Echocardiographic Assessment of Aortic Pulse-Wave Velocity: Validation against Invasive Pressure Measurements

Interpolation time-optimized aortic pulse wave velocity estimation by 4D flow MRI

Four-dimensional flow magnetic resonance imaging-based pulse wave velocity (4D flow PWV) estimation is a promising tool for measuring regional aortic stiffness for non-invasive cardiovascular disease screening. However, the effect of variations in the shape of flow waveforms on 4D flow PWV measurements remains unclear. In this study, 4D flow PWV values were compared using cross-correlation algorithm with different interpolation times (iTs) based on flow rate and beat frequency. A critical iT (iTCrit) was proposed from in vitro study using flexible and stiff phantom models to simultaneously achieve a low difference and a low computation time. In vivo 4D flow PWV values from six healthy volunteers were also compared between iTCrit and the conventionally used interpolation time of 1 ms (iT1 ms). The results indicated that iTCrit reduced the mean difference of in vitro 4D flow PWV values by 19%, compared to iT1 ms. In addition, iTCrit measured in vivo 4D flow PWV, showing differences similar to those obtained with iT1 ms. A difference estimation model was proposed to retrospectively estimate potential differences of 4D flow PWV using known values of PWV and the used iT. This study would be helpful for understanding the differences of PWV generated by physiological changes and time step of obtained flow waveforms.

A Novel Equivalent Time Sampling-Based Method for Pulse Transit Time Estimation with Applications into the Cardiovascular Disease Diagnosis

The increasing incidence of cardiovascular diseases (CVDs) is reflected in additional costs for healthcare systems all over the world. To date, pulse transit time (PTT) is considered a key index of cardiovascular health status and for diagnosis of CVDs. In this context, the present study focuses on a novel image analysis-based method for PTT estimation through the application of equivalent time sampling. The method, which post-processes color Doppler videos, was tested on two different setups: a Doppler flow phantom set in pulsatile mode and an in-house arterial simulator. In the former, the Doppler shift was due to the echogenic properties of the blood mimicking fluid only, since the phantom vessels are non-compliant. In the latter, the Doppler signal relied on the wall movement of compliant vessels in which a fluid with low echogenic properties was pumped. Therefore, the two setups allowed the measurement of the flow average velocity (FAV) and the pulse wave velocity (PWV), respectively. Data were collected through an ultrasound diagnostic system equipped with a phased array probe. Experimental outcomes confirm that the proposed method can represent an alternative tool for the local measurement of both FAV in non-compliant vessels and PWV in compliant vessels filled with low echogenic fluids.

Association between renal sympathetic denervation and arterial stiffness: the ASORAS study

OBJECTIVES

Renal sympathetic denervation (RDN) reduces blood pressure (BP). However, one out of three patients does not exhibit a significant BP response to the therapy. This study investigates the association between noninvasive vascular stiffness indices and RDN-mediated BP reduction.

METHODS

In this prospective, single-arm pilot study, patients with systolic office BP at least 140 mmHg, mean 24-h systolic ambulatory blood pressure (ABP) at least 130 mmHg and at least three prescribed antihypertensive drugs underwent radiofrequency RDN. The primary efficacy endpoint was temporal evolution of mean 24-h systolic ABP throughout 1-year post RDN (measured at baseline and 3-6-12 months). Effect modification was studied for baseline ultrasound carotid-femoral and magnetic resonance (MR) pulse wave velocity (PWV), MR aortic distensibility, cardiac MR left ventricular parameters and clinical variables. Statistical analyses were performed using linear mixed-effects models, and effect modification was assessed using interaction terms.

RESULTS

Thirty patients (mean age 62.5 ± 10.7 years, 50% women) with mean 24-h ABP 146.7/80.8 ± 13.7/12.0 mmHg were enrolled. Following RDN, mean 24-h systolic ABP changed with -8.4 (95% CI: -14.5 to -2.3) mmHg/year ( P  = 0.007). Independent effect modifiers were CF-PWV [+2.7 (0.3 to 5.1) mmHg/year change in outcome for every m/s increase in CF-PWV; P  = 0.03], daytime diastolic ABP [-0.4 (-0.8 to 0.0) mmHg/year per mmHg; P  = 0.03], age [+0.6 (0.2 to 1.0) mmHg/year per year of age; P  = 0.006], female sex [-14.0 (-23.1 to -5.0) mmHg/year as compared with men; P  = 0.003] and BMI [+1.2 (0.1 to 2.2) mmHg/year per kg/m 2 ; P  = 0.04].

