Clinical significance of the bicuspid aortic valve

Infective endocarditis with left to right intracardiac fistula due to Streptococcus anginosus - a rare complication caused by an even rarer bacterium

Although infective endocarditis (IE) has been described in reports dating from the Renaissance, the diagnosis still challenges and the outcome often surprises. In the course of time, diagnostic criteria have been updated and validated to reduce misdiagnosis. Some risk factors and epidemiology have shown dynamic changes since degenerative valvular disease became more predominant in developed countries, and the mean age of the affected population increased. Despite streptococci have been being well known as etiologic agents, some groups, although rare, have been increasingly reported (e.g., Streptococcus milleri.) Intracardiac complications of IE are common and have a worse prognosis, frequently requiring surgical treatment. We report a case of a middle-aged diabetic man who presented with prolonged fever, weight loss, and ultimately severe dyspnea. IE was diagnosed based on a new valvular regurgitation murmur, a positive blood culture for Streptococcus anginosus, an echocardiographic finding of an aortic valve vegetation, fever, and pulmonary thromboembolism. Despite an appropriate antibiotic regimen, the patient died. Autopsy findings showed vegetation attached to a bicuspid aortic valve with an associated septal abscess and left ventricle and aortic root fistula connecting with the pulmonary artery. A large thrombus was adherent to the pulmonary artery trunk and a pulmonary septic thromboemboli were also identified.

Bicuspid aortic cusp fusion morphology alters aortic three-dimensional outflow patterns, wall shear stress, and expression of aortopathy

BACKGROUND

Aortic 3-dimensional blood flow was analyzed to investigate altered ascending aorta (AAo) hemodynamics in bicuspid aortic valve (BAV) patients and its association with differences in cusp fusion patterns (right-left, RL versus right-noncoronary, RN) and expression of aortopathy.

METHODS AND RESULTS

Four-dimensional flow MRI measured in vivo 3-dimensional blood flow in the aorta of 75 subjects: BAV patients with aortic dilatation stratified by leaflet fusion pattern (n=15 RL-BAV, mid AAo diameter=39.9±4.4 mm; n=15 RN-BAV, 39.6±7.2 mm); aorta size controls with tricuspid aortic valves (n=30, 41.0±4.4 mm); healthy volunteers (n=15, 24.9±3.0 mm). Aortopathy type (0-3), systolic flow angle, flow displacement, and regional wall shear stress were determined for all subjects. Eccentric outflow jet patterns in BAV patients resulted in elevated regional wall shear stress (P<0.0125) at the right-anterior walls for RL-BAV and right-posterior walls for RN-BAV in comparison with aorta size controls. Dilatation of the aortic root only (type 1) or involving the entire AAo and arch (type 3) was found in the majority of RN-BAV patients (87%) but was mostly absent for RL-BAV patients (87% type 2). Differences in aortopathy type between RL-BAV and RN-BAV patients were associated with altered flow displacement in the proximal and mid AAo for type 1 (42%-81% decrease versus type 2) and distal AAo for type 3 (33%-39% increase versus type 2).

CONCLUSIONS

The presence and type of BAV fusion was associated with changes in regional wall shear stress distribution, systolic flow eccentricity, and expression of BAV aortopathy. Hemodynamic markers suggest a physiological mechanism by which the valve morphology phenotype can influence phenotypes of BAV aortopathy.

Risk of proximal aortic dissection in patients with bicuspid aortic valve: how to address this controversy?

The risk of acute aortic events in patients with bicuspid aortic valve (BAV) disease is a controversial issue. The real risk of aortic dissection in patients with BAV disease is unknown. An indirect assessment of this risk, however, could be gained with a more detailed understanding of the pathogenesis of BAV aortopathy. There are two major issues that should be clarified before one addresses the question of aortic dissection risk in BAV patients. The first issue, when analysing the data from previous BAV cohorts, is to determine what stage of BAV disease was present in the described patient population. In particular, was the risk of aortic dissection in BAV patients determined before or after aortic valve replacement (AVR) surgery? The second issue to consider is the functional state of the pathological valve within the observed population. In particular, did patients predominantly suffer from BAV stenosis or BAV insufficiency? Unfortunately, the vast majority of published reports do not separate between the different BAV phenotypes, thereby complicating interpretation of the results. Considering these two important clinical variables (i.e. the stage of BAV disease and the functional phenotype), we herein aim to explain the inconsistency of the published data with regard to the risk of aortic dissection in patients with BAV disease.

Factors affecting a dilated ascending aorta in patients with bicuspid aortic valve: the relevance of valve anatomy, body size and age

PURPOSE

Information regarding the appropriate management of patients with moderately dilated ascending aortas is limited. We investigated factors affecting ascending aortic dilatation in BAV patients, such as anatomy, body size and age.

METHODS

We evaluated 130 patients with BAV (age, 59.9 ± 16.1 years; body surface area (BSA), 1.58 ± 0.20 m(2)) who underwent aortic valve surgery. The cusp configuration was determined according to the presence and location of the raphe and the cusp direction. The ascending aortic diameter index (AADI) was calculated using computed tomography and the BSA.

RESULTS

Sixty-four patients had A-P-type BAV, while 66 had R-L-type BAV. The mean ascending aorta diameter was 42.6 ± 6.7 mm, and the mean AADI was 27.1 ± 5.6 mm/m(2). Based on the AADI, cusp configuration (R-L-BAV: 28.3 ± 6.0 mm/m(2) vs.

A-P-BAV

25.8 ± 4.9 mm/m(2), P < 0.05), a female gender, age and the presence of aortic stenosis were found to be related to ascending aortic dilatation, while the mean ascending aortic diameter did not differ between the groups. Among the elderly patients, an AADI greater than 28 mm/m(2) was more frequently observed in the R-L-BAV group than in the A-P-BAV group. Ascending aortic replacement was required after 10 years in two patients with R-L-BAV and no patients with A-P-BAV.

CONCLUSIONS

The relative ascending aortic diameter helped to identify patients with BAV with a risk of dilatation, indicating that the use of ascending aortic replacement should be considered more frequently in patients with R-L-type BAV, while the procedure is avoidable in elderly patients with A-P-type BAV.

From unicuspid to quadricuspid: influence of aortic valve morphology on aortic three-dimensional hemodynamics

PURPOSE

To assess the impact of aortic valve morphology on aortic hemodynamics between normal tricuspid and congenitally anomalous aortic valves ranging from unicuspid to quadricuspid morphology.

