Arterial Distensibility Research Articles

​​Importance of Right Pulmonary Artery Distensibility Index in the Diagnosis and Management of Pulmonary Arterial Hypertension Secondary to Canine Dilated Cardiomyopathy

Background: The measurement of tricuspid regurgitant velocity is the commonly used non-invasive method for the diagnosis of pulmonary hypertension in dogs. It is anticipated that M-mode echocardiographic measurement of right pulmonary artery distensibility (RPAD) index is simple and provides accurate means for the diagnosis of pulmonary arterial hypertension when tricuspid regurgitant velocity is absent. Hence this study was undertaken to evaluate the importance of RPAD index in the diagnosis and management of pulmonary arterial hypertension secondary to dilated cardiomyopathy. Methods: In the present study, a total of 165 dogs were subjected to echocardiography for diagnosis of pulmonary hypertension secondary to dilated cardiomyopathy. The maximum and minimum internal diameter of the right pulmonary artery during systole and diastole were quantified respectively to determine the right pulmonary artery distensibility (RPAD) index in right parasternal short axis M-mode echocardiogram. The M-mode morphology of right pulmonary artery (anterior dicrotic notch) also recorded. Result: Out of 165 dogs ten dogs had pulmonary arterial hypertension with dilated cardiomyopathy. Dogs with pulmonary hypertension showed a significant decrease in the mean right pulmonary artery distensibility index values and Acceleration time/Ejection time (AT/ET) ratio, while the mean tricuspid regurgitant systolic pressure gradient (TRPG) were significantly elevated when compared to the respective control group. The significant difference was observed in the mean values of tricuspid regurgitant systolic pressure gradient and RPAD index before and after the treatment.

COMPARISON BETWEEN TWO NONINVASIVE METHODS USED TO ESTIMATE BIOMECHANICAL PROPERTIES OF THE INTERNAL CAROTID ARTERY

Background: Many cardiovascular diseases modified the arterial wall stiffness. Objectives: This work focuses on the quantification of the elastic biomechanical properties of the internal carotid (ICA) wall by applying the cepstral analysis on healthy volunteers aged from 22 to 86 years old. The purpose of this study is to compare two methods of measurement of arterial compliance ([Formula: see text], arterial distensibility ([Formula: see text], arterial elastance (Eh), and Young’s modulus ([Formula: see text]. Material and methods: First, arterial compliance and arterial distensibility were measured in function of wave speed ([Formula: see text], which is measured in our previous works by using two methods. Second, elastance Eh was estimated through the ratio between diastolic radius ([Formula: see text] and [Formula: see text]. Finally, [Formula: see text] was estimated from a statistical study from the literature on h due to the difficulty of measuring wall thickness ([Formula: see text]. Results: The Student test demonstrated that there is a very significant difference between young and old subjects in terms of elastance, compliance, and Young’s modulus ([Formula: see text]). These findings are in agreement with the reference values reported in the literature. They are very satisfying for distinguishing a pathological change in parietal elasticity. Conclusion: The in vivo application of these methods presents their potential for clinical measurement of arterial stiffness.

Non-Invasive Assessment of Arterial Stiffness: Pulse Wave Velocity, Pulse Wave Analysis and Carotid Cross-Sectional Distensibility: Comparison between Methods.

Background: The stiffening of large elastic arteries is currently estimated in research and clinical practice by propagative and non-propagative models, as well as parameters derived from aortic pulse waveform analysis. Methods: Common carotid compliance and distensibility were measured by simultaneously recording the diameter and pressure changes during the cardiac cycle. The aortic and upper arm arterial distensibility was estimated by measuring carotid–femoral and carotid–radial pulse wave velocity (PWV), respectively. The augmentation index and blood pressure amplification were derived from the analysis of central pulse waveforms, recorded by applanation tonometry directly from the common carotid artery. Results: 75 volunteers were enrolled in this study (50 females, average age 53.5 years). A significant inverse correlation was found between carotid distensibility and carotid–femoral PWV (r = −0.75; p < 0.001), augmentation index (r = −0.63; p < 0.001) and central pulse pressure (r = −0.59; p < 0.001). A strong correlation was found also between the total slope of the diameter/pressure rate carotid curves and aortic distensibility, quantified from the inverse of the square of carotid–femoral PWV (r = 0.67). No correlation was found between carotid distensibility and carotid–radial PWV. Conclusions: This study showed a close correlation between carotid–femoral PWV, evaluating aortic stiffness by using the propagative method, and local carotid cross-sectional distensibility.

