Aortic distensibility in children with the Marfan syndrome

Functional Magnetic Resonance Imaging in the Evaluation of the Elastic Properties of Ascending Aortic Aneurysm

Objective

To evaluate the aortic wall elasticity using the maximal rate of systolic distension (MRSD) and maximal rate of diastolic recoil (MRDR) and their correlation with the aortic size index (ASI).

Methods

Forty-eight patients with thoracic aortic aneurysm were enrolled in this study. A standard magnetic resonance imaging (MRI) protocol was used to calculate MRSD and MRDR. Both MRSD and MRDR were expressed as percentile of maximal area/10^-3 sec. ASI (maximal aortic diameter/body surface area) was calculated. A correlation between MRSD, MRDR, ASI, and the patient’s age was performed using regression plot.

Results

A significant correlation between MRSD (t=-4,36; r²=0.29; P≤0.0001), MRDR (t=3.92; r²=0.25; P=0.0003), and ASI (25±4.33 mm/m²; range 15,48-35,14 mm/m²) is observed. As ASI increases, aortic MRSD and MRDR decrease. Such inverse correlation between MRSD, MRDR, and ASI indicates increased stiffness of the ascending aorta. A significant correlation between the patient’s age and the decrease in MRSD and MRDR is observed.

Conclusion

MRSD and MRDR are significantly correlated with ASI and the patient’s age. They seem to describe properly the increasing stiffness of aortas. These two new indexes provide a promising, accessible, and reproducible approach to evaluate the biomechanical property of the aorta.

Aortic stiffness in families with inherited non-syndromic thoracic aortic disease

BACKGROUND

In families with an inherited form of non-syndromic thoracic aortic disease (TAAD), aortic diameter alone is not a reliable marker for disease occurrence or progression. To identify other parameters of aortic function, we studied aortic stiffness in families with TAAD. We also compared diameter measurements obtained by transthoracic echocardiography (TTE) and magnetic resonance imaging (MRI).

METHODS

Seven families, including 116 individuals, with non-syndromic TAAD, were studied. The aortic diameter was measured by TTE and MRI. Aortic stiffness was assessed as local distensibility in the ascending aorta and as regional and global pulse wave velocity (PWV). Individuals with a dilated thoracic aorta (n = 21) were compared with those without aortic dilatation (n = 95).

RESULTS

Ascending aortic diameter measured by TTE strongly correlated with the diameter measured by MRI (r² = 0.93). The individuals with dilated aortas were older than those without dilatation (49 vs 37 years old). Ascending aortic diameter increased and distensibility decreased with increasing age; while, PWV increased with age and diameter. Some young subjects without aortic dilatation showed increased aortic stiffness. Individuals with a dilated thoracic aorta had significantly higher PWV and lower distensibility, measured by MRI than individuals without dilatation.

CONCLUSIONS

Diameters measured with TTE agree with those measured by MRI. Aortic stiffness might be a complementary marker for aortic disease and progression when used with aortic diameter, especially in young individuals.

Influence of Aortic Stiffness on Aortic-Root Growth Rate and Outcome in Patients With the Marfan Syndrome

The Pediatric Heart Network randomized trial of atenolol versus losartan in the Marfan syndrome showed no treatment differences in the rates of aortic-root growth or clinical outcomes. In this report we present treatment effects on aortic stiffness and determine whether baseline aortic stiffness predicts aortic-root growth and clinical outcomes. Echocardiograms at 0, 6, 12, 24, and 36 months from 608 subjects (6 months to 25 years) who met original Ghent criteria and had a maximum aortic-root z-score (ARz) >3 were centrally reviewed. Stiffness index (SI) and elastic modulus (EM) were calculated for aortic root and ascending aorta. Data were analyzed using multivariable mixed effects modeling and Cox regression. Heart rate-corrected aortic-root SI over 3 years decreased with atenolol but did not change with losartan (-0.298 ± 0.139 vs 0.141 ± 0.139/year, p = 0.01). In the entire cohort, above-median aortic-root SI (>9.1) and EM (>618 mm Hg) predicted a smaller annual decrease in ARz (p ≤0.001). Upper-quartile aortic-root EM (>914 mm Hg) predicted the composite outcome of aortic-root surgery, dissection, or death (hazard ratio 2.17, 95% confidence interval 1.02 to 4.63, p = 0.04). Crude 3-year event rates were 10.4% versus 3.2% for higher versus lower EM groups. In conclusion, atenolol was associated with a decrease in aortic-root SI, whereas losartan was not. Higher baseline aortic-root SI and EM were associated with a smaller decrease in ARz and increased risk for clinical outcomes. These data suggest that noninvasive aortic stiffness measures may identify patients at higher risk of progressive aortic enlargement and adverse clinical outcomes, potentially allowing for closer monitoring and more aggressive therapy.

Biomechanical properties of the thoracic aorta in Marfan patients

BACKGROUND

Marfan syndrome (MFS), a genetic disorder of the connective tissue, has been strongly linked to dilation of the thoracic aorta, among other cardiovascular complications. As a result, MFS patients frequently suffer from aortic dissection and rupture, contributing to the high rate of mortality and morbidity among MFS patients. Despite the significant effort devoted to the investigation of mechanical and structural properties of aneurysmal tissue, studies on Marfan aneurysmal biomechanics are scarce. Ex vivo mechanical characterization of MFS aneurysmal tissue can provide a better insight into tissue strength outside the physiologic loading range and serve as a basis for improved risk assessment and failure prediction.

