Impairment of elastic properties of the aorta in bicuspid aortic valve: relationship between biomolecular and aortic strain patterns

Biomechanical properties of the ascending aorta in patients with arterial hypertension by velocity vector imaging

Aortic stiffness is an important risk factor for cardiovascular events and morbidity. Increased aortic stiffness is associated with an increase in cardiac and vascular hypertension-related organ damage. To evaluate the biomechanical properties of the ascending aorta (AA) in patients with arterial hypertension (AH) by velocity vector imaging (VVI). Ninety-five patients with AH and 53 normal healthy control participants were prospectively enrolled. AA biomechanical properties, i.e., ascending aortic global longitudinal strain (ALS), ascending aortic global circumferential strain (ACS), and fractional area change (FAC), were evaluated by VVI. Relative wall thickness (RWT) and left ventricular mass (LVM) were calculated. Pulsed Doppler early transmitral peak flow velocity (E), early diastolic mitral annular velocity (e'), left ventricular global longitudinal strain (GLS), distensibility (D) and stiffness index (SI) of AA were also obtained. The ALS, ACS and FAC were significantly lower in the AH patients, especially in those with ascending aorta dilatation (AAD), than in the normal healthy control subjects. The patients with AAD had a higher E/e' ratio, RWT, LVM and SI and a lower GLS and D than patients without AAD and normal healthy volunteers (p < 0.05). There were significant associations between biomechanical properties and D, SI, E/e' and GLS (ALS and D: r = 0.606, ALS and SI: r = - 0.645, ALS and E/e': r = - 0.489, ALS and GLS: r = 0.466, ACS and D: r = 0.564, ACS and SI: r = - 0.567, ACS and E/e': r = - 0.313, ACS and GLS: r = 0.320, FAC and D: r = 0.649, FAC and SI: r = - 0.601, FAC and E/e': r = - 0.504, FAC and GLS: r = 0.524, respectively, p < 0.05). The biomechanical properties of AA were impaired in patients with AH, especially patients with ascending aorta dilatation. Hypertension is associated with a high prevalence of diastolic and systolic dysfunction and increased arterial stiffness. Further study is needed to evaluate the clinical application of AA biomechanical properties by VVI.

Single Nucleotide Polymorphisms Mutation of Tropoelastin Gene Affects Tropoelastin mRNA and Elastin Expressions in Human Aortic Smooth Muscle Cells

We aimed to explore the effects of single nucleotide polymorphisms (SNPs) in tropoelastin gene on tropoelastin mRNA and elastin expressions in human aortic smooth muscle cells (HASMCs). Two SNP loci, rs2071307 (G/A) and rs1785598 (G/C), were selected to construct recombinant lentivirus vectors carrying wild-type and mutant tropoelastin gene. Recombinant plasmids including pWSLV-02-ELN, pWSLV-02-ELN-mut1, and pWSLV-02-ELN-mut2 were constructed, before being amplified by polymerase chain reaction (PCR) and sequenced. The prepared plasmids and the packaging plasmids (pVSV-G and psPAX2) were cotransfected into HEK293T cells to obtain recombinant lentiviruses carrying tropoelastin gene. Afterward, HASMCs were infected with recombinant lentiviruses, and the positive cells sorted by flow cytometry were amplified. Four stable HASMCs cell lines including pWSLV-02-ELN, pWSLV-02-ELN-mut1, pWSLV-02-ELN-mut2, and pWSLV-02 vector were constructed. The expressions of tropoelastin mRNA and elastin in HASMCs were detected by real-time quantitative reverse transcription-PCR and western blot, respectively. Recombinant plasmids including pWSLV-02-ELN-mut1, pWSLV-02-ELN-mut2, and pWSLV-02-ELN were successfully constructed. Recombinant lentiviruses carrying tropoelastin gene were obtained via lentivirus packaging. After infection for 24 h, 3 days and 5 days in HASMCs, tropoelastin mRNA expressions in pWSLV-02-ELN-mut1 and pWSLV-02-ELN-mut2 groups were significantly lower than that of pWSLV-02-ELN group. Besides, after infection for 24 h, 3 days, and 5 days, elastin levels in pWSLV-02-ELN-mut1 and pWSLV-02-ELN-mut2 groups were significantly lower than that in pWSLV-02-ELN group. In conclusion, SNPs mutation of tropoelastin gene affected the expression of tropoelastin mRNA and elastin, suggesting that the polymorphisms of rs2071307 and rs17855988 in tropoelastin gene might be important factors for AD development.

Mechanisms of Aortic Dilation in Patients With Bicuspid Aortic Valve: JACC State-of-the-Art Review

Bicuspid aortic valve is the most common congenital heart disease and exposes patients to an increased risk of aortic dilation and dissection. Aortic dilation is a slow, silent process, leading to a greater risk of aortic dissection. The prevention of adverse events together with optimization of the frequency of the required lifelong imaging surveillance are important for both clinicians and patients and motivated extensive research to shed light on the physiopathologic processes involved in bicuspid aortic valve aortopathy. Two main research hypotheses have been consolidated in the last decade: one supports a genetic basis for the increased prevalence of dilation, in particular for the aortic root, and the second supports the damaging impact on the aortic wall of altered flow dynamics associated with these structurally abnormal valves, particularly significant in the ascending aorta. Current opinion tends to rule out mutually excluding causative mechanisms, recognizing both as important and potentially clinically relevant.

