The pathology and pathobiology of bicuspid aortic valve: State of the art and novel research perspectives

Aortopathy and aortic valve surgery in patients with bicuspid aortic valve with and without raphe

AIM

To evaluate the association between raphe in bicuspid aortic valve (BAV) patients and valve dysfunction, aortopathy and aortic valve surgery in the REBECCA registry [REgistro della valvola aortica Bicuspide della Società Italiana di ECocardiografia e CArdiovascular Imaging (SIECVI)].

METHODS

Prevalence of aortic valve dysfunction and aortopathy was investigated in BAV patients with and without raphe. Aortic valve dysfunction (regurgitation or stenosis) was categorized as mild, moderate and severe. Aortopathy was defined as annulus ≥14 mm/m2; root ≥20 mm/m2; sinotubular junction ≥16 mm/m2; ascending aorta ≥17 mm/m2, and classified in Type A, isolated ascending aorta dilatation; Type B, aortic root and ascending aorta dilatation; and Type C, isolated aortic root dilatation.

RESULTS

Overall, 695 patients with BAV were enrolled; 520 (74.8%) with raphe and 175 (25.2%) without raphe. BAV patients with raphe presented more frequently with moderate or severe aortic stenosis than BAV patients without raphe (183 [35.2%] vs 34 [19.4%], p < 0.001). A higher prevalence of aortopathy, particularly Type B, was observed in patients with vs without raphe. At multivariable analysis, raphe was a predictor of aortic valve surgery at three-year follow-up (odds ratio 2.19, 95% confidence interval 1.08-4.44, p < 0.001).

CONCLUSIONS

Patients with BAV and raphe have a higher prevalence of significant aortic stenosis, aortopathy, especially Type B, and a higher risk of undergoing aortic valve surgery at three-year follow-up.

Double Negative Is Positive: Anomalous Aortic Origin of the Left Coronary Artery Saved by a Bicuspid Aortic Valve

Atypical aortic origin of coronary artery (AAOCA) is a rare heart condition that has been identified in only a few autopsy cases and in some patients who have undergone angiographic evaluation. AAOCA is known to be closely linked with aortic valve malformations, with the most common type being the bicuspid aortic valve (BAV). A 77-year-old male with a medical history of hypertension and diabetes presented with dyspnea and orthopnea for three days. During the eventual cardiac catheterization, it was noted that the left coronary artery had an anomalous origin from the right side, coursing between the aorta and pulmonary artery. Contrast-enhanced computerized tomography (CECT) also showed a type 2 BAV and a left main coronary artery arising lower at the level of the pulmonary trunk. The dyspnea in this patient was attributed to diastolic dysfunction, and surgical correction of the coronaries was not done. The patient was managed on an outpatient basis for heart failure. In this case, the patient had an anomalous origin of the left coronary artery and type 2 BAV, which posed significant cardiovascular complications. It is unclear if the presence of the concomitant type 2 BAV led to the origin of the anomalous left coronary artery being at a lower level through its effect on the developmental mechanics. This lower origin may have resulted in lower compressive forces on the coronary artery as the inter-arterial pressures would be lower closer to the heart and farther from the lungs. Our case report aims to highlight this complex presentation where the BAV likely provides a benefit in AAOCA cases.

Influence of cusp morphology and sex on quantitative valve composition in severe aortic stenosis

AIMS

Aortic stenosis is characterized by fibrosis and calcification of the valve, with a higher proportion of fibrosis observed in women. Stenotic bicuspid aortic valves progress more rapidly than tricuspid valves, which may also influence the relative composition of the valve. We aimed to investigate the influence of cusp morphology on quantitative aortic valve composition quantified from contrast-enhanced computed tomography angiography in severe aortic stenosis.

METHODS AND RESULTS

Patients undergoing transcatheter aortic valve implantation with bicuspid and tricuspid valves were propensity matched 1:1 by age, sex, and comorbidities. Computed tomography angiograms were analysed using semi-automated software to quantify the fibrotic and calcific scores (volume/valve annular area) and the fibro-calcific ratio (fibrotic score/calcific score). The study population (n = 140) was elderly (76 ± 10 years, 62% male) and had a peak aortic jet velocity of 4.1 ± 0.7 m/s. Compared with those with tricuspid valves (n = 70), patients with bicuspid valves (n = 70) had higher fibrotic scores [204 (interquartile range 118-267) vs. 144 (99-208) mm3/cm2, P = 0.006] with similar calcific scores (P = 0.614). Women had greater fibrotic scores than men in bicuspid [224 (181-307) vs. 169 (109-247) mm3/cm2, P = 0.042] but not tricuspid valves (P = 0.232). Men had greater calcific scores than women in both bicuspid [203 (124-355) vs. 130 (70-182) mm3/cm2, P = 0.008] and tricuspid [177 (136-249) vs. 100 (62-150) mm3/cm2, P = 0.004] valves. Among both valve types, women had a greater fibro-calcific ratio compared with men [tricuspid 1.86 (0.94-2.56) vs. 0.86 (0.54-1.24), P = 0.001 and bicuspid 1.78 (1.21-2.90) vs. 0.74 (0.44-1.53), P = 0.001].

CONCLUSIONS

In severe aortic stenosis, bicuspid valves have proportionately more fibrosis than tricuspid valves, especially in women.

Feasibility of Wave Intensity Analysis from 4D Cardiovascular Magnetic Resonance Imaging Data

Congenital heart defects (CHD) introduce haemodynamic changes; e.g., bicuspid aortic valve (BAV) presents a turbulent helical flow, which activates aortic pathological processes. Flow quantification is crucial for diagnostics and to plan corrective strategies. Multiple imaging modalities exist, with phase contrast magnetic resonance imaging (PC-MRI) being the current gold standard; however, multiple predetermined site measurements may be required, while 4D MRI allows for measurements of area (A) and velocity (U) in all spatial dimensions, acquiring a single volume and enabling a retrospective analysis at multiple locations. We assessed the feasibility of gathering hemodynamic insight into aortic hemodynamics by means of wave intensity analysis (WIA) derived from 4D MRI. Data were collected in n = 12 BAV patients and n = 7 healthy controls. Following data acquisition, WIA was successfully derived at three planes (ascending, thoracic and descending aorta) in all cases. The values of wave speed were physiological and, while the small sample limited any clinical interpretation of the results, the study shows the possibility of studying wave travel and wave reflection based on 4D MRI. Below, we demonstrate for the first time the feasibility of deriving wave intensity analysis from 4D flow data and open the door to research applications in different cardiovascular scenarios.

Diagnosis and Management of Aortic Valvular Disease in the Elderly

Aortic valvular disease, including aortic stenosis and aortic regurgitation, is increasingly common with age. Due to the aging population, more elderly patients are presenting with aortic valve pathology and expectations for prompt diagnosis and efficacious treatment. The current paradigm for aortic valve disease is based on surgical or interventional therapy. In this review, we discuss the approach to diagnosing aortic valvular disease and the different options for treatment based on the most recent evidence.