CONCLUSION

Higher CF-PWV at baseline was associated with a smaller reduction in systolic ABP following RDN. These findings could contribute to improve identification of RDN responders.

Noninvasive Aortic Ultrafast Pulse Wave Velocity Associated With Framingham Risk Model: in vivo Feasibility Study

Background

Aortic pulse wave velocity (PWV) enables the direct assessment of aortic stiffness, which is an independent risk factor of cardiovascular (CV) events. The aim of this study is to evaluate the association between aortic PWV and CV risk model classified into three groups based on the Framingham risk score (FRS), i.e., low-risk (<10%), intermediate-risk (10~20%) and high-risk (>20%).

Methods

To noninvasively estimate local PWV in an abdominal aorta, a high-spatiotemporal resolution PWV measurement method (>1 kHz) based on wide field-of-view ultrafast curved array imaging (ufcPWV) is proposed. In the ufcPWV measurement, a new aortic wall motion tracking algorithm based on adaptive reference frame update is performed to compensate errors from temporally accumulated out-of-plane motion. In addition, an aortic pressure waveform is simultaneously measured by applanation tonometry, and a theoretical PWV based on the Bramwell-Hill model (bhPWV) is derived. A total of 69 subjects (aged 23–86 years) according to the CV risk model were enrolled and examined with abdominal ultrasound scan.

Results

The ufcPWV was significantly correlated with bhPWV (r = 0.847, p < 0.01), and it showed a statistically significant difference between low- and intermediate-risk groups (5.3 ± 1.1 vs. 8.3 ± 3.1 m/s, p < 0.01), and low- and high-risk groups (5.3 ± 1.1 vs. 10.8 ± 2.5 m/s, p < 0.01) while there is no significant difference between intermediate- and high-risk groups (8.3 ± 3.1 vs. 10.8 ± 2.5 m/s, p = 0.121). Moreover, it showed a significant difference between two evaluation groups [low- (<10%) vs. higher-risk group (≥10%)] (5.3 ± 1.1 vs. 9.4 ± 3.1 m/s, p < 0.01) when the intermediate- and high-risk groups were merged into a higher-risk group.

Conclusion

This feasibility study based on CV risk model demonstrated that the aortic ufcPWV measurement has the potential to be a new approach to overcome the limitations of conventional systemic measurement methods in the assessment of aortic stiffness.

Ultrasonography to detect cardiovascular damage in children with essential hypertension

Background

Essential hypertension in adults may begin in childhood. The damages to the heart and blood vessels in children with essential hypertension are hidden and difficult to detect. We noninvasively examined changes in cardiovascular structure and function in children with hypertension at early stage using ultrasonography.

Methods

All patients with essential hypertension admitted from March 2020 to May 2021 were classified into simple hypertension (group 1, n = 34) and hypertension co-existing with obesity (group 2, n = 11) isolation. Meanwhile 32 healthy children were detected as control heathly group (group 3). We used pulse-wave Doppler to measure carotid–femoral pulse wave velocity (cfPWV), intimal–medial thickness (cIMT) and distensibility of carotid artery (CD). Cardiac structure and function (left atrial diameter [LAD], left ventricular mass [LVM], LVM index [LVMI], relative wall thicknes [RWT], end-diastolic left ventricular internal diameter [LVIDd], diastolic interventricular septum thickness [IVSd], diastolic left ventricular posterior wall thickness [LVPWd], root diameter of aorta [AO], E peak, A peak, E' peak, A' peak, E/E' ratio, and E/A ratio) were measured by echocardiography.

Results

The cfPWV of children in group 1 and group 2 were significantly higher than healthy children in group 3. Significant differences were observed in LVM, LVMI, RWT, LVIDd, IVSd, LVPWd, LAD, A peak, E' peak, A' peak, and E/E’ among three groups.

Conclusion

Children and adolescents with essential hypertension demonstrate target organ damages in the heart and blood vessels.