METHODS

The mechanical and microstructural properties of MFS aneurysmal thoracic aorta (MFS, n=15, 39.5±3.91 years), non-MFS aneurysmal thoracic aorta (TAA, n=8, 52.8±4.9 years), healthy human thoracic aorta (HH, n=8, 75.4±6.1 years), and porcine thoracic aorta (n=10) are investigated. Planar biaxial tensile testing and uniaxial failure testing were utilized to characterize the mechanical and failure properties of the tissue, respectively. Verhoeff-Van Gieson (VVG) and PicroSirius Red stains were utilized to visualize the elastin and collagen fiber architecture, respectively.

RESULTS

MFS tissue was found to have age-dependent but diameter-independent mechanical, structural, and morphological properties, also showing extensive elastin fiber degradation. Non-MFS thoracic aneurysmal aorta was thicker and stiffer than age-matched MFS tissue. Moreover, non-MFS thoracic aneurysmal mechanics resembled closely the mechanics of older healthy human tissue. Younger MFS tissue (<40 years) exhibited similar mechanical and structural properties to aged porcine tissue.

CONCLUSIONS

Both age and aneurysmal presence were found to be factors associated with increased stiffness in aortic tissue, and aortic diameter was not a significant determinant of mechanical property deterioration. Additionally, the presence of MFS was found to induce stiffening of the thoracic aorta, although not to the extent of the non-MFS aneurysm.

Vascular Smooth Muscle Cells and Arterial Stiffening: Relevance in Development, Aging, and Disease

The cushioning function of large arteries encompasses distension during systole and recoil during diastole which transforms pulsatile flow into a steady flow in the microcirculation. Arterial stiffness, the inverse of distensibility, has been implicated in various etiologies of chronic common and monogenic cardiovascular diseases and is a major cause of morbidity and mortality globally. The first components that contribute to arterial stiffening are extracellular matrix (ECM) proteins that support the mechanical load, while the second important components are vascular smooth muscle cells (VSMCs), which not only regulate actomyosin interactions for contraction but mediate also mechanotransduction in cell-ECM homeostasis. Eventually, VSMC plasticity and signaling in both conductance and resistance arteries are highly relevant to the physiology of normal and early vascular aging. This review summarizes current concepts of central pressure and tensile pulsatile circumferential stress as key mechanical determinants of arterial wall remodeling, cell-ECM interactions depending mainly on the architecture of cytoskeletal proteins and focal adhesion, the large/small arteries cross-talk that gives rise to target organ damage, and inflammatory pathways leading to calcification or atherosclerosis. We further speculate on the contribution of cellular stiffness along the arterial tree to vascular wall stiffness. In addition, this review provides the latest advances in the identification of gene variants affecting arterial stiffening. Now that important hemodynamic and molecular mechanisms of arterial stiffness have been elucidated, and the complex interplay between ECM, cells, and sensors identified, further research should study their potential to halt or to reverse the development of arterial stiffness.

Long-term miR-29b suppression reduces aneurysm formation in a Marfan mouse model

Aortic root aneurysm formation and subsequent dissection and/or rupture remain the leading cause of death in patients with Marfan syndrome. Our laboratory has reported that miR‐29b participates in aortic root/ascending aorta extracellular matrix remodeling during early aneurysm formation in Fbn1^C1039G/+ Marfan mice. Herein, we sought to determine whether miR‐29b suppression can reduce aneurysm formation long‐term. Fbn1^C1039G/+ Marfan mice were treated with retro‐orbital LNA‐anti‐miR‐29b inhibitor or scrambled‐control‐miR before aneurysms develop either (1) a single dose prenatally (pregnant Fbn1^C1039G/+ mice at 14.5 days post‐coitum) (n = 8–10, each group) or (2) postnatally every other week, from 2 to 22 weeks of age, and sacrificed at 24 weeks (n = 8–10, each group). To determine if miR‐29b blockade was beneficial even after aneurysms develop, a third group of animals were treated every other week, starting at 8 weeks of age, until sacrificed (n = 4–6, each group). miR‐29b inhibition resulted in aneurysm reduction, increased elastogenesis, decreased matrix metalloproteinase activity and decreased elastin breakdown. Prenatal LNA‐anti‐miR‐29b inhibitor treatment decreased aneurysm formation up to age 32 weeks, whereas postnatal treatment was effective up to 16 weeks. miR‐29b blockade did not slow aortic growth once aneurysms already developed. Systemic miR‐29b inhibition significantly reduces aneurysm development long‐term in a Marfan mouse model. Drug administration during aortic wall embryologic development appears fundamental. miR‐29b suppression could be a potential therapeutic target for reducing aneurysm formation in Marfan syndrome patients.

Age-dependent changes in elastic properties of thoracic aorta evaluated by magnetic resonance in normal subjects

OBJECTIVES

Aortic stiffness is an independent cardiovascular risk factor. Cardiac magnetic resonance (CMR) allows evaluation of aortic elastic properties by different indexes such as distensibility, the maximum rate of systolic distension (MRSD) and pulse wave velocity (PWV). We sought to define age-dependent changes of indexes of elastic properties of the thoracic aorta in healthy subjects.