Z-score regression model for coronary artery diameter in healthy Chinese Han children.

Coronary artery distension and aneurysm are complications of Kawasaki disease in children. To develop a Z-score regression model for coronary artery diameter in children that could be used as reference. This retrospective analysis included children with normal heart structure between March 2013 and April 2017. Body surface area (BSA) was calculated. The diameters of the right coronary, left main coronary, left anterior descending, and circumflex arteries were measured by echocardiography. Pearson correlation analysis was used to establish linear, exponential, logarithmic, power, and square root regression models. The analysis included 509 children (280 boys) aged 1 day to 15.2 years. Coronary artery diameters were significantly correlated with age, height, body mass, BSA, and (r = 0.663-0.826; P < 0.05), with a stronger correlation for than BSA (P < 0.05). The adjusted determination coefficients () were higher for the exponential and square root models than for the other models (P < 0.05). The random error term variance was constant for the exponential model (P > 0.05), and processing with the weighted least-square methods eliminated heteroscedasticity in the other models. The Z-scores were normally distributed for the exponential and square root models (P > 0.05). Overall, the square root model was the optimal equation for the calculation of coronary artery Z-score in Chinese Han children. This model could be used to facilitate the diagnosis of coronary artery distension in children with suspected Kawasaki disease.

Abstract P162: Cardiovascular Disease And Periodontal Disease In Type 1 Diabetes

Type 1 diabetes (T1D) is a condition in which the body’s immune system destroys insulin-producing beta cells, resulting in hyperglycemia. Cardiovascular disease (CVD) is the leading cause of morbidity and mortality in those with T1D. Periodontal disease (PD) is the 6th major complication of T1D. Oral bacteria have been detected in atherosclerotic plaques. Thus, oral bacteria may play a causal role in cardiovascular disease. The aims of this study are to determine how subclinical measures of cardiovascular disease differ by diabetes status and how they are related to the extent of periodontal disease. It is hypothesized that people with T1D will have stiffer vessels with higher pulse wave velocity (PWV), lower brachial artery distensibility (BrachD), and higher carotid intima-media thickness (cIMT) compared to non-diabetic controls. It is also hypothesized that people with T1D will have a higher prevalence of PD compared to non-diabetic controls. Study visits were performed to assess cardiovascular and periodontal outcomes in people with T1D (n=144) and non-diabetic controls (n=147). Univariate analysis was performed using t-test and chi-square to test for significant differences in vascular measures and periodontal status between T1D and controls. Age and sex-adjusted multivariate linear and logistic regression was used to further examine differences in vascular measures and periodontal disease by diabetes status. PWV was significantly higher in people with T1D compared to controls (8.390 +/- 0.111 vs. 7.822 +/- 0.108, p=0.0003). BrachD was significantly lower in people with T1D compared to controls (5.795 +/- 0.095 vs. 6.413 +/- 0.094, p&lt;0.0001). cIMT was significantly higher in people with T1D compared to controls (0.679 +/- 0.009 vs. 0.626 +/- 0.009, p&lt;0.0001). Adults with T1D were significantly more likely to have moderate to severe PD compared to controls (OR = 2.759, 95% CI [1.310-5.811], p=0.0076). Adults with T1D have worse cardiovascular health as measured by stiffer central vessels, more subclinical atherosclerosis, and lower peripheral vessel distensibility. Adults with T1D had almost 3-fold higher risk of moderate to severe PD compared to non-diabetic adults. The relationship between PD and the increased CVD risk in people with T1D warrants further examination.

Physiological basis for longitudinal motion of the arterial wall.