MATERIALS AND METHODS

Aortic three-dimensional (3D) blood flow was evaluated by 4D flow MRI in 14 healthy volunteers with normal trileaflet valves and 14 patients with unicuspid (n = 3), bicuspid (n = 9, 3 "true" bicuspid, 3 right-left (RL), 3 right-noncoronary (RN) leaflet fusion, and quadricuspid aortic valves (n = 2). Data analysis included the co-registered visualization of aortic valve morphology with systolic 3D blood flow. The influence of valve morphology on aortic hemodynamics was quantified by valve flow angle.

RESULTS

All RL-bicuspid aortic valve (BAV) were associated with flow jets directed toward the right anterior aortic wall while RN-fusion and unicuspid valves resulted in flow jet patterns toward the right-posterior or posterior wall. Flow angles were clearly influenced by valve morphology (47° ± 10, 28° ± 2, 29° ± 18, 18° ± 12, 15° ± 2 for unicuspid, true BAV, RN-BAV, RL-BAV, quadricuspid valves) and increased compared with controls (7.2° ± 1.1, P = 0.001).

CONCLUSION

Altered 3D aortic hemodynamics are impacted by the morphology of congenitally malformed aortic valves.

Association between leaflet fusion pattern and thoracic aorta morphology in patients with bicuspid aortic valve

PURPOSE

To determine if patients with certain bicuspid aortic valve (BAV) phenotypes are predisposed to particular morphological abnormalities of the thoracic aorta.

MATERIALS AND METHODS

One hundred ninety-two patients with BAV who underwent magnetic resonance angiography between January 2007 and July 2010 were retrospectively identified. Aortic morphology was examined through measurements of aortic size index at nine levels along the thoracic aorta, three-dimensional volume of the ascending aorta, vessel asymmetry, and assessment of aortic root morphology.

RESULTS

We found 140 patients (73%) with right and left coronary cusps (R-L) fusion, 46 patients (24%) with R-N fusion, and 6 patients (3%) with left and noncoronary cusps (L-N) fusion. Mean aortic volume in the proximal ascending aorta was significantly greater in R-L patients (0.93 versus 0.60 cm(3)/m(2); P < 0.01). R-N patients possessed greater aortic size index at the distal ascending aorta and proximal aortic arch, and were also significantly more likely to have Type 2 patterns of aortic dilatation.

CONCLUSION

Our results suggest that BAV with R-L fusion is associated with increased dimensions of the aortic root, while BAV with R-N fusion is associated with increased dimensions of the distal ascending aorta and proximal arch. Our findings illustrate the morphological heterogeneity that exists among BAV phenotypes.

Screening of families of patients with left-sided cardiovascular anomalies

BACKGROUND

There is increasing evidence of clustering of certain cardiac anomalies in some families. The frequency and echocardiographic features of such anomalies among the relatives of patients with bicuspid aortic valve (BAV) or other left-sided cardiovascular anomalies (LSCA) were evaluated.

METHODS

The patients with BAV or any other LSCA and their relatives were enrolled in the study. They underwent an echocardiographic examination. The probands were assessed in three groups: BAV, BAV + coarctation of aorta (CoA), and other LSCA. Their relatives were also grouped and evaluated accordingly. The echocardiographic measurements were standardized by Z-scores.

RESULTS

Eighty-six probands and 261 relatives were evaluated. The numbers of the patients in the BAV, BAV + CoA, and other LSCA group were 52, 14, and 20, respectively. Any LSCA was determined in 17 (6.5%) of the relatives. Thirteen (5%) had aortic dilatation and the remainder (1.5%) had BAV. Accordingly, BAV incidence among relatives of patients with BAV was found to be 1.9%. A second individual with an LSCA was observed in 12.8% of 86 families investigated. The frequencies of aortic stenosis, aortic regurgitation, aortic stenosis + aortic regurgitation, and aortic dilatation in the patients with BAV were found to be 37.9%, 53%, 25.8% and 48.5%, respectively. In contrast to previous reports, no enlargement was observed in the pulmonary arteries of BAV patients.

CONCLUSIONS

BAV and other LSCA are of clinical significance. Because the clustering of LSCA in some families is observed, we recommend echocardiographic screening of those relatives. If this is not possible, at least it should be achieved for BAV patients.

Fluid dynamics of coarctation of the aorta and effect of bicuspid aortic valve

Up to 80% of patients with coarctation of the aorta (COA) have a bicuspid aortic valve (BAV). Patients with COA and BAV have elevated risks of aortic complications despite successful surgical repair. The development of such complications involves the interplay between the mechanical forces applied on the artery and the biological processes occurring at the cellular level. The focus of this study is on hemodynamic modifications induced in the aorta in the presence of a COA and a BAV. For this purpose, numerical investigations and magnetic resonance imaging measurements were conducted with different configurations: (1) normal: normal aorta and normal aortic valve; (2) isolated COA: aorta with COA (75% reduction by area) and normal aortic valve; (3) complex COA: aorta with the same severity of COA (75% reduction by area) and BAV. The results show that the coexistence of COA and BAV significantly alters blood flow in the aorta with a significant increase in the maximal velocity, secondary flow, pressure loss, time-averaged wall shear stress and oscillatory shear index downstream of the COA. These findings can contribute to a better understanding of why patients with complex COA have adverse outcome even following a successful surgery.

Aortic dilation in bicuspid aortic valve disease: flow pattern is a major contributor and differs with valve fusion type

BACKGROUND

Ascending aortic dilation is important in bicuspid aortic valve (BAV) disease, with increased risk of aortic dissection. We used cardiovascular MR to understand the pathophysiology better by examining the links between 3-dimensional flow abnormalities, aortic function, and aortic dilation.

METHODS AND RESULTS

A total of 142 subjects underwent cardiovascular MR (mean age, 40 years; 95 with BAV, 47 healthy volunteers). Patients with BAV had predominantly abnormal right-handed helical flow in the ascending aorta, larger ascending aortas (18.3±3.3 versus 15.2±2.2 mm/m²; P<0.001), and higher rotational (helical) flow (31.7±15.8 versus 2.9±3.9 mm²/s; P<0.001), systolic flow angle (23.1°±12.5° versus 7.0°±4.6°; P<0.001), and systolic wall shear stress (0.85±0.28 versus 0.59±0.17 N/m²; P<0.001) compared with healthy volunteers. BAV with right-handed flow and right-non coronary cusp fusion (n=31) showed more severe flow abnormalities (rotational flow, 38.5±16.5 versus 27.8±12.4 mm²/s; P<0.001; systolic flow angle, 29.4°±10.9° versus 19.4°±11.4°; P<0.001; in-plane wall shear stress, 0.64±0.23 versus 0.47±0.22 N/m²; P<0.001) and larger aortas (19.5±3.4 versus 17.5±3.1 mm/m²; P<0.05) than right-left cusp fusion (n=55). Patients with BAV with normal flow patterns had similar aortic dimensions and wall shear stress to healthy volunteers and younger patients with BAV showed abnormal flow patterns but no aortic dilation, both further supporting the importance of flow pattern in the pathogenesis of aortic dilation. Aortic function measures (distensibility, aortic strain, and pulse wave velocity) were similar across all groups.