Perspectives on pediatric congenital aortic valve stenosis: Extracellular matrix proteins, post translational modifications, and proteomic strategies

In heart valve biology, organization of the extracellular matrix structure is directly correlated to valve function. This is especially true in cases of pediatric congenital aortic valve stenosis (pCAVS), in which extracellular matrix (ECM) dysregulation is a hallmark of the disease, eventually leading to left ventricular hypertrophy and heart failure. Therapeutic strategies are limited, especially in pediatric cases in which mechanical and tissue engineered valve replacements may not be a suitable option. By identifying mechanisms of translational and post-translational dysregulation of ECM in CAVS, potential drug targets can be identified, and better bioengineered solutions can be developed. In this review, we summarize current knowledge regarding ECM proteins and their post translational modifications (PTMs) during aortic valve development and disease and contributing factors to ECM dysregulation in CAVS. Additionally, we aim to draw parallels between other fibrotic disease and contributions to ECM post-translational modifications. Finally, we explore the current treatment options in pediatrics and identify how the field of proteomics has advanced in recent years, highlighting novel characterization methods of ECM and PTMs that may be used to identify potential therapeutic strategies relevant to pCAVS.

Cellular Senescence, Aging and Non-Aging Processes in Calcified Aortic Valve Stenosis: From Bench-Side to Bedside

Aortic valve stenosis (AS) is the most common valvular heart disease. The incidence of AS increases with age, however, a significant proportion of elderly people have no significant AS, indicating that both aging and nonaging pathways are involved in the pathomechanism of AS. Age-related and stress-induced cellular senescence accompanied by further active processes represent the key elements of AS pathomechanism. The early stage of aortic valve degeneration involves dysfunction and disruption of the valvular endothelium due to cellular senescence and mechanical stress on blood flow. These cells are replaced by circulating progenitor cells, but in an age-dependent decelerating manner. When endothelial denudation is no longer replaced by progenitor cells, the path opens for focal lipid deposition, initiating subsequent oxidation, inflammation and micromineralisation. Later stages of AS feature a complex active process with extracellular matrix remodeling, fibrosis and calcification. Echocardiography is the gold standard method for diagnosing aortic valve disease, although computed tomography and cardiac magnetic resonance are useful additional imaging methods. To date, no medical treatment has been proven to halt the progression of AS. Elucidation of differences and similarities between vascular and valvular calcification pathomechanisms may help to find effective medical therapy and reduce the increasing health burden of the disease.

Anatomical and Clinical Factors Associated With Valvulopathy and Aortopathy in Mexican Patients With Bicuspid Aortic Valves

The bicuspid aortic valve (BAV) is associated with significant aortic valve dysfunction. We aimed to study Mexican patients with BAV to assess phenotypic expressions of BAV, and associations of valvulopathy and aortopathy and their predictors. A cross-sectional, retrospective study was designed. The patients were divided according to (1) normally or minimally dysfunctional BAV, (2) predominant aortic regurgitation (AR), and (3) predominant aortic stenosis (AS). A total of 189 patients were included with a high prevalence of males (68%). The overall median age was 42 (23 to 52) years. The distribution of fused BAV phenotypes was right-left fusion (77%), right noncoronary fusion (17%) and left noncoronary fusion (6%). AS-predominant group was the oldest with a high prevalence of hypertension, type 2 diabetes mellitus (T2DM), and raphe. In multivariable analysis T2DM (odds ratio [OR] 10.5 [95% confidence interval (CI) 2.1 to 52], p <0.01) and presence of raphe (OR 2.58 [95% CI 1.02 to 6.52], p = 0.04) were independently associated with AS. The AR-predominant group was composed mostly of males with significantly fewer cardiovascular risk factors. Male gender (OR 2.84 [95%CI 121 to 6.68], p = 0.01) and aortic dilatation (OR 3.58 [95% CI 1.73 to 7.39], p <0.01) were associated with AR-predominance in multivariable analysis. Aortic dilatation was associated with age (OR 1.03 [95% CI 1.008 to 1.05], p <0.01) and AR (OR 4.31 [95% CI 2.05 to 9.06], p <0.01). Independent factors associated with the root phenotype were male gender (OR 12.4 [95% CI 1.6 to 95], p <0.01) and AR (OR 5.25 [95% CI 2.18 to 12.6], p <0.01).In conclusion, in a mestizo population, the distribution of BAV-fused phenotypes was similar to European and North American populations, the presence of raphe and T2DM were independently associated with AS-predominance, and male gender and aortic dilatation were independently associated with AR-predominance.

Contribution of Oxidative Stress (OS) in Calcific Aortic Valve Disease (CAVD): From Pathophysiology to Therapeutic Targets

Calcific aortic valve disease (CAVD) is a major cause of cardiovascular mortality and morbidity, with increased prevalence and incidence. The underlying mechanisms behind CAVD are complex, and are mainly illustrated by inflammation, mechanical stress (which induces prolonged aortic valve endothelial dysfunction), increased oxidative stress (OS) (which trigger fibrosis), and calcification of valve leaflets. To date, besides aortic valve replacement, there are no specific pharmacological treatments for CAVD. In this review, we describe the mechanisms behind aortic valvular disease, the involvement of OS as a fundamental element in disease progression with predilection in AS, and its two most frequent etiologies (calcific aortic valve disease and bicuspid aortic valve); moreover, we highlight the potential of OS as a future therapeutic target.

Uncoupling the Vicious Cycle of Mechanical Stress and Inflammation in Calcific Aortic Valve Disease

Calcific aortic valve disease (CAVD) is a common acquired valvulopathy, which carries a high burden of mortality. Chronic inflammation has been postulated as the predominant pathophysiological process underlying CAVD. So far, no effective medical therapies exist to halt the progression of CAVD. This review aims to outline the known pathways of inflammation and calcification in CAVD, focussing on the critical roles of mechanical stress and mechanosensing in the perpetuation of valvular inflammation. Following initiation of valvular inflammation, dysregulation of proinflammatory and osteoregulatory signalling pathways stimulates endothelial-mesenchymal transition of valvular endothelial cells (VECs) and differentiation of valvular interstitial cells (VICs) into active myofibroblastic and osteoblastic phenotypes, which in turn mediate valvular extracellular matrix remodelling and calcification. Mechanosensitive signalling pathways convert mechanical forces experienced by valve leaflets and circulating cells into biochemical signals and may provide the positive feedback loop that promotes acceleration of disease progression in the advanced stages of CAVD. Mechanosensing is implicated in multiple aspects of CAVD pathophysiology. The mechanosensitive RhoA/ROCK and YAP/TAZ systems are implicated in aortic valve leaflet mineralisation in response to increased substrate stiffness. Exposure of aortic valve leaflets, endothelial cells and platelets to high shear stress results in increased expression of mediators of VIC differentiation. Upregulation of the Piezo1 mechanoreceptor has been demonstrated to promote inflammation in CAVD, which normalises following transcatheter valve replacement. Genetic variants and inhibition of Notch signalling accentuate VIC responses to altered mechanical stresses. The study of mechanosensing pathways has revealed promising insights into the mechanisms that perpetuate inflammation and calcification in CAVD. Mechanotransduction of altered mechanical stresses may provide the sought-after coupling link that drives a vicious cycle of chronic inflammation in CAVD. Mechanosensing pathways may yield promising targets for therapeutic interventions and prognostic biomarkers with the potential to improve the management of CAVD.