METHODS

We enrolled 85 healthy subjects (53 males) free of overt cardiovascular disease subdivided into 6 classes of age (from 15 to >60 years). Distensibility, MRSD and PWV were measured by the analysis of CMR images acquired using a 1.5 T clinical scanner.

RESULTS

MRSD and distensibility decreased progressively through the classes of age (P < 0.001) after an initial plateau between 20 and 30 years in males and 15 and 20 years in females. Pulse wave velocity increased progressively with the age (P < 0.001). Distensibility was related to body mass index (P = 0.002), surface area (P < 0.005), weight (P = 0.005) and to left ventricular parameters such as mass index (P < 0.001) and end-diastolic volume index (P = 0.002). MRSD was related to end-diastolic volume index (P < 0.001) but not to body parameters. PWV was not related to body and ventricular parameters.

CONCLUSIONS

This study confirmed that physiological ageing is associated with a progressive impairment of the elastic properties of the aortic wall. Results of this study may be useful for the early identification of subjects with impaired aortic wall properties providing referral values of elasticity indexes assessed by CMR in different classes of age.

Elastic properties of aortic wall in patients with bicuspid aortic valve by magnetic resonance imaging

Bicuspid aortic valve (BAV) is frequently associated with aortic wall abnormalities, including dilation of the ascending aorta and even dissection. We propose 2 new indexes of aortic wall biophysical properties, the maximum rates of systolic distension and diastolic recoil (MRSD and MRDR, respectively), in patients with BAV and matched control subjects. We evaluated 53 consecutive young patients with BAV (36 males, mean age 16 ± 4 years) with mild aortic valve disease and a control group of 22 age- and gender-matched healthy volunteers. All subjects underwent a cardiac magnetic resonance imaging study that included phase velocity mapping and cine acquisition at several aortic levels. The MRSD and MRDR were measured in the ascending aorta in both patients with BAV and controls. Of the 53 patients with BAV, 26 had enlarged ascending aortas (dilated BAV), and 27 had a normal aortic diameter (nondilated BAV). Compared to controls, the MRSD was significantly lower in the whole BAV group (4.37 ± 1.1 vs 9.1 ± 2.1), in patients with dilated BAV (4.5 ± 1.1 p <0.0001), and in those with nondilated BAV (4.3 ± 1.0, p <0.0001). The MRDR was greater in the whole BAV group (-4 ± 1.2 vs -7.6 ± 2.7, p <0.0001), in the dilated BAV group (-3.9 ± 1.3, p <0.0001), and in the nondilated BAV group (-4.1 ± 1.2, p <0.0001). A receiver operating characteristic curve analysis of MRSD distinguished BAV from controls with 100% sensitivity and 95% specificity. In conclusion, MRSD and MRDR were slower in the patients with BAV than in the controls, regardless of the dimensions of the ascending aorta.

Automated analysis of four-dimensional magnetic resonance images of the human aorta

The purpose of the study was to demonstrate the accuracy and clinical utility of an automated method of image analysis of 4D (3D + time) magnetic resonance (MR) imaging of the human aorta. Serial MR images of the entire thoracic aorta were acquired on 32 healthy individuals. Graph theory based segmentation was applied to the images and cross sectional area (CSA) was determined for the entire length of thoracic aorta. Mean CSA was compared between the 3 years. CSA values at the level of sinuses of Valsalva and sino-tubular junction were used to calculate average diameters for comparison to Roman-Devereux norms. A robust automated segmentation method was developed that accurately reproduced CSA measurements for the entire length of thoracic aorta in serially acquired scans with a 1% error compared to expert tracing. Calculated aortic root diameters based on CSA correlated with Roman-Devereux norms. Mean CSA for the aortic root agreed well with previously published manually derived values. Automated analysis of 4D MR images of the thoracic aorta provides accurate and reproducible results for CSA in healthy human subjects. The ability to simultaneously analyze the entire length of thoracic aorta throughout the cardiac cycle opens the door to the calculation of novel indices of aortic biophysical properties. These novel indices may lead to earlier detection of patients at risk for adverse events.

Augmentation index relates to progression of aortic disease in adults with Marfan syndrome

BACKGROUND

Noninvasive applanation tonometry (APT) is useful to assess aortic stiffness and pulse wave reflection. Moreover, APT can predict outcome in many conditions such as arterial hypertension. In this study, we test whether APT measurements relate to progression of aortic disease in Marfan syndrome (MFS).

METHODS

We performed APT in 50 consecutive, medically treated adults with MFS (19 men and 31 women aged 32 +/- 13 years), who had not undergone previous cardiovascular surgery. During 22 +/- 16 months of follow-up, 26 of these patients developed progression of aortic disease, which we defined as progression of aortic root diameters >or=5 mm/annum (18 individuals), aortic surgery >or=3 months after APT (seven individuals), or onset of acute aortic dissection any time after APT (one individual).