A Novel Methodology for Semi-automatic Measurement of Arterial Stiffness by Doppler Ultrasound: Clinical Feasibility and Reproducibility

The conventional manual approach to measurement of aortic pulse wave velocity (PWV) by Doppler ultrasonography is time consuming and operator dependent. Here we report a new semi-automated methodology for more efficient and objective measurement of aortic PWV and results of tests of its clinical feasibility and reproducibility. Carotid-femoral pulse wave velocity (cfPWV) was measured in 50 patients with suspected coronary artery disease (aged 59.2 ± 10.0 y, 36 males) by three independent observers, including two experienced sonographers and one cardiologist without ultrasonographic experience. The cfPWV measured by the semi-automatic method (cfPWV_A) was compared with reference values obtained by averaging measurements by two experienced sonographers using the conventional standard manual method (cfPWV_M). Measurements of cfPWV_A were feasible in all 50 patients and exhibited excellent agreement with averaged cfPWV_M from the two experienced sonographers, with an intraclass correlation coefficient (ICC) of 0.915 (95% confidence interval: 0.876-0.942). The inexperienced observer-measured cfPWV_A did not differ from the cfPWV_M measured by the two experienced sonographers (8.04 ± 1.29 vs. 8.14 ± 1.32 m/s, p > 0.05), with a high consistency by ICC of 0.877 (0.793-0.928). Bland-Altman plots further illustrated the good agreement between the two methods and good intra- and inter-observer reproducibility. Time consumption for cfPWV measurement using the new method was significantly less than that for the manual method (122 ± 35 s vs. 455 ± 105 s, p < 0.0001), saving about 73% of the time. This new semi-automatic methodology for aortic PWV measurement not only has an accuracy similar to that of the conventional standard manual method but is also highly feasible and time saving. It may provide a reliable, simple and reproducible approach to arterial stiffness evaluation in clinical settings.

Non-Invasive Methods for PWV Measurement in Blood Vessel Stiffness Assessment

In recent years, statistical studies highlighted an increasing incidence of cardiovascular diseases (CVD) which reflected on additional costs on the healthcare systems worldwide. Pulse wave velocity (PWV) measurement is commonly considered a CVD predictor factor as well as a marker of Arterial Stiffness (AS), since it is closely related to the mechanical characteristics of the arterial wall. An increase in PWV is due to a more rigid arterial system. Because of the prevalence of the elastic component, in young people the PWV is lower than in the elderly. Nowadays, invasive and non-invasive methods for PWV assessment are employed: there is an increasing attention in the development of non-invasive devices which mostly perform a regional PWV measurement (over a long arterial portion) rather than local (over a short arterial portion). The accepted gold-standard for non-invasive AS measurement is the carotid-femoral PWV used to evaluate the arterial damage, the corresponding cardiovascular risk and to adapt the proper therapy. This review article considers the main commercially available devices underlining their operating principles in terms of sensors, execution mode, pulse waveform acquired, site of measurement, distance and time estimation methods, as well as their main limitations in clinical practice.

The Progress of Advanced Ultrasonography in Assessing Aortic Stiffness and the Application Discrepancy between Humans and Rodents

Aortic stiffening is a fundamental pathological alteration of atherosclerosis and other various aging-associated vascular diseases, and it is also an independent risk factor of cardiovascular morbidity and mortality. Ultrasonography is a critical non-invasive method widely used in assessing aortic structure, function, and hemodynamics in humans, playing a crucial role in predicting the pathogenesis and adverse outcomes of vascular diseases. However, its applications in rodent models remain relatively limited, hindering the progress of the research. Here, we summarized the progress of the advanced ultrasonographic techniques applied in evaluating aortic stiffness. With multiple illustrative images, we mainly characterized various ultrasound techniques in assessing aortic stiffness based on the alterations of aortic structure, hemodynamics, and tissue motion. We also discussed the discrepancy of their applications in humans and rodents and explored the potential optimized strategies in the experimental research with animal models. This updated information would help to better understand the nature of ultrasound techniques and provide a valuable prospect for their applications in assessing aortic stiffness in basic science research, particularly with small animals.