Unraveling Bicuspid Aortic Valve Enigmas by Multimodality Imaging: Clinical Implications

Multimodality imaging is the basis of the diagnosis, follow-up, and surgical management of bicuspid aortic valve (BAV) patients. Transthoracic echocardiography (TTE) is used in our clinical routine practice as a first line imaging for BAV diagnosis, valvular phenotyping and function, measurement of thoracic aorta, exclusion of other aortic malformations, and for the assessment of complications such are infective endocarditis and aortic. Nevertheless, TTE is less useful if we want to assess accurately other aortic segments such as mid-distal ascending aorta, where computed tomography (CT) and magnetic resonance (CMR) could improve the precision of aorta size measurement by multiplanar reconstructions. A major advantage of CT is its superior spatial resolution, which affords a better definition of valve morphology and calcification, accuracy, and reproducibility of ascending aorta size, and allows for coronary artery assessment. Moreover, CMR offers the opportunity of being able to evaluate aortic functional properties and blood flow patterns. In this setting, new developed sequences such as 4D-flow may provide new parameters to predict events during follow up. The integration of all multimodality information facilitates a comprehensive evaluation of morphologic and dynamic features, stratification of the risk, and therapy guidance of this cohort of patients.

Hemodynamic Assessment in Bicuspid Aortic Valve Disease and Aortic Dilation: New Insights From Voxel-By-Voxel Analysis of Reverse Flow, Stasis, and Energetics

Objectives: Clinical management decisions surrounding ascending aorta (AAo) dilation in bicuspid aortic valve (BAV) disease benefit from personalized predictive tools. 4D-flow MRI may provide patient-specific markers reflective of BAV-associated aortopathy. This study aims to explore novel 4D-flow MRI parametric voxel-by-voxel forward flow, reverse flow, kinetic energy and stasis in BAV disease. We hypothesize that novel parametric voxel-by-voxel markers will be associated with aortic dilation and referral for surgery and can enhance our understanding of BAV hemodynamics beyond standard metrics.

Methods: A total of 96 subjects (73 BAV patients, 23 healthy controls) underwent MRI scan. Healthy controls had no known cardiovascular disease. Patients were clinically referred for AAo dilation assessment. Indexed diameters were obtained by dividing the aortic diameter by the patient’s body surface area. Patients were followed for the occurrence of aortic surgery. 4D-flow analysis was performed by a single observer in five regions: left ventricular outflow tract (LVOT), AAo, arch, proximal descending aorta (PDAo), and distal descending aorta (DDAo). In each region peak velocity, kinetic energy (KE), forward flow (FF), reverse flow (RF), and stasis were measured on a voxel-by-voxel basis. T-tests (or non-parametric equivalent) compared flow parameters between cohorts. Univariate and multivariate analyses explored associations between diameter and parametric voxel-by-voxel parameters.

Results: Compared to controls, BAV patients showed reduced stasis (p < 0.01) and increased RF and FF (p < 0.01) throughout the aorta, and KE remained similar. In the AAo, indexed diameter correlated with age (R = 0.326, p = 0.01), FF (R = −0.648, p < 0.001), RF (R = −0.441, p < 0.001), and stasis (R = −0.288, p < 0.05). In multivariate analysis, FF showed a significant inverse association with AAo indexed diameter, independent of age. During a median 179 ± 180 days of follow-up, 23 patients (32%) required aortic surgery. Compared to patients not requiring surgery, they showed increased KE and peak velocity in the proximal aorta (p < 0.01), accompanied by increased RF and reduced stasis throughout the entire aorta (p < 0.01).

Conclusion: Novel voxel-by-voxel reverse flow and stasis were altered in BAV patients and are associated with aortic dilation and surgical treatment.

How to mimic a type A intramural hematoma: A case of IgG4-related aortitis associated with cerebral hemorrhage

IgG4-related aortitis is an inflammatory condition of the aorta, characterized by aortic wall thickening and periaortic soft-tissue involvement. Therefore, this condition can mimic an aortic intramural hematoma (IMH), due to similar radiological findings. We hereby report the case of an IgG4-related aortitis misdiagnosed as an IMH, associated with cerebral hemorrhage, possibly due to cerebral vascular system involvement.

Non-calcific aortic tissue quantified from computed tomography angiography improves diagnosis and prognostication of patients referred for transcatheter aortic valve implantation

AIMS

We aimed to investigate the role of aortic valve tissue composition from quantitative cardiac computed tomography angiography (CTA) in patients with severe aortic stenosis (AS) for the differentiation of disease subtypes and prognostication after transcatheter aortic valve implantation (TAVI).

METHODS AND RESULTS

Our study included 447 consecutive AS patients from six high-volume centres reporting to a prospective nationwide registry of TAVI procedures (POL-TAVI), who underwent cardiac CTA before TAVI, and 224 matched controls with normal aortic valves. Components of aortic valve tissue were identified using semi-automated software as calcific and non-calcific. Volumes of each tissue component and composition [(tissue component volume/total tissue volume) × 100%] were quantified. Relationship of aortic valve composition with clinical outcomes post-TAVI was evaluated using Valve Academic Research Consortium (VARC)-2 definitions.High-gradient (HG) AS patients had significantly higher aortic tissue volume compared to low-flow low-gradient (LFLG)-AS (1672.7 vs. 1395.3 mm3, P < 0.001) as well as controls (509.9 mm3, P < 0.001), but increased non-calcific tissue was observed in LFLG compared to HG patients (1063.6 vs. 860.2 mm3, P < 0.001). Predictive value of aortic valve calcium score [area under the curve (AUC) 0.989, 95% confidence interval (CI): 0.981-0.996] for severe AS was improved after addition of non-calcific tissue volume (AUC 0.995, 95% CI: 0.991-0.999, P = 0.011). In the multivariable analysis of clinical and quantitative computed tomography parameters of aortic valve tissue, non-calcific tissue volume [odds ratio (OR) 5.2, 95% CI 1.8-15.4, P = 0.003] and history of stroke (OR 2.6, 95% CI 1.1-6.5, P = 0.037) were independent predictors of 30-day major adverse cardiovascular event (MACE).

CONCLUSION

Quantitative CTA assessment of aortic valve tissue volume and composition can improve detection of severe AS, differentiation between HG and LFLG-AS in patients referred for TAVI as well as prediction of 30-day MACEs post-TAVI, over the current clinical standard.