RESULTS

Univariate Cox regression analysis suggested an association of aortic disease progression with age (P = 0.001), total cholesterol levels (P = 0.04), aortic root diameter (P = 0.007), descending aorta diameter (P = 0.01), aortic root ratio (P = 0.02), and augmentation index (AIx@HR75; P < 0.006). Multivariate Cox regression analysis confirmed an independent impact on aortic disease progression exclusively for baseline aortic root diameters (hazard ratio = 1.347; 95% confidence interval (CI) 1.104-1.643; P = 0.003) and AIx@HR75 (hazard ratio = 1.246; 95% CI 1.029-1.508; P = 0.02). In addition, Kaplan-Meier survival curve analysis illustrated significantly lower rates of aortic root disease progression both with lower AIx@HR75 (P = 0.025) and with lower pulse wave velocity (PWV) values (P = 0.027).

CONCLUSIONS

We provide evidence that APT parameters relate to aortic disease progression in medically treated patients with MFS. We believe that APT has a potential to improve risk stratification in the clinical management of MFS patients.

Different patterns of aortic wall elasticity in patients with Marfan syndrome: A noninvasive follow-up study

OBJECTIVE

Aortic complications determine the life expectancy of most patients with Marfan syndrome. To find out whether there is heterogenous aortic involvement among patients and, if there is, to characterize aortic patterns and response to long-term beta-blocker therapy, we investigated aortic elastic properties before and during beta-blocker treatment.

METHODS

In 46 patients with Marfan syndrome (age, 17.4 +/- 11.1 years) and 46 healthy control subjects, ascending and descending aortic elastic parameters were determined noninvasively before and after 39 +/- 16 months of beta-blocker treatment with atenolol.

RESULTS

Aortic diameters and distensibility distinguished Marfan patients and controls with a sensitivity of 85% and a specificity of 87%. Cluster analysis revealed 4 patterns of aortic phenotypic expression: (1) reduced ascending aortic elasticity (46% of patients), (2) diminished ascending and descending aortic elasticity (17%), (3) minimal alterations of ascending and descending aortic elasticity (20%), and (4) reduced descending aortic elasticity (17%). During follow-up, aortic elastic properties improved in 21 (70%) of 30 patients and deteriorated in 9 (30%) irrespective of beta-blocker dosage. Improvement was observed in 100% of patients (n = 7; age, 5.3 +/- 4.2 years) with end-diastolic aortic root diameters between 20 and 30 mm and in 61% of patients (14/23; age, 20.5 +/- 10.0 years) with root diameters between 30 and 52 mm.

CONCLUSIONS

Aortic elastic parameters distinguish between patients with Marfan syndrome and healthy controls and show the pattern of regional aortic involvement. Improvement or deterioration during follow-up can influence therapeutic decisions to prevent aortic dissection and rupture. Young age, small root diameter, and high distensibility are favorable prognostic factors.

A bioinformatics framework for genotype–phenotype correlation in humans with Marfan syndrome caused by FBN1 gene mutations

Mutations in the human FBN1 gene are known to be associated with the Marfan syndrome, an autosomal dominant inherited multi-systemic connective tissue disorder. However, in the absence of solid genotype-phenotype correlations, the identification of an FBN1 mutation has only little prognostic value. We propose a bioinformatics framework for the mutated FBN1 gene which comprises the collection, management, and analysis of mutation data identified by molecular genetic analysis (DHPLC) and data of the clinical phenotype. To query our database at different levels of information, a relational data model, describing mutational events at the cDNA and protein levels, and the disease's phenotypic expression from two alternative views, was implemented. For database similarity requests, a query model which uses a distance measure based on log-likelihood weights for each clinical manifestation, was introduced. A data mining strategy for discovering diagnostic markers, classification and clustering of phenotypic expressions was provided which enabled us to confirm some known and to identify some new genotype-phenotype correlations.

Echocardiographic Doppler assessment of the biophysical properties of the aorta in pediatric patients with the Marfan syndrome

In the Marfan syndrome (MS), aortic root involvement is usually clinically monitored according to the aortic sinus of Valsalva dilation. Using an echocardiographic Doppler method in this cross-sectional study, abnormal biophysical properties of the ascending aorta were found in pediatric patients with MS compared with healthy controls but not consistently in association with the aortic sinus of Valsalva dilation.

Impaired elastic properties of the ascending aorta in newborns before and early after successful coarctation repair: proof of a systemic vascular disease of the prestenotic arteries?

BACKGROUND

Despite successful surgical correction, morbidity of patients with coarctation of the aorta is increased. It is well known that these patients have impaired elastic properties of the prestenotic arteries. To find out whether these abnormalities are primarily present or develop later, we studied 17 newborns before and early after surgical repair.

METHODS AND RESULTS

Aortic wall stiffness index and distensibility were calculated using ascending and abdominal aortic diameters determined by M-mode echocardiography and noninvasive estimation of aortic pulse pressure in the right arm and leg. Seventeen patients with aortic coarctation (mean age, 20+/-26 days) were compared with 17 normal neonates (mean age, 13+/-7 days) preoperatively and postoperatively (10+/-6 days after surgery). Ascending aortic distensibility in patients was significantly reduced preoperatively (79+/-58 versus 105+/-36; P=0.03) and postoperatively (65+/-24 versus 105+/-36; P<0.005). Preoperative and postoperative ascending aortic stiffness index was higher in patients (preoperative, 5.2+/-4.4 versus 2.7+/-0.9; P=0.04; postoperative, 4.0+/-1.6 versus 2.7+/-0.9; P<0.005). Elastic properties of the descending aorta did not differ preoperatively or postoperatively compared with those in normal subjects.