Acute Changes in Carotid-Femoral Pulse-Wave Velocity Are Tracked by Heart-Femoral Pulse-Wave Velocity

Background: Carotid-femoral pulse-wave velocity (cfPWV) is the reference standard measure of central arterial stiffness. However, it requires assessment of the carotid artery, which is technically challenging, and subject-level factors, including carotid artery plaque, may confound measurements. A promising alternative that overcomes these limitations is heart-femoral PWV (hfPWV), but it is not known to what extent changes in cfPWV and hfPWV are associated.

Objectives: To determine, (1) the strength of the association between hfPWV and cfPWV; and (2) whether change in hfPWV is associated with change in cfPWV when central arterial stiffness is perturbed.

Methods: Twenty young, healthy adults [24.0 (SD: 3.1) years, 45% female] were recruited. hfPWV and cfPWV were determined using Doppler ultrasound at baseline and following a mechanical perturbation in arterial stiffness (120 mmHg thigh occlusion). Agreement between the two measurements was determined using mixed-effects regression models and Bland-Altman analysis.

Results: There was, (1) strong (ICC > 0.7) agreement between hfPWV and cfPWV (ICC = 0.82, 95%CI: 0.69, 0.90), and, (2) very strong (ICC > 0.9) agreement between change in hfPWV and cfPWV (ICC = 0.92, 95%CI: 0.86, 0.96). cfPWV was significantly greater than hfPWV at baseline and during thigh occlusion (both P < 0.001). Inspection of the Bland-Altman plot, comparing cfPWV and corrected hfPWV, revealed no measurement magnitude bias.

Discussion: The current findings indicate that hfPWV and cfPWV are strongly associated, and that change in cfPWV is very strongly associated with change in hfPWV. hfPWV may be a simple alternative to cfPWV in the identification of cardiovascular risk in clinical and epidemiological settings.

Age-related values of aortic pulse wave velocity in healthy subjects measured by Doppler echocardiography

Aortic pulse wave velocity (aPWV) is a measure of aortic stiffness, which is an indicator of vascular aging and prognostic marker for cardiovascular complications. aPWV can be measured with various methods, but with different reference values depending on the technique used. Therefore, we decided to evaluate age-related values of aPWV, measured by Doppler echocardiography. We included 134 healthy adults (mean age 44.1 ± 13.2 years, 54% of females) divided into five groups based on age decades (D1 21-30 years, n = 29; D2 31-40 years, n = 24; D3 41-50 years, n = 34; D4 51-60 years, n = 25; and D5 61-70 years, n = 22). With the use of a cardiac probe and ECG tracing, ten Doppler waveforms were sequentially recorded, first in the distal aortic arch, and than in the left external iliac artery. Transit time was measured as a delay of the foot of the Doppler waveform in the distal, relative to the proximal location. The distance was measured over the body surface. aPWV was calculated as distance/transit time. Median aPWV in the whole group was 5.05 m/s [4.55-5.99] and did not differ according to sex (females, 5.28 m/s [4.50-6.1] vs. males, 4.95 m/s [4.59-5.77], p = 0.46). Mean aPWV values with 95% confidence intervals (95% CI) for each decade were as follows: D1, 4.54 m/s (4.37-4.72), D2, 4.61 m/s (4.36-4.87), D3, 5.11 m/s (4.89-5.33), D4, 6.04 m/s (5.63-6.45), and D5, 6.77 m/s (6.35-7.19). We report age-related values of aPWV, in a healthy population, measured by Doppler echocardiography. This may be helpful in future research exploring the associations between aortic stiffness, cardiac function, and cardiovascular risk.

Aortic elasticity indices as predictors of coronary artery disease severity assessed by SYNTAX score

Background:

Aortic elastic properties have been related to coronary artery disease (CAD) morbidity and mortality. We aimed to assess the relation of aortic elasticity indices to the severity and complexity of CAD assessed using the SYNTAX Score (SS), evaluating which of these indices have better predictivity for CAD severity.

Materials and Methods:

We prospectively enrolled 150 individuals who underwent elective coronary angiography for suspected CAD, out of them 29 (19.3%) had normal or nonsignificant angiographic findings (Group I), whereas 121 (80.7%) had significant CAD (Group II) for whom the SS was calculated. Echo-derived aortic elasticity indices were performed for all patients.

