Evaluation of arterial stiffness in children with Williams syndrome: Does it play a role in evolving hypertension?

Numerical study of hemodynamic flow in the aortic vessel of Williams syndrome patient with congenital heart disease

Congenital arterial stenosis such as supravalvar aortic stenosis (SVAS) are highly prevalent in Williams syndrome (WS) and other arteriopathies pose a substantial health risk. Conventional tools for severity assessment, including clinical findings and pressure gradient estimations, often fall short due to their susceptibility to transient physiological changes and disease stage influences. Moreover, in the pediatric population, the severity of these and other congenital heart defects (CHDs) often restricts the applicability of invasive techniques for obtaining crucial physiological data. Conversely, evaluating CHDs and their progression requires a comprehensive understanding of intracardiac blood flow. Current imaging modalities, such as blood speckle imaging (BSI) and four-dimensional magnetic resonance imaging (4D MRI) face limitations in resolving flow data, especially in cases of elevated flow velocities. To address these challenges, we devised a computational framework employing zero-dimensional (0D) lumped parameter models coupled with patient-specific reconstructed geometries pre- and post-surgical intervention to execute computational fluid dynamic (CFD) simulations. This framework facilitates the analysis and visualization of intricate blood flow patterns, offering insights into geometry and flow dynamics alterations impacting cardiac function. In this study, we aim to assess the efficacy of surgical intervention in correcting an extreme aortic defect in a patient with WS, leading to reductions in wall shear stress (WSS), maximum velocity magnitude, pressure drop, and ultimately a decrease in cardiac workload.

Relation of Pulse Wave Velocity to Contemporaneous and Historical Blood Pressure in Female Twins

BACKGROUND

An association between blood pressure and aortic stiffness is well known, but ambiguity remains as to whether one precedes the other. This study aimed to investigate the association of aortic stiffness with contemporaneous versus historic blood pressure and direction of causality between aortic stiffening and hypertension in female twins.

METHODS

Aortic stiffness, measured by carotid-femoral pulse wave velocity (PWV), and mean arterial pressure (MAP) was recorded in 2037 female TwinsUK participants (mean age: 62.4±9.7 years) at a single time point. A subset of 947 participants had repeat PWV and MAP measures (mean interval 5.5±1.7 years) with additional historic MAP (mean interval 6.6±3.3 years before baseline).

RESULTS

Cross-sectional multivariable linear regression analysis confirmed PWV significantly associated with age and MAP. In longitudinal analysis, annual progression of PWV was not associated with historic MAP (standardized beta coefficient [β]=-0.02, P=0.698), weakly associated with baseline MAP (β=0.09, P=0.049) but strongly associated with progression (from baseline to most recent measurement) of MAP (β= 0.26, P<0.001). Progression of MAP associated with both baseline and progression of PWV (β=0.13, P=0.003 and β=0.24, P<0.001, respectively).

CONCLUSIONS

Progression of aortic stiffness associates more strongly with contemporaneous MAP compared with historic MAP. In contrast, progression of MAP is associated with prior arterial stiffness. These findings suggest a bidirectional relationship between arterial stiffness and blood pressure, and that lowering blood pressure may prevent a cycle of arterial stiffening and hypertension.

Hypertension in Turner syndrome: a review of proposed mechanisms, management and new directions

Acquired cardiovascular diseases account for much of the increased risk of premature death in patients with Turner syndrome (TS). Hypertension is a major modifiable cardiovascular risk factor. It has a high prevalence in TS developing at an early age and thus leading to prolonged exposure to high blood pressure. The aetiology for hypertension in TS is largely unknown. It is likely multifactorial, and recent hypotheses include altered sympathetic tone, vasculopathy and endocrine factors. In this review article we aim to provide a comprehensive review of data on mechanisms of hypertension in TS and their implication for diagnostics and optimal choice of antihypertensive treatments. Ultimately this knowledge should help prevent hypertension-related complications, and improve quality of life and life expectancy for patients with TS.

Hypertension and cardiomyopathy associated with chronic kidney disease: epidemiology, pathogenesis and treatment considerations

Chronic kidney disease (CKD) is a complex condition with a prevalence of 10-15% worldwide. An inverse-graded relationship exists between cardiovascular events and mortality with kidney function which is independent of age, sex, and other risk factors. The proportion of deaths due to heart failure and sudden cardiac death increase with progression of chronic kidney disease with relatively fewer deaths from atheromatous, vasculo-occlusive processes. This phenomenon can largely be explained by the increased prevalence of CKD-associated cardiomyopathy with worsening kidney function. The key features of CKD-associated cardiomyopathy are increased left ventricular mass and left ventricular hypertrophy, diastolic and systolic left ventricular dysfunction, and profound cardiac fibrosis on histology. While these features have predominantly been described in patients with advanced kidney disease on dialysis treatment, patients with only mild to moderate renal impairment already exhibit structural and functional changes consistent with CKD-associated cardiomyopathy. In this review we discuss the key drivers of CKD-associated cardiomyopathy and the key role of hypertension in its pathogenesis. We also evaluate existing, as well as developing therapies in the treatment of CKD-associated cardiomyopathy.