CONCLUSIONS

Elastic properties of the prestenotic aorta of patients with coarctation seem to be impaired primarily, even in neonates, and remain unchanged early after successful operation. Surgical correction does not resolve inborn pathology of the prestenotic aortic vascular bed.

Diagnostic power of aortic elastic properties in young patients with Marfan syndrome

BACKGROUND

In patients with Marfan syndrome, progressive aortic dilation implicates a still-unpredictable risk of life-threatening aortic dissection and rupture. We sought to quantify aortic wall dysfunction noninvasively, determine the diagnostic power of various aortic parameters, and establish a diagnostic model for the early detection of aortic abnormalities associated with Marfan syndrome.

METHODS

In 19 patients with Marfan syndrome (age, 17.7 +/- 9.5 years) and 19 age- and sex-matched healthy control subjects, computerized ascending and abdominal aortic wall contour analysis with continuous determination of aortic diameters was performed out of transthoracic M-mode echocardiographic tracings. After simultaneous oscillometric blood pressure measurement, aortic elastic properties were determined automatically.

RESULTS

The following ascending aortic elastic parameters showed statistically significant differences between the Marfan group and the control group: (1) decreased aortic distensibility ( P < .001), (2) increased wall stiffness index ( P < .01), (3) decreased systolic diameter increase ( P < .01), and (4) decreased maximum systolic area increase ( P < .001). The diagnostic power of all investigated parameters was tested by single logistic regression models. A multiple logistic regression model including solely aortic parameters yielded a sensitivity of 95% and a specificity of 100%.

CONCLUSIONS

In young patients with Marfan syndrome, a computerized image-analyzing technique revealed decreased aortic elastic properties expressed by parameters showing high diagnostic power. A multiple logistic regression model including merely aortic parameters can serve as useful predictor for Marfan syndrome.

Biophysical properties of the normal-sized aorta in patients with Marfan syndrome: evaluation with MR flow mapping

PURPOSE

To investigate the feasibility of magnetic resonance (MR) flow mapping in the assessment of aortic biophysical properties in patients with Marfan syndrome and to detect differences in biophysical properties in the normal-sized aorta distal to the aortic root between these patients and matched control subjects.

MATERIALS AND METHODS

Seventy-eight patients with Marfan syndrome with aortic root dilatation and 23 matched control subjects underwent MR flow mapping in four locations in the normal-sized aorta (1, ascending aorta; 2, thoracic descending aorta; 3, descending aorta at the level of the diaphragm; and 4, abdominal descending aorta). Distensibility at each location and flow wave velocity between locations were calculated.

RESULTS

Compared with the control subjects, patients with Marfan syndrome had decreased aortic distensibility at three of the four locations (levels 1, 2, and 4; P <.05) and increased flow wave velocity between all locations (P <.05) in the aorta. In patients with Marfan syndrome, flow wave velocity was also significantly increased along the entire aortic tract beyond the aortic root (from level 1 to level 4).

CONCLUSION

MR imaging reveals abnormal biophysical properties of the normal-sized aorta in patients with Marfan syndrome. Monitoring of these properties is relevant for evaluating disease progression and treatment options.

Sports and marfan syndrome: awareness and early diagnosis can prevent sudden death

Marfan syndrome is an autosomal dominant disorder of the connective tissues. Its major manifestations are in the cardiovascular, musculoskeletal, and ocular systems. Recognizing the phenotypic presentation of tall stature, long limbs and fingers, chest deformity, myopia, midsystolic click, and systolic or diastolic murmur can lead to early diagnosis. Morbidity and mortality are primarily caused by cardiovascular involvement. The goal of medical therapy is to retard the aortic root dilation that leads to sudden death from dissection or rupture. Surgical interventions for mitral valve regurgitation and resection of aortic aneurysms are highly effective. In addition, individuals with Marfan syndrome should be restricted from participation in certain sports.

The genetic basis of aortic disease. Marfan syndrome and beyond

The Marfan syndrome and related disorders are systemic disorders of connective tissue. Proximal aorta is usually dilated. The molecular basis of Marfan syndrome has been elucidated, thus allowing prenatal diagnosis. Life expectancy has markedly improved due to the widespread use of beta-adrenergic receptor inhibitors and improved surgical management of the aortic disease.

Central pulse pressure is a major determinant of ascending aorta dilation in Marfan syndrome

BACKGROUND

In patients with Marfan syndrome (MFS), brachial pulse pressure (PP) has been recognized as a risk factor for aortic dilatation, leading to aortic dissection, the main cause of premature death. However, the relationships between aortic PP, aortic stiffness, and aortic root dilation have not been investigated. Our main objective was to determine whether central PP, which takes into account wave reflections and aortic stiffness, is a better determinant of ascending aorta diameter than brachial PP in MFS patients.

METHODS AND RESULTS

Twenty patients with confirmed MFS and 20 age- and sex-matched control subjects were included in this cross-sectional, noninvasive study. Elastic properties of the abdominal aorta and common carotid, common femoral, and radial arteries were calculated from the pulsatile changes in arterial diameter and pressure. The ascending aorta diameter, measured with conventional echocardiography, was 37% larger in MFS than in control subjects (P<0.001). Arterial distensibility was 38% lower in MFS than in control subjects at the site of the abdominal aorta (P<0.01) but not at other sites (common carotid, common femoral, and radial arteries). Independently of age and body surface area, ascending aorta diameter was positively correlated with carotid PP in MFS (P<0. 01) and negatively in control subjects (P<0.01) but was not correlated with brachial PP and mean blood pressure.