Therapeutic approach comparison in bicuspid aortic valve aortopathy and clinical practice implications

Bicuspid aortic valve (BAV) is the most common heart valve malformation, and it may be associated with the development of long-term complications, such as aortic stenosis (AS) secondary to valvular calcification and aortic insufficiency (AI), with or without ascending aortic aneurysm (AAA). This study was performed at the Institute of Cardiovascular Diseases, Timişoara, Romania, from 2015 through 2018 and included a total of 105 patients with BAV. Out of the 105 BAV patients, 14 displayed AAA, alongside either AS or AI, and were selected undergo aortic valve replacement (AVR) alongside surgical replacement or aortoplasty of the ascending aorta, and the elastic fiber loss in the ascending aortic wall was evaluated for each patient. Two surgical interventions used alongside AVR in BAV patients with AAA and AS or AI were compared in this study: reduction ascending aortoplasty (RAA) and ascending aorta replacement (AAR). Postoperative follow-ups have shown RAA is useful short-term but that, in contrast to AAR, it leads to aortic redilatation over time. These results can contribute to a major future meta-analysis with the goal of improving the current clinical practice guidelines for BAV aortopathy.

Impact of Regular Physical Activity on Aortic Diameter Progression in Paediatric Patients with Bicuspid Aortic Valve

Patients with bicuspid aortic valve (BAV) have an increased risk of aortic dilation and aortic dissection or rupture. The impact of physical training on the natural course of aortopathy in BAV patients remains unclear. The aim of this study was to evaluate the impact of regular physical activity on aortic diameters in a consecutive cohort of paediatric patients with BAV. Consecutive paediatric BAV patients were evaluated and categorized into two groups: physically active and sedentary subjects. Only the subjects with a complete 2-year follow-up were included in the study. To evaluate the potential impact of physical activity on aortic size, aortic diameters were measured at the sinus of Valsalva and mid-ascending aorta using echocardiography. We defined aortic diameter progression the increase of aortic diameter ≥ 10% from baseline. Among 90 BAV patients (11.5 ± 3.4 years of age, 77% males), 53 (59%) were physically active subjects. Compared to sedentary, physically active subjects were not significantly more likely to have > 10% increase in sinus of Valsalva (13% vs. 8%, p-value = 0.45) or mid-ascending aorta diameter (9% vs. 13%, p-value = 0.55) at 2 years follow-up, both in subjects with sinus of Valsalva diameter progression (3.7 ± 1.0 mm vs. 3.5 ± 0.8 mm, p-value = 0.67) and in those with ascending aorta diameter progression (3.0 ± 0.8 mm vs. 3.2 ± 1.3 mm, p-value = 0.83). In our paediatric cohort of BAV patients, the prevalence and the degree of aortic diameter progression was not significantly different between physically active and sedentary subjects, suggesting that aortic dilation is unrelated to regular physical activity over a 2-year period.

Oscillatory fluid-induced mechanobiology in heart valves with parallels to the vasculature

Forces generated by blood flow are known to contribute to cardiovascular development and remodeling. These hemodynamic forces induce molecular signals that are communicated from the endothelium to various cell types. The cardiovascular system consists of the heart and the vasculature, and together they deliver nutrients throughout the body. While heart valves and blood vessels experience different environmental forces and differ in morphology as well as cell types, they both can undergo pathological remodeling and become susceptible to calcification. In addition, while the plaque morphology is similar in valvular and vascular diseases, therapeutic targets available for the latter condition are not effective in the management of heart valve calcification. Therefore, research in valvular and vascular pathologies and treatments have largely remained independent. Nonetheless, understanding the similarities and differences in development, calcific/fibrous pathologies and healthy remodeling events between the valvular and vascular systems can help us better identify future treatments for both types of tissues, particularly for heart valve pathologies which have been understudied in comparison to arterial diseases.

Changes in inflammation and oxidative stress signalling pathways in coarcted aorta triggered by bicuspid aortic valve and growth in young children

Neonates with coarctation of the aorta (CoA) combined with a bicuspid aortic valve (BAV) show significant structural differences compared to neonatal CoA patients with a normal tricuspid aortic valve (TAV). These effects are likely to change over time in response to growth. This study investigated proteomic differences between coarcted aortic tissue of BAV and TAV patients in children older than one month. Aortic tissue just proximal to the coarctation site was collected from 10 children (BAV; n=6, 1.9±1.7 years, TAV; n=4, 1.7±1.5 years, (mean ± SEM, P=0.92.) Tissue were snap frozen, proteins extracted, and the extracts used for proteomic and phosphoproteomic analysis using Tandem Mass Tag (TMT) analysis. A total of 1811 protein and 76 phosphoprotein accession numbers were detected, of which 40 proteins and 6 phosphoproteins were significantly differentially expressed between BAV and TAV patients. Several canonical pathways involved in inflammation demonstrated enriched protein expression, including acute phase response signalling, EIF2 signalling and macrophage production of IL12 and reactive oxygen species. Acute phase response signalling also demonstrated enriched phosphoprotein expression, as did Th17 activation. Other pathways with significantly enriched protein expression include degradation of superoxide radicals and several pathways involved in apoptosis. This work suggests that BAV CoA patients older than one month have an altered proteome consistent with changes in inflammation, apoptosis and oxidative stress compared to TAV CoA patients of the same age. There is no evidence of structural differences, suggesting the pathology associated with BAV evolves with age in paediatric CoA patients.

Bicuspid Aortic Valve Repair: Causes of Valve Failure and Long-Term Outcomes

BACKGROUND

Repair of bicuspid aortic valves (BAVs) for aortic regurgitation (AR) has favorable outcomes, but the impact of natural disease progression on durability of repair is uncertain. We evaluated causes of reoperation and compared outcomes of BAV repair to those of patients undergoing aortic valve replacement (AVR).

METHODS

Between January 1993 and December 2016, 113 patients had BAV repair at our institution for significant AR. Operative notes and pathology reports were studied to identify late causes of repair failure. For comparison with AVR, we utilized propensity score weighting with the score derived from preoperative and operative characteristics using gradient boosting machine model.

RESULTS

A total of 26 patients had late AVR after initial repair. Causes of late valve dysfunction included calcification or fibrosis of the cusps (68%), concomitant replacement addressing moderate degree of aortic valve disease to avoid future operation (20%), and cusp prolapse (12%). Pathological evaluation of these excised valves reported calcification and fibrosis in 88% of the valves. Ten-year survival of patients undergoing BAV repair was 91% compared with 90% for patients undergoing AVR with a mechanical valve and 79% for AVR with a bioprosthesis (P = .6). Incidence of reoperation after AVR with a bioprosthesis was similar to risk after repair whereas AVR with mechanical valve showed significant advantage.

CONCLUSIONS

Disease progression with calcification or fibrosis is the most common cause of valve failure after initial repair of BAV. Clinical outcomes of BAV repair for severe AR appear superior to AVR with bioprosthesis.

