Impaired Central Pulsatile Hemodynamics in Children and Adolescents With Marfan Syndrome

Are aortic biomechanical properties early markers of dilatation in patients with Marfan syndrome? A systematic review and meta-analysis

Although tissue stiffness is known to play an important role in aortic dilatation, the current guidelines for offering preventative surgery in patients with Marfan syndrome rely solely on the aortic diameter. In this systematic review and meta-analysis, we analyze and compare literature on in vivo aortic stiffness measures in Marfan patients. Our aim is to assess the potential of these measurements as early indicators of aortic dilatation. Following the PRISMA guidelines, we collected literature on diameter and three in vivo stiffness measures: Pulse wave velocity (PWV), β -stiffness index (SI) and distensibility, at five different aortic locations in patients with Marfan syndrome. Results were reviewed and compared against each other. For meta-analysis, an augmented dataset was created by combining data from the literature. Regression with respect to age and statistical comparisons were performed. Thirty articles reporting data from 1925 patients with Marfan and 836 patients without Marfan were reviewed. PWV was found to be higher in Marfan, but only in dilated aortas. Distensibility was found to be lower even in non-dilated aortas, and its decrease was associated with higher chances of developing aortic dilatation. β -SI was higher in Marfan patients and was positively correlated with the rate of aortic dilatation, emphasizing its role as a valuable indicator. In our meta-analysis, all stiffness measures showed a significant variation with age. Distensibility and β -stiffness index were different in Marfan patients at all locations, and the difference was more pronounced after accounting for age-related variation. From the literature, β -SI and distensibility emerge as the best predictors of future aortic dilatation. Our meta-analysis quantifies age-related changes in aortic stiffness and highlights the importance of accounting for age in comparing these measurements. Missing diameter values in the literature limited our analysis. Further investigation of criteria combining stiffness and diameter is recommended to better assist clinical decisions for prophylactic surgery.

Superiority of a Representative MRI Flow Waveform over Doppler Ultrasound for Aortic Wave Reflection Assessment in Children and Adolescents With/Without a History of Heart Disease

Wave separation analysis (WSA) reveals the impact of forward- and backward-running waves on the arterial pressure pulse, but the calculations require a flow waveform. This study investigated (1) the variability of the ascending aortic flow waveform in children and adolescents with/without a childhood heart disease history (CHD); (2) the accuracy of WSA obtained with a representative flow waveform (RepFlow), compared with the triangulation method and published ultrasound-derived adult representative flow; (3) the impact of limitations in Doppler ultrasound on WSA; and (4) generalizability of results to adults with a history of CHD. Phase contrast MRI was performed in youth without (n = 45, Group 1, 10-19 years) and with CHD (n = 79, Group 2, 7-18 years), and adults with CHD history (n = 29, Group 3, 19-59 years). Segmented aortic cross-sectional area was used as a surrogate for the central pressure waveform in WSA. A subject-specific virtual Doppler ultrasound was performed on MRI data by extracting velocities from a sample volume. Time/amplitude-normalized ascending aortic flow waveforms were highly consistent amongst all groups. WSA with RepFlow therefore yielded errors < 10% in all groups for reflected wave magnitude and return time. Absolute errors were typically 1.5-3 times greater with other methods, including subject-specific (best-case/virtual) Doppler ultrasound, for which velocity profile skewing introduced waveform errors. Our data suggest that RepFlow is the optimal approach for pressure-only WSA in children and adolescents with/without CHD, as well as adults with CHD history, and may even be more accurate than subject-specific Doppler ultrasound in the ascending aorta.

