Towards an individualized approach to bicuspid aortopathy: different valve types have unique determinants of aortic dilatation

Changes in aorta hemodynamics in Left-Right Type 1 bicuspid aortic valve patients after replacement with bioprosthetic valves: An in-silico study

Bicuspid aortic valve (BAV) is the most common cardiac congenital abnormality with a high rate of concomitant aortic valve and ascending aorta (AAo) pathologic changes throughout the patient's lifetime. The etiology of BAV-related aortopathy was historically believed to be genetic. However, recent studies theorize that adverse hemodynamics secondary to BAVs also contribute to aortopathy, but their precise role, specifically, that of wall shear stress (WSS) magnitude and directionality remains controversial. Moreover, the primary therapeutic option for BAV patients is aortic valve replacement (AVR), but the role of improved post-AVR hemodynamics on aortopathy progression is also not well-understood. To address these issues, this study employs a computational fluid dynamics model to simulate personalized AAo hemodynamics before and after TAVR for a small cohort of 6 Left-Right fused BAV patients. Regional distributions of five hemodynamic metrics, namely, time-averaged wall shear stress (TAWSS) and oscillating shear index (OSI), divergence of wall shear (DWSS), helicity flux integral & endothelial cell activation potential (ECAP), which are hypothesized to be associated with potential aortic injury are computed in the root, proximal and distal ascending aorta. BAVs are characterized by strong, eccentric jets, with peak velocities exceeding 4 m/s and axially circulating flow away from the jets. Such conditions result in focused WSS loading along jet attachment regions on the lumen boundary and weaker, oscillating WSS on other regions. The jet attachment regions also show alternating streaks of positive and negative DWSS, which may increase risk for local tissue stretching. Large WSS magnitudes, strong helical flows and circumferential WSS have been previously implicated in the progression of BAV aortopathy. Post-intervention hemodynamics exhibit weaker, less eccentric jets. Significant reductions are observed in flow helicity, TAWSS and DWSS in localized regions of the proximal AAo. On the other hand, OSI increases post-intervention and ECAP is observed to be low in both pre- and post-intervention scenarios, although significant increases are also observed in this ECAP. These results indicate a significant alleviation of pathological hemodynamics post AVR.

Navigating the challenges of bicuspid aortic valve-aortopathy

Bicuspid aortic valve (BAV) is a congenital heart defect that affects 0.5-2% of the general population with familial predominance. The modifications in hemodynamics and structure change at cellular level contribute to the dilation of aorta, resulting in bicuspid aortopathy, which can result in catastrophic aortic events. The American Heart Association recommends screening first-degree relatives of patients with bicuspid aortic valve and aortic root disease. BAV may or may not be associated with a syndrome, with the non-syndromic variety having a higher chance of predisposition to congenital and vascular abnormalities. Many genes have been implicated in the etiology of non-syndromic aortic aneurysm such as ACTA2, MYH11, FLNA, and SMAD3. Common diagnostic modalities include transthoracic echocardiography (TTE), transesophageal echocardiography (TEE), multi system computer tomography (MSCT), and cardiac MRI. Medical management reduces the rate of disease progression and surgical management is indicated based on the diameter of the ascending aorta, which differs in American and European guidelines. Our article aims to explore the current understanding of the pathophysiology, clinical aspects, and surgical management of bicuspid aortic valve disease. Additionally, we have included a discussion on the management of this condition in special populations, such as athletes and pregnant women, who require distinct treatment recommendations.

Location of Aortic Enlargement and Risk of Type A Dissection at Smaller Diameters

BACKGROUND

Previous work has demonstrated that more than one-half of acute type A aortic dissections (ATADs) occur at a maximal aortic diameter (MAD) of <5.5 cm. However, no analysis has investigated whether ATAD risk at smaller MADs is more common with modest dilation of the aortic root (AR) or supracoronary ascending aorta (AA) in patients without genetically triggered aortopathy.

OBJECTIVES

This study sought to determine if the segment of modest aortic dilation affects risk of ATAD.

METHODS

Using the International Registry of Acute Aortic Dissection (IRAD) database from May 1996 to October 2016, we identified 667 ATAD patients with MAD <5.5 cm. Patients were stratified by location of the largest proximal aortic segment (AR or AA). Patients with known genetically triggered aortopathy were excluded. MADs at time of dissection were compared between AR and AA groups. Secondary outcomes included operation, postoperative outcomes, and long-term survival.

RESULTS

Of patients with ATAD at an MAD <5.5 cm, 79.5% (n = 530) were in the AA group and 20.5% (n = 137) in the AR group. Modestly dilated ARs (median MAD 4.6 cm [IQR: 4.1-5.0 cm]) dissected at a significantly smaller diameter than modestly dilated AAs (median MAD 4.8 cm [IQR: 4.4-5.1 cm]) (P < 0.01). AR patients were significantly younger than AA patients (58.5 ± 13.0 years vs 63.2 ± 13.3 years; P < 0.01) and more commonly male (78% vs 65%; P < 0.01). Postoperative and long-term outcomes did not differ between groups.

CONCLUSIONS

ATAD appears to occur at smaller diameters in patients with modest dilation in the AR vs the AA (4.6 vs 4.8 cm). These findings may have implications for future consensus guidelines regarding the management of patients with aortic disease.

Natural history of bicuspid aortic valves and ascending aortic aneurysms: Aortic center experience

BACKGROUND AND AIM

The American Association of Thoracic Surgery published guidelines in 2018 encouraging regular surveillance rather than surgical intervention for ascending aortic aneurysms under 5.5 cm in both bicuspid aortic valve (BAV) and tricuspid aortic valve (TAV) patients. Since then, there have been limited studies reporting outcomes, especially by valve type. We aimed to analyze clinical outcomes including survival and aortic events in a cohort of BAV and TAV patients with ascending aortic aneurisms followed conservatively with routine computerized tomography  (CT) surveillance per current guidelines.

METHODS

We followed 188 patients in our clinic between 2016 and 2019; 147 had two or more CT scans which allowed measurement of aortic growth. Echocardiogram data was evaluated for each patient. We identified similar cohorts of BAV (n = 32) and TAV (n = 64) patients matched by age, sex, hypertension, smoking history, family history of aortic disease, coronary artery disease, and hyperlipidemia. Univariate and multivariate analyses of the unmatched cohorts were performed.

RESULTS

The mean aneurysm size was 4.3 ± 0.58 cm with 95% confidence interval (3.14, 5.46). This did not differ between BAV and TAV patients, nor did aneurysm growth rates. Overall adverse event rate (dissection, rupture, and death) was low for the entire cohort (BAV group, 3% and TAV group, 3.5%). Survival at 10 years for the entire cohort was 90 ± 32%.

CONCLUSIONS

Regardless of aortic valve type, there was a similar natural history and low adverse event rate. In the absence of risk factors, conservative management can be accomplished with minimal risk to the patient.