Arterial stiffness precedes hypertension and metabolic risks in youth: a review

Arterial stiffness is a strong predictor of cardiovascular events and all-cause mortality in middle-aged and old adults. Arterial stiffness has been limited to being an intermediate marker of atherosclerotic cardiovascular events in adolescents and young adult studies. The paucity of normative longitudinal data and repeated gold-standard assessments of arterial stiffness among the young population has occasioned a huge knowledge gap in its clinical utility. This review summarizes recent longitudinal evidence in a large adolescent population, supporting the value of arterial stiffness as a novel risk factor for hypertension, overweight/obesity and insulin resistance. Preventing or decreasing arterial stiffness during adolescence may confer cardiometabolic health benefits in later life, but further pathological and mechanistic research is needed. The review also offers suggestions for incorporating arterial stiffness measures into routine paediatric and young adult clinical practice.

Cardiovascular Prevention Among Young Adults with Congenital Heart Disease

PURPOSE OF REVIEW

There are over a million adults living with congenital heart disease (CHD) in the USA. There have been improvements in CHD management which have led to an expansion of the adult congenital heart disease (ACHD) population. There is a high prevalence of atherosclerotic cardiovascular disease (ASCVD) encountered in the aging ACHD population. This review focuses on the most recent literature regarding the primary prevention of ASCVD in young ACHD patients.

RECENT FINDINGS

There are unique considerations for ASCVD risk reduction in ACHD patients. ASCVD may be as prevalent in ACHD compared in the general population. However, there may be a perceived shorter life expectancy in ACHD patients; therefore, primary prevention of ASCVD may not be considered important. Preventative strategies for ASCVD are underutilized in ACHD patients. As these patients are followed for a lifetime by cardiologists, we can truly pursue primary prevention in this aging population.

Numerical analysis of stenoses severity and aortic wall mechanics in patients with supravalvular aortic stenosis

Supravalvular aortic stenosis (SVAS) is an aortic malformation characterized by a narrowing of the ascending aorta, resulting in abnormal hemodynamics and pressure drop across the stenosed region. It has been observed that the pressure drops measured from Doppler ultrasound exams often tend to be higher than those obtained from invasive cardiac catheterization. These misleadingly elevated pressure measurements may drive the decision to refer patients for surgical treatment prematurely. Considering this strong clinical association, the purpose of this work is to develop a computational modeling approach using a two-way coupled fluid-structure interaction methodology to determine an accurate prediction of trans-stenotic pressure drop and to further highlight the discrepancy between the SVAS assessment methods. Blood is modeled using Navier-Stokes equations while the aortic wall is simulated by a composite poroelastic structure to represent the three main layers of the arterial wall. The relationship between aortic wall elasticity and the blood flow conditions is examined in varying levels of stenosis, ranging from mild to severe degrees of vessel diameter narrowing. A substantial overestimation of the traditional Doppler pressure drop measurement is observed, especially for severe stenosis levels. The simulation results indicate that elasticity of the aortic wall has a relatively little effect on trans-stenotic pressure drop for the range of mild to moderate SVAS cases, but predicted to have a profound effect for severe SVAS cases. Moreover, significant sensitivity to the pressure drop across the SVAS region from stenosis severity is observed.

Sex modification of the association of the radial augmentation index and incident hypertension in a Chinese community-based population

BACKGROUND

Arterial stiffness, as assessed by aortic ultrasound and pulse wave velocity, is associated with incident hypertension. However, there is still no consensus on whether the augmentation index (AI) affects new onset of hypertension. This study investigated the relationship of radial AI (rAI) and incident hypertension in a Chinese community-based population without hypertension at baseline.

METHOD

A total of 1,615 Chinese non-hypertensive participants from an atherosclerosis cohort in Beijing, China were included in our analysis. Baseline rAI normalized to heart rate of 75 beats/min (rAIp75) was obtained using HEM-9000AI. New-onset hypertension was defined as blood pressure ≥ 140/90 mmHg or self-reported hypertension or taking anti-hypertensive medications at the follow up survey. Multivariate regression models were used to evaluate the impact of rAIp75 on the risk of new-onset hypertension.

RESULTS

After a mean 2.35-year follow-up, 213 (13.19%) participants developed incident hypertension. No significant relation between rAIp75 and incident hypertension was observed in the whole population after adjustment for possible confounders (adjusted odds ratio (OR) and 95% confidence interval (CI): 1.09 [0.95-1.27];P = 0.2260). However, rAIp75 was significantly associated with incident hypertension in women, but not in men (adjusted OR and 95% CI: 1.29 [1.06-1.56],P = 0.0113 for women; 0.91 [0.72-1.15],P = 0.4244 for men; P for interaction = 0.0133).

CONCLUSIONS

Sex modified the effect of the rAI on incident hypertension in a Chinese, community-based, non-hypertensive population. Screening of the rAI could be considered in women with a high risk of hypertension for the purpose of primary intervention.

