for a bolus of contrast to pass from the right to the left ventricle, measured according to the indicator dilution principles using CEUS. We investigated the hypothesis that PTT is a measure of general cardiac performance in patient populations eligible for cardiac resynchronization therapy (CRT). Methods: The study population consisted of heart failure patients referred for CRT with NYHA class II–IV, left ventricular ejection fraction (LVEF)≤35% and QRS≥120 ms. CEUS, ECG, and blood were analyzed, and participants completed a quality of life questionnaire at baseline and 3 months after CRT implantation. Normalized PTT (nPTT) was calculated to compensate for the heart rate. Correlations were assessed with Pearson's or Spearman's coefficients and stratified for rhythm and NYHA class. Results: The study population consisted of 94 patients (67 men) with a mean age of 70±8.9 years. (n)PTT was significantly correlated with left ventricular parameters (r\u3csub\u3es\u3c/sub\u3e=−.487, P<.001), right ventricular parameters (r=−.282, P=.004), N-terminal pro-B-type natriuretic peptide (NT-proBNP) (r\u3csub\u3es\u3c/sub\u3e=.475, P<.001), and quality of life (r\u3csub\u3es\u3c/sub\u3e=.364, P<.001). Stronger significant correlations were found in patients in sinus rhythm. Conclusion: CEUS-derived PTT and nPTT correlate to a fair degree with measures of systolic and diastolic function, NT-pro-BNP, and quality of life. As CEUS-derived PTT can be obtained easily, noninvasively and at the bedside, it is a promising future measure of general cardiac performance.\u3c/p\u3

Pressure-dependence of arterial stiffness:potential clinical implications

BACKGROUND: \u3cbr/\u3eArterial stiffness measures such as pulse wave velocity (PWV) have a known dependence on actual blood pressure, requiring consideration in cardiovascular risk assessment and management. Given the impact of ageing on arterial wall structure, the pressure-dependence of PWV may vary with age.\u3cbr/\u3eMETHODS: \u3cbr/\u3eUsing a noninvasive model-based approach, combining carotid artery echo-tracking and tonometry waveforms, we obtained pressure-area curves in 23 hypertensive patients at baseline and after 3 months of antihypertensive treatment. We predicted the follow-up PWV decrease using modelled baseline curves and follow-up pressures. In addition, on the basis of these curves, we estimated PWV values for two age groups (mean ages 41 and 64 years) at predefined hypertensive (160/90 mmHg) and normotensive (120/80 mmHg) pressure ranges.\u3cbr/\u3eRESULTS: \u3cbr/\u3eFollow-up measurements showed a near 1 m/s decrease in carotid PWV when compared with baseline, which fully agreed with our model-prediction given the roughly 10 mmHg decrease in diastolic pressure. The stiffness-blood pressure-age pattern was in close agreement with corresponding data from the 'Reference Values for Arterial Stiffness' study, linking the physical and empirical bases of our findings.\u3cbr/\u3eCONCLUSION: \u3cbr/\u3eOur study demonstrates that the innate pressure-dependence of arterial stiffness may have implications for the clinical use of arterial stiffness measurements, both in risk assessment and in treatment monitoring of individual patients. We propose a number of clinically feasible approaches to account for the blood pressure effect on PWV measurements.\u3cbr/\u3