Wall Shear Stress Predicts Aortic Dilation in Patients With Bicuspid Aortic Valve

OBJECTIVES

This study sought to assess the predictive value of wall shear stress (WSS) for colocalized ascending aorta (AAo) growth rate (GR) in patients with bicuspid aortic valve (BAV).

BACKGROUND

BAV is associated with AAo dilation, but there is limited knowledge about possible predictors of aortic dilation in BAV patients with BAV. An increased WSS has been related to aortic wall damage in patients with BAV, but no previous prospective study tested its predictive value for dilation rate. Recently, a registration-based technique for the semiautomatic mapping of aortic GR has been presented and validated.

METHODS

Forty-seven patients with BAV free from valvular dysfunction prospectively underwent 4-dimensional flow cardiac magnetic resonance to compute WSS and subsequent follow-up with 2 electrocardiogram-gated high-resolution contrast-enhanced computed tomography angiograms for GR assessment.

RESULTS

During a median follow-up duration of 43 months, mid AAo GR was 0.24 mm/year. WSS and its circumferential component showed statistically significant association with mid AAo GR in bivariate (P = 0.049 and P = 0.014, respectively) and in multivariate analysis corrected for stroke volume and either baseline AAo diameter (P = 0.046 and P = 0.014, respectively) or z-score (P = 0.036 and P = 0.012, respectively). GR mapping further detailed that GR was heterogeneous in the AAo and that circumferential WSS, but not WSS magnitude, showed statistically significant positive associations with GR in the regions with the fastest growth.

CONCLUSIONS

4D flow cardiac magnetic resonance-derived WSS and, in particular, its circumferential component predict progressive dilation of the ascending aorta in patients with BAV. Thus, the assessment of WSS may be considered in the follow-up of these patients.

Valve disease and aortopathy associations of bicuspid aortic valve phenotypes differ between men and women

OBJECTIVE

Determine whether associations between bicuspid aortic valve (BAV) phenotypes, valve disease and aortopathy differ between sexes.

METHODS

1045 patients with BAV (76.0% men, n=794) from two surgical centres were included in this cross-sectional study. Valve phenotype was classified intraoperatively as right-left (RL), right-non-coronary (RN), left-non-coronary (LN) or 2-sinus BAV. Echocardiography was used to determine type and degree of valve disease, and aortic dimensions. Aortic dilatation was defined as diameter ≥4.5 cm.

RESULTS

RL was the most common phenotype (73.6%), followed by RN (16.2%), 2-sinus BAV (9.2%) and LN (1.1%), with no difference in phenotype distribution between men and women (p=0.634). Aortic valve insufficiency (AI) prevalence differed significantly with valve phenotype in men (p=0.047), with RL and LN having the highest prevalence (34.1% and 44.0%, respectively). In women, RN had a higher proportion of AI than RL (21.3% vs 7.3%, p=0.017). Men with RL had larger root dimensions, in particular at the sinus (mean difference 0.24 cm compared with RN, p=0.002). Men with 2-sinus BAV had the highest prevalence of root phenotype dilatation (7.0%, other phenotypes ≤2.3%, p=0.031), whereas women with 2-sinus BAV did not have root dilatation and smaller sinus dimensions (mean difference: 0.35 cm compared with RL, p=0.021). Aortic root segments were larger in men with AI compared with aortic stenosis (sinus mean difference: 0.40 cm, p<0.001). The difference was even larger in women (mean difference: 0.78 cm, p<0.001), and women with AI also had larger tubular segments (mean difference: 0.61 cm, p=0.001).

CONCLUSIONS

There are significant sex differences in clinical associations of BAV phenotypes, which should be considered in further studies on the role of phenotypes in individualised patient management.

MicroRNAs involve in bicuspid aortic aneurysm: pathogenesis and biomarkers

The incidence of bicuspid aortic valves (BAV) is high in the whole population, BAV-related thoracic aortic aneurysm (TAA) is accompanied by many adverse vascular events. So far, there are two key points in dealing with BAV-related TAA. First is fully understanding on its pathogenesis. Second is optimizing surgical intervention time. This review aims to illustrate the potential role of miRNAs in both aspects, that is, how miRNAs are involved in the occurrence and progression of BAV-related TAA, and the feasibilities of miRNAs as biomarkers.

Assessing the methodology used to study the ascending aorta haemodynamics in bicuspid aortic valve

Aims

Modern imaging techniques provide evermore-detailed anatomical and physiological information for use in computational fluid dynamics to predict the behaviour of physiological phenomena. Computer modelling can help plan suitable interventions. Our group used magnetic resonance imaging and computational fluid dynamics to study the haemodynamic variables in the ascending aorta in patients with bicuspid aortic valve before and after isolated tissue aortic valve replacement. Computer modelling requires turning a physiological model into a mathematical one, solvable by equations that undergo multiple iterations in four dimensions. Creating these models involves several steps with manual inputs, making the process prone to errors and limiting its inter- and intra-operator reproducibility. Despite these challenges, we created computational models for each patient to study ascending aorta blood flow before and after surgery.

Methods and results

Magnetic resonance imaging provided the anatomical and velocity data required for the blood flow simulation. Patient-specific in- and outflow boundary conditions were used for the computational fluid dynamics analysis. Haemodynamic variables pertaining to blood flow pattern and derived from the magnetic resonance imaging data were calculated. However, we encountered problems in our multi-step methodology, most notably processing the flow data. This meant that other variables requiring computation with computational fluid dynamics could not be calculated.

Conclusion

Creating a model for computational fluid dynamics analysis is as complex as the physiology under scrutiny. We discuss some of the difficulties associated with creating such models, along with suggestions for improvements in order to yield reliable and beneficial results.

Bicuspid aortic valve disease - the influence of valve morphotype on age at and types of surgical treatment

BACKGROUND

Patients with bicuspid aortic valve (BAV) with zero or two raphes have been under-represented in previous studies. Whether these patients have unique clinical courses remains unclear. We describe the indications for and types of surgery in patients with BAV, and describe differences between valve morphotypes.

METHODS

Adults who had undergone aortic and/or aortic valve surgery for BAV disease at our centres were identified and classified according to the Sievers definitions.

RESULTS

317 patients were included (74.4% male, median age at surgery 62 years). Of these, 187 (59.0%) had aortic valve surgery, 7 (2.2%) aortic surgery, 120 (37.9%) combined valve and aortic surgery and 3 had a Ross procedure. Most patients had aortic stenosis (71.9%), followed by aortic regurgitation (16.7%). 30-day mortality was low (1.6%).The commonest valve morphology was type-1 (one raphe) in 89.6%; type-0 (no raphes) occurred in 7.9% and type-2 (two raphes) in 2.5%. Patients with type-2 valves were substantially younger at time of surgery than type-1 patients (median 36 vs 63 years, p = 0.008). A higher proportion of patients with type-0 valves required aortic surgery than those with type-1 (68.0% vs 37.3%, p = 0.007). There were no differences between groups for the indication for surgery, valvular abnormality or 30-day mortality.