Genetic Diagnosis and the Severity of Cardiovascular Phenotype in Patients With Elastin Arteriopathy

Supplemental Digital Content is available in the text.

Elastin insufficiency causes recurrent vascular stenoses. Hemizygous deletion of the elastin gene (ELN) causes Williams-Beuren syndrome (WBS), while single nucleotide variants in ELN cause nonsyndromic supravalvar aortic stenosis (SVAS). Our objective was to compare cardiovascular disease outcomes in patients with WBS and nonsyndromic SVAS.

Brachial-Ankle Pulse Wave Velocity Predicts New-Onset Hypertension and the Modifying Effect of Blood Pressure in a Chinese Community-Based Population

Brachial-ankle pulse wave velocity (baPWV) was proven to be a prognostic indicator of cardiovascular events. However, the modifying effect of blood pressure (BP) on the longitudinal association between baPWV and new-onset hypertension is not well established. This study included 1849 non-hypertensive Chinese subjects from Shougang cohort study during December 2011 to July 2014. BaPWV was obtained using an Omron Colin BP-203RPE III device. Multivariate logistic regression models were used to evaluate associations of baPWV and outcomes. During a mean follow-up time of 2.36 years, 248 (13.41%) developed hypertension. BaPWV independently and gradably predicted the risk of incident hypertension and the SBP level at revisit (odds ratio or β (95% confidence interval) for participants with baPWV in quartile 4 vs. quartile 1: 2.72 (1.54, 4.78) for incident hypertension and 5.92 (4.26, 7.58) for SBP, P for trend: <0.001) after adjusting demonstrated risk factors. Besides, the effects of baseline baPWV on either incident hypertension or SBP at revisit were interactively modified by the level of baseline SBP; the effect size increased as the SBP level decreased. baPWV independently predicted the risk of hypertension and BP progression, modified by the level of SBP at baseline in this Chinese community-based population. The combination of baPWV and SBP can help differentiate the potential high-risk candidates who will develop hypertension quickly and benefit from early diagnosis and treatment.

Stenosis coexists with compromised α1-adrenergic contractions in the ascending aorta of a mouse model of Williams-Beuren syndrome

Williams-Beuren syndrome (WBS) is a rare disorder caused by a heterozygous deletion of 26–28 contiguous genes that affects the brain and cardiovascular system. Here, we investigated whether WBS affects aortic structure and function in the complete deletion (CD) mouse model harbouring the most common deletion found in WBS patients. Thoracic aortas from 3–4 months-old male CD mice and wild-type littermates were mounted in wire myographs or were processed for histomorphometrical analysis. Nitric oxide synthase (NOS) isoforms and oxidative stress levels were assessed. Ascending aortas from young adult CD mice showed moderate (50%) luminal stenosis, whereas endothelial function and oxidative stress were comparable to wild-type. CD mice showed greater contractions to KCl. However, α1-adrenergic contractions to phenylephrine, but not with a thromboxane analogue, were compromised. Decreased phenylephrine responses were not affected by selective inducible NOS blockade with 1400 W, but were prevented by the non-selective NOS inhibitor L-NAME and the selective neuronal NOS inhibitor SMTC. Consistently, CD mice showed increased neuronal NOS expression in aortas. Overall, aortic stenosis in CD mice coexists with excessive nNOS-derived NO signaling that compromises ascending aorta α1-adrenergic contractions. We suggest that increased neuronal NOS signaling may act as a physiological ‘brake’ against the detrimental effects of stenosis.

Anesthetic Considerations for Patients With Williams Syndrome

Williams syndrome (WS) is a relatively rare congenital disorder which manifests across multiple organ systems with a wide spectrum of severity. Cardiovascular anomalies are the most common and concerning manifestations of WS, with supravalvar aortic stenosis present in up to 70% of patients with WS. Although a relatively rare disease, these patients frequently require sedation or anesthesia for a variety of medical procedures. The risk of sudden death in this population is 25 to 100 times that of the general population, with many documented deaths associated with sedation or anesthesia. This increased risk coupled with a disproportionately frequent need for anesthetic care renders it prudent for the anesthesiologist to have a firm understanding of the manifestations of WS. In the following review, the authors discuss pertinent clinical characteristics of WS along with particular anesthetic considerations for the anesthesiologist caring for patients with WS presenting for non-cardiac surgery.

Lysyl Oxidase Induces Vascular Oxidative Stress and Contributes to Arterial Stiffness and Abnormal Elastin Structure in Hypertension: Role of p38MAPK

AIMS

Vascular stiffness, structural elastin abnormalities, and increased oxidative stress are hallmarks of hypertension. Lysyl oxidase (LOX) is an elastin crosslinking enzyme that produces H2O2 as a by-product. We addressed the interplay between LOX, oxidative stress, vessel stiffness, and elastin.