As opposed to arterial distension in the radial plane, longitudinal wall motion (LWM) is a multiphasic and bidirectional displacement of the arterial wall in the anterograde (i.e., in the direction of blood flow) and retrograde (i.e., opposing direction of blood flow) directions. Although initially disregarded as imaging artifact, LWM has been consistently reported in ultrasound investigations in the past decade and is reproducible beat-to-beat, albeit with large interindividual variability across healthy and diseased populations. Emerging literature has sought to examine the mechanistic control of LWM to explain the shape and variability of the motion pattern but lacks considerations for key foundational vascular principles at the level of the arterial wall ultrastructure. The purpose of this review is to summarize the potential factors that underpin the causes and control of arterial LWM, spanning considerations from the arterial extracellular matrix to systems-level integrative theories. First, an overview of LWM and relevant aspects wall composition will be discussed, including major features of the multiphasic pattern, arterial wall extracellular components, tunica fiber orientations, and arterial longitudinal prestretch. Second, current theories on the systems-level physiological mechanisms driving LWM will be discussed in the context of available evidence including experimental human research, porcine studies, and mathematical models. Throughout, we discuss implications of these observations with suggestions for future priority research areas.

Semiautomated Software to Improve Stability and Reduce Operator-Induced Variation in Vascular Ultrasound Speckle Tracking.

Ultrasound is useful in predicting arteriovenous fistula (AVF) maturation, which is essential for hemodialysis in end-stage renal disease patients. We developed ultrasound software that measures circumferential vessel wall strain (distensibility) using conventional ultrasound Digital Imaging and Communications in Medicine (DICOM) data. We evaluated user-induced variability in measurement of arterial wall distensibility and upon finding considerable variation we developed and tested 2 methods for semiautomated measurement. Ultrasound scanning of arteries of 10 subjects scheduled for AVF surgery were performed. The top and bottom of the vessel wall were tracked using the Kanade-Lucas-Tomasi (KLT) feature-tracking algorithm over the stack of images in the DICOM cine loops. The wall distensibility was calculated from the change of vessel diameter over time. Two semiautomated methods were used for comparison. The location of points selected by users for the cine loops varied significantly, with a maximum spread of up to 120 pixels (7.8 mm) for the top and up to 140 pixels (9.1 mm) for the bottom of the vessel wall. This variation in users' point selection contributed to the variation in distensibility measurements (ranging from 5.63 to 41.04%). Both semiautomated methods substantially reduced variation and were highly correlated with the median distensibility values obtained by the 10 users. Minimizing user-induced variation by standardizing point selection will increase reproducibility and reliability of distensibility measurements. Our recent semiautomated software may help expand use in clinical studies to better understand the role of vascular wall compliance in predicting the maturation of fistulas.

Does the Internal Carotid Artery Attenuate Blood-Flow Pulsatility in Small Vessel Disease? A 7T 4D-Flow MRI Study.

BackgroundIncreased cerebral blood‐flow pulsatility is associated with cerebral small vessel disease (cSVD). Reduced pulsatility attenuation over the internal carotid artery (ICA) could be a contributing factor to the development of cSVD and could be associated with intracranial ICA calcification (iICAC).PurposeTo compare pulsatility, pulsatility attenuation, and distensibility along the ICA between patients with cSVD and controls and to assess the association between iICAC and pulsatility and distensibility.Study TypeRetrospective, explorative cross‐sectional study.SubjectsA total of 17 patients with cSVD, manifested as lacunar infarcts or deep intracerebral hemorrhage, and 17 age‐ and sex‐matched controls.Field Strength/SequenceThree‐dimensional (3D) T1‐weighted gradient echo imaging and 4D phase‐contrast (PC) MRI with a 3D time‐resolved velocity encoded gradient echo sequence at 7 T.AssessmentBlood‐flow velocity pulsatility index (vPI) and arterial distensibility were calculated for seven ICA segments (C1–C7). iICAC presence and volume were determined from available brain CT scans (acquired as part of standard clinical care) in patients with cSVD.Statistical TestsIndependent t‐tests and linear mixed models. The threshold for statistically significance was P < 0.05 (two tailed).ResultsThe cSVD group showed significantly higher ICA vPI and significantly lower distensibility compared to controls. Controls showed significant attenuation of vPI over the carotid siphon (−4.9% ± 3.6%). In contrast, patients with cSVD showed no attenuation, but a significant increase of vPI (+6.5% ± 3.1%). iICAC presence and volume correlated positively with vPI (r = 0.578) in patients with cSVD and negatively with distensibility (r = −0.386).ConclusionDecreased distensibility and reduced pulsatility attenuation are associated with increased iICAC and may contribute to cSVD. Confirmation in a larger prospective study is required.Evidence Level2Technical EfficacyStage 2

Increased Arterial Stiffness Is Associated With Reduced Diastolic Function in Youth With Obesity and Type 2 Diabetes.