Impaired Elastic Properties of the Ascending Aorta in Fetuses With Coarctation of the Aorta

Background Abnormal aortic elastic properties are major notable vasculopathy involved in coarctation of the aorta (CoA). However, there are no reports on aortic wall elastic characteristics in fetuses with CoA. Methods and Results Fifty-six fetuses with CoA and 56 normal controls were included in this prospective case-control study. The dimensions of the cardiac chamber, the size of the aorta, left ventricular myocardial performance indexes, and aortic elastic properties, including the global circumferential strain, fractional area change and mean longitudinal strain, were measured serially in utero. The global circumferential strain, fractional area change, and mean longitudinal strain in fetuses with CoA were smaller than those in the normal group at both the first and last examinations (18.50% versus 37.73% for global circumferential strain, 38.90% versus 57.55% for fractional area change, 6.61% versus 11.81% for mean longitudinal strain at first scan, 16.62% versus 42.05% for global circumferential strain, 36.54% versus 59.7% for fractional area change, 6.2% versus 11.46% for mean longitudinal strain at last scan, all P<0.001). There were negative correlations between aortic elastic properties and left ventricular myocardial performance indexes in fetuses with CoA (P<0.01). Aortic elastic properties were correlated positively with aortic isthmus size in fetuses with CoA (P<0.01). Conclusions Aortic strain and the fractional area change were decreased in fetuses with CoA. Impairments of these aortic elastic properties were associated with diminished heart function and aortic isthmus size in utero. Further large-scale longitudinal studies are required to confirm the potential predictive value of cardiovascular morbidity (ie, hypertension) in fetuses with CoA.

The association between cardiac magnetic resonance-derived aortic stiffness parameters and aortic dilation in young adults with bicuspid aortic valve: With and without coarctation of aorta

Background

Bicuspid aortic valve (BAV) is associated with progressive aortic dilation. Studies in aortopathies have shown a correlation between increased aortic stiffness and aortic dilation. We aimed to evaluate aortic stiffness measures as predictors of progressive aortic dilation by cardiac magnetic resonance (CMR) in BAV patients.

Methods

This is a retrospective study of 49 patients with BAV (median age 21.1 years at first CMR visit) with ≥2 CMR at the Wisconsin Adult Congenital Heart Disease Program (WAtCH). Circumferential aortic strain, distensibility, and β-stiffness index were obtained from CMR-derived aortic root cine imaging, and aortic dimensions were measured at aortic root and ascending aorta. A linear mixed-model and logistic regression were used to identify important predictors of progressive aortic dilation.

Results

Over a median of 3.8 years follow-up, the annual growth rates of aortic root and ascending aorta dimensions were 0.25 and 0.16 mm/year, respectively. Aortic strain and distensibility decreased while β-stiffness index increased with age. Aortic root strain and distensibility were associated with progressive dilation of the ascending aorta. Baseline aortic root diameter was an independent predictor of >1 mm/year growth rate of the aortic root (adjusted OR 1.34, 95 % CI 1.03-1.74, p = 0.028). Most patients (61 %) had coexisting coarctation of aorta. Despite the higher prevalence of hypertension in patients with aortic coarctation, hypertension or coarctation had no effect on baseline aorta dimensions, stiffness, or progressive aortic dilation.

Conclusion

Some CMR-derived aortic stiffness parameters correlated with progressive aortic dilation in BAV and should be further investigated in larger and older BAV cohorts.

Patient-derived microphysiological model identifies the therapeutic potential of metformin for thoracic aortic aneurysm

Background

Thoracic aortic aneurysm (TAA) is the permanent dilation of the thoracic aortic wall that predisposes patients to lethal events such as aortic dissection or rupture, for which effective medical therapy remains scarce. Human-relevant microphysiological models serve as a promising tool in drug screening and discovery.

Methods

We developed a dynamic, rhythmically stretching, three-dimensional microphysiological model. Using patient-derived human aortic smooth muscle cells (HAoSMCs), we tested the biological features of the model and compared them with native aortic tissues. Drug testing was performed on the individualized TAA models, and the potentially effective drug was further tested using β-aminopropionitrile-treated mice and retrospective clinical data.

Findings

The HAoSMCs on the model recapitulated the expressions of many TAA-related genes in tissue. Phenotypic switching and mitochondrial dysfunction, two disease hallmarks of TAA, were highlighted on the microphysiological model: the TAA-derived HAoSMCs exhibited lower alpha-smooth muscle actin expression, lower mitochondrial membrane potential, lower oxygen consumption rate and higher superoxide accumulation than control cells, while these differences were not evidently reflected in two-dimensional culture flasks. Model-based drug testing demonstrated that metformin partially recovered contractile phenotype and mitochondrial function in TAA patients’ cells. Mouse experiment and clinical investigations also demonstrated better preserved aortic microstructure, higher nicotinamide adenine dinucleotide level and lower aortic diameter with metformin treatment.

Interpretation

These findings support the application of this human-relevant microphysiological model in studying personalized disease characteristics and facilitating drug discovery for TAA. Metformin may regulate contractile phenotypes and metabolic dysfunctions in diseased HAoSMCs and limit aortic dilation.