CONCLUSIONS

Flow abnormalities may be a major contributor to aortic dilation in BAV. Fusion type affects the severity of flow abnormalities and may allow better risk prediction and selection of patients for earlier surgical intervention.

Subtypes of bicuspid aortic valves in coarctation of the aorta

Bicuspid aortic valves (BAVs) represent a wide morphologic and functional spectrum. In coarctation of the aorta, BAVs are common, but the proportion of BAV subtypes and their relation to aortic dimensions and development of late valve dysfunction are unknown. Sixty-two cardiovascular magnetic resonance investigations of patients with coarctation of the aorta were reviewed with respect to aortic valve morphology, aortic valve function, and aortic dimensions. BAVs were identified in 45 patients (72.6%), of which 13 (20.9%) were type-0 (two commissures), 28 (45.1%) type-1 (three commissures but fusion of one commissure with a raphe) and 4 (6.5%) valves were bicuspid but not possible to classify further. Patients with BAVs type-0 had larger dimensions in their sinus of Valsalva (35.5 ± 6.8 vs. 29.7 ± 2.7 mm, p = 0.002), ascending aorta (33.1 ± 6.2 vs. 26.0 ± 4.3 mm, p = 0.005) and sino-tubular junction (29.3 ± 7.4 vs. 24.2 ± 3.5 mm, p = 0.040) compared with tricuspid aortic valves (TAVs). Moderate and severe aortic valve disease was more common in BAV type-0 compared with BAV type-1 (p = 0.030) and TAV (p = 0.016). In a multivariate linear regression model BAV type-0 (p = 0.005), BAV type-1 (p = 0.011), age (p < 0.001), patient height (p = 0.009), and aortic valve disease (p = 0.035) were independently associated with increased diameter of the ascending aorta (R (2) of the model 0.54, p < 0.001). BAV type-0 is relatively common in coarctation of the aorta. Both BAV type-0 and type-1 are associated with increased diameter of the ascending aorta but this association is stronger for BAV type-0. Development of aortic valve disease is more common in BAV type-0 than in BAV type-1. Discrimination between BAV subtypes may potentially provide clinical and prognostic information in patients with coarctation of the aorta.

Difference in hemodynamic and wall stress of ascending thoracic aortic aneurysms with bicuspid and tricuspid aortic valve

The aortic dissection (AoD) of an ascending thoracic aortic aneurysm (ATAA) initiates when the hemodynamic loads exerted on the aneurysmal wall overcome the adhesive forces holding the elastic layers together. Parallel coupled, two-way fluid-structure interaction (FSI) analyses were performed on patient-specific ATAAs obtained from patients with either bicuspid aortic valve (BAV) or tricuspid aortic valve (TAV) to evaluate hemodynamic predictors and wall stresses imparting aneurysm enlargement and AoD. Results showed a left-handed circumferential flow with slower-moving helical pattern in the aneurysm's center for BAV ATAAs whereas a slight deviation of the blood flow toward the anterolateral region of the ascending aorta was observed for TAV ATAAs. Blood pressure and wall shear stress were found key hemodynamic predictors of aneurysm dilatation, and their dissimilarities are likely associated to the morphological anatomy of the aortic valve. We also observed discontinues, wall stresses on aneurysmal aorta, which was modeled as a composite with two elastic layers (i.e., inhomogeneity of vessel structural organization). This stress distribution was caused by differences on elastic material properties of aortic layers. Wall stress distribution suggests AoD just above sinotubular junction. Moreover, abnormal flow and lower elastic material properties that are likely intrinsic in BAV individuals render the aneurysm susceptible to the initiation of AoD.

Endothelial nitric oxide signaling regulates Notch1 in aortic valve disease

The mature aortic valve is composed of a structured trilaminar extracellular matrix that is interspersed with aortic valve interstitial cells (AVICs) and covered by endothelium. Dysfunction of the valvular endothelium initiates calcification of neighboring AVICs leading to calcific aortic valve disease (CAVD). The molecular mechanism by which endothelial cells communicate with AVICs and cause disease is not well understood. Using a co-culture assay, we show that endothelial cells secrete a signal to inhibit calcification of AVICs. Gain or loss of nitric oxide (NO) prevents or accelerates calcification of AVICs, respectively, suggesting that the endothelial cell-derived signal is NO. Overexpression of Notch1, which is genetically linked to human CAVD, retards the calcification of AVICs that occurs with NO inhibition. In AVICs, NO regulates the expression of Hey1, a downstream target of Notch1, and alters nuclear localization of Notch1 intracellular domain. Finally, Notch1 and NOS3 (endothelial NO synthase) display an in vivo genetic interaction critical for proper valve morphogenesis and the development of aortic valve disease. Our data suggests that endothelial cell-derived NO is a regulator of Notch1 signaling in AVICs in the development of the aortic valve and adult aortic valve disease.

Patterns of aortic dilatation in bicuspid aortic valve-associated aortopathy

BACKGROUND

Bicuspid aortic valves (BAVs) are associated with aortopathy. Recent studies suggest that aortic dilatation is more likely to be seen with left-right coronary cusp fusion (type I) compared with right-noncoronary cusp fusion (type II). The aim of this study was to investigate the association between BAV morphology and patterns of aortopathy.

METHODS

Aortic dimensions and BAV morphology were obtained retrospectively from archived cine loops of 581 consecutive patients with BAVs and 277 matched normal controls from the Vancouver General Hospital echocardiography database. Patient demographics and other echocardiographic parameters were extracted from the database.