Background: Increased arterial stiffness is associated with diastolic dysfunction in adults. Data in youth are lacking, so we examined the impact of arterial stiffness on diastolic function in youth.Methods: We obtained diastolic function and augmentation index, pulse wave velocity, brachial artery distensibility, and carotid stiffness on 612 youth [10–24 years, 65% female, 38% normal weight, 36% obese, and 26% with type 2 diabetes mellitus (T2DM)]. Participants were classified as compliant (C) vs. stiff (S) arteries based on seven arterial stiffness parameters [Global Stiffness Index (GSI), S = GSI > 4). Mean differences in covariates were evaluated by Student's t-tests. A stepwise regression analysis was performed to determine if GSI was an independent predictor of diastolic function.Results: Lower diastolic function and more adverse cardiovascular disease (CVD) risk factors were present in the S group (n = 67) than the C group (n = 545) (p < 0.001). Covariates that were associated with diastolic dysfunction were higher GSI, male sex, higher body mass index (BMI), and systolic blood pressure (SBP) z-score (R2 = 0.18 to 0.25; p ≤ 0.05).Conclusion: Adverse diastolic function is seen in youth with increased arterial stiffness independent of CVD risk factors. Interventions to improve arterial stiffness prior to clinical onset of diastolic dysfunction are needed to prevent development of heart failure.

Abstract 10585: Racial Differences in Arterial Stiffness Following Acute Bouts of Anaerobic Exercise

African Americans (AA) experience an exaggerated hemodynamic response during recovery from aerobic exercise compared to Caucasian Americans (CA). There is also evidence that local arterial stiffness increases and systemic vasculature stiffness decreases following aerobic exercise. Despite the growing popularity of high-intensity anaerobic exercise, no study has examined racial differences in arterial stiffness following maximal anaerobic exercise between AA and CA women. Purpose: To compare local and systemic arterial stiffness during recovery from repeated bouts of maximal anaerobic exercise in young, healthy AA and CA women. Methods: Twenty (AA: n=8, age = 22±1yrs, BMI = 24.7±0.8 kg/m 2 ; CA: n=12, age = 22±1 yrs, BMI = 22.9 ±0.7 kg/m 2 ) healthy women without hypertension completed two bouts of maximal anaerobic exercise on a cycle ergometer with 30 minutes of recovery between bouts. Hemodynamic measurements were taken at resting, and 5 (P5-post-EX1), 15 (P15 post-EX1), and 30 minutes (P30 post-EX1) following a maximal anaerobic exercise test on cycle ergometer, and 5 (P5 post-EX2), 15 (P15 post-EX2), and 30 (P30 post-EX2) minutes following the second maximal anaerobic exercise test. Local carotid arterial compliance (AC) was assessed using ultrasonography and systemic arterial stiffness was assessed by augmentation index (AIx@75) and segmental arterial stiffness assessed by central Pulse Wave Velocity (cPWV) using SphygmoCor. Data were analyzed by 2 by 7 (race *time) repeated measures ANOVA. Results: See Table 1. Conclusion: There is less variation in local carotid arterial compliance in AA women compared to CA women following repeated bouts of maximal anaerobic exercise despite similar systemic or segmental arterial stiffness. Racial differences in arterial distensibility between AA and CA women in response to maximal anaerobic exercise may be limited to localized changes in the predominantly elastic carotid artery.