RESULTS

Angiotensin II (Ang II)-infused hypertensive mice and spontaneously hypertensive rats (SHR) showed increased vascular LOX expression and stiffness and an abnormal elastin structure. Mice over-expressing LOX in vascular smooth muscle cells (TgLOX) exhibited similar mechanical and elastin alterations to those of hypertensive models. LOX inhibition with β-aminopropionitrile (BAPN) attenuated mechanical and elastin alterations in TgLOX mice, Ang II-infused mice, and SHR. Arteries from TgLOX mice, Ang II-infused mice, and/or SHR exhibited increased vascular H2O2 and O2.- levels, NADPH oxidase activity, and/or mitochondrial dysfunction. BAPN prevented the higher oxidative stress in hypertensive models. Treatment of TgLOX and Ang II-infused mice and SHR with the mitochondrial-targeted superoxide dismutase mimetic mito-TEMPO, the antioxidant apocynin, or the H2O2 scavenger polyethylene glycol-conjugated catalase (PEG-catalase) reduced oxidative stress, vascular stiffness, and elastin alterations. Vascular p38 mitogen-activated protein kinase (p38MAPK) activation was increased in Ang II-infused and TgLOX mice and this effect was prevented by BAPN, mito-TEMPO, or PEG-catalase. SB203580, the p38MAPK inhibitor, normalized vessel stiffness and elastin structure in TgLOX mice.

INNOVATION

We identify LOX as a novel source of vascular reactive oxygen species and a new pathway involved in vascular stiffness and elastin remodeling in hypertension.

CONCLUSION

LOX up-regulation is associated with enhanced oxidative stress that promotes p38MAPK activation, elastin structural alterations, and vascular stiffness. This pathway contributes to vascular abnormalities in hypertension. Antioxid. Redox Signal. 27, 379-397.

mTOR (Mechanistic Target of Rapamycin) Inhibition Decreases Mechanosignaling, Collagen Accumulation, and Stiffening of the Thoracic Aorta in Elastin-Deficient Mice

OBJECTIVE

Elastin deficiency because of heterozygous loss of an ELN allele in Williams syndrome causes obstructive aortopathy characterized by medial thickening and fibrosis and consequent aortic stiffening. Previous work in Eln-null mice with a severe arterial phenotype showed that inhibition of mTOR (mechanistic target of rapamycin), a key regulator of cell growth, lessened the aortic obstruction but did not prevent early postnatal death. We investigated the effects of mTOR inhibition in Eln-null mice partially rescued by human ELN that manifest a less severe arterial phenotype and survive long term.

APPROACH AND RESULTS

Thoracic aortas of neonatal and juvenile mice with graded elastin deficiency exhibited increased signaling through both mTOR complex 1 and 2. Despite lower predicted wall stress, there was increased phosphorylation of focal adhesion kinase, suggestive of greater integrin activation, and increased transforming growth factor-β-signaling mediators, associated with increased collagen expression. Pharmacological blockade of mTOR by rapalogs did not improve luminal stenosis but reduced mechanosignaling (in delayed fashion after mTOR complex 1 inhibition), medial collagen accumulation, and stiffening of the aorta. Rapalog administration also retarded somatic growth, however, and precipitated neonatal deaths. Complementary, less-toxic strategies to inhibit mTOR via altered growth factor and nutrient responses were not effective.

CONCLUSIONS

In addition to previously demonstrated therapeutic benefits of rapalogs decreasing smooth muscle cell proliferation in the absence of elastin, we find that rapalogs also prevent aortic fibrosis and stiffening attributable to partial elastin deficiency. Our findings suggest that mTOR-sensitive perturbation of smooth muscle cell mechanosensing contributes to elastin aortopathy.

Deficient Circumferential Growth Is the Primary Determinant of Aortic Obstruction Attributable to Partial Elastin Deficiency

OBJECTIVE

Williams syndrome is characterized by obstructive aortopathy attributable to heterozygous loss of ELN, the gene encoding elastin. Lesions are thought to result primarily from excessive smooth muscle cell (SMC) proliferation and consequent medial expansion, although an initially smaller caliber and increased stiffness of the aorta may contribute to luminal narrowing. The relative contributions of such abnormalities to the obstructive phenotype had not been defined.

APPROACH AND RESULTS

We quantified determinants of luminal stenosis in thoracic aortas of Eln^-/- mice incompletely rescued by human ELN. Moderate obstruction was largely because of deficient circumferential growth, most prominently of ascending segments, despite increased axial growth. Medial thickening was evident in these smaller diameter elastin-deficient aortas, with medial area similar to that of larger diameter control aortas. There was no difference in cross-sectional SMC number between mutant and wild-type genotypes at multiple stages of postnatal development. Decreased elastin content was associated with medial fibrosis and reduced aortic distensibility because of increased structural stiffness but preserved material stiffness. Elastin-deficient SMCs exhibited greater contractile-to-proliferative phenotypic modulation in vitro than in vivo. We confirmed increased medial collagen without evidence of increased medial area or SMC number in a small ascending aorta with thickened media of a Williams syndrome subject.