RESULTS

The study population was composed of 71% type I BAVs (415 patients) and 26% type II BAVs (149 patients). Aortic dilatation was present in 30% of the population. Type I BAV was associated with increased dimensions indexed to body surface area at the sinus of Valsalva compared with type II BAV. No difference in proximal ascending aortic dimension was seen between different BAV morphologies. The pattern of dilatation with type I BAV was more likely to be at the level of the annulus or sinus of Valsalva compared with type II BAV (62% vs 33%, P= .002). Type I BAV was an independent predictor of proximal aortic dilatation (odds ratio, 3.42; 95% confidence interval, 1.07-10.9).

CONCLUSIONS

Type I BAV is associated with a greater likelihood of dilatation at the annulus and sinus of Valsalva. There is relative sparing of this region of the aorta in patients with type II BAVs. Individuals with different BAV morphologies may require different strategies of aortopathy surveillance.

Pre-participation screening for the prevention of sudden cardiac death in athletes

Pre-partecipation screening is the systematic practice of medically evaluating large populations of athletes before participation in sport activities for the purpose of identifying abnormalities that could cause disease progression or sudden death. In order to prevent sudden cardiac death (SCD), cardiovascular screening should include a strategy for excluding high-risk subjects from athletic and vigorous exercise. There are two major screening programmes in the world. In the United States competitive athletes are screened by means of family and personal history and physical examination. In Italy there is a mandatory screening for competitive athletes, which includes a resting electrocardiogram (ECG) for the detection of cardiac abnormalities. The most important issue to be addressed is whether a screened subject is really guaranteed that she/he is not suffering from any cardiac disease or at risk for SCD. Conceivably, the introduction of echocardiogram during the pre-participation screening, could be reasonable, despite the discrete sensitivity of ECG, in raising clinical suspicions of severe cardiac alterations predisposing to SCD. It is clear that the cost-benefit ratio per saved lives of the ECG screening is a benchmark of the Public Health policy. On the contrary, the additional introduction of echocardiography in a large population screening programme seems to be too much expansive for the Public Health and for this reason not easily practicable, even if useful and not invasive. Even if we strongly believe that a saved life is more important than any cost-efficacy evaluation, the issue of the economical impact of this approach should be further assessed.

Insufficient versican cleavage and Smad2 phosphorylation results in bicuspid aortic and pulmonary valves

Bicuspid or bifoliate aortic valve (BAV) results in two rather than three cusps and occurs in 1-2% of the population placing them at higher risk of developing progressive aortic valve disease. Only NOTCH-1 has been linked to human BAV, and genetically modified mouse models of BAV are limited by low penetrance and additional malformations. Here we report that in the Adamts5(-/-) valves, collagen I, collagen III, and elastin were disrupted in the malformed hinge region that anchors the mature semilunar cusps and where the ADAMTS5 proteoglycan substrate versican, accumulates. ADAMTS5 deficient prevalvular mesenchyme also exhibited a reduction of α-smooth muscle actin and filamin A suggesting versican cleavage may be involved in TGFβ signaling. Subsequent evaluation showed a significant decrease of pSmad2 in regions of prevalvular mesenchyme in Adamts5(-/-) valves. To test the hypothesis that ADAMTS5 versican cleavage is required, in part, to elicit Smad2 phosphorylation we further reduced Smad2 in Adamts5(-/-) mice through intergenetic cross. The Adamts5(-/-);Smad2(+/-) mice had highly penetrant BAV and bicuspid pulmonary valve (BPV) malformations as well as increased cusp and hinge size compared to the Adamts5(-/-) and control littermates. These studies demonstrate that semilunar cusp malformations (BAV and BPV) can arise from a failure to remodel the proteoglycan-rich provisional ECM. Specifically, faulty versican clearance due to ADAMTS5 deficiency blocks the initiation of pSmad2 signaling, which is required for excavation of endocardial cushions during aortic and pulmonary valve development. Further studies using the Adamts5(-/-); Smad2(+/-) mice with highly penetrant and isolated BAV, may lead to new pharmacological treatments for valve disease.

Computational assessment of bicuspid aortic valve wall-shear stress: implications for calcific aortic valve disease

The bicuspid aortic valve (BAV) is associated with a high prevalence of calcific aortic valve disease (CAVD). Although abnormal hemodynamics has been proposed as a potential pathogenic contributor, the native BAV hemodynamic stresses remain largely unknown. Fluid-structure interaction models were designed to quantify the regional BAV leaflet wall-shear stress over the course of CAVD. Systolic flow and leaflet dynamics were computed in two-dimensional tricuspid aortic valve (TAV) and type-1 BAV geometries with different degree of asymmetry (10 and 16% eccentricity) using an arbitrary Lagrangian–Eulerian approach. Valvular performance and regional leaflet wallshear stress were quantified in terms of valve effective orifice area (EOA), oscillatory shear index (OSI) and temporal shear magnitude (TSM). The dependence of those characteristics on the degree of leaflet calcification was also investigated. The models predicted an average reduction of 49% in BAV peak-systolic EOA relative to the TAV. Regardless of the anatomy, the leaflet wall-shear stress was side-specific and characterized by high magnitude and pulsatility on the ventricularis and low magnitude and oscillations on the fibrosa. While the TAV and non-coronary BAV leaflets shared similar shear stress characteristics, the base of the fused BAV leaflet fibrosa exhibited strong abnormalities, which were modulated by the degree of calcification (6-fold, 10-fold and 16-fold TSM increase in the normal, mildly and severely calcified BAV, respectively, relative to the normal TAV). This study reveals the existence of major differences in wall-shear stress pulsatility and magnitude on TAV and BAV leaflets. Given the ability of abnormal fluid shear stress to trigger valvular inflammation, the results support the existence of a mechano-etiology of CAVD in the BAV.

Quantitative assessment of asymmetric aortic dilation with valve-related aortic disease

RATIONALE AND OBJECTIVES

Previous work suggests that ascending aortic (AsAo) dilation can be asymmetric and is potentially related to valve-related blood flow abnormalities. The aim of this study was to investigate the relationship between the aortic valve and AsAo dilation using a quantitative, three-dimensional assessment of aortic shapes.

MATERIALS AND METHODS

Computed tomographic and magnetic resonance images of the thorax were retrospectively reviewed. Four groups with aortic dilation were studied: those with tricuspid aortic valves (TAVs) with and without stenosis and those with bicuspid aortic valves (BAVs) with and without stenosis. Controls had either TAVs or BAVs but no aortic stenosis or dilation. In additional to standard orthogonal diameters, a unique measurement of AsAo asymmetry was used: the ratio of the greater to lesser curvatures measured using three-dimensional reformats in a "candy-cane" orientation.