Abstract 14367: Elevated Creatinine Levels Are Associated With Vascular Dysfunction in Liver Transplant Recipients

Introduction: Liver transplant (LT) recipients have an increased risk of developing cardiovascular disease (CVD) after transplant. The physiological mechanisms driving LT-related CVD are not fully understood. Renal impairment post-transplant may contribute to CVD risk in LT recipients. The aim of this study was to investigate the relationship between plasma creatinine levels and vascular function in LT patients. Methods: Conduit artery endothelial function was measured via flow-mediated dilation of the brachial artery (FMD BA ) with duplex ultrasound in 13 LT patients (7 Male, 6 Female; Median [IQR]: Age 59 [56 - 64] years). Parameters of carotid artery function (distension, distensibility, compliance and stiffness) were assessed using B mode ultrasound and central aortic pressure waves that were synthesized from radial artery waveforms acquired by applanation tonometry in 13 LT patients (6 Male, 7 Female; Age 57 [56 - 64] years). Blood samples were analyzed for plasma creatinine by nuclear magnetic resonance spectroscopy. Results: Conduit artery endothelial function via FMD BA (4.07 [3.52 - 6.40] %) was negatively associated with plasma creatinine levels (1.30 [1.08 - 1.56] mg/dL; r = -0.63, p = 0.03). Plasma creatinine levels were also inversely associated with carotid artery distension (0.53 [0.35 - 0.61] mm, r = -0.74, p = 0.006), distensibility (25.62 [20.65 - 33.03] 10 -3 ·kPa -1 , r = -0.59, p = 0.04), and compliance (1.19 [0.82 - 1.41] 10 -6 ·m 2 ·kPa -1 , r = -0.66, p = 0.02), and positively associated with carotid stiffness (6.07 [5.35 - 6.76] m·s -1 , r = 0.59, p = 0.04) as shown in Figure 1. Conclusions: Our results indicate that LT patients with higher levels of creatinine have impaired conduit artery endothelial function and compromised carotid artery function, making these individuals more susceptible to the development of atherosclerosis and stroke. The presence of renal dysfunction after LT may contribute to CVD risk and warrants investigation in future trials.

Abstract 10288: Reduced Pulmonary Artery Distensibility: A Predictor of Persistent Pulmonary Hypertension and 2-Year Mortality Post-Transcatheter Aortic Valve Replacement in High-Risk Patients with Severe Aortic Stenosis

Introduction: Persistent pulmonary hypertension (PH) post-TAVR is a better predictor of poor outcome than pre-TAVR PH, possibly due to longstanding vascular damage involving loss of pulmonary artery (PA) elasticity. In this study we sought to evaluate whether PA distensibility (D PA ) measured on pre-procedural ECG-gated CTA is associated with persistent-PH and 2-year mortality after TAVR. Hypothesis: Reduced D PA is a predictor of persistent-PH and mortality post-TAVR. Methods: 336 patients undergoing TAVR between July 2012 and March 2016 were retrospectively included. All patients underwent retrospectively ECG-gated CTA of the chest, with reconstruction of 10 phases over the cardiac cycle (0%- 90% of the R-R interval) prior to TAVR. Patients were followed for all-cause mortality. Main pulmonary artery (MPA) area was measured at 20% (area-MPA 20 ) and 80% (area-MPA 80 ) of the R-R interval. D PA was calculated as follows: [(area-MPA 20 -area-MPA 80 )/area-MPA 20 ]%. Persistent-PH was defined as pre-TAVR RVSP&gt;35mmHg which persisted &gt;35mmHg in post-TAVR echocardiography. 2 groups were compared based on D PA &lt;8% (specificity of 70% for persistent-PH). Kaplan-Meier, Cox proportional-hazard and logistic regression analyses were performed. Results: Median follow-up time was 413 (interquartiles 339-757) days. A total of 68 (20%) patients died within 2 years after TAVR and 183 (54%) had persistent-PH. Those with D PA &lt;8% had significantly more atrial fibrillation (50% vs 35%, p&lt;0.001), 2-year deaths (28% vs 15%, p=0.006) and persistent-PH (67% vs 47%, p&lt;0.001), compared to those with D PA &gt;8%. Multivariable regression analyses adjusted for age, sex, STS-score, cardiac risk, frailty≥2 and NYHA≥III, showed that D PA &lt;8% was independently associated with two-year mortality (HR 2.91 [95%-CI 1.5-5.8], p=0.002) and persistent-PH (OR 2.10 [95%-CI 1.3-4.5], p=0.007). Kaplan-Meier analysis showed that mortality of patients with D PA &lt;8% was significantly higher compared to patients with D PA ≥8% (mortality 28% vs 15%; log-rank p=0.003). Conclusion: D PA on pre-procedural CTA is independently associated with persistent-PH and two-year mortality in patients who undergo TAVR and could be a valuable parameter for risk stratification of TAVR candidates.