CONCLUSIONS

Deficient circumferential growth is the predominant mechanism for moderate obstructive aortic disease resulting from partial elastin deficiency. Our findings suggest that diverse aortic manifestations in Williams syndrome result from graded elastin content, and SMC hyperplasia causing medial expansion requires additional elastin loss superimposed on ELN haploinsufficiency.

Williams syndrome predisposes to vascular stiffness modified by antihypertensive use and copy number changes in NCF1

Williams syndrome is caused by the deletion of 26 to 28 genes, including elastin, on human chromosome 7. Elastin insufficiency leads to the cardiovascular hallmarks of this condition, namely focal stenosis and hypertension. Extrapolation from the Eln(+/-) mouse suggests that affected people may also have stiff vasculature, a risk factor for stroke, myocardial infarction, and cardiac death. NCF1, one of the variably deleted Williams genes, is a component of the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase complex and is involved in the generation of oxidative stress, making it an interesting candidate modifier for vascular stiffness. Using a case-control design, vascular stiffness was evaluated by pulse wave velocity in 77 Williams cases and matched controls. Cases had stiffer conducting vessels than controls (P<0.001), with increased stiffness observed in even the youngest children with Williams syndrome. Pulse wave velocity increased with age at comparable rates in cases and controls, and although the degree of vascular stiffness varied, it was seen in both hypertensive and normotensive Williams participants. Use of antihypertensive medication and extension of the Williams deletion to include NCF1 were associated with protection from vascular stiffness. These findings demonstrate that vascular stiffness is a primary vascular phenotype in Williams syndrome and that treatment with antihypertensives or agents inhibiting oxidative stress may be important in managing patients with this condition, potentially even those who are not overtly hypertensive.

Increased aortic stiffness can predict perioperative cardiovascular outcomes in patients undergoing noncardiac, nonvascular surgery

BACKGROUND

Aortic stiffness is an early marker of arteriosclerosis and associated with cardiovascular mortality. However, the impact of aortic stiffness on perioperative cardiovascular outcomes in patients undergoing noncardiac surgery is unknown.

METHODS

The study population was composed of 660 consecutive adults aged 18 years and over (mean age = 65.3 ± 14 years) who underwent intermediate-risk (nonvascular), noncardiac surgery between January 2010 and February 2011. Nonemergency, non-day-case, open surgical procedures were enrolled. Aortic stiffness indices were calculated from the aortic diameters measured by echocardiography. Electrocardiography and cardiac biomarkers were evaluated 1 day before surgery, and on days 1, 3, and 7 after surgery.

RESULTS

Eighty patients (12.1%) experienced perioperative cardiovascular events (PCE). Preoperative aortic distensibility (AD) (2 ± 1.3 vs. 2.9 ± 1.1 cm2/dyn/10(3), P < 0.001) and aortic strain (AS) (4.4 ± 2.4 vs. 6.4 ± 1.9, P < 0.001) of the patients with PCE were significantly lower than in patients without PCE. Univariate analysis showed a significant association between age, diabetes mellitus (DM), coronary artery disease, preoperative atrial fibrillation, American Society of Anesthesiologists (ASA) status, Revised Cardiac Risk Index, left ventricle ejection fraction (LVEF), AD, aortic strain, and in-hospital PCE. However, on multivariate logistic regression analysis, only AD (OR: 1.94, 95% CI: 1.1-3.4; P = 0.02), AS (OR: 0.45, 95% CI: 0.3-0.6; P < 0.001), DM (OR: 2.28, 95% CI: 1.08-4.82; P = 0.03), and LVEF (OR: 0.96, 95% CI: 0.93-0.99; P = 0.03) remained as significant variables associated with PCE.

CONCLUSION

Impaired elastic properties of the aorta are associated with increased PCE rates in patients undergoing noncardiac, nonvascular surgery.

A rare case of visceral arterial stenoses in Williams-Beuren syndrome treated by complex revascularization

Williams-Beuren syndrome is a rare neurodevelopmental disorder. We present the case of a 27-year-old patient with Williams-Beuren syndrome and a juxtarenal abdominal aorta coarctation. As arterial hypertension (AHT) was not controlled, bilateral renal artery bypasses were performed at the age of 2 years by means of a hepatorenal bypass and a splenorenal bypass. Twenty years later, the patient presented with abdominal pain, diarrhea, and recurrence of AHT, and severe celiac artery and superior mesenteric artery stenoses were discovered. The distal arterial complications of this syndrome are uncommon. After 5 years of medical treatment, aggravation of the patient's symptoms prompted us to consider possible surgical management. The patient was successfully treated using a complex direct and indirect procedure that consisted of a bypass between the celiac aorta and infrarenal aorta, associated with a celiac artery bypass. Instead of endovascular management, this surgical procedure could be considered effective and long lasting for treating this rare cause of renal AHT.