GATA6 Regulates Aortic Valve Remodeling, and Its Haploinsufficiency Leads to Right-Left Type Bicuspid Aortic Valve

BACKGROUND

Bicuspid aortic valve (BAV), the most common congenital heart defect affecting 1% to 2% of the population, is a major risk factor for premature aortic valve disease and accounts for the majority of valve replacement. The genetic basis and mechanisms of BAV etiology and pathogenesis remain largely undefined.

METHODS

Cardiac structure and function was assessed in mice lacking a Gata6 allele. Human GATA6 gene variants were analyzed in 452 BAV cases from the BAV consortium and 1849 controls from the Framingham GWAS (Genome Wide Association Study). GATA6 expression was determined in mice and human tissues using quantitative real-time polymerase chain reaction and immunohistochemistry. Mechanistic studies were carried out in cultured cells.

RESULTS

Gata6 heterozygous mice have highly penetrant right-left (RL)-type BAV, the most frequent type in humans. GATA6 transcript levels are lower in human BAV compared with normal tricuspid valves. Mechanistically, Gata6 haploinsufficiency disrupts valve remodeling and extracellular matrix composition through dysregulation of important signaling molecules, including matrix metalloproteinase 9. Cell-specific inactivation of Gata6 reveals an essential role for GATA6 in secondary heart field myocytes because loss of 1 Gata6 allele from Isl- 1-positive cells-but not from endothelial or neural crest cells-recapitulates the phenotype of Gata6 heterozygous mice.

CONCLUSIONS

The data identify a new cellular and molecular mechanism underlying BAV. The availability of an animal model for the most frequent human BAV opens the way for the elucidation of BAV pathogenesis and the development of much needed therapies.

Contemporary Etiologies, Mechanisms, and Surgical Approaches in Pure Native Aortic Regurgitation

OBJECTIVE

To study contemporary etiologies, mechanisms, and corresponding surgical approaches in isolated aortic regurgitation (AR).

PATIENTS AND METHODS

Consecutive patients undergoing surgery for moderately severe and severe AR were retrospectively identified from January 1, 2006, through October 20, 2017. Intraoperative echocardiograms, surgical reports, and pathology reports were reviewed.

RESULTS

Of 382 patients (54±16 years, 82% men), there were 207 (54%) tricuspid (TAV), 167 (44%) bicuspid (BAV), 5 quadricuspid, and 3 unicuspid aortic valves. Isolated AR mechanisms (n=116, 30%) included cusp prolapse (n=44, 11%), restriction/retraction (n=33, 9%), aortic root dilatation (n=33, 9%), perforation (n=5, 1%), and fenestration (<1%); mixed mechanisms were present in 266 (70%). The most common mixed mechanism was root dilatation and prolapse (27% BAV vs 16% TAV, P=.01). Valve repair (AVr) was performed in 31% BAV and 23% TAV (P=.06). Aortic surgery was more common in BAV (37% vs 27%, P<.001). Overall, root dilatation was associated with AVr. In TAV, cusp prolapse and restriction/retraction were associated with replacement; in BAV, prolapse was associated with AVr. AR etiology was idiopathic in 43% TAV patients, 47% of whom had root dilatation.

CONCLUSIONS

BAV accounted for 44% of surgical referrals for AR and, compared with TAV, was more often associated with prolapse, root dilatation, and mixed mechanisms of AR. Because mechanisms affected the choice of AVr differently in BAV and TAV, comprehensive mechanistic description of surgical AR is critical.

Clinical-pathological correlations of BAV and the attendant thoracic aortopathies. Part 1: Pluridisciplinary perspective on their hemodynamics and morphomechanics

Clinical BAV manifestations pertain to faulty aortic valve (AOV) function, the associated aortopathy, and other complications such as endocarditis, thrombosis and thromboembolism. BAV arises during valvulogenesis when 2 of the 3 leaflets/cusps of the AOV are fused together. Ensuing asymmetric BAV morphologies alter downstream ejection jet flow-trajectories. Based on BAV morphologies, ejection-flows exhibit different wall-impingement and scouring patterns in the proximal aorta, with excessive hydrodynamic wall-shear that correlates closely with mural vascular smooth muscle cell and extracellular matrix disruptions, revealing hemodynamic participation in the pathogenesis of BAV-associated aortopathies. Since the embryologic regions implicated in both BAV and aortopathies derive from neural crest cells and second heart field cells, there may exist a common multifactorial/polygenic embryological basis linking the abnormalities. The use of Electronic Health Records - encompassing integrated NGS variant panels and phenotypic data - in clinical studies could speed-up comprehensive understanding of multifactorial genetic-phenotypic and environmental factor interactions. This Survey represents the first in a 2-article pluridisciplinary work. Taken in toto, the series covers hemodynamic/morphomechanical and environmental (milieu intérieur) aspects in Part 1, and molecular, genetic and associated epigenetic aspects in Part 2. Together, Parts 1-2 should serve as a reference-milestone and driver for further pluridisciplinary research and its urgent translations in the clinical setting.

Aortopathy and regurgitation in bicuspid valve patients increase the risk of aortopathy in relatives

BACKGROUND

Bicuspid aortic valve (BAV) is the most frequent cardiac congenital valvular disease. Although the BAV risk of first degree relatives (FDR) has been assessed (7-9%), there is little information as to the heritable risk for aortopathy.

OBJECTIVE

Identify the specific risk for regional aortopathy in FDR with tricuspid aortic valve (TAV) of BAV patients according to their aortic phenotype and aortic regurgitation (AR).

METHODS

Using an international consortium, BAV probands were assessed for aortopathy of the root, ascending aorta and for AR. Aortopathy was defined by the presence of segmental dilatation. The presence of segmental aortopathy and AR in BAV probands was evaluated as predictor for aortopathy in FDR with TAV.

RESULTS

We identified 74 FDR related to 49 probands with aortopathy and 66 FDR related to 31 probands without aortopathy. Demographic variables were similar between proband groups. Among FDR, 16 individuals had BAV (11.4%). TAV-FDR of probands with ascending aortopathy had higher incidence of root aortopathy (18.8% vs. 3.6% p < 0.05) while TAV-FDR of probands with root aortopathy had higher incidence of aortopathy at all aortic segments (55%vs25%, 55%vs21%, and 4%vs29% at annulus, root and ascending respectively, p < 0.05 for all). Independent predictors for root aortopathy in TAV-FDR were: ascending (OR = 6.23;95%CI:1.27-30.5) and root aortopathy (OR = 9.00;95%CI:1.58-51.1) in probands; and for ascending aortopathy: root aortopathy (OR = 4.04;95%CI:1.33-12.3) and AR in probands (OR = 4.84; 95%CI:1.75-13.4).

CONCLUSION

Root and ascending aortopathy in BAV probands are strong predictors of aortopathy in their TAV-FDR. AR in BAV patients has an independent effect on the risk for ascending aortopathy in TAV-FDR.