Funding

This work was supported by grants from National Key R&D Program of China (2018YFC1005002), National Natural Science Foundation of China (82070482, 81771971, 81772007, 51927805, and 21734003), the Science and Technology Commission of Shanghai Municipality (20ZR1411700, 18ZR1407000, 17JC1400200, and 20YF1406900), Shanghai Municipal Science and Technology Major Project (2017SHZDZX01), and Shanghai Municipal Education Commission (Innovation Program 2017-01-07-00-07-E00027). Y.S.Z. was not supported by any of these funds; instead, the Brigham Research Institute is acknowledged.

Evaluation of aortic biomechanics in patients with aortic disease via imaging: A review

As a bridge between the heart and the arteries, the aorta plays an important role in the cardiovascular system. The morbidity and mortality of aortic disease are extremely high, which is a serious threat to human life. The biomechanical abnormality of the aorta is an important factor of a series of pathological changes in the aortic wall. At present, there are many imaging methods to evaluate the biomechanics of the aorta, which will benefit to the early diagnosis and treatment of aortic disease. In this review, we describe the application of various imaging methods and parameters in aortic disease.

The Evaluation of Longitudinal Strain of Large and Small Abdominal Aortic Aneurysm by Two-Dimensional Speckle-Tracking Ultrasound

OBJECTIVES

Abdominal aortic aneurysm (AAA) is a dangerous and lethal vascular disease. Non-invasive two-dimensional speckle-tracking imaging (2D STI) plays an important role in assessing aortic biomechanical properties. Our study aimed to evaluate the alterations of biomechanical characteristics using 2D STI in 91 AAA patients with different size.

METHODS

Aneurysm strain, elastic modulus, stiffness index β, and aortic distensibility determined by M-Mode ultrasound (US), and longitudinal strain (LS) derived from 2D STI were compared in 40 large AAA patients (diameter ≥ 55 mm) and 51 small AAA patients (diameter < 55 mm).

RESULTS

Compared with small AAA group, anterior wall longitudinal strain (ALS) and posterior wall longitudinal strain (PLS) were significantly decreased in large AAA group (all P < .05) and not affected by age, symptom, hypertension, and thrombus. Meanwhile, ALS and PLS correlated negatively with maximal aneurysm diameters (r = -0.628 and -0.469, respectively, all P < .001). And only ALS was associated with M-Mode US parameters (all P < .05). Based on receiver operating characteristic (ROC) analysis, ALS and PLS had strong diagnostic values for large AAA with the area under the curve (AUC) of 0.82 and 0.72, and cut-off points of 1.71 and 1.64% with a sensitivity of 78 and 72%, and a specificity of 75 and 70%, respectively.

CONCLUSIONS

LS measured by 2D STI could evaluate the biomechanical properties of aneurysm wall with different size, and add additional diagnostic value in distinguishing between small and large AAA.

Evaluation of Ascending Aortic Longitudinal Strain Via Two-Dimensional Speckle Tracking Echocardiography in Hypertensive Patients Complicated by Type A Aortic Dissection

OBJECTIVE

To explore the value of ascending aortic longitudinal strain (LS) in identification of hypertensive (HP) patients with a high risk of type A aortic dissection (AAD).

METHODS

Total 40 primary HP patients with AAD (group C), 80 selected age- and sex-matched primary HP patients (group A, normal-sized ascending aorta (AA), n = 40; group B, dilated AA, n = 40) and 40 healthy volunteers were enrolled in this study. Brachial blood pressures were measured, and the aortic stiffness index (β) determined by M-mode analysis was calculated as a conventional parameter of arterial stiffness. The LS of the anterior and posterior ascending aortic wall (AW-LS and PW-LS) were determined.

RESULTS

Compared to the control group (34.21 ± 5.25%), the mean LS of AA in HP patients (group A 28.6 ± 5.95%; group B 23.64 ± 4.98%; group C 17.93 ± 3.96%; P < .001) were significantly reduced. Multivariate logistic regression analysis showed that the mean LS (OR 0.719, 95% CI 0.615-0.839, P < .001) and pulse pressure (PP) (OR 1.055, 95% CI 1.006-1.106, P = .028) were identified as independent predictors of AAD in HP patients. The AUC of mean LS combined with PP reached 0.926 (sensitivity, 95.0%; specificity, 82.5%), which was higher than the mean LS, PP, stiffness index, and ascending aortic diameter (AAd) separately. Besides, the AW-LS and PW-LS were negatively correlated with the AAd, stiffness index, stroke volume, systolic blood pressure, and PP, respectively (P < .001).

CONCLUSION

The LS of AA evaluated by two-dimensional speckle tracking echocardiography decreased significantly along with the expansion of aortic lumen and the occurrence of AAD in HP patients. It is also an independent predictor of AAD in HP patients.

Maturation Fetus Ascending Aorta Elastic Properties: Circumferential Strain and Longitudinal Strain by Velocity Vector Imaging

Objective

This study aimed to assess the circumferential and longitudinal strain of the fetal ascending aortic (AA) wall and establish a gestational age-associated longitudinal reference for aortic wall strain during the second half of pregnancy.

Methods

Singleton fetuses with gestational age (GA) at 20 + 0 to 24 + 6 weeks were prospectively collected from a low-risk population. Global circumferential strain (GCS) and mean longitudinal strain (MLS) of the ascending aorta were measured serially at 4-week intervals using the velocity vector imaging (VVI) technique. Fractional polynomials were conducted to obtain the best-fitting curves between GA and AA strains. GA-specific reference percentiles of GCS and MLS were established by multilevel modeling.