Genetic modifiers of cardiovascular phenotype caused by elastin haploinsufficiency act by extrinsic noncomplementation

Elastin haploinsufficiency causes the cardiovascular complications associated with Williams-Beuren syndrome and isolated supravalvular aortic stenosis. Significant variability exists in the vascular pathology in these individuals. Using the Eln(+/-) mouse, we sought to identify the source of this variability. Following outcrossing of C57Bl/6J Eln(+/-), two backgrounds were identified whose cardiovascular parameters deviated significantly from the parental strain. F1 progeny of the C57Bl/6J; Eln(+/-)x129X1/SvJ were more hypertensive and their arteries less compliant. In contrast, Eln(+/-) animals crossed to DBA/2J were protected from the pathologic changes associated with elastin insufficiency. Among the crosses, aortic elastin and collagen content did not correlate with quantitative vasculopathy traits. Quantitative trait locus analysis performed on F2 C57; Eln(+/-)x129 intercrosses identified highly significant peaks on chromosome 1 (LOD 9.7) for systolic blood pressure and on chromosome 9 (LOD 8.7) for aortic diameter. Additional peaks were identified that affect only Eln(+/-), including a region upstream of Eln on chromosome 5 (LOD 4.5). Bioinformatic analysis of the quantitative trait locus peaks revealed several interesting candidates, including Ren1, Ncf1, and Nos1; genes whose functions are unrelated to elastic fiber assembly, but whose effects may synergize with elastin insufficiency to predispose to hypertension and stiffer blood vessels. Real time RT-PCR studies show background-specific increased expression of Ncf1 (a subunit of the NOX2 NAPDH oxidase) that parallel the presence of increased oxidative stress in Eln(+/-) aortas. This finding raises the possibility that polymorphisms in genes affecting the generation of reactive oxygen species alter cardiovascular function in individuals with elastin haploinsufficiency through extrinsic noncomplementation.

Chronic intrauterine hypoxia interferes with aortic development in the late gestation ovine fetus

This study explored arterial remodelling in fetuses growth restricted by hypoxia. Chronically catheterized fetal sheep were made moderately or severely hypoxic by placental embolization for 15 days starting at gestational age 116-118 (term ∼147 days). Cross-sections of the aorta were analysed for collagen and elastin content using histological procedures, while immunofluorescence was applied to measure markers of vascular smooth muscle cell (VSMC) type. In frozen aortae quantitative PCR was used to measure mRNA levels of extracellular matrix (ECM) precursor proteins as well as molecular regulators of developmental and pathological remodelling. Relative to Control (n =6), aortic wall thickness was increased by 23% in the Moderate group (n =5) and 33% (P <0.01) in the Severe group (n =5). Relative to Control, the Severe group exhibited a 5-fold increase in total collagen content (P <0.01) that paralleled increases in mRNA levels of procollagen I (P <0.05) and III and transforming growth factor β (TGF-β1) (P <0.05). The percentage area stained for α-actin was inversely related to fetal arterial oxygen saturation (P <0.05) and total α-actin content was 45% higher in the Moderate group and 65% (P <0.05) higher in the Severe group, compared to Control. A 12% and 39% (P <0.05) reduction in relative elastic fibre content was observed in Moderate and Severe fetuses, respectively. mRNA levels of the elastolytic enzyme, matrix metalloproteinase-2 (MMP-2) were inversely correlated with fetal arterial oxygen saturation (P <0.05) (Fig. 7) and mRNA levels of its activator, membrane-type MMP (MTI-MMP), were elevated in the Severe group (P <0.05). Marked neointima formation was apparent in Severe fetuses (P <0.05) concomitant with an increase in E-selectin mRNA expression (P <0.05). Thus, aberrant aortic formation in utero mediated by molecular regulators of arterial growth occurs in response to chronic hypoxaemia.

Arterial stiffness in the young: assessment, determinants, and implications

Arterial stiffness describes the rigidity of the arterial wall. Its significance owes to its relationship with the pulsatile afterload presented to the left ventricle and its implications on ventricular-arterial coupling. In adults, the contention that arterial stiffness as a marker and risk factor for cardiovascular morbidity and mortality is gaining support. Noninvasive methods have increasingly been adopted in both the research and clinical arena to determine local, segmental, and systemic arterial stiffness in the young. With adoption of these noninvasive techniques for use in children and adolescents, the phenomenon and significance of arterial stiffening in the young is beginning to be unveiled. The list of childhood factors and conditions found to be associated with arterial stiffening has expanded rapidly over the last decade; these include traditional cardiovascular risk factors, prenatal growth restriction, vasculitides, vasculopathies associated with various syndromes, congenital heart disease, and several systemic diseases. The findings of arterial stiffening have functional implications on energetic efficiency, structure, and function of the left ventricle. Early identification of arterial dysfunction in childhood may provide a window for early intervention, although longitudinal studies are required to determine whether improvement of arterial function in normal and at-risk paediatric populations will be translated into clinical benefits.