CONCLUSIONS

The number of BAV raphes was independently and significantly associated with age at surgery and the need for aortic intervention. Patients with type 0 and type 2 valves are a small but important proportion of the BAV population, potentially requiring different clinical surveillance and management.

Natural history and outcomes of non-replaced aortic sinuses in patients with bicuspid aortic valves

BACKGROUND

Enlargement of the sinus of Valsalva (SOV) is common in patients with bicuspid aortic valves (BAV), and management at the time of aortic valve replacement (AVR) and concomitant ascending aorta replacement/repair is controversial.

METHODS

Between January 2000 and July 2017, 400 patients with BAV underwent AVR and concomitant ascending aorta repair (79%, graft replacement; 21%, aortoplasty). To assess the impact of the initial SOV dimension on future dilatation and outcomes, patients were stratified into two groups: SOV<40mm (n=209) and SOV≥40mm (n=191).

RESULTS

Patients with SOV≥40 mm were older, and more often male. At a median follow-up of 8.1 years (IQR 7.4-9.1), 6 patients underwent reoperations on the ascending or sinus portion of the aorta due to aneurysmal dilatation; enlargement of the sinus was the primary indication for operation in one patient. Adjusted analysis showed that baseline SOV and SOV dimension over time were not associated with late outcomes. A gradual increase in SOV diameter over time was identified (P=0.004). Patients with smaller baseline SOV diameters showed an initial early decrease in diameter followed by gradual increase, while those with larger baseline diameters had a stable early phase followed by gradual dilatation.

CONCLUSIONS

Ascending aorta replacement may lead to an initial remodeling/stabilizing effect on the spared bicuspid aortic root, which is more pronounced in patients with lower SOV diameters. In addition, our data demonstrate that the retained aortic sinuses enlarge slowly, and within the limited follow-up of our study, SOV diameter was not a risk factor for survival or reoperation.

Transcatheter Aortic Valve Replacement in Bicuspid Aortic Valve Stenosis

After 15 years of successive randomized, controlled trials, indications for transcatheter aortic valve replacement (TAVR) are rapidly expanding. In the coming years, this procedure could become the first line treatment for patients with a symptomatic severe aortic stenosis and a tricuspid aortic valve anatomy. However, randomized, controlled trials have excluded bicuspid aortic valve (BAV), which is the most frequent congenital heart disease occurring in 1% to 2% of the total population and representing at least 25% of patients 80 years of age or older referred for aortic valve replacement. The use of a less invasive transcatheter therapy in this elderly population became rapidly attractive, and approximately 10% of patients currently undergoing TAVR have a BAV. The U.S. Food and Drug Administration and the "European Conformity" have approved TAVR for low-risk patients regardless of the aortic valve anatomy whereas international guidelines recommend surgical replacement in BAV populations. Given this progressive expansion of TAVR toward younger and lower-risk patients, heart teams are encountering BAV patients more frequently, while the ability of this therapy to treat such a challenging anatomy remains uncertain. This review will address the singularity of BAV anatomy and associated technical challenges for the TAVR procedure. We will examine and summarize available clinical evidence and highlight critical knowledge gaps regarding TAVR utilization in BAV patients. We will provide a comprehensive overview of the role of computed tomography scans in the diagnosis, and classification of BAV and TAVR procedure planning. Overall, we will offer an integrated framework for understanding the current role of TAVR in the treatment of bicuspid aortic stenosis and for guiding physicians in clinical decision-making.

The Association between Morphological and Functional Characteristics of the Bicuspid Aortic Valve and Bicuspid Aortopathy

Objective

To identify the association between morphological and functional characteristics of the bicuspid aortic valve (BAV) and bicuspid aortopathy and to identify the determinants of aortic dilatation using transthoracic echocardiography (TTE) and cardiac computed tomography (CCT).

Materials and Methods

This study included 312 subjects (mean [SD] age, 52.7 [14.3] years; 227 males [72.8%]) who underwent TTE and CCT. The BAVs were classified by anterior-posterior (BAV-AP) or right-left (BAV-RL) orientation of the cusps and divided according to the presence (raphe+) or absence of a raphe (raphe−) based on the CCT and intraoperative findings. The dimensions of the sinus of Valsalva and the proximal ascending aorta were measured by CCT. We assessed the determinants of aortic root and proximal ascending aortic dilatation (size index > 2.1 cm/m²) by Univariable and multivariable logistic regression analyses.

Results

Of the 312 patients, BAV-AP was present in 188 patients (60.3%), and 185 patients (59.3%) were raphe+. Moderate-to-severe aortic stenosis (AS) was the most common hemodynamic abnormality (54.8%). The most common type of aortopathy was the combined dilated root and mid-ascending aortic phenotype (62.5%). On multivariable analysis, age and AS severity were significantly associated with aortic root dilatation (p < 0.05), and age, sex, and AS severity were significantly associated with ascending aortic dilatation (p < 005). However, the orientation of the cusps, presence of a raphe, and severity of aortic regurgitation were not associated with aortic root and ascending aortic dilatation.

Conclusion

BAV morphological characteristics were not determinants of aortic dilatation. Age, sex, and AS severity were predictors of bicuspid aortopathy. Therefore, age, sex, and AS severity, rather than valve morphology, need to be considered when planning treatment for BAV patients.

Does the Leaflet Fusion Subtype Affect Pattern and Rate of Growth in BAV Aortopathy?: A Study of 102 BAV Aortopathy Cases With A Literature Review

BACKGROUND

Bicuspid aortic valves (BAV) and related aortopathy remain an intriguing topic. Not all BAVs get diseased and around 40% would develop aortic dilatation in their lifetime. If haemodynamic theory is to be believed, then leaflet fusion pattern should have an impact. This study sought to compare the association of aortic morphologies and rate of growth in a set of 102 BAV acropathies operated at a single centre, based on the fusion patterns.

METHODS

Data on aortic valve replacements over a 10-year period was analysed from a prospectively maintained database. Of the 198 BAV undergoing surgery, 102 had aortic dilatation above 40 mm on echocardiogram. These underwent computed tomography (CT) aortograms and were followed up as a part of a database. The impact of leaflet fusion patterns on aortic dilatation pattern and rate was analysed.

RESULTS

Of the 102, two patients had type 0 pathology and one had left-noncoronary (LN) leaflet fusion. Seventy-four (74) had type 1A or left-right (RL) fusion and 25 had type 1B right-noncoronary (RN) fusion. RL fusion had more males, were taller, bigger and had more proportion of aortic stenosis (AS). Aortic diameters, angles and growth rates at root, ascending/descending aorta and arch were not different. Regression analyses for size or growth did not show any significant impact of fusion pattern.

CONCLUSIONS

Left-right fusion pattern comprised three-quarters of BAV in this cohort and these patients were bigger, taller and had a greater proportion of males with increased rate of aortic stenosis. Despite these differences, there was no significant impact of fusion pattern on aortic size or rate of growth.