Results:

Logistic regression analyses showed that each of aortic distensibility, stiffness index, elastic modulus, aortic strain, and aortic peak early diastolic velocity were predictors for significant CAD and further for more complex CAD as indicated by intermediate-high SS. Receiver operator characteristic curves-derived cutoff points were performed for each of the aortic elasticity indices. Along with diabetes, decreased aortic strain ≤10.2% was the only independent predictor of intermediate-high SS (odds ratio = 4.31, 95% confidence interval = 1.38–13.50, P = 0.01).

Conclusion:

Simple M-mode derived aortic elasticity indices, particularly aortic strain ≤10.2%, might predict patients with more severe and complex CAD.

The use of ultrasound to assess aortic biomechanics: Implications for aneurysm and dissection

Arterial stiffening, which occurs when conduit arteries thicken and lose elasticity, has been associated with cardiovascular disease and increased risk for future cardiovascular events. Specifically, aortic stiffening plays a large role in the pathogenesis of vascular diseases, such as aneurysm formation and dissection. Current parameters used to assess risk of aortic rupture include absolute diameter and growth rate. However, these properties lack the reliability required to accurately risk-stratify patients. As with any elastic conduit, it is important to assess the biomechanical properties of the aorta in order to assess cardiovascular risk and prevent disease progression. There are several invasive and noninvasive methods by which stiffness of the large arteries can be assessed. Of particular interest are ultrasound-based methods, such as tissue Doppler imaging and speckle-tracking echocardiography, due to their noninvasive and feasible nature. In this review, we summarize studies demonstrating utility of noninvasive ultrasound imaging methods for measuring aortic biomechanics for the assessment and management of aortic aneurysms.

Current assessment of pulse wave velocity: comprehensive review of validation studies

OBJECTIVE

Carotid-femoral pulse wave velocity (PWV) is considered the gold standard for arterial stiffness assessment in clinical practice. A large number of devices to measure PWV have been developed and validated. We reviewed different validation studies of PWV estimation techniques and assessed their conformity to the Artery Society Guidelines and the American Heart Association recommendations.

METHODS

Pubmed and Medline (1995-2017) were searched to identify PWV validation studies. Of the 96 article retrieved, 26 met the inclusion criteria.

RESULTS

Several devices had been developed and validated to noninvasively measure arterial stiffness, using applanation tonometry (SphygmoCor, PulsePen), piezoelectric mechanotransducers (Complior), cuff-based oscillometry (Arteriograph, Vicorder and Mobil-O-Graph), photodiode sensors (pOpmètre) and devices assessing brachial-ankle pulse wave velocity and cardiac-ankle PWV. Ultrasound technique and MRI remain confined to clinical research. Good agreement was found with the Artery Society Guidelines. Two studies (Complior, SphygmoCor Xcel) showed best adherence with the guidelines. In Arteriograph, MRI, ultrasound and SphygmoCor Xcel validation studies sample size was smaller than the minimum suggested by the guidelines. High discrepancies between devices were shown in distance estimation: in two studies (Arteriograph, Complior) path length was estimated in conformity to the guidelines. Transit time was calculated using the intersecting tangent method, but in two studies (Vicorder, pOpmètre) best agreement was found using the maximum of the second derivative. Six studies reached the accuracy level 'excellent' defined in the Artery guidelines.

CONCLUSION

Method to assess transit time and path length need validation in larger populations. Further studies are required in different risk population to implement clinical applicability of every device.

Echocardiographic assessment of aortic pulse wave velocity as a diagnostic and prognostic parameter for left ventricular diastolic dysfunction

BACKGROUND

Aortic pulse wave velocity (PWV) is a standard measurement of aortic stiffness. It has been suggested that increased arterial stiffness promotes left ventricular diastolic dysfunction (LVDD). We designed this study to evaluate role of aortic PWV as a new diagnostic parameter for LVDD by correlation with echocardiographic LVDD indices and to evaluate its prognostic value in patients with LVDD by correlation with brain natriuretic peptide (BNP).