RESULTS

A total of 105 patients were identified. Ratios of greater to lesser curvature in patients with aortic dilation and nonstenotic TAVs were not significantly different from those in controls (1.69 vs 1.55, P > .20), but the asymmetry reflected by this ratio was markedly increased in patients with aortic dilation and stenotic TAVs (1.94, P < .001). Patients with aortic dilation and BAVs had significantly elevated ratios regardless of the status of the aortic valve (1.96 for nonstenotic and 2.05 for stenotic vs 1.53 for controls, P < .001).

CONCLUSIONS

Asymmetric AsAo dilation with relative bulging of the greater curvature is linked to aortic stenosis, but it is also seen with nonstenotic BAVs. This suggests that the hemodynamic forces that contribute to aortic dilation are not fully revealed by conventional assessment of the aortic valve.

Left ventricular systolic and diastolic function in subjects with a bicuspid aortic valve without significant valvular dysfunction

BACKGROUND

The bicuspid aortic valve (BAV) represents the most common cardiac congenital malformation in adults. It is frequently associated with dilation, aneurysm and dissection of the ascending aorta.

OBJECTIVE

To evaluate left ventricular systolic and diastolic function in subjects with BAVs.

METHODS

Thirty-five subjects with BAV (mean [± SD] age 25.9±5.7 years [range 17 to 36 years]; 18 male, 17 female) with either no valvular impairment or mild valvular impairment were recruited along with 30 control subjects (24.5±4.4 years of age [range 15 to 35 years]; 15 male, 15 female) who were matched for age, sex and body surface area. Left ventricular systolic and diastolic function were evaluated using conventional and tissue Doppler echocardiography. Left ventricular systolic and diastolic parameters were compared between the two groups.

RESULTS

In subjects with BAVs, the ratio of mitral early diastolic velocity to late diastolic velocity was lower (0.95±0.4 versus 1.27±0.9; P=0.001), the ratio of mitral early diastolic velocity to myocardial early diastolic velocity was higher (10.1±3.2 versus 6.5±2.4; P=0.001) and the myocardial early diastolic velocity was lower (8.4±2.1 versus 15.3±3.6; P<0.001) compared with control subjects. In addition, the myocardial performance index was higher in subjects with BAVs than in control subjects (P=0.03). The left ventricular ejection fraction was also lower (53±11% versus 64±13%; P<0.001). No other statistically significant differences were observed between the two groups with regard to left ventricular systolic and diastolic parameters. In addition, the number of mitral valve prolapses and atrial septal aneurysms was higher in subjects with BAVs.

CONCLUSION

BAVs may be associated with left ventricular systolic and diastolic dysfunction.

Early results with annular support in reconstruction of the bicuspid aortic valve

OBJECTIVE

Repair of the bicuspid aortic valve may be performed in aortic regurgitation and aneurysm. Dilatation of the atrioventricular junction has been identified as a risk factor for repair failure, and we have used suture annuloplasty to correct atrioventricular junction enlargement. The objective was to compare the early results of aortic repair with and without annuloplasty.

METHODS

Between November 1995 and January 12, a total of 559 patients were treated with bicuspid aortic valve repair for predominant regurgitation (n = 389), aortic aneurysm (n = 158), or acute dissection (n = 12). Isolated valve repair (aortic valve repair) was performed for aortic valve regurgitation with preserved aortic dimensions (n = 208) and sinotubular junction remodeling plus valve repair for aortic aneurysm and preserved root size (n = 116). Root remodeling was used for dilatation involving the root (n = 235). In 193 patients, dilatation of the atrioventricular junction (>27 mm) was corrected with suture annuloplasty.

RESULTS

Hospital mortality was 0.5% (n = 3); 2 patients required pacemaker implantation. Reoperation was necessary for recurrent regurgitation (n = 54) or stenosis (n = 2); 10-year freedom from reoperation was 82% but was inferior after isolated valve repair (70%, P = .007) compared with the 2 other techniques. Application of suture annuloplasty improved 3-year freedom from reoperation after isolated repair (84%) to 92% (P = .07). In all groups, the proportion of patients with no or trivial regurgitation was significantly higher with annuloplasty.

CONCLUSIONS

Preservation of the bicuspid aortic valve is feasible in many patients. Long-term stability of the repaired valves is good; the negative impact of a dilated atrioventricular junction can be reduced by suture annuloplasty.

Patient-specific bicuspid valve dynamics: overview of methods and challenges

About 1-2 % of the babies are born with bicuspid aortic valves instead of the normal aortic valve with three leaflets. A significant portion of the patients with the congenital bicuspid valve morphology suffer from aortic valve stenosis and/or ascending aortic dilatation and dissection thus requiring surgical intervention when they are young adults. Patients with bicuspid aortic valves (BAVs) have also been found to develop valvular stenosis earlier than those with the normal aortic valve. This paper overviews current knowledge of BAVs, where several studies have suggested that the mechanical stresses induced on the valve leaflets and the abnormal flow development in the ascending aorta may be an important factor in the diseases of the valve and the aortic root. The long-term goals of the studies being performed in our laboratory are aimed towards potential stratification of bicuspid valve patients who may be at risk for developing these pathologies based on analyzing the hemodynamic environment of these valves using fluid-structure interaction (FSI) modeling. Patient-specific geometry of the normal tri-cuspid and bicuspid valves are reconstructed from real-time 3D ultrasound images and the dynamic analyses performed in order to determine the potential effects of mechanical stresses on the valve leaflet and aortic root pathology. This paper describes the details of the computational tools and discusses challenges with patient-specific modeling.

Morphology of the bicuspid aortic valve and elasticity of the adjacent aorta in children

Bicuspid aortic valve (BAV) is a common congenital malformation with the known sequela of ascending aortic dilation. The morphology of the BAV and the elasticity of the adjacent ascending aorta appear to influence the outcome. We prospectively examined 48 pediatric patients with an isolated, native BAV for the morphology and size of the aortic valve, aortic root, sinotubular junction, and ascending aorta and their elasticity indexes. A cohort of 48 matching subjects with tricuspid aortic valves was investigated as controls. A comparison of the aortic valve subtypes showed normal-size aortic dimensions in the tricuspid aortic valves. In contrast, in the BAVs, the ascending aorta and aortic valve itself tended to dilate with age and aortic elasticity deteriorated. In the BAVs, the stiffness was significantly greater (4.43 ± 1.82 vs 3.43 ± 0.81 in the tricuspid aortic valves; p = 0.001). The distensibility indexes decreased inversely in the BAVs (6.57 ± 2.83 vs 7.84 ± 2.04 cm(2) × dynes(-1) × 10(-6), p = 0.013; and 53.5 ± 26.0 versus 64.3 ± 17.9 kPa(-1) × 10(-3), p = 0.020). The anteroposterior-oriented phenotype of BAVs showed significantly stiffer and less distensible elasticity even after correction for congenital valve dysfunction, which was more frequent in the left-right-oriented phenotype. In conclusion, the morphology of the BAV seems to play a major role in the outcome of BAV disease, although the left-right phenotype is more prone to congenital valve dysfunction, the anteroposterior phenotype showed worse elasticity quality.