Haemodynamic assessment of bicuspid aortic valve aortopathy: a systematic review of the current literature

Both genetic and haemodynamic theories explain the aetiology, progression and optimal management of bicuspid aortic valve aortopathy. In recent years, the haemodynamic theory has been explored with the help of magnetic resonance imaging and computational fluid dynamics. The objective of this review was to summarize the findings of these investigations with focus on the blood flow pattern and associated variables, including flow eccentricity, helicity, flow displacement, cusp opening angle, systolic flow angle, wall shear stress (WSS) and oscillatory shear index. A structured literature review was performed from January 1990 to January 2018 and revealed the following 3 main findings: (i) the bicuspid aortic valve is associated with flow eccentricity and helicity in the ascending aorta compared to healthy and diseased tricuspid aortic valve, (ii) flow displacement is easier to obtain than WSS and has been shown to correlate with valve morphology and type of aortopathy and (iii) the stenotic bicuspid aortic valve is associated with elevated WSS along the greater curvature of the ascending aorta, where aortic dilatation and aortic wall thinning are commonly found. We conclude that new haemodynamic variables should complement ascending aorta diameter as an indicator for disease progression and the type and timing of intervention. WSS describes the force that blood flow exerts on the vessel wall as a function of viscosity and geometry of the vessel, making it a potentially more reliable marker of disease progression.

Surgical management of the aorta in BAV patients

Patients with a bicuspid aortic valve (BAV) frequently develop aneurysms of the aortic root and tubular ascending aorta. Aneurysms of the aortic arch, in the absence of concomitant aortopathies, are much less common. According to the 2018 American Association of Thoracic Surgery consensus guidelines on BAV-related aortopathy, prophylactic surgical aortic repair / replacement is recommended starting at a maximum aortic diameter of 50 mm in patients with risk factors. Concomitant aortic surgery is also recommended at an aortic diameter of 45 mm in those patients with other indications for cardiac surgery (most commonly aortic valve procedures). The ultimate goal of prophylactic aortic surgery is the prevention of aortic catastrophes, e.g. aortic rupture or acute aortic dissection, which are associated with high morbidity and mortality. The surgical technique used - in elective and emergency cases - depends on the involvement and nature of the aortic valve disease, as well as the extent of aortic aneurysm formation. The current review focusses on the surgical management of the aortic root, tubular ascending aorta, and proximal aortic arch in BAV patients. Despite the abovementioned recommendations, many BAV patients develop acute aortic syndromes below the recommended aortic diameter thresholds. Further research is therefore required in order to identify high-risk BAV subgroups that would benefit from earlier surgical repair.

The science of BAV aortopathy

The aortopathy associated with bicuspid aortic valve (BAV) is an epidemiologically relevant source of chronic and acute aortic disease (aneurysm and dissection). However, its pathogenesis is still the object of scientific uncertainties and debates. Indeed, the mechanisms determining the diseases of the ascending aorta in BAV patients are most likely complex and multifactorial, i.e. resulting from variable modes of interplay between genetic and hemodynamic factors. Although few scientific studies have so far taken into adequate account this complexity, leaving the precise sequence of pathogenetic events still undiscovered, the accumulated evidence from previous research approaches have at least brought about important insights. While genetic studies have so far identified variants relevant to either valve malformation or aortic complications (including those in the genes NOTCH1, TGFBR2, ACTA2, GATA5, NKX2.5, SMAD6, ROBO4), however each explaining not more than 5% of the study population, other investigations have thoroughly described both the flow features, with consequent forces acting on the arterial wall (including skewed flow jet direction, rotational flow, wall shear stress), and the main changes in the molecular and cellular wall structure (including extracellular matrix degradation, smooth muscle cell changes, oxidative stress, unbalance of TGF-β signaling, aberrant endothelial-to-mesenchymal transition). All of this evidence, together with the recognition of the diverse phenotypes that the aortopathy can assume in BAV patients, holding possible prognostic significance, is reviewed in this chapter. The complex and multifaceted body of knowledge resulting from clinical and basic science studies on BAV aortopathy has the potential to importantly influence modes of clinical management of this disease in the near future.

Functional characterization and circulating expression profile of dysregulated microRNAs in BAV-associated aortopathy

Compelling evidence has shown that microRNAs (miRs) are involved in the pathophysiology of BAV-associated aortopathy. The purpose of this study was to assess the biological role as well as the circulating expression of two miRs (miR-424-3p and miR-3688-3p) that have been previously identified as significantly dysregulated in thoracic aortic aneurysm specimens of BAV patients. Bioinformatic tools were used to predict miR gene targets followed by functional validation transfecting synthetic miR mimics and negative controls into human aortic smooth muscle cells (HASMCs). Levels of miRs and target genes were evaluated by qRT-PCR. The circulating miR expression profile analysis was assessed on plasma samples collected from a cohort of 72 patients with aortopathy including 39 BAV (33 males; 58 ± 13 years) and 33 TAV patients (26 males; 67 ± 9 years). Computational analysis revealed that SMAD7 and YAP1 were potential targets of miR-424-3p and miR-3688-3p, respectively. Transfection with mimics confirmed a significantly decreased gene expression of SMAD7 and YAP1 compared to mimic negative control (p = 0.04 and p = 0.0005, respectively) or blank control (p = 0.01 and p = 0.0007, respectively). Overexpression of miR-3688-3p also significantly upregulated pro-apoptotic caspase-3 gene expression compared to mimic negative control (p = 0.02) or blank control (p = 0.01). Furthermore, a significant down-regulation of the circulating miR-424-3p was observed in BAV compared to TAV patients (p = 0.001). In multiple linear regression analysis, the aortic valve morphology (β = - 0.29, p = 0.04) and the presence of aortic stenosis (β = - 0.28, p = 0.03) had a significant effect on the miR-424-3p expression. In conclusion, our study demonstrated that miR-424-3p and miR-3688-3p directly targeted SMAD7 and YAP1 in HASMCs, pivotal genes of the TGF-β and Hippo-signaling pathways. Circulating miR-424-3p was also found to be significantly decreased in BAV patients when compared to TAV patients, especially in patients with aortic stenosis. Further large studies of well-characterized BAV patient cohorts are needed to define the clinical significance of the miR-424-3p.