Abstract 11903: Assessment of Left Ventricular Relaxation Time by Pulse Wave Analysis: Association With Arterial Compliance

Introduction: The long left ventricular relaxation (LVR) has been shown as a marker of diastolic dysfunction. This parameter is usually measured by such complex methods as echocardiography and radionuclide technique. This study tests a possibility to evaluate LVR time by applanation tonometry and explores its association with arterial distensibility basing on the assumption of a parallelism in contractile mechanics between striated cardiac muscle and arterial smooth muscle. Methods: Overall, 352 normotensive subjects (age 18-76 yrs.) were enrolled in this study. The LVRT was assessed by pulse wave analysis (SphygmoCor) and measured as difference between the end of systole (ejection duration point, ED, corresponding to the closure of aortic valve) and the time of peak pressure (T1, figure) generated by systolic antegrade wave in aortic root (LVRT,%=(ED-T1)/Tf*100). Intima-media thickness of brachiocephalic arteries and heart dimensional indices were measured by ultrasonography. Results: A difference was established in LVRT between age-matched female (47.9 yr., 24.8±2.8 %, M±SD, n=158) and male groups (47.1 yr., 21.7±2.9 %, n=192, p&lt;0.001, T-test). In men, LVRT was associated with age (r=0.33), end systolic volume (partial r=0.39; age and HR= const.), augmentation index (AIx@75, r=0.33), aorta-to-radial pulse pressure amplification (r=-0.24), and time to reflection wave (r=-0.25, two-sided p&lt;=0.001 for all cases). The association of LVRT with AIx remains significant after adjusting for age, Tf, and SBP in multiple regression analysis (GLM module, SPSS). In women, less pronounced associations were found. No relations were seen of LVRT with intima-media thickness of brachiocephalic arteries and carotid-radial pulse wave velocity in both sex groups. Conclusions: In healthy subjects, the long LVR assessed by PWA was associated with stiff conduit arteries of upper limbs. Figure . Pulse pressure profile in the aortic root as a result of pulse wave analysis

Candesartan prevents arteriopathy progression in cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy model.

Cerebral small vessel disease (CSVD) causes dementia and gait disturbance due to arteriopathy. Cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL) is a hereditary form of CSVD caused by loss of high-temperature requirement A1 (HTRA1) serine protease activity. In CARASIL, arteriopathy causes intimal thickening, smooth muscle cell (SMC) degeneration, elastic lamina splitting, and vasodilation. The molecular mechanisms were proposed to involve the accumulation of matrisome proteins as substrates or abnormalities in transforming growth factor β (TGF-β) signaling. Here, we show that HTRA1-/- mice exhibited features of CARASIL-associated arteriopathy: intimal thickening, abnormal elastic lamina, and vasodilation. In addition, the mice exhibited reduced distensibility of the cerebral arteries and blood flow in the cerebral cortex. In the thickened intima, matrisome proteins, including the hub protein fibronectin (FN) and latent TGF-β binding protein 4 (LTBP-4), which are substrates of HTRA1, accumulated. Candesartan treatment alleviated matrisome protein accumulation and normalized the vascular distensibility and cerebral blood flow. Furthermore, candesartan reduced the mRNA expression of Fn1, Ltbp-4, and Adamtsl2, which are involved in forming the extracellular matrix network. Our results indicate that these accumulated matrisome proteins may be potential therapeutic targets for arteriopathy in CARASIL.

High-Framerate A-Mode Ultrasound for Vascular Structural Assessments: In-Vivo Validation in a Porcine Model.