METHODS

One hundred patients with age >50 were divided into two groups: case group consisted of 80 patients with asymptomatic LVDD with EF ≥50% while controlgroup consisted of 20 patients with normal LVDD. BNP blood test and echocardiography with assessment of aortic PWV were done.

RESULTS

Mean age was 59±7.47 vs. 57±6.35 years in case and control groups respectively (P= 0.73), 38 (47.5%) males in case vs. 9 (45%) in control (P=0.84). Aortic PWV showed positive correlation with E/e' (r=0.957, P<0.001), tricuspid regurgitation (TR) velocity (r=0.941, P<0.001), and LA volume index (r=0.947, P<0.001). Negative correlation with septal e' (r=-0.970, P<0.001) and lateral e' (r=-0.932, P<0.001) were reported. Moreover, positive correlation with plasma BNP (r=0.958, P<0.001) was reported. The area under the ROC curve for aortic PWV to detect DD was 0.86 (95% CI, 0.76-0.98; P<0.001) and the optimal cutoff point of 12.5 m/s produced 92.3% sensitivity and 75.0% specificity with an accuracy of 89.0%.

CONCLUSIONS

Echocardiographic assessment of aortic PWV appears not only to be a sensitive and reliable for LVDD detection but also has a promising prognostic value in patients with LVDD.

Modified high-resolution wavenumber analysis for detection of pulse wave velocity using coefficient of variation of arterial wall acceleration waveforms

PURPOSE

In high-resolution wavenumber analysis for detection of pulse wave velocity (PWV), phase information of analytic signals is used to estimate the wavenumber. However, the phase information could be affected by the adjacent signals in the temporal direction. Therefore, we propose a modified high-resolution wavenumber analysis technique using real acceleration waveforms of the arterial wall.

METHOD

In the modified wavenumber analysis, we propose a new evaluation function that corresponds to the inverse of the squared coefficient of variation. The accuracy of estimation of PWV was investigated by performing simulations, and the feasibility was also examined in an in vivo experiment.

RESULTS

In the simulation experiments, the estimation accuracy using the proposed method was comparable to that using the previous method using phase information. However, when the pulse wave included the reflection components, the PWV estimated using the proposed method was more stable than that estimated using the previous method. Also, in the in vivo experiments, at opening of the aortic valve, the velocity estimated by the proposed method was almost equal to that estimated by the previous method (previous: 2.97 ± 1.2 m/s, proposed: 4.82 ± 1.4 m/s). Meanwhile, when the reflection components were present, the estimated PWV values yielded by the previous and proposed methods were - 1.13 and - 3.50 ± 0.9 m/s, respectively. The PWVs at those two time points estimated by the previous method were quite different, and the PWV estimate was considered to be more affected by the reflected waves.

CONCLUSION

The results of the simulations and in vivo experiments indicated that the modified high-resolution wavenumber analysis method was less affected by the reflected waves and more accurate in estimation of PWVs of both the forward and reflected waves.

A novel methodology for rat aortic pulse wave velocity assessment by Doppler ultrasound: validation against invasive measurements

There is still lack of a simple, accurate, and noninvasive method for rat aortic pulse wave velocity (PWV) measurement, especially the transit distance cannot be accurately measured. Thus, we aimed to derive an equation for aortic transit distance as a function of the nose-to-rump length (L) and to test the hypothesis that aortic PWV measured by new equation combined with Doppler ultrasound (the "equation method") may have stronger correlation with invasive measurements than traditional "body surface method." Two-hundred male Sprague-Dawley (SD) rats (age ranged 5-24 wk) were included in protocol 1, and the aortic transit distances were measured postmortem. In protocol 2, heart-femoral PWV and carotid-femoral PWV were measured by equation method (hfPWV_E, cfPWV_E) and also by traditional body surface method (hfPWV_S, cfPWV_S) in another 30 young and 28 old rats. These measurements were then validated against invasively measured hfPWV_I and cfPWV_I from the same animal. Protocol 1 showed that the heart-femoral transit distance could be calculated by 0.6086 × L - 1.6523, and the carotid-femoral transit distance by 0.4614 × L + 1.8335. In protocol 2, in young rats, the Pearson r between hfPWV_E, cfPWV_E, hfPWV_S, and cfPWV_S and their corresponding invasive measurement were 0.8962, 0.8509, 0.8387, and 0.7828, respectively (all P < 0.0001). In the old group, the results were 0.8718, 0.7999, 0.8330, and 0.7112, respectively (all P < 0.0001). The hfPWV_E and cfPWV_E showed better agreement with hfPWV_I and cfPWV_I and lower intra- and interobserver variability compared with hfPWV_S and cfPWV_S in both groups. These findings demonstrate that this novel methodology provides a simple and reliable method for rat noninvasive aortic PWV measurement.NEW & NOTEWORTHY First, when measuring aortic PWV in SD rat models, the heart-femoral transit distance can be estimated by 0.6086 × L - 1.6523, and the carotid-femoral distance transit distance can be estimated by 0.4614 × L + 1.8335, where L (in mm) is nose-to-rump length. Second, this novel methodology for aortic PWV measurement was validated with a closer correlation with the invasive measurements than traditional approach in young and old rats. Third, this study provides a simple and reliable method for rat noninvasive aortic PWV measurement.