Bicuspid Aortic Valve in 2 Model Species and Review of the Literature

Bicuspid aortic valve (BAV) is the most common human congenital cardiac malformation. Although the etiology is unknown for most patients, formation of the 2 main BAV anatomic types (A and B) has been shown to rely on distinct morphogenetic mechanisms. Animal models of BAV include 2 spontaneous hamster strains and 27 genetically modified mouse strains. To assess the value of these models for extrapolation to humans, we examined the aortic valve anatomy of 4340 hamsters and 1823 mice from 8 and 7 unmodified strains, respectively. In addition, we reviewed the literature describing BAV in nonhuman mammals. The incidences of BAV types A and B were 2.3% and 0.03% in control hamsters and 0% and 0.3% in control mice, respectively. Hamsters from the spontaneous model had BAV type A only, whereas mice from 2 of 27 genetically modified strains had BAV type A, 23 of 27 had BAV type B, and 2 of 27 had both BAV types. In both species, BAV incidence was dependent on genetic background. Unlike mice, hamsters had a wide spectrum of aortic valve morphologies. We showed interspecific differences in the occurrence of BAV between humans, hamsters, and mice that should be considered when studying aortic valve disease using animal models. Our results suggest that genetic modifiers play a significant role in both the morphology and incidence of BAV. We propose that mutations causing anomalies in specific cardiac morphogenetic processes or cell lineages may lead to BAV types A, B, or both, depending on additional genetic, environmental, and epigenetic factors.

Utilizing wall shear stress as a clinical biomarker for bicuspid valve-associated aortopathy

PURPOSE OF REVIEW

Bicuspid aortic valve (BAV) results from fusion of two adjacent aortic valve cusps, and is associated with dilatation of the aorta, known as BAV-associated aortopathy, or bicuspid aortopathy. Bicuspid aortopathy is progressive, increasing the risk of life-threatening clinical events, such as aortic dissection. Regular monitoring and timely intervention with prophylactic surgical resection of the proximal aorta is recommended.

RECENT FINDINGS

Aortopathy is heterogeneous among patients. Studies have shown that different flow patterns lead to specific phenotypes of aortopathy. Although not uniform, BAV morphology affects flow patterns. Recent work has demonstrated the role of wall shear stress (WSS) in driving aortopathy, and it is suggested that individualized WSS 'heat maps' can be used for clinically monitoring patients with BAV. WSS has the potential to be an imaging biomarker for directing resection timing, surgical strategies, and postsurgical follow-up care.

SUMMARY

Finding and validating noninvasive hemodynamic biomarkers of aortic risk to assist in the management of BAV patients is of clinical importance. Herein, we will review the latest findings pertaining to the utility of WSS as a specific biomarker of risk for BAV patients with aortopathy.

Does the pattern of bicuspid aortic valve leaflet fusion determine the success of the Ross procedure?

BACKGROUND

In addition to being associated with aortopathy, a bicuspid aortic valve (BAV) has been posed to be a risk factor for the dilation of the pulmonary autograft in the aortic position. The aim of this study is to assess the association between the subtype of native aortic valve leaflet fusion (right and noncoronary leaflets [R/N] vs right and left leaflets [R/L]) and autograft dilation and valve dysfunction after the Ross procedure.

METHODS

We performed a retrospective review of 43 patients with BAV who underwent a Ross procedure in our center from 1993 to 2013. Serial transthoracic echocardiography was used to measure changes in autograft and ascending aortic diameter over time. The aortic diameter was measured at four levels, and Z values were computed. Aortic dilation was defined as a Z value greater than 3.

RESULTS

The mean age at the time of the Ross procedure was 13.5 ± 9.2 years. R/L was the most prevalent native aortic valve subtype (R/L, n = 26, 61% vs R/N, n = 17, 39%). PreRoss procedure, aortic dilation was more frequent in patients with R/N fusion (P = .02), whereas the initial aortic valve gradient and grade of aortic insufficiency (AI) did not differ between the subgroups. At follow-up, (mean = 9.6 ± 4.3 years) dilation of the autograft and ascending aorta was seen more often in patients with R/N leaflet fusion (P = .03). Conversely, the prevalence of more than moderate AI was significantly higher in patients with R/L leaflet fusion (P = .03). There was no significant difference between groups among numbers of late reintervention on the aortic valve or root (P = .75); however the type of intervention varied by morphologic subtype. Patients with R/L fusion underwent more aortic valve replacements (AVRs) while patients with R/N fusion underwent more valve-sparing aortic root replacements.

CONCLUSIONS

After Ross procedure, both groups of patients were likely to have a combination of dilation of the aortic root and the tubular portion of the ascending aorta at follow-up. Patients with R/L fusion were more likely to have a prevalence of root dilation, while patients with R/N fusion were more likely to have tubular ascending aorta dilation. The R/L phenotype is associated with a slightly more rapid dilation at follow-up and is more likely to have postoperative autograft insufficiency. This information may serve to guide patient and procedure selection for AVR.

The American Association for Thoracic Surgery consensus guidelines on bicuspid aortic valve-related aortopathy: Full online-only version

Bicuspid aortic valve disease is the most common congenital cardiac disorder, being present in 1% to 2% of the general population. Associated aortopathy is a common finding in patients with bicuspid aortic valve disease, with thoracic aortic dilation noted in approximately 40% of patients in referral centers. Several previous consensus statements and guidelines have addressed the management of bicuspid aortic valve-associated aortopathy, but none focused entirely on this disease process. The current guidelines cover all major aspects of bicuspid aortic valve aortopathy, including natural history, phenotypic expression, histology and molecular pathomechanisms, imaging, indications for surgery, surveillance, and follow-up, and recommendations for future research. It is intended to provide clinicians with a current and comprehensive review of bicuspid aortic valve aortopathy and to guide the daily management of these complex patients.

Computational modeling of bicuspid aortopathy: Towards personalized risk strategies

This paper describes current advances on the application of in-silico for the understanding of bicuspid aortopathy and future perspectives of this technology on routine clinical care. This includes the impact that artificial intelligence can provide to develop computer-based clinical decision support system and that wearable sensors can offer to remotely monitor high-risk bicuspid aortic valve (BAV) patients. First, we discussed the benefit of computational modeling by providing tangible examples of in-silico software products based on computational fluid-dynamic (CFD) and finite-element method (FEM) that are currently transforming the way we diagnose and treat cardiovascular diseases. Then, we presented recent findings on computational hemodynamic and structural mechanics of BAV to highlight the potentiality of patient-specific metrics (not-based on aortic size) to support the clinical-decision making process of BAV-associated aneurysms. Examples of BAV-related personalized healthcare solutions are illustrated.

The role of hemodynamics in bicuspid aortopathy: a histopathologic study

BACKGROUND

A bicuspid aortic valve (BAV) is the most common congenital cardiac malformation and is associated with ascending aortic dilation in 60%-80% of patients. In this study, we aimed to address the role of hemodynamic influences on the development of aortopathy in BAV patients.

PATIENT AND METHODS

BAV (n=36) and tricuspid aortic valve (TAV) patients (n=17) undergoing aortic valve replacement underwent preoperative flow magnetic resonance imaging (MRI) assessment to detect the area of maximal flow-induced stress in the proximal aorta. Based on these MRI data, paired ascending aortic wall samples [i.e., area of maximal jet impact (jet sample) and the opposite aortic wall (nonjet sample)] were collected during surgery. To study and describe the effects of jet stream on the complete vascular wall, a pathology score was developed based on the recently published aortic consensus paper statement on surgical pathology of the aorta using routine histologic stainings (resorcin fuchsin, hematoxylin-eosin, and Movat) and immunohistochemistry (alpha smooth muscle actin, smooth muscle 22 alpha, platelet endothelial cell adhesion molecule).