At the bottom of the differential diagnosis list: unusual causes of pediatric hypertension

Hypertension affects 1-5% of children and adolescents, and the incidence has been increasing in association with obesity. However, secondary causes of hypertension such as renal parenchymal diseases, congenital abnormalities and renovascular disorders still remain the leading cause of pediatric hypertension, particularly in children under 12 years old. Other less common causes of hypertension in children and adolescents, including immobilization, burns, illicit and prescription drugs, dietary supplements, genetic disorders, and tumors will be addressed in this review.

Assessment of aortic wall stiffness in patients with Familial Mediterranean Fever

INTRODUCTION

To evaluate aortic wall stiffness and its relation between the aortic stiffness and the left ventricular function in patients with Familial Mediterranean Fever (FMF).

METHODS

The study population was composed of 31 patients with FMF in attack-free period (12 men, 19 women; mean age: 36+/-7 years) and 27 healthy subjects (10 men, 17 women; mean age: 34+/-7 years) who had volunteered to participate. Aortic stiffness indices, aortic strain and distensibility, were calculated from the aortic diameters measured by echocardiography and blood pressure obtained by sphygmomanometry.

RESULTS

There were significant differences between the control and the patient group in aortic strain (mean (SD), 7.23+/-2.14 versus 4.91+/-1.66%, p=0.01) and distensibility (4.02+/-1.42 versus 2.84+/-1.46, 10(-6)cm(2)dyn(-1), p=0.001). Although there was no correlation between the aortic stiffness parameters and the left ventricular function parameters, there were significant negative correlations between the disease duration and aortic strain index (r=-0.29, p<0.001), and between the disease duration and distensibility (r=-0.32, p<0.001).

CONCLUSION

Aortic stiffness measurements were found abnormal in patients with FMF. We have also demonstrated that there were significant correlations between aortic stiffness parameters and disease duration.

Postnatal alterations in elastic fiber organization precede resistance artery narrowing in SHR

Resistance artery narrowing and stiffening are key elements in the pathogenesis of essential hypertension, but their origin is not completely understood. In mesenteric resistance arteries (MRA) from spontaneously hypertensive rats (SHR), we have shown that inward remodeling is associated with abnormal elastic fiber organization, leading to smaller fenestrae in the internal elastic lamina. Our current aim is to determine whether this alteration is an early event that precedes vessel narrowing, or if elastic fiber reorganization in SHR arteries occurs because of the remodeling process itself. Using MRA from 10-day-old, 30-day-old, and 6-mo-old SHR and normotensive Wistar Kyoto rats, we investigated the time course of the development of structural and mechanical alterations (pressure myography), elastic fiber organization (confocal microscopy), and amount of elastin (radioimmunoassay for desmosine) and collagen (picrosirius red). SHR MRA had an impairment of fenestrae enlargement during the first month of life. In 30-day-old SHR, smaller fenestrae and more packed elastic fibers in the internal elastic lamina were paralleled by increased wall stiffness. Collagen and elastin levels were unaltered at this age. MRA from 6-mo-old SHR also had smaller fenestrae and a denser network of adventitial elastic fibers, accompanied by increased collagen content and vessel narrowing. At this age, elastase digestion was less effective in SHR MRA, suggesting a lower susceptibility of elastic fibers to enzymatic degradation. These data suggest that abnormal elastic fiber deposition in SHR increases resistance artery stiffness at an early age, which might participate in vessel narrowing later in life.

Elastic fibres and vascular structure in hypertension

Blood vessels are dynamic structures composed of cells and extracellular matrix (ECM), which are in continuous cross-talk with each other. Thus, cellular changes in phenotype or in proliferation/death rate affect ECM synthesis. In turn, ECM elements not only provide the structural framework for vascular cells, but they also modulate cellular function through specific receptors. These ECM-cell interactions, together with neurotransmitters, hormones and the mechanical forces imposed by the heart, modulate the structural organization of the vascular wall. It is not surprising that pathological states related to alterations in the nervous, humoral or haemodynamic environment-such as hypertension-are associated with vascular wall remodeling, which, in the end, is deleterious for cardiovascular function. However, the question remains whether these structural alterations are simply a consequence of the disease or if there are early cellular or ECM alterations-determined either genetically or by environmental factors-that can predispose to vascular remodeling independent of hypertension. Elastic fibres might be key elements in the pathophysiology of hypertensive vascular remodeling. In addition to the well known effects of hypertension on elastic fibre fatigue and accelerated degradation, leading to loss of arterial wall resilience, recent investigations have highlighted new roles for individual components of elastic fibres and their degradation products. These elements can act as signal transducers and regulate cellular proliferation, migration, phenotype, and ECM degradation. In this paper, we review current knowledge regarding components of elastic fibres and discuss their possible pathomechanistic associations with vascular structural abnormalities and with hypertension development or progression.