Capturing vascular dynamics using ultrasound at a high framerate provided a unique way to track time-dependent and transient physiologic events non-invasively. In this work, we present an A-model high-framerate (500 frames per second) image-free ultrasound system for monitoring vascular structural and material properties. It was developed based on our clinically validated ARTSENS® technology. Following in-vitro verification on arterial flow phantoms, its measurement accuracy and high-framerate data acquisition and processing were verified in-vivo on 2 anesthetized Sus scrofa swine. Measurements of the carotid artery (the luminal diameter, distension, and wall thickness) obtained using the high-framerate system were comparable to those provided by a clinical-grade reference ultrasound imaging device (absolute error < 4%, < 6.3%, and < 6.6%, respectively). Notably, the morphology of the arterial distension waveforms obtained at high-framerate depicted vital physiological fiduciary points compared to the low-framerate reference waveform. The compression-decompression pattern of the arterial wall was also captured with the high-framerate system, which is challenging with low-framerate ultrasound. Potential applications of these high temporal structural waveforms have also been discussed.

Non-invasive local pulse wave velocity using 4D-flow MRI

Pulse Wave Velocity (PWV) corresponds to the velocity at which pressure waves, generated by the systolic contraction in the heart, propagate along the arterial tree. Due to the complex interplay between blood flow and the artery wall, PWV is related to inherent mechanical properties and arterial morphology. PWV has been widely accepted as a biomarker and early predictor to evaluate global arterial distensibility. Still, several local abnormalities often remain hidden or difficult to detect using non-invasive techniques. Here, we introduce a novel method to efficiently construct a local estimate of PWV along the aorta using 4D-Flow MRI data. A geodesic distance map was used to track advancing pulses for efficient flow calculations, based on the observation that the propagation of velocity wavefronts strongly depends on the arterial morphology. This procedure allows us a robust evaluation of the local transit time due to the pulse wave at each position in the aorta. Moreover, the estimation of the local PWV map did not require centerlines, and the final result is projected back to 3D using the same geodesic map. We evaluated PWV values in healthy young and adult volunteers and patients with univentricular physiology after a Fontan procedure. Our method is fast, semi-automatic, and depicts differences between young versus adult volunteers and young volunteers versus Fontan patients, showing consistent results compared to global methods. Remarkably, the technique could detect local differences of PWV on the aortic arch for all subjects, being consistent with previous findings of reduced PWV in the aortic arch.

Vascular Ageing and Aerobic Exercise.

Impairment of vascular function, in particular endothelial dysfunction and large elastic artery stiffening, represents a major link between ageing and cardiovascular risk. Clinical and experimental studies identified numerous mechanisms responsible for age-related decline of endothelial function and arterial compliance. Since most of these mechanisms are related to oxidative stress or low-grade inflammation, strategies that suppress oxidative stress and inflammation could be effective for preventing age-related changes in arterial function. Indeed, aerobic physical activity, which has been shown to improve intracellular redox balance and mitochondrial health and reduce levels of systemic inflammatory markers, also improves endothelial function and arterial distensibility and reduces risk of cardiovascular diseases. The present paper provides a brief overview of processes underlying age-related changes in arterial function, as well as the mechanisms through which aerobic exercise might prevent or interrupt these processes, and thus attenuate vascular ageing.

An active approach of pressure waveform matching for stress-based testing of arteries.

BackgroundArterial compliance assists the cardiovascular system with three key roles: (i) storing up to 50% of the stroke volume; (ii) ensuring blood flow during diastole; (iii) dampening pressure oscillations through arterial distension. In mock circulation loops (MCLs), arterial compliance was simulated either with membrane, spring, or Windkessel chambers. Although they have been shown to be suitable for cardiac device testing, their passive behavior can limit stress‐based testing of arteries. Here we present an active compliance chamber with a feedback control of variable compliance as part of an MCL designed for biomechanical evaluation of arteries under physiological waveforms.Materials and MethodsThe chamber encloses a piston that changes the volume via a cascaded controller when there is a difference between the real‐time pressure and the physiological reference pressure with the aim to equilibrate both pressures.ResultsThe experimental results showed repeatable physiological waveforms of aortic pressure in health (80–120 mm Hg), systemic hypertension (90–153 mm Hg), and heart failure reduced ejection fraction (78–108 mm Hg). Statistical validation (n = 20) of the function of the chamber is presented against compared raw data.ConclusionWe demonstrate that the active compliance chamber can track the actual pressure of the MCL and balance it in real time (every millisecond) with the reference values in order to shape the given pressure waveform. The active compliance chamber is an advanced tool for MCL applications for biomechanical examination of stented arteries and for preclinical evaluation of vascular implants.