RESULTS

Comparing the jet and nonjet samples in both BAV and TAV, regions of maximal jet impact did not show any difference in the pathology score in the adventitia and the middle and outer media. In the jet samples, the inner media however showed loss of actin expression in both BAV (P<.0001) and the TAV (P=.0074), and the intimal thickness was significantly enlarged in both patient groups (BAV P=.0005, TAV P=.0041), which was not accompanied by loss of elastic lamellae or vascular smooth muscle cell nuclei.

CONCLUSIONS

In our study population, we could not demonstrate a potential distinct role for hemodynamics in the development of aortopathy in BAV patients even if corrected for aortic diameter, raphe position, or whether the valve is stenotic or regurgitant. The intimal layer and inner media however showed alterations in all jet specimens.

Evolving Surgical Approaches to Bicuspid Aortic Valve Associated Aortopathy

Bicuspid aortic valve (BAV) is the most common congenital cardiac pathology which results from the fusion of two adjacent aortic valve cusps. It is associated with dilatation of the aorta, known as bicuspid valve-associated aortopathy or bicuspid aortopathy. Bicuspid aortopathy is progressive and is linked with adverse clinical events. Hence, frequent monitoring and early intervention with prophylactic surgical resection of the proximal aorta is often recommended. Over the past two decades resection strategies and surgical interventions have mainly been directed by surgeon and institution preferences. These practices have ranged from conservative to aggressive approaches based on aortic size and growth criteria. This strategy, however, may not best reflect the risks of important aortic events. A new set of guidelines was proposed for the treatment of bicuspid aortopathy. Herein, we will highlight the most recent findings pertinent to bicuspid aortopathy and its management in the context of a case presentation.

Evaluation of relationship between bicuspid aortic valve phenotype with valve dysfunction and associated aortopathy

Introduction: Morphology of bicuspid aortic valve (BAV) may have implication in the associated pathologies including aortic stenosis (AS), aortic insufficiency (AI) and aortic dilation. The aim of this study is to investigate the frequency and patterns of valvular dysfunction and aortopathy associated with different phenotypes of BAV in a referral center in northwest of Iran. Methods: In this prospective study patients who presented to our echocardiography lab between January 2014 and December 2015 and were diagnosed with BAV were assessed. Frequency of various BAV phenotypes and their association with valvular dysfunction and aortopathy was evaluated. A P value less than 0.05 was considered statistically significant. Results: The average age of the study patients was 40±16 years, with predominance of male sex (72%). Patients with anteroposteriorly located BAV (BAV-AP) phenotype constituted majority of our cases with prevalence of 62.7%, while 37.3% of cases had right-left (BAV-RL) located valves. BAV-RL patients when compared to BAV-AP patients had higher frequencies of dilated aortic arch (25% vs. 4.3%, P < 0.001), AS (56.3% vs. 31.4%, P < 0.001), mass or vegetation on aortic valve (14.3 vs. 6.4%, P = 0.023) and lower frequencies of dilated aortic root (42.9% vs. 57.4%, P = 0.01), aortic insufficiency (68.8% vs. 79.8%, P = 0.034) and co-arctation of aorta (3.6% vs. 11.7%, P = 0.01). Conclusion: There seems to be a relationship between various BAV phenotypes, and frequency and pattern of aortic valve dysfunction and aortopathy. These findings suggest that examining leaflet morphology in BAV might help in risk stratification of these patients.

Abnormal aortic stiffness in patients with bicuspid aortic valve: phenotypic variation determined by magnetic resonance imaging

The aim of this study was to assess aortic stiffness in patients with bicuspid aortic valve (BAV), and to determine if differences exist among the BAV phenotypes. Stiffness was measured by pulse wave velocity (PWV) determined using velocity-encoded magnetic resonance imaging (VENC-MRI). VENC-MRI was performed in 100 BAV patients and 45 normal controls. PWV was determined between the mid ascending and mid descending aorta. The BAV phenotypes were characterized using steady-state free precession (SSFP) images acquired across the face of the aortic valve, and classified as follows: right-left cusp (R-L) fusion, right and non-coronary cusp (R-NC) fusion, and left and non-coronary cusp (L-NC) fusion. The following BAV phenotypes were identified: 76 R-L, 23 R-NC, and 1 L-NC fusion. BAV patients demonstrated significantly greater PWV compared to normal controls, after adjusting for age (9.16 vs. 3.83 m/s; p < 0.0001). Furthermore, PWV was significantly greater in patients with R-NC fusion than those with R-L fusion phenotype (12.27 vs. 7.97 m/s; p < 0.001). There was significantly increased PWV from VENC-MRI in BAV patients compared to normal controls. Thisis the first to demonstrate the association of different BAV phenotypes and aortic stiffness. VENC-MRI PWV assessment potentially represents a novel parameter for enhanced surveillance and may alter surgical triage of aorta in this high risk group.

Bicuspid aortic valve morphology and its impact on aortic diameters-A systematic review with meta-analysis and meta-regression

AIM

To evaluate the impact of the 2 most common bicuspid aortic valve (BAV) morphology patterns [right-left (RL) vs right-noncoronary (RN) cusp fusion] on the aortic diameters and the impact of gender, aortic stenosis (AS), aortic regurgitation (AR), and age on the observed effects.

METHODS

The PubMed databases was searched up to December 31, 2016 to identify studies investigating the morphology of BAV and aortic diameters. Inclusion criteria were as follows: the data on diameter of sinuses of Valsalva (SVD) and/or ascending aorta (AAD) and BAV morphology. The additional characteristics [gender, AS and AR (% of patients with moderate or severe AS/AR) and mean age] were collected to perform a meta-regression analysis.

RESULTS

A total of 12 studies with 2192 patients with indexed AAD, 15 studies with 3104 patients with nonindexed AAD and 8 studies with 1271 patients with indexed SVD, and 16 studies with 3454 patients with nonindexed SVD were included. There was no difference between RL and RN group in indexed/nonindexed AAD-mean difference (MD): 0.06 mm/m² (95% CI: -0.65 to 0.77 mm/m² , P = .87) and -0.06 mm (95% CI: 1.10-0.97 mm, P = .91). Differently, the RL BAV was associated with larger indexed/nonindexed SVD than RN phenotype-MD: 1.66 mm/m² (95% CI: 0.83-2.49 mm/m² , P < .001) and 2.03 mm (95% CI: 0.97-3.09 mm, P < .001). Age, gender, AS, and AR had no influence on observed differences.

CONCLUSIONS

RL BAV phenotype is associated with larger SVD than RN BAV, and the observed differences are independent from aortic valve dysfunction degree, age, and gender.