Marfan Syndrome: Enhanced Diagnostic Tools and Follow-up Management Strategies

Marfan syndrome (MFS) is a rare inherited autosomic disorder, which encompasses a variety of systemic manifestations caused by mutations in the Fibrillin-1 encoding gene (FBN1). Cardinal clinical phenotypes of MFS are highly variable in terms of severity, and commonly involve cardiovascular, ocular, and musculoskeletal systems with a wide range of manifestations, such as ascending aorta aneurysms and dissection, mitral valve prolapse, ectopia lentis and long bone overgrowth, respectively. Of note, an accurate and prompt diagnosis is pivotal in order to provide the best treatment to the patients as early as possible. To date, the diagnosis of the syndrome has relied upon a systemic score calculation as well as DNA mutation identification. The aim of this review is to summarize the latest MFS evidence regarding the definition, differences and similarities with other connective tissue pathologies with severe systemic phenotypes (e.g., Autosomal dominant Weill-Marchesani syndrome, Loeys-Dietz syndrome, Ehlers-Danlos syndrome) and clinical assessment. In this regard, the management of MFS requires a multidisciplinary team in order to accurately control the evolution of the most severe and potentially life-threatening complications. Based on recent findings in the literature and our clinical experience, we propose a multidisciplinary approach involving specialists in different clinical fields (i.e., cardiologists, surgeons, ophthalmologists, orthopedics, pneumologists, neurologists, endocrinologists, geneticists, and psychologists) to comprehensively characterize, treat, and manage MFS patients with a personalized medicine approach.

Factors associated with arterial stiffness assessed by pulse pressure amplification in healthy children and adolescents: a cross-sectional study

BACKGROUND

Increasing evidence suggests that reducing pulse pressure amplification (PPA) plays an important role in pathogenesis and progression of cardiovascular disease. This is a cross-sectional, observational, and analytical study in which we evaluated the associated factors with a greater chance of reducing PPA in 136 healthy children and adolescents aged 8 to 19 years old stratified by gender and age group.

METHODS

Arterial stiffness and vascular and hemodynamic parameters were non-invasively measured using Mobil-O-Graph® (IEM, Stolberg, Germany), a cuff-based oscillometric device. PPA was expressed as the peripheral-to-central pulse pressure ratio (PPp / PPc). Participants with PPA < 1.49 were considered as part of the arterial stiffness group.

RESULTS

In a univariate model, the increase in total vascular resistance, the reflection coefficient and the augmentation pressure were more likely to have arterial stiffness in all groups. The factors most likely to have arterial stiffness (as assessed by the reduction of the PPA) in the multivariate model were increasing age, the reflection coefficient and cardiac index in the total sample, male group and child and adolescent groups. In addition to age in the female group, cardiac output, stroke volume, and AIx@75 were the factors most likely to present arterial stiffness.

CONCLUSIONS

The results show for the first time in children and adolescents that the factors most likely to reduce PPA are related to the reflection wave, which determines aortic pressures and, therefore, left ventricular afterload.

CHARACTERISTICS OF THE FOVEAL MICROVASCULATURE IN CHILDREN WITH MARFAN SYNDROME: An Optical Coherence Tomography Angiography Study

PURPOSE

To investigate the characteristics of foveal microvasculature in children with Marfan syndrome (MFS).

METHODS

Ninety eyes from 45 MFS patients and 76 eyes from 38 healthy individuals of age-matched, sex-matched, and axial length-matched were enrolled. Characteristics of the superficial capillary plexus including the vessel density, perfusion density, and foveal avascular zone were analyzed by optical coherence tomography angiography.

RESULTS

The vessel density and the circularity index of the foveal avascular zone were significantly decreased in the MFS group compared with the controls (P = 0.017 and P = 0.004 respectively). In MFS group, the central vessel density (P = 0.003) and perfusion density (P = 0.001) were negatively correlated with the best-corrected visual acuity. The foveal avascular zone area was correlated with the aortic diameters (P = 0.001) and the paratemporal perfusion density was correlated with the ejection fraction (P = 0.003). Moreover, the paratemporal perfusion density and the circularity index of foveal avascular zone were found to be correlated with the aortic Z-score (P < 0.001 and P = 0.003 respectively).

CONCLUSION

Retinal microvascular decrease and its correlation with best-corrected visual acuity and cardiac functions were observed in the MFS group. The optical coherence tomography angiography may help to characterize the underlying pathophysiology features of MFS and enable early detection and prevention of vascular changes in MFS.

Postoperative and mid-term hemodynamic changes after replacement of the ascending aorta

OBJECTIVES

To evaluate aortic distensibility and pulse waveform patterns associated with the ascending aortic aneurysm, and to analyze the postoperative and mid-term hemodynamic changes induced by prosthetic replacement of the ascending aorta.