Branch Pulmonary Artery Regurgitation in Repaired Tetralogy of Fallot: Correlation with Pulmonary Artery Morphology, Distensibility, and Right Ventricular Function.

Background: The aim was to determine the effect of pulmonary artery (PA) morphology on the branch pulmonary artery-regurgitation fraction (BPA-RF), the relationship of pulmonary insufficiency (PI) to BPA-RF and PA-distensibility, and factors (BPA-RF and PA-distensibility) associated with right ventricular function (RVF) in repaired tetralogy of Fallot (rTOF). Methods: A total of 182 rTOF patients (median age 17.1 years) were analyzed for length, angle of PA, BPA-RF, PI, and PA-distensibility, using magnetic resonance imaging. Results: The left PA had a significant greater RF than the right PA (median (interquartile range)): LPA 43.1% (32.6–51.5) and RPA 35.2% (24.7–44.7), p < 0.001. The LPA was shorter with a narrower angle than the RPA (p < 0.001). The anatomy of the branch-PA was not a factor for the greater LPA-RF (odds ratio, 95% confidence interval: CI, p-value): length 0.44 (0.95–2.00), p = 0.28; angle 0.63 (0.13–2.99), p = 0.56. There was a strong positive correlation between PI and BPA-RF-coefficients (95% CI), p-value: LPA 0.78% (0.70–0.86), p < 0.001; RPA 0.78% (0.71–0.84), p < 0.001 and between BPA-RF and distensibility-coefficients (95%CI), p-value: LPA 0.73% (0.37–1.09), p < 0.001; RPA 1.63% (1.22–2.03), p < 0.001, respectively. The adjusted BPA-RF did not predict RVF, RPA (p = 0.434), LPA (p = 0.268). Conclusions: PA morphology is not a significant factor for the differential BPA-RF. The vascular wall in rTOF patients responds to chronic increased intravascular volume by increasing distensibility. BPA-RF is not a determinant of RVF.

Relationship between life-time exposure to ambient fine particulate matter and carotid artery intima-media thickness in Australian children aged 11–12 years

Long-term exposure to air pollutants, especially particulates, in adulthood is related to cardiovascular diseases and vascular markers of atherosclerosis. However, whether vascular changes in children is related to exposure to air pollutants remains unknown. This study examined whether childhood exposure to air pollutants was related to a marker of cardiovascular risk, carotid intima–media thickness (CIMT) in children aged 11–12 years old. Longitudinal Study of Australian Children (LSAC) recruited parents and their children born in 2003–4. Among the participants, CheckPoint examination was conducted when the children were 11–12 years old. Ultrasound of the right carotid artery was performed using standardized protocols. Average and maximum far-wall CIMT, carotid artery distensibility, and elasticity were quantified using semiautomated software. Annual and life-time exposure to air pollutants was estimated using satellite-based land-use regression by residential postcodes. A total of 1063 children (50.4% girls) with CIMT data, serum cholesterol, and modeled estimates of NO2 and PM2.5 exposure for the period 2003 to 2015 were included. The average and maximum CIMT, carotid distensibility, and elasticity were 497 μm (standard deviation, SD 58), 580 μm (SD 44), 17.4% (SD 3.2), and 0.48%/mmHg (SD 0.09), respectively. The life-time average concentrations of PM2.5 and NO2 were 6.4 μg/m3 (SD 1.4) and 6.4 ppb (SD 2.4), respectively. Both average and maximum CIMT were significantly associated with average ambient PM2.5 concentration (average CIMT: +5.5 μm per μg/m3, 95% confidence interval, CI 2.4 to 8.5, and maximum CIMT: +4.9 μm per μg/m3, CI 2.3 to 7.6), estimated using linear regression, adjusting for potential confounders. CIMT was not significantly related to NO2 exposure. Carotid artery diameter, distensibility, and elasticity were not significantly associated with air pollutants. We conclude that life-time exposure to low levels of PM2.5 in children might have measurable adverse impacts on vascular structure by age 11–12 years.