Aortic Dilatation Associated With Bicuspid Aortic Valve: Relation to Sex, Hemodynamics, and Valve Morphology (the National Heart Lung and Blood Institute-Sponsored National Registry of Genetically Triggered Thoracic Aortic Aneurysms and Cardiovascular Conditions)

This study analyzed the impact of sex, hemodynamic profile, and valve fusion pattern on aortopathy associated with bicuspid aortic valve (BAV). The National Heart Lung and Blood Institute-sponsored National Registry of Genetically Triggered Thoracic Aortic Aneurysms and Cardiovascular Conditions (GenTAC) provided comprehensive information on a large population of well-characterized patients with BAV. Of 969 enrolled patients with BAV, 551 (57%, 77% male) had already undergone valvular and/or aortic surgery. Echocardiographic imaging data were available on 339 unoperated or preoperative participants who formed the basis of this study. BAV function was normal in 45 (14%), with a predominant aortic regurgitation (AR) in 127 (41%) and a predominant aortic stenosis (AS) in 76 (22%). Moderate-severe AR was associated with larger sinus of Valsalva (SOV) diameters compared with normal function and AS (all p <0.01). Moderate-severe AS was associated with a larger ascending aortic (AscAo) diameter compared with normal function (p = 0.003) but not with AR. The SOV diameter was larger in men than in women (3.7 ± 0.7 vs 3.3 ± 0.6 cm, p <0.0001), whereas AscAo diameters were comparable (3.9 ± 0.9 vs 3.7 ± 0.9 cm, p = 0.08). Right-left commissural fusion was associated with a larger SOV diameter (3.7 ± 0.7 vs 3.3 ± 0.6 cm, p <0.0001) compared with a right-noncoronary fusion pattern. Predominant AR was more common in men (45% vs 27%, p = 0.004), whereas AS was more common in women (29% vs 18%, p = 0.04). In conclusion, in the GenTAC Registry, AR was associated with diffuse (annular, SOV, and AscAo) enlargement, whereas moderate-severe AS was only associated with AscAo enlargement. Male sex and right-left cusp pattern of cusp fusion were associated with larger SOV diameters and a greater likelihood of AR, whereas women had a higher prevalence of AS.

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.

Evolution of Precision Medicine and Surgical Strategies for Bicuspid Aortic Valve-Associated Aortopathy

Bicuspid aortic valve (BAV) is a common congenital cardiac malformation affecting 1–2% of people. BAV results from fusion of two adjacent aortic valve cusps, and is associated with dilatation of the aorta, known as bicuspid valve associated aortopathy. Bicuspid valve aortopathy is progressive and associated with catastrophic clinical events, such as aortic dissection and rupture. Therefore, frequent monitoring and early intervention with prophylactic surgical resection of the proximal aorta is often recommended. However, the specific pattern of aortopathy is highly variable among patients, with different segments of the ascending aorta being affected. Individual patient risks are sometimes difficult to predict. Resection strategies are informed by current surgical guidelines which are primarily based on aortic size and growth criteria. These criteria may not optimally reflect the risk of important aortic events. To address these issues in the care of patients with bicuspid valve aortopathy, our translational research group has focused on validating use of novel imaging techniques to establish non-invasive hemodynamic biomarkers for risk-stratifying BAV patients. In this article, we review recent efforts, successes, and ongoing challenges in the development of more precise and individualized surgical approaches for patients with bicuspid aortic valves and associated aortic disease.

Fate of remnant sinuses of Valsalva in patients with bicuspid and trileaflet valves undergoing aortic valve, ascending aorta, and aortic arch replacement

OBJECTIVE

In patients presenting with aortic valvulopathy with concomitant ascending aortic aneurysm, surgical management of the sinus of Valsalva segment remains undefined, especially for moderately dilated aortic roots. In patients with this pathology undergoing aortic valve replacement with supracoronary ascending aorta replacement, we assessed the fate of the remnant preserved sinus of Valsalva segment stratified by aortic valve morphology and pathology.

METHODS

From 2002 to 2015, 428 patients underwent elective aortic valve replacement with supracoronary ascending aorta replacement. Patients were stratified on the basis of valvular morphology (bicuspid aortic valve [n = 254] and tricuspid aortic valve [n = 174]), valvular pathology (bicuspid aortic valve with aortic stenosis [n = 178], bicuspid aortic valve with aortic insufficiency [n = 76], tricuspid aortic valve with aortic stenosis [n = 61], tricuspid aortic valve with aortic insufficiency [n = 113]), and preoperative sinus of Valsalva dimensions (<40, 40-45, >45 mm).

RESULTS

Kaplan-Meier analysis revealed no significant difference in freedom from reoperation in tricuspid aortic valve versus bicuspid aortic valve (P = .576). Multivariable Cox regression model performed with sinus of Valsalva dimensions at baseline and follow-up as time-varying covariates did not adversely affect survival. A repeated-measure, mixed-effects model constructed to assess longitudinal sinus of Valsalva trends revealed that the retained sinus of Valsalva dimensions remain stable over long-term follow-up (discharge to ≥10 years), irrespective of valvular morphology/pathology (bicuspid aortic valve with aortic insufficiency, tricuspid aortic valve with aortic insufficiency, tricuspid aortic valve with aortic stenosis) and preoperative sinus of Valsalva groups (<40, 40-45, >45 mm).

CONCLUSIONS

In patients with nonaneurysmal sinuses of Valsalva undergoing aortic valve replacement with supracoronary ascending aorta replacement, the sinus segment can be preserved irrespective of the type of valvular pathology (aortic stenosis vs aortic insufficiency) or valvular morphology (bicuspid aortic valve vs tricuspid aortic valve). Aortic valve replacement with supracoronary ascending aorta replacement may have a stabilizing effect on the sinus segment over long-term follow-up in patients with tricuspid aortic valves or bicuspid aortic valves.

Association between bicuspid aortic valve morphotype and regional dilatation of the aortic root and trunk

Thoracic aortic disease, including thoracic aortic aneurysm (TAA), is frequently seen in patients with bicuspid aortic valve (BAV). We hypothesized that BAV morphotype would be associated with aortic aneurysm phenotypes but that other patient variables would significantly modify this relationship. 829 patients between 18 and 90 years with BAV and available raw imaging of the aortic valve and the ascending aorta to its mid-portion prior to aortic valve and aortic surgery were examined. The sinuses of Valsalva and proximal ascending aorta were measured from 2-dimensional co-planar echocardiographic images. We observed strong associations between patient habitus and raw and normalized dimensions of the aortic root and ascending aorta. Patients with R-L morphotype presented at an older age with larger aortic root but similar ascending aortic dimensions. After accounting for patient morphometric characteristics and severity of aortic valve disease, patients with R-L valve morphotype were marginally more likely to have an aortic root aneurysm (86% vs. 78%; P = 0.043), defined as aortic root dimension Z score ≥3. We observed only small differences in aortic dimensions between BAV morphotypes, that are eclipsed by variation in patient habitus. We interpret these findings to mean that BAV patients will not likely benefit from therapies based on aortic valve morphotype. Rather, we propose that all BAV patients should undergo longitudinal follow-up, independent of valve morphotype. Guidelines for aortic surgery based upon dimensions alone may be improved by considering patient characteristics such as age, body size and other characteristics.