Wall motion velocities of abdominal aorta measured by tissue Doppler imaging in normal children

Tissue Doppler imaging (TDI) offers a new technique for assessing aortic wall expansion/contraction velocities and may provide a noninvasive approach to aortic wall mechanics. The purpose of this study was to determine the normal values of abdominal aortic wall motion velocities and the effect of age on these velocities in normal children. We examined 103 normal children. Using TDI, maximum wall expansion velocity during systole (peak S) and maximum wall contraction velocity during diastole (peak D) were measured. M-mode diameter of the abdominal aorta and systolic, diastolic, and mean arterial pressures were measured. Aortic stiffness was measured as (I(n)[BP(syst)/BP(diast)])/(D(s)-D(d)/D(d), where I(n) is the natural log, D(s) is the maximal abdominal aortic diameter during systole, and D(d) is the abdominal aortic diameter at end-diastole. In all subjects, wall motion velocities of the abdominal aorta were recorded. The mean values for peak S and peak D were 4.23, 1.14 and 2.16, 0.45 cm/sec, respectively. Both peak S and peak D were low in infants and increased significantly with age (r = 0.63, p < 0.0001 and r = 0.36, p = 0.0002, respectively), systolic blood pressure (r = 0.42 and 0.47, respectively, p < 0.0001), and diastolic blood pressure (r = 0.24, p = 0.016 and r = 0.28, p = 0.0038, respectively). Aortic stiffness index of the abdominal aorta was constant with age and did not correlate with peak S or peak D. Abdominal aortic wall motion velocities can be easily assessed by TDI. Age-related changes in the aortic wall motion velocities are observed in normal children. This study provides baseline information for further quantitative assessment of arterial stiffness in children with congenital or acquired heart disease.

Usefulness of tissue doppler imaging for assessing aortic wall stiffness in children with the Marfan syndrome

The purpose of this study was to assess wall motion velocities of the abdominal aorta using tissue Doppler imaging (TDI) in 12 patients with Marfan syndrome and 30 age-matched normal controls. The patients with Marfan syndrome displayed an increased aortic stiffness index in the abdominal aorta, and significant relationships were observed between wall motion velocities of the abdominal aorta and the aortic stiffness index. Thus, TDI analyzes aortic expansion and contraction velocities and allows the identification of abdominal aortic stiffness in patients with Marfan syndrome.

PI3-Kinase Upregulation and Involvement in Spontaneous Tone in Arteries From DOCA-Salt Rats

Increased expression of phosphoinositide 3-kinase (PI3-kinase) mediates elevated tone in the aorta from hypertensive deoxycorticosterone acetate (DOCA)-salt rats. In this article, we hypothesized that (1) alterations observed with respect to PI3-kinase observed in the aorta would also occur in mesenteric resistance arteries responsible for determining total peripheral resistance (TPR) and (2) p110δ activity was increased and localized to vascular smooth muscle cells (VSMCs), and was responsible for the increase in spontaneous tone in aortae from DOCA-salt rats. Mesenteric resistance arteries and aorta were isolated from DOCA-salt (190±3 mm Hg) and sham (121±2 mm Hg) rats. Myograph experiments revealed LY294002 (20 μmol/L), a PI3-kinase inhibitor, significantly decreased tone in mesenteric resistance arteries from DOCA-salt rats as compared with sham (−49±12 mg versus −10±7 mg). Western analyses of resistance artery protein homogenate revealed p85α and p110δ subunit protein, with significantly elevated levels of p110δ protein in the DOCA-salt compared with sham rats (0.30±0.07 versus 0.16±0.04% smooth muscle alpha-actin arbitrary units). Immunohistochemistry revealed p110δ-specific staining in VSMCs, with more intense staining in aortae from DOCA-salt rats. Compared with aortae from sham, p110δ-associated PI3-kinase activity was increased in DOCA-salt (158% of sham) and likely responsible for spontaneous tone because the p110δ specific inhibitor IC87114 decreased spontaneous tone in a concentration-dependent manner. Collectively, these data further implicate the p110δ isoform of PI3-kinase in arterial hyperresponsiveness in hypertension at the level of both large and small arteries.

Developmental adaptation of the mouse cardiovascular system to elastin haploinsufficiency

Supravalvular aortic stenosis is an autosomal-dominant disease of elastin (Eln) insufficiency caused by loss-of-function mutations or gene deletion. Recently, we have modeled this disease in mice (Eln+/-) and found that Eln haploinsufficiency results in unexpected changes in cardiovascular hemodynamics and arterial wall structure. Eln+/- animals were found to be stably hypertensive from birth, with a mean arterial pressure 25-30 mmHg higher than their wild-type counterparts. The animals have only moderate cardiac hypertrophy and live a normal life span with no overt signs of degenerative vascular disease. Examination of arterial mechanical properties showed that the inner diameters of Eln+/- arteries were generally smaller than wild-type arteries at any given intravascular pressure. Because the Eln+/- mouse is hypertensive, however, the effective arterial working diameter is comparable to that of the normotensive wild-type animal. Physiological studies indicate a role for the renin-angiotensin system in maintaining the hypertensive state. The association of hypertension with elastin haploinsufficiency in humans and mice strongly suggests that elastin and other proteins of the elastic fiber should be considered as causal genes for essential hypertension.