Results

A total of 223 fetuses with a total of 1,127 serial observations were enrolled. GCS presented a second-degree fractional polynomial smoothing regression along GA (R2 = 0.635, P &lt; 0.05). Fetal aortic GCS remained unchanged at ~27.29% (20.36–35.6%) before 31 weeks and increased significantly from 31.36% (26.38–37.12%) at 31 weeks to 43.29% (30.5–56.78%) at term. MLS presented a third-degree fractional polynomial smoothing regression along GA (R2 = 0.465, P &lt; 0.05). MLS remained steady at ~10.03% (3.28–17.62%) between 20 and 31 weeks and then increased significantly from 12.68% (7.42–20.1%) at 32 weeks to 17.5% (9.67–25.34%) at term. The GCS was significantly higher than the MLS in the ascending aorta wall (p &lt; 0.001).

Conclusion

The fetal ascending aorta wall demonstrates obviously greater circumferential strain than longitudinal strain. Both strains remained steady before the late trimester and then gradually increased until delivery, suggesting progressive maturation of aortic elasticity mechanics.

Bicuspid aortic valve and aortopathy: novel prognostic predictors for the identification of high-risk patients

AIMS

Bicuspid aortic valve (BAV) may be complicated by aortic aneurysms and dissection. This study aimed to evaluate the prognostic efficacy of markers from cardiac imaging, as well as genetic and new biomarkers, to early predict aortic complications.

METHODS AND RESULTS

We re-evaluated after a mean time of 48 ± 11 months 47 BAV patients who had undergone previous echocardiography for evaluation of aortic stiffness and 2D aortic longitudinal strain (LS) (by speckle-tracking analysis), and who had given a blood sample for the assessment of a single-nucleotide polymorphism of elastin gene (ELN rs2 071307) and quantification of elastin soluble fragments (ESF). Surgical treatment of aortic aneurysm/dissection was the primary endpoint, and an aortic dimension increase (of one or more aortic segments) ≥1 mm/year was the secondary endpoint. Nine patients underwent surgical treatment of ascending aorta (AA) aneurysms. Out of the 38 patients who did not need surgical intervention, 16 showed an increase of aortic root and/or AA dimension ≥1 mm/year. At multivariate Cox regression analysis, an impaired AA LS was an independent predictor of aortic surgery [P = 0.04; hazard ratio (HR) 0.961; 95% confidence interval (CI) 0.924-0.984] and aortic dilatation (P = 0.007; HR 0.960; 95% CI 0.932-0.989). An increased quantity of ESF was correlated (P = 0.015) with the primary endpoint at univariate Cox regression analysis but it did not keep statistical significance at multivariate analysis.

CONCLUSION

In BAV patients, impairment of elastic properties of the AA, as assessed by 2D LS, is an effective predictor of aortic complications.

Update in Biomolecular and Genetic Bases of Bicuspid Aortopathy

Bicuspid aortic valve (BAV) associated with aortopathy is the most common congenital heart disease in the general population. Far from being a simple harmless valve malformation, it can be a complex and heterogeneous disease and a source of chronic and acute pathology (early valvular disease, aneurysm, dissection). In the previous years, intense research has been carried out to find out and understand its mechanisms, but the pathophysiology of the disease is still not fully understood and many questions remain open. Recent studies have discovered several genetic mutations involved in the development of valvular and aortic malformations, but still cannot explain more than 5–10% of cases. Other studies have also focused on molecular alterations and cellular processes (TGF-β pathway, microRNAs, degradation of the extracellular matrix, metalloproteinases, etc.), being a field in constant search and development, looking for a therapeutic target to prevent the development of the disease. Increased knowledge about this multifaceted disorder, derived from both basic and clinical research, may influence the diagnosis, follow-up, prognosis, and therapies of affected patients in the near future. This review focuses on the latest and outstanding developments on the molecular and genetic investigations of the bicuspid aortopathy.

Towards a Clinical Implementation of Measuring the Elastic Modulus of the Aorta from Cardiac Computed Tomography Images

OBJECTIVE

The elasticity of the aortic wall varies depending on age, vessel location, and the presence of aortic diseases. Noninvasive measurement will be a powerful tool to understand the mechanical state of the aorta in a living human body. This study aimed to determine the elastic modulus of the aorta using computed tomography images.

METHODS

We constructed our original formulae based on mechanics of materials. Then, we performed computed tomography scans of a silicon rubber tube by applying four pressure conditions to the lumen. The segment elastic modulus was calculated from the scanned images using our formulae. The actual modulus was measured using a tensile loading test for comparison.

RESULTS

The segment moduli of elasticity from the images were 0.525 [0.524, 0.527], 0.524 [0.520, 0.524], 0.520 [0.515, 0.523], and 0.522 [0.516, 0.532] (unit: MPa, median [25%, 75% quantiles]) for the four pressure conditions, respectively. The corresponding measurements in the tensile test were 0.548 [0.539, 0.566], 0.535 [0.528, 0.553], 0.526 [0.513, 0.543], and 0.523 [0.508, 0.530], respectively. These results indicated errors of 4.2%, 2.1%, 1.1%, and 0.2%, respectively.

CONCLUSION

Our formulae provided good estimations of the segment elastic moduli of a silicon rubber tube under physiological pressure conditions using the computed tomography images.