Chronic inflammation: A key role in degeneration of bicuspid aortic valve

INTRODUCTION

Bicuspid aortic valve (BAV) is the most common congenital valvular heart defect resulting from abnormal aortic cusp formation during heart development, where two of the three normal and equal sized cusps fuse into a single large cusp resulting in a two cusps aortic valve. Over the past years, much interest has been given in understanding the pathogenesis of BAV and its complications. In this review, we focused on the role of inflammation, involved in the degeneration of BAV and the development of its complications.

ROLE OF INFLAMMATION

From a pathophysiological point of view, BAV may rapidly progress into aortic stenosis (AS) and is related to aortopathy. Several histopathologic studies have demonstrated that the development and progression of alterations in bicuspid aortic valve are related to an active process that includes: oxidative stress, shear stress, endothelial dysfunction, disorganized tissue architecture, inflammatory cells and cytokines. These factors are closely related one to each other, constituting the basis of the structural and functional alterations of the BAV.

CONCLUSION

Chronic inflammation plays a key role in the degeneration of BAV. Severe aortic stenosis in bicuspid aortic valves is associated with a more aggressive inflammatory process, increased inflammatory cells infiltration and neovascularization when compared to tricuspid AS. These findings might help to explain the more frequent onset and rapid progression of AS and the heavy aortic valve calcification seen in patients with BAV.

Comparing the Role of Mechanical Forces in Vascular and Valvular Calcification Progression

Calcification is a prevalent disease in most fully developed countries and is predominantly observed in heart valves and nearby vasculature. Calcification of either tissue leads to deterioration and, ultimately, failure causing poor quality of life and decreased overall life expectancy in patients. In valves, calcification presents as Calcific Aortic Valve Disease (CAVD), in which the aortic valve becomes stenotic when calcific nodules form within the leaflets. The initiation and progression of these calcific nodules is strongly influenced by the varied mechanical forces on the valve. In turn, the addition of calcific nodules creates localized disturbances in the tissue biomechanics, which affects extracellular matrix (ECM) production and cellular activation. In vasculature, atherosclerosis is the most common occurrence of calcification. Atherosclerosis exhibits as calcific plaque formation that forms in juxtaposition to areas of low blood shear stresses. Research in these two manifestations of calcification remain separated, although many similarities persist. Both diseases show that the endothelial layer and its regulation of nitric oxide is crucial to calcification progression. Further, there are similarities between vascular smooth muscle cells and valvular interstitial cells in terms of their roles in ECM overproduction. This review summarizes valvular and vascular tissue in terms of their basic anatomy, their cellular and ECM components and mechanical forces. Calcification is then examined in both tissues in terms of disease prediction, progression, and treatment. Highlighting the similarities and differences between these areas will help target further research toward disease treatment.

The Genetic Regulation of Aortic Valve Development and Calcific Disease

Heart valves are dynamic, highly organized structures required for unidirectional blood flow through the heart. Over an average lifetime, the valve leaflets or cusps open and close over a billion times, however in over 5 million Americans, leaflet function fails due to biomechanical insufficiency in response to wear-and-tear or pathological stimulus. Calcific aortic valve disease (CAVD) is the most common valve pathology and leads to stiffening of the cusp and narrowing of the aortic orifice leading to stenosis and insufficiency. At the cellular level, CAVD is characterized by valve endothelial cell dysfunction and osteoblast-like differentiation of valve interstitial cells. These processes are associated with dysregulation of several molecular pathways important for valve development including Notch, Sox9, Tgfβ, Bmp, Wnt, as well as additional epigenetic regulators. In this review, we discuss the multifactorial mechanisms that contribute to CAVD pathogenesis and the potential of targeting these for the development of novel, alternative therapeutics beyond surgical intervention.

Investigation of raphe function in the bicuspid aortic valve and its influence on clinical criteria-A patient-specific finite element study

The aortic valve is normally composed of 3 cusps. In one common lesion, 2 cusps are fused together. The conjoined area of the fused cusps is termed raphe. Occurring in 1% to 2% of the population, the bicuspid aortic valve (BAV) is the most common congenital cardiac malformation. The majority of BAV patients eventually require surgery. There is a lack in the literature regarding modeling of the raphe (geometry and material properties), its role and its influence on BAV function. The present study aims to propose improvements on these aspects. Three patient-specific finite element models of BAVs were created based on 3D trans-esophageal echocardiography measurements, and assuming age-dependent material properties. The raphe was initially given the same material properties as its underlying cusps. Two levels of validation were performed; one based on the anatomical validation of the pressurized geometry in diastole (involving 7 anatomical measures), as simulated starting from the unpressurized geometry, and the other based on a functional assessment using clinical measurements in both systole and diastole (involving 16 functional measures). The pathology was successfully reproduced in the FE models of all 3 patients. To further investigate the role of the raphe, 2 additional scenarios were considered; (1) the raphe was considered as almost rigid, (2) the raphe was totally removed. The results confirmed the interpretation of the raphe as added stiffness in the fused cusp's rotation with respect to the aortic wall, as well as added support for stress distribution from the fused cusps to the aortic wall.

Does statin therapy impact the proximal aortopathy in aortic valve disease?

BACKGROUND

Studies have demonstrated that statin therapy decreases the growth rate of abdominal aneurysms. However, the effect of statin therapy on the proximal aortic disease has not been sufficiently elucidated.

AIM

We aimed to analyse the association between statin treatment and the severity of proximal aortopathy in patients with aortic valve disease.

DESIGN

Cross-sectional study.

METHODS

We prospectively identified 458 patients who were referred for aortic valve surgery from 2008 to 2014. Pre-operative measurement of the proximal aorta was performed by TEE, CT or MRT scan. Data of dyslipidemia treatment was obtained by questionnaire.

RESULTS

The mean ascending aortic diameter in the whole study population was comparable in patients with vs. without statin therapy (i.e. 42.7 mm vs. 43.6 mm, P = 0.46). Logistic regression analysis showed no significant association between statin therapy and proximal aortopathy ≥ 40 mm in the whole study group (OR = 0.69, P = 0.10). For the BAV sub-group, HDL (OR = 0.54, P = 0.038) and cholesterol levels (OR = 2.00, P = 0.038) were found significantly associated with the proximal aortic disease. In the BAV cohort, the statin users with target HDL levels presented a significantly smaller proximal aortic diameter (40.1 mm vs. 46 mm, P = 0.02).

CONCLUSION

Pre-operative statin therapy demonstrated no significant association with the expression of proximal aortopathy. However, more than 40% of the statin users presented uncontrolled lipid levels at the time of the study. In the BAV sub-group, the statins users with target HDL levels showed a significantly smaller ascending aorta diameter. Target HDL and cholesterol levels were strongly associated with proximal aortic dilation in BAV patients.

Wall Shear Stress Directional Abnormalities in BAV Aortas: Toward a New Hemodynamic Predictor of Aortopathy?