CONCLUSIONS

In patients with MFS, local PP, estimated from carotid PP, was a major determinant of ascending aorta diameter, whereas brachial PP was not. Increased arterial stiffness was confined to the aorta.

Estimation of arterial mechanics in clinical practice and as a research technique

1. Large conduit artery pathophysiology is associated with considerable morbidity with even normal ageing, irrespective of concurrent influences, associated with impaired arterial function. 2. Recent technical advances have enabled high-resolution non-invasive assessment of pulsatile arterial properties, but this has been largely confined to more muscular superficial arteries. There has been less study of arterial regions prone to disease that would, theoretically at least, benefit from pharmacological or other intervention to improve function. 3. Based on studies in animal models and, in particular, human arterial segments, specific pharmacological agents have been proposed as improving arterial behaviour. If this is to become a therapeutic target, it behoves increased effort to understand and measure meaningful indices of arterial function and to find ways of assessing response and outcome. 4. A number of different approaches to assessment and quantification of arterial mechanics are available in the literature. The present review compares and discusses some of these different techniques and looks at differences between arterial segments and evidence that appropriate intervention may beneficially modify arterial behaviour. 5. For clinical or research usefulness, assessment of arterial mechanics must provide more information than currently derived from simple numerical measurement of brachial blood pressure. This is particularly true because epidemiological risk evidence is based on brachial rather than central blood pressure recordings. There has been an explosion of work in this field in recent years and the present review does not pretend to reference all relevant material; rather, it tries to provide a broad coverage of the topic and hopes to support the need for continued endeavours in the field of arterial mechanics.

Changes in aortic distensibility and pulse wave velocity assessed with magnetic resonance imaging following beta-blocker therapy in the Marfan syndrome

It has been shown that beta-adrenergic blocking agents may reduce the rate of aortic root dilation and the development of aortic complications in patients with the Marfan syndrome. This may be due to beta-blocker-induced changes in aortic stiffness, of which distensibility and pulse wave velocity are in vivo measurable derivatives. We studied changes in distensibility at 4 levels of the aorta and pulse wave velocity along the entire aorta after 2 weeks of beta-blocker therapy in 6 Marfan syndrome patients and in 6 healthy volunteers, using magnetic resonance imaging (MRI) combined with brachial artery blood pressure measurements. In both groups, mean blood pressure decreased significantly (Marfan: 86 +/- 6 vs 78 +/- 5 mm Hg, p <0.05; control: 80 +/- 8 vs 73 +/- 3 mm Hg, p <0.05) (all data expressed as mean +/- 1 SD). At baseline, the Marfan syndrome patients exhibited decreased distensibility at the level of the ascending aorta (2 +/- 1 vs 6 +/- 2 10(-3)mm Hg(-1), p <0.01) and increased pulse wave velocity (6.2 +/- 0.4 vs 3.9 +/- 0.4 ms(-1), p <0.01) compared with control subjects. Only the Marfan syndrome patients had a significant increase in aortic distensibility at multiple levels and a significant decrease in pulse wave velocity after beta-blocker therapy (ascending aorta distensibility: 2 +/- 1 vs 4 +/- 1 10(-3)mm Hg(-1), p <0.05; abdominal aorta distensibility: 5 +/- 2 vs 8 +/- 3 10(-3)mm Hg(-1), p <0.05; pulse wave velocity: 6.2 +/- 0.4 vs 5.0 +/- 1.0 ms(-1), p <0.05). Thus, aortic stiffness in Marfan syndrome, together with mean blood pressure, is reduced by beta-blocker therapy, and MRI is well suited to detect these changes by measuring distensibility and pulse wave velocity.

Intravascular ultrasound assessment of regional aortic wall stiffness, distensibility, and compliance in patients with coarctation of the aorta

BACKGROUND

Impaired aortic pulsatility has been demonstrated by angiography in children and in studies of experimental animals with coarctation of the aorta.

OBJECTIVES

The purpose of this study was to assess regional aortic stiffness, distensibility, and compliance before and after balloon dilation in patients with coarctation of the aorta.

METHODS AND RESULTS

Intravascular ultrasound examination was performed in 13 pediatric patients with the diagnosis of coarctation of the aorta to yield aortic diameter. Area transverse sections at both systolic and diastolic period were measured at three aortic levels: the proximal, distal, and coarctation segments. Balloon dilation was also performed in eight of 13 patients. By using pressures measured in the same areas, an aortic stiffness index (beta) was calculated as In(Ps/Pd)/(Ds-Dd), where In is natural logarithm, Ps is systolic pressure, Pd is diastolic pressure, Ds is systolic diameter, and Dd is diastolic diameter. Aortic distensibility and an estimation of aortic compliance were also calculated. The beta stiffness index of the coarctation and the proximal segments of the aorta were significantly greater than that of the distal segment of the aorta (p < 0.01). The aortic wall stiffness beta index did not acutely change after successful balloon dilation, but the distensibility and compliance of distal aorta were nonetheless significantly decreased after balloon dilation (p < 0.01, p < 0.05) as a function of changes of pulsatility of flow.