Arterial Stiffness Can Be Modulated by Pressure-Independent Mechanisms in Hypertension

Background Effects of short-term interventions on large-artery stiffness assessed by pulse wave velocity (PWV) have mainly been explained by concomitant changes in blood pressure (BP). However, lower body negative pressure, which increases sympathetic activity and has other hemodynamic effects, has a specific effect on PWV in healthy volunteers. Methods and Results We examined effects of lower-limb venous occlusion (LVO), a similar intervention to lower-body negative pressure that reduces BP but increases sympathetic activity and device-guided breathing (DGB), which reduces both BP and sympathetic activity, on PWV in patients with essential hypertension (n=70 after LVO, n=45 after DGB and LVO in random order). The short-acting calcium channel antagonist nifedipine was used as a control for changes in BP. LVO produced a small but significant reduction in mean arterial pressure of 1.8 (95% CI 0.3-3.4) mm Hg. Despite this, aortic and carotid-femoral PWV increased during LVO by 0.8 (0.2-1.4) m/s and 0.7 (0.3-1.05) m/s, respectively. DGB reduced PWV by 1.2 (0.9-1.4) m/s, to a greater extent than did nifedipine 10 mg (reduction of 0.7 [0.1-1.3] m/s, P<0.05 compared with reduction during DGB). This occurred despite a greater decrease in BP with nifedipine compared with DGB. Conclusions Arterial stiffness can be modulated independently of BP over the short term. The mechanism could involve alterations in sympathetic activity or other as yet uncharacterized effects of LVO and DGB.

Thoracic Aortic Intima-Media Thickness in Preschool Children Born Small for Gestational Age

OBJECTIVE

To assess thoracic aortic intima-media thickness (aIMT) as a marker of thoracic aortic remodeling in children born small for gestational age (SGA).

STUDY DESIGN

We assessed thoracic aIMT, carotid intima-media thickness (cIMT), and pulse wave velocity (PWV) in 239 patients (117 SGA; 122 appropriate for gestational age controls) age 6-8 years. Each SGA participant was matched 1:1 based on sex, gestational age, and birth date. Thoracic aIMT was determined by 2-dimensional transthoracic echocardiography.

RESULTS

SGA children showed a significant increase in both aIMT (0.89 mm [0.12] vs 0.79 mm [0.11], P < .001) and cIMT (.50 mm [0.05] vs 0.49 mm [0.04], P < .001) compared with appropriate for gestational age controls, but the magnitude of the difference in aIMT was greater than that in cIMT (standardized difference of the means: +84% vs +27%). aIMT was linearly correlated with aortic arch PWV as measured by echocardiography (r = 0.211, P < .001) but not with carotid-femoral PWV (r = 0.113, P = .111). Born SGA was independently associated with increased aIMT after controlling for perinatal, anthropometric, and biochemical determinants in linear regression models.

CONCLUSIONS

SGA children exhibit increased thoracic aIMT and aortic arch PWV in early childhood that may suggest the presence of structural changes in the thoracic aorta wall architecture. Measurement of ascending aIMT by transthoracic echocardiography is feasible and reproducible and may be a useful marker of vascular disease.