SIGNIFICANCE

In addition to the elasticity, the formulae provide the strain energy as well. These properties can be better predictors of aortic diseases. The formulae consist of clinical parameters commonly used in medical settings (pressure, diameter, and wall thickness).

Aortic strain in bicuspid aortic valve: an analysis

Bicuspid aortic valve (BAV) is monitored by transthoracic echocardiography and computed tomography (CT) angiography. However, it does not have any early marker of disease progression. This study evaluated speckle-tracking echocardiography (STE) aortic and left ventricular (LV) strain prognostic values, their discriminative power, and their correlation with the degree of valvular regurgitation. We conducted a retrospective analysis of a prospectively enrolled cohort of 45 diagnosed with BAV and 20 gender and age matched controls. We performed 2D-STE aortic and LV strain analysis of the selected population. The cohort was followed-up during a median period of 19.9 months (IQR 12.9-25.2), and outcomes (hospital admission for heart failure (HF), aortic valve replacement (AVR), and death) were determined. The mean patient age was 46.6 ± 15.5 years and 80 % were male. LV indexed volumes and aortic diameter were higher in BAV patients. LV global longitudinal strain (GLS) was impaired (p < 0.001) and aortic GLS was significantly augmented (p = 0.027) in BAV patients. Aortic global circumferential strain (GCS) did not vary between groups. Aortic diameter was the best parameter related to BAV (AUC 0.92) and aortic GLS was best correlated with significant AR (AUC 0.76). AVR was the only outcome observed and its only predictor was indexed LV end-diastolic volume. BAV had impaired LV-GLS values. Aortic GLS was abnormally augmented in BAV patients, which might reflect higher aortic diameters that distorted strain calculations. STE aortic strain is related to AR but does not appear to be a reliable predictor of surgery in BAV patients, at 19 months.

Aortic root movement correlation with the function of the left ventricle

Echocardiographic assessment of systolic and diastolic function of the heart is often limited by image quality. However, the aortic root is well visualized in most patients. We hypothesize that the aortic root motion may correlate with the systolic and diastolic function of the left ventricle of the heart. Data obtained from 101 healthy volunteers (mean age 46.6 ± 12.4) was used in the study. The data contained sequences of standard two-dimensional (2D) echocardiographic B-mode (brightness mode, classical ultrasound grayscale presentation) images corresponding to single cardiac cycles. They also included sets of standard echocardiographic Doppler parameters of the left ventricular systolic and diastolic function. For each B-mode image sequence, the aortic root was tracked with use of a correlation tracking algorithm and systolic and diastolic values of traveled distances and velocities were determined. The aortic root motion parameters were correlated with the standard Doppler parameters used for the assessment of LV function. The aortic root diastolic distance (ARDD) mean value was 1.66 ± 0.26 cm and showed significant, moderate correlation (r up to 0.59, p < 0.0001) with selected left ventricular diastolic Doppler parameters. The aortic root maximal diastolic velocity (ARDV) was 10.8 ± 2.4 cm/s and also correlated (r up to 0.51, p < 0.0001) with some left ventricular diastolic Doppler parameters. The aortic root systolic distance (ARSD) was 1.63 ± 0.19 cm and showed no significant moderate correlation (all r values < 0.40). The aortic root maximal systolic velocity (ARSV) was 9.2 ± 1.6 cm/s and correlated in moderate range only with peak systolic velocity of medial mitral annulus (r = 0.44, p < 0.0001). Based on these results, we conclude, that in healthy subjects, aortic root motion parameters correlate significantly with established measurements of left ventricular function. Aortic root motion parameters can be especially useful in patients with low ultrasound image quality precluding usage of typical LV function parameters.

Patient-specific computational evaluation of stiffness distribution in ascending thoracic aortic aneurysm

Quantifying local aortic stiffness properties in vivo is acknowledged as essential to assess the severity of an ascending thoracic aortic aneurysm (ATAA). Recently, the LESI (local extensional stiffness identification) methodology has been established to quantify non-invasively local stiffness properties of ATAAs using electrocardiographic-gated computed tomography (ECG-gated CT) scans. The aim of the current study was to determine the most sensitive markers of local ATAA stiffness estimation with the hypothesis that direct measures of local ATAA stiffness could better detect the high-risk patients. A cohort of 30 patients (12 BAV and 18 TAV) referred for aortic size evaluation by ECG-gated CT were recruited. For each patient, the extensional stiffness Q was evaluated by the LESI methodology whilst computational flow analyses were also performed to derive hemodynamics markers such as the wall shear stress (WSS). A strong positive correlation was found between the extensional stiffness and the aortic pulse pressure (R = 0.644 and p < 0.001). Interestingly, a significant positive correlation was also found between the extensional stiffness and patients age for BAV ATAAs (R = 0.619 and p = 0.032), but not for TAV ATAAs (R = -0.117 and p = 0.645). No significant correlation was found between the extensional stiffness and WSS evaluated locally. There was no significant difference either in the extensional stiffness between BAV ATAAs and TAV ATAAs (Q = 3.6 ± 2.5 MPa.mm for BAV ATAAs vs Q = 5.3 ± 3.1 MPa.mm for TAV ATAAs, p = 0.094). Future work will focus on relating the extensional stiffness to the patient-specific rupture risk of ATAAs on larger cohorts to confirm the promising interest of the LESI methodology.