The bicuspid aortic valve (BAV) generates wall shear stress (WSS) abnormalities in the ascending aorta (AA) that may be responsible for the high prevalence of aortopathy in BAV patients. While previous studies have analyzed the magnitude and oscillatory characteristics of the total or streamwise WSS in BAV AAs, the assessment of the circumferential component is lacking despite its expected significance in this highly helical flow environment. This gap may have hampered the identification of a robust hemodynamic predictor of BAV aortopathy. The objective of this study was to perform a global and component-specific assessment of WSS magnitude, oscillatory and directional characteristics in BAV AAs. The WSS environments were computed in the proximal and middle convexity of tricuspid aortic valve (TAV) and BAV AAs using our previous valve-aorta fluid-structure interaction (FSI) models. Component-specific WSS characteristics were investigated in terms of temporal shear magnitude (TSM) and oscillatory shear index (OSI). WSS directionality was quantified in terms of mean WSS vector magnitude and angle, and angular dispersion index (D_α). Local WSS magnitude and multidirectionality were captured in a new shear magnitude and directionality index (SMDI) calculated as the product of the mean WSS magnitude and D_α. BAVs subjected the AA to circumferential TSM overloads (2.4-fold increase vs. TAV). TAV and BAV AAs exhibited a unidirectional circumferential WSS (OSI < 0.04) and an increasingly unidirectional longitudinal WSS between the proximal (OSI > 0.21) and middle (OSI < 0.07) sections. BAVs generated mean WSS vectors skewed toward the anterior wall and WSS angular distributions exhibiting decreased uniformity in the proximal AA (0.27-point increase in D_α vs. TAV). SMDI was elevated in all BAV AAs but peaked in the proximal LR-BAV AA (3.6-fold increase vs. TAV) and in the middle RN-BAV AA (1.6-fold increase vs. TAV). This analysis demonstrates the significance of the circumferential WSS component and the existence of substantial WSS directional abnormalities in BAV AAs. SMDI abnormality distributions in BAV AAs follow the morphotype-dependent occurrence of dilation in BAV AAs, suggesting the predictive potential of this metric for BAV aortopathy.

Enlightening the Association between Bicuspid Aortic Valve and Aortopathy

Bicuspid aortic valve (BAV) patients have an increased incidence of developing aortic dilation. Despite its importance, the pathogenesis of aortopathy in BAV is still largely undetermined. Nowadays, intense focus falls both on BAV morphology and progression of valvular dysfunction and on the development of aortic dilation. However, less is known about the relationship between aortic valve morphology and aortic dilation. A better understanding of the molecular pathways involved in the homeostasis of the aortic wall, including the extracellular matrix, the plasticity of the vascular smooth cells, TGFβ signaling, and epigenetic dysregulation, is key to enlighten the mechanisms underpinning BAV-aortopathy development and progression. To date, there are two main theories on this subject, i.e., the genetic and the hemodynamic theory, with an ongoing debate over the pathogenesis of BAV-aortopathy. Furthermore, the lack of early detection biomarkers leads to challenges in the management of patients affected by BAV-aortopathy. Here, we critically review the current knowledge on the driving mechanisms of BAV-aortopathy together with the current clinical management and lack of available biomarkers allowing for early detection and better treatment optimization.

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.

Non-destructive two-photon excited fluorescence imaging identifies early nodules in calcific aortic-valve disease

Calcifications occur during the development of healthy bone, and at the onset of calcific aortic-valve disease (CAVD) and many other pathologies. Although the mechanisms regulating early calcium deposition are not fully understood, they may provide targets for new treatments and for early interventions. Here, we show that two-photon excited fluorescence (TPEF) can provide quantitative and sensitive readouts of calcific nodule formation, in particular in the context of CAVD. Specifically, by means of the decomposition of TPEF spectral images from excised human CAVD valves and from rat bone prior to and following demineralization, as well as from calcific nodules formed within engineered gels, we identified an endogenous fluorophore that correlates with the level of mineralization in the samples. We then developed a ratiometric imaging approach that provides a quantitative readout of the presence of mineral deposits in early calcifications. TPEF should enable non-destructive, high-resolution imaging of three-dimensional tissue specimens for the assessment of the presence of calcification.

Cardiac, mandibular and thymic phenotypical association indicates that cranial neural crest underlies bicuspid aortic valve formation in hamsters

Bicuspid aortic valve (BAV) is the most prevalent human congenital cardiac malformation. It may appear isolated, associated with other cardiovascular malformations, or forming part of syndromes. Cranial neural crest (NC) defects are supposed to be the cause of the spectrum of disorders associated with syndromic BAV. Experimental studies with an inbred hamster model of isolated BAV showed that alterations in the migration or differentiation of the cardiac NC cells in the embryonic cardiac outflow tract are most probably responsible for the development of this congenital valvular defect. We hypothesize that isolated BAV is not the result of local, but of early alterations in the behavior of the NC cells, thus also affecting other cranial NC-derived structures. Therefore, we tested whether morphological variation of the aortic valve is linked to phenotypic variation of the mandible and the thymus in the hamster model of isolated BAV, compared to a control strain. Our results show significant differences in the size and shape of the mandible as well as in the cellular composition of the thymus between the two strains, and in mandible shape regarding the morphology of the aortic valve. Given that both the mandible and the thymus are cranial NC derivatives, and that the cardiac NC belongs to the cephalic domain, we propose that the causal defect leading to isolated BAV during embryonic development is not restricted to local alterations of the cardiac NC cells in the cardiac outflow tract, but it is of pleiotropic or polytopic nature. Our results suggest that isolated BAV may be the forme fruste of a polytopic syndrome involving the cranial NC in the hamster model and in a proportion of affected patients.

Pathogenic Mechanisms of Bicuspid Aortic Valve Aortopathy

Bicuspid aortic valve (BAV) is the most common congenital valvular defect and is associated with ascending aortic dilation (AAD) in a quarter of patients. AAD has been ascribed both to the hemodynamic consequences of normally functioning and abnormal BAV morphology, and to the effect of rare and common genetic variation upon function of the ascending aortic media. AAD manifests in two overall and sometimes overlapping phenotypes: that of aortic root aneurysm, similar to the AAD of Marfan syndrome; and that of tubular AAD, similar to the AAD seen with tricuspid aortic valves (TAVs). These aortic phenotypes appear to be independent of BAV phenotype, have different embryologic origins and have unique etiologic factors, notably, regarding the role of hemodynamic changes inherent to the BAV phenotype. Further, in contrast to Marfan syndrome, the AAD seen with BAV is infrequently present as a strongly inherited syndromic phenotype; rather, it appears to be a less-penetrant, milder phenotype. Both reduced levels of normally functioning transcriptional proteins and structurally abnormal proteins have been observed in aneurysmal aortic media. We provide evidence that aortic root AAD has a stronger genetic etiology, sometimes related to identified common non-coding fibrillin-1 (FBN1) variants and other aortic wall protein variants in patients with BAV. In patients with BAV having tubular AAD, we propose a stronger hemodynamic influence, but with pathology still based on a functional deficit of the aortic media, of genetic or epigenetic etiology. Although it is an attractive hypothesis to ascribe common mechanisms to BAV and AAD, thus far the genetic etiologies of AAD have not been associated to the genetic etiologies of BAV, notably, not including BAV variants in NOTCH1 and GATA4.