Ex vivo evidence for the contribution of hemodynamic shear stress abnormalities to the early pathogenesis of calcific bicuspid aortic valve disease

The bicuspid aortic valve (BAV) is the most common congenital cardiac anomaly and is frequently associated with calcific aortic valve disease (CAVD). The most prevalent type-I morphology, which results from left-/right-coronary cusp fusion, generates different hemodynamics than a tricuspid aortic valve (TAV). While valvular calcification has been linked to genetic and atherogenic predispositions, hemodynamic abnormalities are increasingly pointed as potential pathogenic contributors. In particular, the wall shear stress (WSS) produced by blood flow on the leaflets regulates homeostasis in the TAV. In contrast, WSS alterations cause valve dysfunction and disease. While such observations support the existence of synergies between valvular hemodynamics and biology, the role played by BAV WSS in valvular calcification remains unknown. The objective of this study was to isolate the acute effects of native BAV WSS abnormalities on CAVD pathogenesis. Porcine aortic valve leaflets were subjected ex vivo to the native WSS experienced by TAV and type-I BAV leaflets for 48 hours. Immunostaining, immunoblotting and zymography were performed to characterize endothelial activation, pro-inflammatory paracrine signaling, extracellular matrix remodeling and markers involved in valvular interstitial cell activation and osteogenesis. While TAV and non-coronary BAV leaflet WSS essentially maintained valvular homeostasis, fused BAV leaflet WSS promoted fibrosa endothelial activation, paracrine signaling (2.4-fold and 3.7-fold increase in BMP-4 and TGF-β1, respectively, relative to fresh controls), catabolic enzyme secretion (6.3-fold, 16.8-fold, 11.7-fold, 16.7-fold and 5.5-fold increase in MMP-2, MMP-9, cathepsin L, cathepsin S and TIMP-2, respectively) and activity (1.7-fold and 2.4-fold increase in MMP-2 and MMP-9 activity, respectively), and bone matrix synthesis (5-fold increase in osteocalcin). In contrast, BAV WSS did not significantly affect α-SMA and Runx2 expressions and TIMP/MMP ratio. This study demonstrates the key role played by BAV hemodynamic abnormalities in CAVD pathogenesis and suggests the dependence of BAV vulnerability to calcification on the local degree of WSS abnormality.

Genotype-phenotype correlation in patients with bicuspid aortic valve and aneurysm

OBJECTIVES

Bicuspid aortic valve is the most common congenital cardiac abnormality, occurring in 1% to 2% of the population, and often associates with ascending aortic aneurysm. Based on familial studies, bicuspid aortic valve with aneurysm segregates in an autosomal dominant manner with incomplete penetrance. NOTCH1 mutations have been reported in 6 families with prominent valve calcification and dysfunction and low penetrance of aneurysm. We sought to determine the contribution of NOTCH1 mutations to the more common phenotype of highly penetrant aneurysms with low penetrance of bicuspid aortic valve and with rare valve calcification or dysfunction.

METHODS

All exons and splice junctions of NOTCH1 were sequenced in probands from 13 affected families presenting with bicuspid aortic valve with ascending aortic aneurysm in the absence of valve calcification. In addition, mutation analysis was performed on a single individual with aneurysm and calcified tricuspid aortic valve. Sequences were aligned and compared with the reference genomic sequence.

RESULTS

Corroborating previous studies, analysis of the single sporadic patient with calcified aortic valve in the presence of ascending aortic aneurysm revealed a novel heterozygous missense mutation in NOTCH1 resulting in a nonsynonymous amino acid substitution (p.T1090S, c.C3269G) of an evolutionarily conserved residue. This change was not observed in controls. In contrast, we did not identify any pathologic NOTCH1 mutations in the 13 families segregating noncalcified bicuspid aortic valve with highly penetrant aortic aneurysm.

CONCLUSIONS

These data suggest that there are phenotypic differences that distinguish families with and without NOTCH1 mutations, indicating a genotype-phenotype correlation with potential implications for patient diagnosis, counseling, and management.

Stanford type a aortic dissection in pregnancy: a diagnostic and management challenge

BACKGROUND

In women under the age of 40, over 50% of type A aortic dissections occur in the obstetric population. This is a complex situation, with potential catastrophic outcomes for mother and child. Time to diagnosis is often delayed by a low degree of suspicion, atypical presentation and difficulties investigating pregnant women. Management requires early involvement of multiple teams and appreciation of potential complications. We report our experience (the largest series described) and describe our surgical strategy.

METHODS

A retrospective search of the cardiothoracic surgical database at our centre from 2002 to 2010 identified five pregnant women with type A dissections.

RESULTS

Median time to diagnosis was 18.5 h (range 5.5-150 h) and median time from diagnosis to arrival in the operating theatre was 1.5 h (range 0.5-54 h). Four patients underwent concomitant Caesarean section and dissection repair. There was one maternal death and one unrelated foetal death.

CONCLUSION

Occurrence of type A aortic dissection in pregnant women is uncommon but potentially catastrophic. A high index of suspicion and timely investigations are necessary to expedite definitive management. Sound surgical strategies and collaboration with appropriate teams are necessary to optimise outcome.

Ascending aorta dilatation in patients with bicuspid aortic valve stenosis: a prospective CMR study

BACKGROUND

The aim of this study was to evaluate the natural progression of aortic dilatation and its association with aortic valve stenosis (AoS) in patients with bicuspid aortic valve (BAV).

METHODS

Prospective study of aorta dilatation in patients with BAV and AoS using cardiac magnetic resonance (CMR). Aortic root, ascending aorta, aortic peak velocity, left ventricular systolic and diastolic function and mass were assessed at baseline and at 3-year follow-up.