Comprehensive assessment of local and regional aortic stiffness in patients with tricuspid or bicuspid aortic valve aortopathy using magnetic resonance imaging

BACKGROUND

We aimed to provide a comprehensive aortic stiffness description using magnetic resonance imaging (MRI) in patients with ascending thoracic aorta aneurysm and tricuspid (TAV-ATAA) or bicuspid (BAV) aortic valve.

METHODS

This case-control study included 18 TAV-ATAA and 19 BAV patients, with no aortic valve stenosis/severe regurgitation, who were 1:1 age-, gender- and central blood pressures (BP)-matched to healthy volunteers. Each underwent simultaneous aortic MRI and BP measurements. 3D anatomical MRI provided aortic diameters. Stiffness indices included: regional ascending (AA) and descending (DA) aorta pulse wave velocity (PWV) from 4D flow MRI; local AA and DA strain, distensibility and theoretical Bramwell-Hill (BH) model-based PWV, as well as regional arch PWV from 2D flow MRI.

RESULTS

Patient groups had significantly higher maximal AA diameter (median[interquartile range], TAV-ATAA: 47.5[42.0-51.3]mm, BAV: 45.0[41.0-47.0]mm) than their respective controls (29.1[26.8-31.8] and 28.1[26.0-32.0]mm, p < 0.0001), while BP were similar (p ≥ 0.25). Stiffness indices were significantly associated with age (ρ ≥ 0.33), mean BP (arch PWV: ρ = 0.25, p = 0.05; DA distensibility: ρ = -0.30, p = 0.02) or AA diameter (arch PWV: ρ = 0.28, p = 0.03; DA PWV: ρ = 0.32, p = 0.009). None of them, however, was significantly different between TAV-ATAA or BAV patients and their matched controls. Finally, while direct PWV measures were significantly correlated to BH-PWV estimates in controls (ρ ≥ 0.40), associations were non-significant in TAV-ATAA and BAV groups (p ≥ 0.18).

CONCLUSIONS

The overlap of MRI-derived aortic stiffness indices between patients with TAV or BAV aortopathy and matched controls highlights another heterogeneous feature of aortopathy, and suggests the urgent need for more sensitive indices which might help better discriminate such diseases.

The impact of the aortic cusps fusion pattern and valve disease severity on the aortic wall mechanics in patients with bicuspid aortic valve

The ascending aorta dilatation in the bicuspid aortic valve (BAV) patients is often attributed to congenital abnormalities of the aortic wall, but it may be related to hemodynamic disturbances in the course of BAV disease. At present, ascending aortic diameter is used as almost sole but weak predictor of aortic dissection and rupture in BAV. We examined the association between aortic wall mechanics and severity of aortic valve disease including different cusps fusion patterns using conventional echocardiography and tissue Doppler imaging (TDI). We prospectively studied 106 BAV patients: 72 with right-left (R-L) coronary cusp fusion were matched 1:1 to 34 patients with right-noncoronary (R-N) cusp fusion obtaining 34 pairs of patients. Peak systolic radial velocity and acceleration of the ascending aortic wall, measured by TDI, were used as an index of hemodynamic stress imposed on the aorta. Paired analysis showed higher aortic wall radial velocity (4.71 ± 1.61 cm/s vs. 3.33 ± 1.44 cm/s, p = 0.001) and acceleration (1.08 ± 0.46 m/s² vs. 0.80 ± 0.34 m/s², p = 0.015) in-R-L compared to R-N fusion. Pearson correlation showed association of ascending tubular aortic diameter with age (r = 0.258, p = 0.012), weight (r = 0.323, p = 0.001), peak aortic valve gradient (r = 0.386, p = 0.0001), aortic root diameter (r = 0.439, p < 0.0001), and R-N fusion pattern (r = 0.209, p = 0.043). Aortic root diameter was related to male gender (r = 0.296, p = 0.003), weight (r = 0.381, p = 0.0001), ascending aortic diameter (r = 0.439, p < 0.0001), and severity of aortic regurgitation (r = 0.337, p = 0.0009). Regional differences in aortic wall motion between different BAV cusp fusion patterns and association of aortic diameters with the severity of aortic valve disease, both suggest a deleterious hemodynamic impact of cusp fusion patterns and aortic valve dysfunction on ascending aortic wall. Assessment of aortic hemodynamic by TDI is feasible and could be potentially used to improve prediction of acute aortic complications, thus helping to establish optimal timing of aortic surgery in BAV patients.

Precocious Preclinical Cardiovascular Sonographic Markers in Metabolically Healthy and Unhealthy Childhood Obesity