CONCLUSIONS

Abnormal proximal aortic stiffness may be a strong contributing factor that promotes the genesis of hypertension in patients with coarctation even after successful repair or balloon angioplasty.

Bentall operation for a child with Marfan syndrome: a case report

Children with Marfan syndrome rarely undergo surgery for annuloaortic ectasia and aortic regurgitation in the first decade. A 7-year-old girl presented with congestive heart failure due to severe aortic regurgitation associated with annuloaortic ectasia (6 cm). She also had funnel chest. She underwent a Bentall operation and sternal turn-over with a satisfactory result. Since the aortic valve cusps had rolled edges, the aortic valve was not spared. Histology of the aortic valve cusps showed myxoid degeneration and fragmentation of elastic fibers.

Detection of abnormal aortic elastic properties in asymptomatic patients with Marfan syndrome by combined transoesophageal echocardiography and acoustic quantification

OBJECTIVE

To evaluate the potential value of transoesophageal echocardiography combined with automated border detection and acoustic quantification for the assessment of elastic properties of the thoracic aorta in patients with Marfan syndrome.

SUBJECTS

16 patients with Marfan syndrome and 12 age matched normal controls.

METHODS

Transoesophageal echocardiography was performed in all subjects. Minimum and maximum diameters of the descending thoracic aorta were obtained from M mode images and acoustic quantification was used for the on-line evaluation of cross sectional aortic area and peak positive area changes over time. Compliance, distensibility, and stiffness index were calculated using M mode data and non-invasively measured blood pressure and were compared with the indices derived from acoustic quantification.

RESULTS

Aortic dimensions normalised for body surface area were not statistically different between patients and normal controls, but there were significant differences for all elasticity indices except compliance. Marfan patients had a lower distensibility [4.2 (SD 1.8) v 5.8 (2.1) cm2/dyn, P < 0.05] and a higher stiffness index [9.7 (3.0) v 7.1 (1.8), P < 0.05]. The dynamic indices derived from the acoustic quantification were significantly smaller in Marfan patients [peak positive area change: 5.1 (1.0) v 7.7 (1.7) cm2/s; P < 0.001; and normalised peak positive area change: 2.5 (1.2) v 4.0 (0.8) cm2/s respectively, P < 0.001] and were suitable to discriminate between normal and abnormal elastic properties.

CONCLUSIONS

In Marfan syndrome elastic properties of the descending aorta are significantly different from normal controls, even in the absence of vessel dilatation. In addition to established static indices, indices derived from acoustic quantification reflect dynamic changes of the cross sectional area for the evaluation of regional vessel mechanics. The on-line assessment of peak positive area change allows differentiation from normal individuals and may be more accurate than standard M mode measurements.

Effects of angiotensin-converting enzyme inhibition versus beta-adrenergic blockade on aortic stiffness in essential hypertension

We assessed the effects of 6 months of treatment with an angiotensin-converting enzyme (ACE) inhibitor (cilazapril) or a beta 1-adrenergic blocker (atenolol) on aortic stiffness in essential hypertension. Forty patients (16 women) aged 47 +/- 9 years (mean +/- SD) with baseline systolic and diastolic blood pressures of 162 +/- 15 and 105 +/- 5 mm Hg, respectively, were entered into a double-blind, parallel-group study with cilazapril, 5 mg once daily, or atenolol, 100 mg once daily. The treatment period was preceded by a 4-week placebo washout phase. Aortic elastic modulus (Ep) was determined by cine magnetic resonance imaging (MRI) and indirect brachial artery blood pressure measurements prior to and after 3 weeks and 6 months of therapy. The reductions in systolic and diastolic blood pressures from baseline to 6 months averaged -17 +/- 13 and -10 +/- 6 mm Hg, respectively, with cilazapril and -23 +/- 16 and -14 +/- 6 mm Hg with atenolol. Concomitantly, Ep of the ascending aorta decreased with cilazapril from a median of 2,234 10(3)dyn/cm2 (interquartile range, 866-3,740) to 868 10(3)dyn/cm2 (515-1,486) and with atenolol from a median of 1,611 10(3)dyn/cm2 (895-2,790) to 1,054 10(3)dyn/cm2 (616-1,860). In repeated-measurements analysis of variance, the change in Ep with time was statistically significant (p < 0.001) but the group x time interaction was not. We conclude that 6 months of treatment with either cilazapril or atenolol reduces the stiffness of the ascending aorta in essential hypertension. No statistically significant differences between the effects of the two drugs were observed. The mechanisms and clinical significance of improved aortic distensibility with antihypertensive therapy deserve further study.

Aortic distensibility and stiffness index measured by magnetic resonance imaging in patients with Marfan's syndrome

OBJECTIVES

To use magnetic resonance imaging to measure the elastic properties of the aorta of adults with Marfan's syndrome and to compare these results with those obtained by echocardiography.

PATIENTS AND METHODS

12 patients with Marfan's syndrome and 12 controls matched for age. Transverse luminal areas of the ascending and descending aorta were measured using electrocardiographic gated magnetic resonance imaging. Echocardiography was used to measure the diameter of the ascending aorta and aortic arch in patients with Marfan's syndrome. Blood pressure was measured during both scans.