A role for primary cilia in aortic valve development and disease

BACKGROUND

Bicuspid aortic valve (BAV) disease is the most common congenital heart defect, affecting 0.5-1.2% of the population and causing significant morbidity and mortality. Only a few genes have been identified in pedigrees, and no single gene model explains BAV inheritance, thus supporting a complex genetic network of interacting genes. However, patients with rare syndromic diseases that stem from alterations in the structure and function of primary cilia ("ciliopathies") exhibit BAV as a frequent cardiovascular finding, suggesting primary cilia may factor broadly in disease etiology.

RESULTS

Our data are the first to demonstrate that primary cilia are expressed on aortic valve mesenchymal cells during embryonic development and are lost as these cells differentiate into collagen-secreting fibroblastic-like cells. The function of primary cilia was tested by genetically ablating the critical ciliogenic gene Ift88. Loss of Ift88 resulted in abrogation of primary cilia and increased fibrogenic extracellular matrix (ECM) production. Consequentially, stratification of ECM boundaries normally present in the aortic valve were lost and a highly penetrant BAV phenotype was evident at birth.

CONCLUSIONS

Our data support cilia as a novel cellular mechanism for restraining ECM production during aortic valve development and broadly implicate these structures in the etiology of BAV disease in humans. Developmental Dynamics 246:625-634, 2017. © 2017 Wiley Periodicals, Inc.

Bicuspid aortic valve syndrome: a multidisciplinary approach for a complex entity

Bicuspid aortic valve (BAV) or bicuspid aortopathy is the most common congenital heart disease. It can be clinically silent and it is often identified as an incidental finding in otherwise healthy, asymptomatic patients. However, it can be dysfunctioning at birth, even requiring neonatal intervention, or, in time, lead to aortic stenosis, aortic insufficiency, and endocarditis, and also be associated with aortic aneurysm and aortic dissection. Given its prevalence and significant complications, it is estimated that BAV is responsible for more deaths and morbidity than the combined effects of all the other congenital heart defects. Pathology of BAV is still not well known and many questions are unresolved. In this manuscript we review some aspects on bicuspid aortopathy, a heterogeneous and frequent disease in which like some authors have previously described, complex gene environment are present. Further investigations and, what is more, multidisciplinary teams are needed to improve our knowledge on this really fascinating disease.

Specific circulating microRNA signature of bicuspid aortic valve disease

BACKGROUND

We aimed to determine the circulating miRNA expression profile associated with BAV and aortic dilation to provide diagnostic and prognostic biomarkers for BAV and/or aortic dilation.

METHODS AND RESULTS

We applied a miRNome-wide microarray approach using plasma samples (n = 24) from healthy tricuspid aortic valve individuals, BAV patients and BAV patients with aortic dilation to compare and identify the specific miRNAs associated with BAV and aortic dilation. In a second stage, the expression patterns of the miRNA candidates were validated by RT-qPCR in an independent cohort (n = 43). The miRNA microarray data and RT-qPCR analyses revealed that the expression levels of circulating miR-122, miR-130a and miR-486 are significantly influenced by the morphology of the aortic valve (bicuspid/tricuspid) and could be functionally involved in the regulation of TGF-β₁ signalling. Furthermore, the expression pattern of miR-718 in the plasma was strongly influenced by dilation of the ascending aorta. miR-718 expression was inversely correlated with the aortic diameter (R = -0.63, p = 3.1 × 10^-5) and was an independent predictor of aortic dilation (β = -0.41, p = 0.022). The genes targeted by miR-718 are involved in the regulation of vascular remodelling.

CONCLUSIONS

We propose that miR-122, miR-130a, miR-486 and miR-718 are new molecular features associated with BAV and aortic dilation principally by the activation of TGF-β₁ pathway and vascular remodelling mediated by VEGF signalling pathways.

Elevated circulating fasting glucagon-like peptide-1 in surgical patients with aortic valve disease and diabetes

BACKGROUND

Diabetes is a risk factor for peripheral, coronary, and cerebrovascular disease. In contrast, results also indicate that patients with diabetes have reduced prevalence of aortic aneurysms, although the mechanisms remain largely unknown. We hypothesize that altered endogenous secretion of the intestinal hormone glucagon-like peptide-1 (GLP-1)-previously shown to protect from aneurysm formation, and governing many of the mechanisms thought to be involved in aneurysm formation-may provide insights into the mechanisms underlying the inverse relationship of diabetes and aneurysm.

METHODS

We undertook a case-control study to characterize circulating plasma GLP-1 levels in diabetic and non-diabetic surgical patients with aortic valve disease, and with or without ascending aortic dilation. The cohort included patients with a bicuspid aortic valve (BAV), a common congenital disorder associated with ascending aortic aneurysm, as well as patients with a tricuspid aortic valve (TAV).

RESULTS

In our patient group, diabetes was characterized by a significant increase in fasting plasma GLP-1 levels. Further, we show that aortic dilation in these patients was associated with a significant increase in fasting plasma GLP-1, although a significant increase in the intact and bioactive peptide could not be detected in BAV patients with aortic dilation.

CONCLUSION

A subgroup of diabetic patients with aortic valve pathology have increased fasting plasma GLP-1 levels, which may be of importance for the low prevalence of aortic dilation in this patient group. Further, in TAV patients, GLP-1 secretion and plasma levels of intact GLP-1 are upregulated in association with aortic dilation, possibly indicating a compensatory mechanism.

Calcific aortic stenosis

Calcific aortic stenosis (AS) is the most prevalent heart valve disorder in developed countries. It is characterized by progressive fibro-calcific remodelling and thickening of the aortic valve leaflets that, over years, evolve to cause severe obstruction to cardiac outflow. In developed countries, AS is the third-most frequent cardiovascular disease after coronary artery disease and systemic arterial hypertension, with a prevalence of 0.4% in the general population and 1.7% in the population >65 years old. Congenital abnormality (bicuspid valve) and older age are powerful risk factors for calcific AS. Metabolic syndrome and an elevated plasma level of lipoprotein(a) have also been associated with increased risk of calcific AS. The pathobiology of calcific AS is complex and involves genetic factors, lipoprotein deposition and oxidation, chronic inflammation, osteoblastic transition of cardiac valve interstitial cells and active leaflet calcification. Although no pharmacotherapy has proved to be effective in reducing the progression of AS, promising therapeutic targets include lipoprotein(a), the renin-angiotensin system, receptor activator of NF-κB ligand (RANKL; also known as TNFSF11) and ectonucleotidases. Currently, aortic valve replacement (AVR) remains the only effective treatment for severe AS. The diagnosis and staging of AS are based on the assessment of stenosis severity and left ventricular systolic function by Doppler echocardiography, and the presence of symptoms. The introduction of transcatheter AVR in the past decade has been a transformative therapeutic innovation for patients at high or prohibitive risk for surgical valve replacement, and this new technology might extend to lower-risk patients in the near future.