Background: Childhood obesity is related to a wide spectrum of cardiovascular and metabolic comorbidities. Objectives: (1) To identify precocious, preclinical, cardiovascular sonographic modifications, in a cohort of overweight (OW) and obese (OB) children and adolescents compared to lean controls; (2) to investigate the association between clinical and metabolic variables and cardiovascular sonographic parameters; (3) to evaluate their relation with two different phenotypes of obesity: metabolically healthy obesity (MHO) and metabolically unhealthy obesity (MUO). Materials and Methods: Fifty-nine OW and OB children and adolescents (9.8 ± 2.9 years) and 20 matched lean controls underwent anthropometric, biochemical, echocardiography assessment, and sonographic evaluation of carotid artery and ascending aorta (AA). OW and OB subjects were divided in MHO and MUO, according to the Camhi et al. definition. Results: OW and OB children showed significantly higher left ventricular (LV) dimensions and mass, carotid artery intima-media thickness (CIMT), carotid stiffness [β-index, pulse wave velocity (PWV)], significantly lower mitral peak early (E) and late (A) velocity ratio (E/A ratio), and significantly impaired global longitudinal strain (GLS) compared to controls. BMI SD and HOMA-IR were positively significantly related to LV dimensions, LA volume and epicardial adipose tissue (EAT), and negative to E/A ratio. Waist circumference (WC) was positively correlated to LV dimensions, LA volume, CIMT, PWV, AA diameter, and EAT. Furthermore, WC was a strong predictor of LV dimensions, LA volume and strain, AA stiffness and diameter; BMI SD was significantly associated with EAT, LVM index, and E/A ratio; HOMA-IR and triglycerides were significant predictors of GLS. MUO patients showed higher BMI SD (p = 0.02), WC (p = 0.001), WHtR (p = 0.001), HOMA-IR (p = 0.004), triglycerides (p = 0.01), SBP (p = 0.001), as well as LV dimensions, EAT (p = 0.03), CIMT (p = 0.01), AA diameter (p = 0.02), β-index (p = 0.03) and PWV (p = 0.002), AA stiffness (p = 0.006), and significantly impaired GLS (p = 0.042) compared to MHO. Conclusions: Severity of overweight, abdominal obesity, insulin resistance, and MUO phenotype negatively affect cardiovascular remodeling and subclinical myocardial dysfunction in OW and OB children. MUO phenotype is likely to increase the risk of developing cardiometabolic complications since the pediatric age. Distinction between MHO and MUO phenotypes might be useful in planning a personalized follow-up approach in obese children.

The year 2018 in the European Heart Journal-Cardiovascular Imaging: Part II

European Heart Journal - Cardiovascular Imaging was launched in 2012 as a multimodality cardiovascular imaging journal. It has gained an impressive impact factor during its first 5 years and is now established as one of the top cardiovascular journals and has become the most important cardiovascular imaging journal in Europe. The most important studies from 2018 will be highlighted in two reports. Part I of the review has focused on studies about myocardial function and risk prediction, myocardial ischaemia, and emerging techniques in cardiovascular imaging, while Part II will focus on cardiomyopathies, congenital heart diseases, valvular heart diseases, and heart failure.

Caught between a "Rho" and a hard place: are CCN1/CYR61 and CCN2/CTGF the arbiters of microvascular stiffness?

The extracellular matrix (ECM) is a deformable dynamic structure that dictates the behavior, function and integrity of blood vessels. The composition, density, chemistry and architecture of major globular and fibrillar proteins of the matrisome regulate the mechanical properties of the vasculature (i.e., stiffness/compliance). ECM proteins are linked via integrins to a protein adhesome directly connected to the actin cytoskeleton and various downstream signaling pathways that enable the cells to respond to external stimuli in a coordinated manner and maintain optimal tissue stiffness. However, cardiovascular risk factors such as diabetes, dyslipidemia, hypertension, ischemia and aging compromise the mechanical balance of the vascular wall. Stiffening of large blood vessels is associated with well-known qualitative and quantitative changes of fibrillar and fibrous macromolecules of the vascular matrisome. However, the mechanical properties of the thin-walled microvasculature are essentially defined by components of the subendothelial matrix. Cellular communication network (CCN) 1 and 2 proteins (aka Cyr61 and CTGF, respectively) of the CCN protein family localize in and act on the pericellular matrix of microvessels and constitute primary candidate markers and regulators of microvascular compliance. CCN1 and CCN2 bind various integrin and non-integrin receptors and initiate signaling pathways that regulate connective tissue remodeling and response to injury, the associated mechanoresponse of vascular cells, and the subsequent inflammatory response. The CCN1 and CCN2 genes are themselves responsive to mechanical stimuli in vascular cells, wherein mechanotransduction signaling converges into the common Rho GTPase pathway, which promotes actomyosin-based contractility and cellular stiffening. However, CCN1 and CCN2 each exhibit unique functional attributes in these processes. A better understanding of their synergistic or antagonistic effects on the maintenance (or loss) of microvascular compliance in physiological and pathological situations will assist more broadly based studies of their functional properties and translational value.

Aortic Wall Elastic Properties in Case of Bicuspid Aortic Valve

Purpose of the Review

Bicuspid aortic valve (BAV) is associated with a significant risk of development of aneurysm and dissection of the ascending thoracic aorta. Development of what is called BAV associated aortopathy is particularly heterogeneous with an uncertain prognosis and with no prognostic biomarkers except for the aortic diameter. This situation leads to an important variability of the therapeutic strategy of this aortopathy. By reviewing the literature on aortic stiffness in the case of BAV, we aimed at evaluating its potential prognostic role in the development of aortic dilatation.

Recent Findings

Studies evaluating aortic stiffness, with ultrasound or magnetic resonance imaging, converge toward the description of an increased segmental aortic stiffness in BAV patients regardless of age, diameter or aortic level, from the root to the arch. Even though there is a lack of longitudinal studies evaluating the progression of aortic dilatation, new data have recently shown the potential prognostic role of the maximal rate of systolic distension of the aortic wall with magnetic resonance imaging.