Year in review: bicuspid aortopathy

PURPOSE OF REVIEW

This article outlines the key research contribution to bicuspid aortic valve (BAV) aortopathy over the past 18 months.

RECENT FINDINGS

Investigators have further defined the current gaps in knowledge and the scope of the clinical problem of BAV aortopathy. Support for aggressive resection strategies is waning as evidence mounts to suggest that BAV is not similar to genetic connective tissue disorders with respect to aortic risks. The role of cusp fusion patterns and valve-mediated hemodynamics in disease progression is a major area of discovery. Molecular and cellular mechanisms remain elusive and contradictory.

SUMMARY

BAV aortopathy is a major public health problem that remains poorly understood. New insights on valve-mediated hemodynamics using novel imaging modalities may lead to more individualized resection strategies and improved clinical guidelines.

Valve-Related Hemodynamics Mediate Human Bicuspid Aortopathy: Insights From Wall Shear Stress Mapping

BACKGROUND

Suspected genetic causes for extracellular matrix (ECM) dysregulation in the ascending aorta in patients with bicuspid aortic valves (BAV) have influenced strategies and thresholds for surgical resection of BAV aortopathy. Using 4-dimensional (4D) flow cardiac magnetic resonance imaging (CMR), we have documented increased regional wall shear stress (WSS) in the ascending aorta of BAV patients.

OBJECTIVES

This study assessed the relationship between WSS and regional aortic tissue remodeling in BAV patients to determine the influence of regional WSS on the expression of ECM dysregulation.

METHODS

BAV patients (n = 20) undergoing ascending aortic resection underwent pre-operative 4D flow CMR to regionally map WSS. Paired aortic wall samples (i.e., within-patient samples obtained from regions of elevated and normal WSS) were collected and compared for medial elastin degeneration by histology and ECM regulation by protein expression.

RESULTS

Regions of increased WSS showed greater medial elastin degradation compared to adjacent areas with normal WSS: decreased total elastin (p = 0.01) with thinner fibers (p = 0.00007) that were farther apart (p = 0.001). Multiplex protein analyses of ECM regulatory molecules revealed an increase in transforming growth factor β-1 (p = 0.04), matrix metalloproteinase (MMP)-1 (p = 0.03), MMP-2 (p = 0.06), MMP-3 (p = 0.02), and tissue inhibitor of metalloproteinase-1 (p = 0.04) in elevated WSS regions, indicating ECM dysregulation in regions of high WSS.

CONCLUSIONS

Regions of increased WSS correspond with ECM dysregulation and elastic fiber degeneration in the ascending aorta of BAV patients, implicating valve-related hemodynamics as a contributing factor in the development of aortopathy. Further study to validate the use of 4D flow CMR as a noninvasive biomarker of disease progression and its ability to individualize resection strategies is warranted.

The Association Between Aortic Valve Leaflet Morphology and Patterns of Aortic Dilation in Patients With Bicuspid Aortic Valves

BACKGROUND

Dilation of the aorta is a frequent complication in patients with bicuspid aortic valves. The aim of this study was to determine the relationship between the subtype of leaflet fusion, right and noncoronary leaflet (R/N) fusion versus right and left leaflet (R/L) fusion, and the patterns of aortic dilation and valve dysfunction in young patients with bicuspid aortic valves.

METHODS

We performed a retrospective review of 642 patients who presented with bicuspid aortic valves between 1994 and 2014. Of these patients, 210 (33%) had aortic dilation (z score >3) by echocardiogram. For each patient, the most recent study or the last study before intervention was reviewed.

RESULTS

Median patient age was 15 years (range, 0 to 40 years) with patients with R/N fusion being younger. The most prevalent subtype was R/N fusion (R/N, n = 114, 54% versus R/L, n = 96, 46%). Dilation of the ascending aorta was seen more often in patients with R/N fusion (R/N, 88% versus R/L, 68%; p = 0.004), whereas the prevalence of dilation of the sinuses of Valsalva was significantly higher in patients with R/L fusion (R/L, 46% versus R/N, 20%; p = 0.01). The magnitude of dilation differed as well. The z value of the sinuses of Valsalva was significantly higher in patients with R/L fusion (R/L, 2.03 versus R/N, 1.2; p = 0.003), whereas the z values of the ascending aorta and sinotubular junction were similar between the groups. Patients with R/N fusion were more likely to have aortic stenosis, and within the R/N group, patients with aortic insufficiency had a greater degree of ascending aorta dilation (p = 0.04).

CONCLUSIONS

Our study suggests that in young patients with bicuspid aortic valves and aortic dilation, aortic valve morphology may be associated with the patterns of aortic dilation and valve dysfunction. Patients with R/N fusion were more likely to have ascending aorta dilation, whereas patients with R/L fusion were more likely to have dilation of the aortic root. In addition, patients with R/N fusion presented at a younger age and were more likely to have aortic stenosis. Recognition of these differences may eventually be helpful for patient counseling and the planning of follow-up.

Aortopathy in patients with bicuspid aortic valve stenosis: role of aortic root functional parameters

OBJECTIVES

We prospectively examined functional characteristics of the aortic root and transvalvular haemodynamic flow in order to define factors associated with the severity of aortopathy in patients undergoing surgery for bicuspid aortic valve (BAV) stenosis.

METHODS

A total of 103 consecutive patients with BAV stenosis (mean age 61 ± 9 years, 66% male) underwent aortic valve replacement ± concomitant aortic surgery from January 2012 through March 2014. All patients underwent preoperative cardiac magnetic resonance imaging (MRI) in order to evaluate the systolic transvalvular flow and the following functional parameters: (i) angulation between the left ventricular outflow axis and the aortic root, (ii) geometrical orientation of residual aortic valve orifice and (iii) BAV cusp fusion pattern. MRI data were used to guide sampling of the ascending aorta during surgery [i.e. jet-sample from the area where the flow-jet impacts on the aortic wall and control sample from the opposite aortic wall (obtained from the aortotomy site)]. Aortopathy was quantified by means of a histological sum-score (0 to 21+) in each sample.

RESULTS

A significant correlation was found between histological sum-score in the jet-sample and the angle between the LV outflow axis and the aortic root (r = 0.6, P = 0.007). Moreover, there was a linear correlation between proximal aortic diameter and the angle between systolic flow-jet and ascending aortic wall (r = 0.5, P = 0.006). Logistic regression identified the angle between the LV outflow axis and the aortic root (OR 1.1, P = 0.04) and the angle between the flow-jet and the aortic wall (OR 1.2, P = 0.001) as independent predictors of an indexed proximal aortic diameter ≥22 mm/m(2).

CONCLUSIONS

Functional parameters of the aortic root may be used to predict the severity of aortopathy in patients with BAV stenosis, and may be useful in predicting future risk of aortic disease in such patients.