No association between aortic stiffness and liver steatosis in morbidly obese patients

BACKGROUND AND AIMS

Patients with non-alcoholic fatty liver disease are characterized by increased aortic stiffness, but it is unclear whether this is related to non-alcoholic fatty liver disease itself or concomitant metabolic syndrome components, including hypertension and diabetes. Previous studies were methodologically limited by ultrasound-based assessment of liver steatosis or performing liver biopsy in patients with more severe disease. Therefore, we prospectively measured aortic pulse wave velocity (aPWV) in non-selected obese subjects admitted for bariatric surgery with liver biopsy, allowing assessment of the association between aortic stiffness and biopsy-confirmed liver steatosis.

METHODS

We evaluated 120 consecutive severely obese patients (79 females; mean age 42 ± 10 years, mean body mass index 45.0 ± 5.3 kg/m²) without cardiac disease or alcohol-induced liver disease, who were admitted for bariatric surgery. The presence or absence of liver steatosis was defined by wedge liver biopsy. aPWV was measured with the Doppler method at the time of preoperative transthoracic echocardiography.

RESULTS

Based on liver biopsy results, 82 patients (68%) had liver steatosis and 38 (32%) had no steatosis. Univariate linear regression analysis showed that age, mean arterial pressure, liver steatosis, heart rate, female gender, and diabetes were significantly associated with aPWV. However, only age, mean arterial pressure, heart rate, and diabetes remained significant in the multivariate model (p ≤ 0.001).

CONCLUSIONS

We found no independent association between biopsy-confirmed liver steatosis and aortic stiffness measured by Doppler aPWV in morbidly obese individuals. Aortic stiffness in these subjects is related to comorbidities and not to non-alcoholic fatty liver disease itself.

Hypertension and transcatheter aortic valve replacement: parallel or series?

Aortic stenosis (AS) is the most common valvular heart disease in the elderly and it causes significant morbidity and mortality. Hypertension is also highly prevalent in elderly patients with AS, and AS patients with hypertension have worse outcomes. Accurate assessment of AS severity and understanding its relationship with arterial compliance has become increasingly important as the options for valve management, particularly transcatheter interventions, have grown. The parameters used for quantifying stenosis severity have traditionally mainly focused on the valve itself. However, AS is now recognized as a systemic disease involving aging ventricles and stiff arteries rather than one limited solely to the valve. Over the last decade, valvuloarterial impedance, a measure of global ventricular load, has contributed to our understanding of the pathophysiology and course of AS in heterogeneous patients, even when segregated by symptoms and severity. This review summarizes our growing understanding of the interplay between ventricle, valve, and vessel, with a particular emphasis on downstream vascular changes after transcatheter aortic valve replacement and the role of valvuloarterial impedance in predicting left ventricular changes and prognosis in patients with various transvalvular flow patterns.

The importance of accurate measurement of aortic stiffness in patients with chronic kidney disease and end-stage renal disease

Cardiovascular (CV) disease is the leading cause of death in chronic kidney disease (CKD) and end-stage renal disease (ESRD). A key driver in this pathology is increased aortic stiffness, which is a strong, independent predictor of CV mortality in this population. Aortic stiffening is a potentially modifiable biomarker of CV dysfunction and in risk stratification for patients with CKD and ESRD. Previous work has suggested that therapeutic modification of aortic stiffness may ameliorate CV mortality. Nevertheless, future clinical implementation relies on the ability to accurately and reliably quantify stiffness in renal disease. Pulse wave velocity (PWV) is an indirect measure of stiffness and is the accepted standard for non-invasive assessment of aortic stiffness. It has typically been measured using techniques such as applanation tonometry, which is easy to use but hindered by issues such as the inability to visualize the aorta. Advances in cardiac magnetic resonance imaging now allow direct measurement of stiffness, using aortic distensibility, in addition to PWV. These techniques allow measurement of aortic stiffness locally and are obtainable as part of a comprehensive, multiparametric CV assessment. The evidence cannot yet provide a definitive answer regarding which technique or parameter can be considered superior. This review discusses the advantages and limitations of non-invasive methods that have been used to assess aortic stiffness, the key studies that have assessed aortic stiffness in patients with renal disease and why these tools should be standardized for use in clinical trial work.