METHODS

Central blood pressure waves were recorded at the carotid artery level by means of a validated transcutaneous arterial tonometer in 30 patients undergoing prosthetic replacement of ascending aortic aneurysm and in 30 control patients. Measurements were obtained the day before surgery and 5 to 7 days and 16 to 20 months after surgery.

RESULTS

The ascending aortic aneurysm was associated with a less steep slope of early systolic phase of the pressure curve (pulsus tardus) compared with a control group (0.54 ± 0.18 mm Hg/ms vs 0.69 ± 0.26 mm Hg/ms; P = .011). Replacing the ascending aorta with a noncompliant vascular prosthesis steepened the pulse pressure slope during the early systolic phase in the postoperative period (0.77 ± .29 mm Hg/ms), providing values comparable with those of the control group in the mid-term (0.67 ± .20 mm Hg/ms). No change in aortic stiffness was found either postoperatively or in the mid-term after ascending aorta surgical replacement (carotid-femoral pulse wave velocity: preoperative, 9.0 ± 2.6 m/s; postoperative, 9.0 ± 2.9 m/s; mid-term postoperative, 9.3 ± 2.8 m/s).

CONCLUSIONS

This study does not confirm the assumption that substitution of the viscoelastic ascending aorta with a rigid prosthesis can cause serious hemodynamic alterations downstream, because we did not observe a worsening of global aortic distensibility after insertion of a rigid prosthetic aorta. The ascending aortic aneurysm is associated with a pulsus tardus.

Unreliable Estimation of Aortic Pulse Wave Velocity Provided by the Mobil-O-Graph Algorithm-Based System in Marfan Syndrome

Background Several devices have been proposed to assess arterial stiffness in clinical daily use over the past few years, by estimating aortic pulse wave velocity (PWV) from a single measurement of brachial oscillometric blood pressure, using patented algorithms. It is uncertain if these systems are able to provide additional elements, beyond the contribution carried by age and blood pressure levels, in the definition of early vascular damage expressed by the stiffening of the arterial wall. Methods and Results The aim of our study was to compare the estimated algorithm-based PWV values, provided by the Mobil-O-Graph system, with the standard noninvasive assessment of aortic PWV in patients with Marfan syndrome (ie, in subjects characterized by premature aortic stiffening and low blood pressure values). Aortic stiffness was simultaneously evaluated by carotid-femoral PWV with a validated arterial tonometer and estimated with an arm cuff-based ambulatory blood pressure monitoring Mobil-O-Graph device on 103 patients with Marfan syndrome (50 men; mean± SD age, 38±15 years). Aortic PWV, estimated by the Mobil-O-Graph, was significantly ( P<0.0001) lower (mean± SD, 6.1±1.3 m/s) than carotid-femoral PWV provided by arterial tonometry (mean± SD , 8.8±3.1 m/s). The average of differences between PWV values provided by the 2 methods (±1.96×SD) was -2.7±5.7 m/s. Conclusions The Mobil-O-Graph provides PWV values related to an ideal subject for a given age and blood pressure, but it is not able to evaluate early vascular aging expressed by high PWV in the individual patient. This is well shown in patients with Marfan syndrome.

Central artery stiffness and thoracic aortopathy

Thoracic aortopathy, especially aneurysm, dissection, and rupture, is responsible for significant morbidity and mortality. Uncontrolled hypertension and aging are primary risk factors for such conditions, and they contribute to an increase in the mechanical stress on the wall and an increase in its structural vulnerability, respectively. Select genetic mutations also predispose to these lethal conditions, and the collection of known mutations suggests that dysfunctional mechanosensing and mechanoregulation of the extracellular matrix may contribute to pathogenesis and disease progression. In the absence of a well-accepted pharmacotherapy, nonsurgical treatments tend to focus on reducing the mechanical loading on the aorta, particularly via the use of antihypertensive medications and recommendations to avoid strenuous exercises such as weight lifting. In this brief review, we discuss the important effects of central artery stiffening on global hemodynamics and, in particular, on the increase in pulse pressure that acts on the proximal thoracic aorta. We consider Marfan syndrome as an illustrative aortopathy but discuss other conditions leading to thoracic aortic aneurysm and dissection. We highlight the importance of phenotyping the aorta biomechanically, not just clinically, and emphasize the utility of mouse models in elucidating molecular and mechanical mechanisms of disease. Notwithstanding the widely recognized role of central artery stiffening in driving end-organ disease, we suggest that there is similarly a need to consider its key role in thoracic aortopathy.