RESULTS

Of the 33 enrolled patients, 5 needed surgery, while 28 patients (17 male; mean age: 31 ± 8 years) completed the study. Aortic diameters significantly increased at the aortic annulus, sinus of Valsalva and tubular ascending aorta levels (P < 0.050). The number of patients with dilated tubular ascending aortas increased from 32 % to 43 %. No significant increase in sino-tubular junction diameter was observed. Aortic peak velocity, ejection fraction and myocardial mass significantly increased while the early/late filling ratio significantly decreased at follow-up (P < 0.050). The progression rate of the ascending aorta diameter correlated weakly with the aortic peak velocity at baseline (R (2) = 0.16, P = 0.040).

CONCLUSION

BAV patients with AoS showed a progressive increase of aortic diameters with maximal expression at the level of the tubular ascending aorta. The progression of aortic dilatation correlated weakly with the severity of AoS.

Bicuspid aortic valve and thoracic aortic aneurysm: three patient populations, two disease phenotypes, and one shared genotype

Bicuspid aortic valve (BAV) and thoracic aortic aneurysm (TAA) are two discrete cardiovascular phenotypes characterized by latent progressive disease states. There is a clear association between BAV and TAA; however the nature and extent of this relationship is unclear. There are both distinct and overlapping developmental pathways that have been established to contribute to the formation of the aortic valve and the aortic root, and the mature anatomy of these different tissue types is intimately intertwined. Likewise, human genetics studies have established apparently separate and common contributions to these clinical phenotypes, suggesting complex inheritance and a shared genetic basis and translating 3 patient populations, namely, BAV, TAA, or both, into a common but diverse etiology. A better understanding of the BAV-TAA association will provide an opportunity to leverage molecular information to modify clinical care through more sophisticated diagnostic testing, improved counseling, and ultimately new pharmacologic therapies.

Including aortic valve morphology in computational fluid dynamics simulations: initial findings and application to aortic coarctation

Computational fluid dynamics (CFD) simulations quantifying thoracic aortic flow patterns have not included disturbances from the aortic valve (AoV). 80% of patients with aortic coarctation (CoA) have a bicuspid aortic valve (BAV) which may cause adverse flow patterns contributing to morbidity. Our objectives were to develop a method to account for the AoV in CFD simulations, and quantify its impact on local hemodynamics. The method developed facilitates segmentation of the AoV, spatiotemporal interpolation of segments, and anatomic positioning of segments at the CFD model inlet. The AoV was included in CFD model examples of a normal (tricuspid AoV) and a post-surgical CoA patient (BAV). Velocity, turbulent kinetic energy (TKE), time-averaged wall shear stress (TAWSS), and oscillatory shear index (OSI) results were compared to equivalent simulations using a plug inlet profile. The plug inlet greatly underestimated TKE for both examples. TAWSS differences extended throughout the thoracic aorta for the CoA BAV, but were limited to the arch for the normal example. OSI differences existed mainly in the ascending aorta for both cases. The impact of AoV can now be included with CFD simulations to identify regions of deleterious hemodynamics thereby advancing simulations of the thoracic aorta one step closer to reality.

The congenital bicuspid aortic valve can experience high-frequency unsteady shear stresses on its leaflet surface

The bicuspid aortic valve (BAV) is a common congenital malformation of the aortic valve (AV) affecting 1% to 2% of the population. The BAV is predisposed to early degenerative calcification of valve leaflets, and BAV patients constitute 50% of AV stenosis patients. Although evidence shows that genetic defects can play a role in calcification of the BAV leaflets, we hypothesize that drastic changes in the mechanical environment of the BAV elicit pathological responses from the valve and might be concurrently responsible for early calcification. An in vitro model of the BAV was constructed by surgically manipulating a native trileaflet porcine AV. The BAV valve model and a trileaflet AV (TAV) model were tested in an in vitro pulsatile flow loop mimicking physiological hemodynamics. Laser Doppler velocimetry was used to make measurements of fluid shear stresses on the leaflet of the valve models using previously established methodologies. Furthermore, particle image velocimetry was used to visualize the flow fields downstream of the valves and in the sinuses. In the BAV model, flow near the leaflets and fluid shear stresses on the leaflets were much more unsteady than for the TAV model, most likely due to the moderate stenosis in the BAV and the skewed forward flow jet that collided with the aorta wall. This additional unsteadiness occurred during mid- to late-systole and was composed of cycle-to-cycle magnitude variability as well as high-frequency fluctuations about the mean shear stress. It has been demonstrated that the BAV geometry can lead to unsteady shear stresses under physiological flow and pressure conditions. Such altered shear stresses could play a role in accelerated calcification in BAVs.

The development of ascending aortic aneurysms after elective aortic valve replacement with St Jude mechanical valve prosthesis in the bicuspid patient: a pilot study

The association between bicuspid aortic valve (BAV) and ascending aorta aneurysm is well described. Replacement of the ascending aorta is now being considered at 4.5 cm. We identified patients confirmed with BAV who underwent elective aortic valve replacement (AVR) with a mechanical St Jude Bioprosthesis from 1994 to 2000 who were ≤65 years of age at the time of surgery. Follow-up imaging was obtained by computed tomography (CT) angiography or echocardiography. A total of 225 patients who underwent AVR were identified; 60 patients had a BAV. Of all, 36 (60%) patients with BAV returned for follow-up imaging of their ascending aorta. Eight patients (22%) had diameters classifiable as aneurysmal (>4.5 cm) that developed within 9.6 ± 4.1 years from implant and requiring surgery. Of all, 7 patients (12%) died within 5.9 ± 2.5 years from their implant date. Lifelong serial monitoring of the ascending aorta for patients with BAV should be the standard of care.

Bicuspid aortic valve disease: a comprehensive review

Bicuspid aortic valve is the commonest congenital cardiac abnormality in the general population. This paper article will discuss our current knowledge of the anatomy, pathophysiology, genetics, and clinical aspects of bicuspid aortic valve disease.