RESULTS

In diastole, transverse luminal areas of the ascending and descending aorta were significantly greater in patients with Marfan's syndrome when measured by magnetic resonance imaging and corrected for body surface area; P < 0.02 and P < 0.05 respectively. Patients with Marfan's syndrome had a higher stiffness index (112.77 v 5.78, P < 0.05) and a lower distensibility (0.0066 v 0.0105, P < 0.05) than controls. Results produced by MRI and echocardiography were not significantly different.

CONCLUSIONS

Magnetic resonance imaging gives good quality reproducible images of the ascending and descending aorta. In patients with Marfan's syndrome, aortic distensibility and stiffness index measured by magnetic resonance imaging were abnormal (but did not always relate directly to the size of the aorta.

Results of cardiovascular surgery in the Marfan syndrome. A retrospective study of 49 patients

To evaluate the outcome of cardiovascular surgery in the Marfan syndrome, the records of 49 patients (median age 35 years) who underwent 60 operations were reviewed. Primary surgery was elective in 39 patients and emergency in ten. Non-dissecting aneurysm with diameter 4-19 cm was present in 34 cases and distal, isolated aneurysm in four. In eight cases there was type A acute aortic dissection with median diameter 5.0 cm. One patient was operated on for mitral valve insufficiency, one for ventricular septal defect and one (acute) for endocarditis. Composite grafts were used for aortic root reconstruction. Operative complications occurred in 24% of the patients. The 30-day survival was 92%. There were five (10%) late deaths. Survival after a median of 8 years postoperatively was 82%. The early and late results of cardiovascular surgery in the Marfan syndrome thus are concluded to be generally favourable. As late reoperation frequently is needed, however, close monitoring is advocated even after successful primary surgery.

Prevalence and predictors of audible physiological third heart sound in a population sample aged 36 to 37 years

BACKGROUND

A physiological third heart sound (S3) is common in youth but allegedly very rare after the age of 40 years. The mechanism of its disappearance is not known. The aim of this work was to study the prevalence and predictors of physiological S3 in a population-based sample of persons approaching 40 years of age.

METHODS AND RESULTS

A random sample of 120 persons born in 1954 was invited; 93 (42 men) entered the study. Their physical activity, alcohol and tobacco consumption, and salt intake were quantified by diary follow-up. The presence of an S3 was determined by auscultation and confirmed by phonocardiography. Left ventricular (LV) size, mass, and systolic function were assessed by M-mode echocardiography and LV filling by Doppler velocimetry of transmitral flow. An audible S3 was detected in 22 subjects, 1 of whom had heart disease. The prevalence of physiological S3 was 23.1%. Subjects with physiological S3 had a lower body mass index (22.3 +/- 2.8 versus 24.6 +/- 4.1 kg/m2 [mean +/- SD], P = .005), lower heart rate (63 +/- 7 versus 68 +/- 10 beats per minute, P = .015), higher peak early diastolic transmitral velocity (67 +/- 10 versus 58 +/- 8 cm/s, P = .002), and higher acceleration of early diastolic velocity (717 +/- 148 versus 622 +/- 122 cm/s2, P = .012) than those without S3. No differences were noted in the lifestyle characteristics, blood pressure, or LV mass and systolic function. Body mass index and peak early diastolic transmitral velocity were independent predictors of physiological S3 in logistic regression analysis.

CONCLUSIONS

Nearly one fourth of persons approaching their forties still have an audible physiological S3. The presence of S3 is predicted by leanness and a high early diastolic LV inflow velocity; the disappearance of S3 is unlikely to be secondary to increasing blood pressure and relative LV hypertrophy, as is widely presented, but reflects a more primary age-related alteration of LV early diastolic function.

Relation of aortic stiffness to factors modifying the risk of atherosclerosis in healthy people

To identify factors predicting aortic stiffness, we studied the modulus of elasticity of the thoracic aorta in relation to sex, obesity, blood pressure, physical activity, smoking, ethanol consumption, salt intake, and serum lipid and insulin levels in 55 healthy people born in 1954. A transverse cine magnetic resonance image of the thoracic aorta was made, and the modulus of elasticity was determined as brachial artery cuff pulse pressure/aortic strain, where strain was determined as the ratio of pulsatile aortic luminal area change to the diastolic luminal area. The average of measurements made in the ascending and descending aorta was used as the elastic modulus of the thoracic aorta. Habitual physical activity, smoking, and alcohol use were quantified by 2-month prospective daily recording and salt intake by 7-day food records. The aortic elastic modulus ranged from 100 to 2091 10(3) dyne/cm2 (median, 390 10(3) dyne/cm2). In multiple regression analyses, log10 aortic elastic modulus was related directly to mean blood pressure (standardized coefficient [beta] = .37, P = .002), serum high-density lipoprotein cholesterol (beta = .36, P = .012), square root of daily energy expenditure in physical activity (beta = .33, P = .005), and log10 serum insulin (beta = .27, P = .047) and inversely to serum low-density lipoprotein cholesterol (beta = -.26, P = .035). A relation to salt intake was also observed, but the regression slope was dependent on mean blood pressure (P = .005 for interaction). These data suggest that many modifiable constitutional and lifestyle characteristics may contribute to the stiffness of the thoracic aorta.