Summary

Although the use of aortic distensibility calculation is a simple evaluation of stiffness that could be easily transposed in daily practice, its interpretation remains uncertain. New arterial stiffening indicators seem more promising but need a stronger validation.

New imaging techniques project the cellular and molecular alterations underlying bicuspid aortic valve development

Bicuspid aortic valve (BAV) disease is the most common congenital cardiac malformation associated with an increased lifetime risk and a high rate of surgically-relevant valve deterioration and aortic dilatation. Genomic data revealed that different genes are associated with BAV. A dominant genetic factor for the recent past was the basis to the recommendation for a more extensive aortic intervention. However very recent evidence that hemodynamic stressors and alterations of wall shear stress play an important role independent from the genetic trait led to more conservative treatment recommendations. Therefore, there is a current need to improve the ability to risk stratify BAV patients in order to obtain an early detection of valvulopathy and aortopathy while also to predict valve dysfunction and/or aortic disease development. Imaging studies based on new cutting-edge technologies, such us 4-dimensional (4D) flow magnetic resonance imaging (MRI), two-dimensional (2D) or three-dimensional (3D) speckle-tracking imaging (STI) and computation fluid dynamics, combined with studies demonstrating new gene mutations, specific signal pathways alterations, hemodynamic influences, circulating biomarkers modifications, endothelial progenitor cell impairment and immune/inflammatory response, all detected BAV valvulopathy progression and aortic wall abnormality. Overall, the main purpose of this review article is to merge the evidences of imaging and basic science studies in a coherent hypothesis that underlies and thus projects the development of both BAV during embryogenesis and BAV-associated aortopathy and its complications in the adult life, with the final goal to identifying aneurysm formation/rupture susceptibility to improve diagnosis and management of patients with BAV-related aortopathy.

Constitutive interpretation of arterial stiffness in clinical studies: a methodological review

Clinical assessment of arterial stiffness relies on noninvasive measurements of regional pulse wave velocity or local distensibility. However, arterial stiffness measures do not discriminate underlying changes in arterial wall constituent properties (e.g., in collagen, elastin, or smooth muscle), which is highly relevant for development and monitoring of treatment. In arterial stiffness in recent clinical-epidemiological studies, we systematically review clinical-epidemiological studies (2012–) that interpreted arterial stiffness changes in terms of changes in arterial wall constituent properties (63 studies included of 514 studies found). Most studies that did so were association studies (52 of 63 studies) providing limited causal evidence. Intervention studies (11 of 63 studies) addressed changes in arterial stiffness through the modulation of extracellular matrix integrity (5 of 11 studies) or smooth muscle tone (6 of 11 studies). A handful of studies (3 of 63 studies) used mathematical modeling to discriminate between extracellular matrix components. Overall, there exists a notable gap in the mechanistic interpretation of stiffness findings. In constitutive model-based interpretation, we first introduce constitutive-based modeling and use it to illustrate the relationship between constituent properties and stiffness measurements (“forward” approach). We then review all literature on modeling approaches for the constitutive interpretation of clinical arterial stiffness data (“inverse” approach), which are aimed at estimation of constitutive properties from arterial stiffness measurements to benefit treatment development and monitoring. Importantly, any modeling approach requires a tradeoff between model complexity and measurable data. Therefore, the feasibility of changing in vivo the biaxial mechanics and/or vascular smooth muscle tone should be explored. The effectiveness of modeling approaches should be confirmed using uncertainty quantification and sensitivity analysis. Taken together, constitutive modeling can significantly improve clinical interpretation of arterial stiffness findings.

Bicuspid Aortic Valve Registry of the Italian Society of Echocardiography and Cardiovascular Imaging (REgistro della valvola aortica bicuspide della società italiana di ECocardiografia e CArdiovascular imaging): Rationale and Study Design

Background:

Bicuspid aortic valve (BAV) is the most common congenital heart disease, affecting 0.5%–2% of the general population. It is associated not only with notable valvular risk (aortic stenosis and/or regurgitation, endocarditis) but also with aortopathy with a wide spectrum of unpredictable clinical presentations, including aneurysmal dilation of the aortic root and/or ascending thoracic aorta, isthmic coarctation, aortic dissection, or wall rupture.

Methods:

The REgistro della Valvola Aortica Bicuspide della Società Italiana di ECocardiografia e CArdiovascular Imaging is a retrospective (from January 1, 2010)/prospective, multicenter, observational registry, expected to enroll 3000 patients with definitive diagnosis of BAV made by transthoracic and/or transesophageal echocardiography, computed tomography, cardiovascular magnetic resonance, or at surgery. Inclusion criteria were definitive diagnosis of BAV. Patients will be enrolled regardless of the presence and severity of aortic valve dysfunction or aortic vessel disease and the coexistence of other congenital cardiovascular malformations. Exclusion criteria were uncertain BAV diagnosis, impossibility of obtaining informed consent, inability to carry out the follow-up. Anamnestic, demographic, clinical, and instrumental data collected both at first evaluation and during follow-up will be integrated into dedicated software. The aim is to derive a data set of unselected BAV patients with the main purpose of assessing the current clinical presentation, management, and outcomes of BAV.

Conclusions:

A multicenter registry covering a large population of BAV patients could have a profound impact on the understanding of the natural history of this disease and could influence its management.