Systolic time intervals assessed from analysis of the carotid pressure waveform

OBJECTIVE

The timing of mechanical cardiac events is usually evaluated by conventional echocardiography as an index of cardiac systolic function and predictor of cardiovascular outcomes. We aimed to measure the systolic time intervals, namely the isovolumetric contraction time (ICT) and pre-ejection period (PEP), by arterial tonometry.

APPROACH

Sixty-two healthy volunteers (age 47  ±  17 years) and 42 patients with heart failure and reduced ejection fraction were enrolled (age 66  ±  14 years). Pulse waves were recorded at the carotid artery by arterial tonometry together with simultaneous aortic transvalvular flow by Doppler-echocardiography, synchronized by electrocardiographic gating. The ICT was determined from the time delay between the electrical R wave and the carotid pressure waveform, after adjustment for the pulse transit time from the aortic valve to the carotid artery site, estimated by an algorithm based on the carotid-femoral pulse wave velocity. The PEP was evaluated by adding the electrical QR duration to the ICT.

MAIN RESULTS

The ICT derived from carotid pulse wave analysis was closely related to that measured by echocardiography (r  =  0.90, p  <  0.0001), with homogeneous distribution in Bland-Altman analysis (mean difference and 95% confidence interval  =  0.2 from  -14.2 to 14.5 ms). ICT and PEP were higher in cardiac patients than in healthy volunteers (p  <  0.0001). The ratio between PEP and left ventricular ejection time was related to the ejection fraction measured with echocardiography (r  =  0.555, p  <  0.0001).

SIGNIFICANCE

The timing of electro-mechanical cardiac events can be reliably obtained from the carotid pulse waveform and carotid-femoral PWV, evaluated using arterial tonometry. Systolic time intervals assessed with this approach showed good agreement with measurements performed with conventional echocardiography and may represent a promising additional application of arterial tonometry.

Ascending Aortic Strain Analysis Using 2-Dimensional Speckle Tracking Echocardiography Improves the Diagnostics for Coronary Artery Stenosis in Patients With Suspected Stable Angina Pectoris

Background

Arterial stiffening and atherosclerosis tend to coexist. Strain imaging, using a 2‐dimensional speckle tracking (2D‐ST) method, has been used for arterial stiffness assessment and early identification of atherosclerosis. We investigated whether the ascending aortic strain assessed by 2D‐ST echocardiography at rest can predict the presence of coronary artery disease (CAD).

Methods and Results

Two hundred seventy‐one consecutive patients with suspected stable angina pectoris sequentially underwent exercise treadmill testing, 2‐dimensional echocardiography, M‐mode echocardiography, 2D‐ST echocardiography, and coronary angiography. Circumferential ascending aortic strain (CAAS) and radial ascending aortic strain were assessed by 2D‐ST echocardiography. Ninety‐two patients with coronary lumen area stenosis ≥70% were categorized as having significant CAD. Global CAAS was significantly lower in patients with significant CAD (7.41±2.30% versus 11.54±4.03%; P<0.001) and remained an independent predictor of significant CAD (odds ratio, 0.64 [0.54–0.75]; P<0.001) after multivariate regression. Based on the receiver operating characteristic curve for diagnosing significant CAD, the optimal cut‐off value of global CAAS was ≤9.22% (sensitivity, 86%; specificity, 70%; area under curve=0.82; P<0.001). Global CAAS decreased with increasing severity of CAD and was significantly associated with 3‐vessel disease (odds ratio, 0.58 [0.42–0.79]; P<0.001). Diagnostics for significant CAD were remarkably better for global CAAS combined with exercise treadmill testing than for exercise treadmill testing alone (area under curve=0.88 versus 0.78; P<0.001).

Conclusions

Global CAAS assessed by 2D‐ST echocardiography at rest was able to predict the presence of significant CAD and identify multivessel disease. In addition, global CAAS combined with exercise treadmill testing remarkably improved the diagnostics for significant CAD.