Rare non-synonymous variations in the transcriptional activation domains of GATA5 in bicuspid aortic valve disease

Bicuspid aortic valve (BAV) is the commonest congenital heart disease and a highly heritable trait; however, only the NOTCH1 gene has been linked to limited cases of BAV in humans. Recently, the transcription factor GATA5 has been shown to have an essential role in aortic valve development, and targeted deletion of Gata5 in mice is associated with partially penetrant BAV formation. Here, we investigated the relationship between GATA5 gene variants and BAV with its associated aortopathy. One hundred unrelated individuals with confirmed BAV were prospectively recruited. Following collection of clinical information and DNA extraction, the coding regions and splice signal sequences of the GATA5 gene were screened for sequence variations. The clinical characteristics of the cohort included a male predominance (77%), mean age of diagnosis 29 ± 22 years, associated aortopathy in 59% and positive family history for BAV in 13%. Genetic analysis identified the presence of 4 rare non-synonymous variations within the GATA5 transcriptional activation domains, namely Gln3Arg, Ser19Trp, Tyr142His and Gly166Ser, occurring in one patient each. Gln3Arg and Tyr142His substitutions affect highly conserved and functionally relevant residues, and are likely to impact on the transcriptional activation of GATA5 target regions. A novel Ser19Trp variation was identified at a highly conserved amino acid residue in one patient, while the Gly166Ser variant was found in a familial case of BAV and associated aortopathy. Rare non-synonymous variations in the functionally important GATA5 transcriptional activation domains may be important in the pathogenesis of BAV disease in humans.

Incidental aortic valve calcification on CT scans: significance for bicuspid and tricuspid valve disease

RATIONALE AND OBJECTIVES

The aim of this study was to evaluate the role of incidental aortic valve calcification on routine computed tomographic scans as a marker for stenosis, as assessed by echocardiography, in patients with bicuspid aortic valve (BAV) and tricuspid aortic valve.

MATERIALS AND METHODS

Computed tomographic and echocardiographic studies were retrospectively reviewed for 182 consecutive, unselected patients and 426 patients identified by a record search for "aortic valve calcification." Location and severity of valve calcification were correlated with aortic valve morphology and stenosis. Differences between subgroups were assessed using χ(2) or Fisher's exact tests.

RESULTS

In unselected patients, calcification was present in 25.8% with tricuspid aortic valves (46 of 178) and 75% (three of four) with BAV. In patients selected for valve calcification, the average age of those with tricuspid aortic valves (n = 395) was 14.3 years older than those with BAV (n = 31). Patients with BAV were more likely to have severe calcification (87% vs 50%, P < .001), and if severe calcification was present, it was more likely to involve only the valve leaflets (41% vs 9%, P < .001) and result in aortic stenosis (85% vs 58%, P = .006). Patients aged < 60 years with severe calcification were more likely to have BAV (56% vs 7%; odds ratio, 7.9; 95% confidence interval, 3.4-18.7).

CONCLUSIONS

Aortic valve calcification was found 14 years earlier in patients with BAV and was more severe and strongly linked to aortic stenosis. Valve calcification on computed tomographic scans should be considered a marker for BAV if found before the seventh decade.

miRNA-141 is a novel regulator of BMP-2-mediated calcification in aortic stenosis

OBJECTIVE

Bone morphogenetic protein-2 (BMP-2) is a major regulator of aortic valve calcification. MicroRNAs (miRNAs) are essential post-transcriptional modulators of gene expression and miRNA-141 is a known repressor of BMP-2-mediated osteogenesis. We hypothesized that miRNA-141 is a key regulator of aortic valve calcification.

METHODS

Porcine valvular interstitial cells were isolated, transfected with miRNA-141 or control, and stimulated with transforming growth factor-β. The BMP-2, extracellular signal-regulated kinase 1/2, and runt-related transcription factor 2 levels were determined by immunoblotting and reverse transcriptase polymerase chain reaction. To determine the role of miRNA-141 in bicuspid aortic valve disease, human bicuspid (n = 19) and tricuspid (n = 17) aortic valve leaflets obtained intraoperatively were submitted for GenoExplorer human microRNA array, immunoblotting, and histologic and immunohistochemical analyses.

RESULTS

Stimulation of porcine aortic valvular interstitial cells with transforming growth factor-β induced morphologic alterations consistent with myofibroblastic transformation, BMP-2 signaling, and calcification. Transfection with miRNA-141 restored transforming growth factor-β-induced valvular interstitial cell activation, BMP-2 signaling, and alkaline phosphatase activity (3.55 ± 0.18 vs 4.01 ± 0.21, P < .05), suggesting upstream regulation by miRNA-141. miRNA microarray demonstrated differential expression of 35 of 1583 miRNA sequences in the bicuspid versus tricuspid aortic valve leaflets, with a 14.5-fold decrease in miRNA-141 in the bicuspid versus tricuspid leaflets (P < .05). This was associated with significantly increased BMP-2 protein expression in bicuspid aortic valve compared with the tricuspid aortic valve leaflets (P < .001).

CONCLUSIONS

We report a completely novel role of miRNA-141 as a regulator of BMP-2-dependent aortic valvular calcification and demonstrate marked attenuation of miRNA-141 expression in patients with bicuspid aortic valve-associated aortic stenosis. Therapeutic targeting of miRNA-141 could serve as a novel strategy to limit progressive calcification in aortic stenosis.

In vitro characterization of bicuspid aortic valve hemodynamics using particle image velocimetry

The congenital bicuspid aortic valve (BAV) is associated with increased leaflet calcification, ascending aortic dilatation, aortic stenosis (AS) and regurgitation (AR). Although underlying genetic factors have been primarily implicated for these complications, the altered mechanical environment of BAVs could potentially accelerate these pathologies. The objective of the current study is to characterize BAV hemodynamics in an in vitro system. Two BAV models of varying stenosis and jet eccentricity and a trileaflet AV (TAV) were constructed from excised porcine AVs. Particle Image Velocimetry (PIV) experiments were conducted at physiological flow and pressure conditions to characterize fluid velocity fields in the aorta and sinus regions, and ensemble averaged Reynolds shear stress and 2D turbulent kinetic energy were calculated for all models. The dynamics of the BAV and TAV models matched the characteristics of these valves which are observed clinically. The eccentric and stenotic BAV showed the strongest systolic jet (V = 4.2 m/s), which impinged on the aortic wall on the non-fused leaflet side, causing a strong vortex in the non-fused leaflet sinus. The magnitudes of TKE and Reynolds stresses in both BAV models were almost twice as large as comparable values for TAV, and these maximum values were primarily concentrated around the central jet through the valve orifice. The in vitro model described here enables detailed characterization of BAV flow characteristics, which is currently challenging in clinical practice. This model can prove to be useful in studying the effects of altered BAV geometry on fluid dynamics in the valve and ascending aorta. These altered flows can be potentially linked to increased calcific responses from the valve endothelium in stenotic and eccentric BAVs, independent of concomitant genetic factors.