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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., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2021. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Background Bicuspid aortic valve (BAV) is the most common congenital heart disease in adults but is clinically heterogeneous. We aimed to describe the echocardiographic characteristics of BAV and compare patients with BAV with moderate-to-severe aortic stenosis (AS) with those with tricuspid aortic valve (TAV) stenosis. Methods and Results Using the National Echo Database of Australia, patients in whom BAV was identified were studied. Those with moderate-to-severe AS (mean gradient >20 mm Hg [BAV-AS]) were compared with those with TAV and moderate-to-severe AS (TAV-AS). Of 264 159 adults whose aortic valve morphology was specified, 4783 (1.8%) had confirmed BAV (aged 49.6±17.4 years, 69% men). Of these, 42% had no AS, and 46% had no aortic regurgitation. Moderate-to-severe AS was detected in a greater proportion of patients with BAV with a recorded mean gradient (n=1112, 34%) compared with those with TAV (n=4377, 4%; P <0.001). Patients with BAV-AS were younger (aged 55.3±16.7 years versus 77.3±11.0 years; P <0.001), and where measured had larger ascending aortic diameters (37±8 mm versus 35±5 mm; P <0.001). Age and sex-adjusted mortality risk was significantly lower in patients with BAV-AS (hazard ratio, 0.53; 95% CI, 0.45-0.63; P <0.001). Conclusions In this large study of patients across the spectrum of BAV disease, the largest proportion had no significant valvulopathy or aortopathy. Compared with those with TAV-AS, patients with BAV were more likely to have moderate-to-severe AS, have larger ascending aortas, and were over 2 decades younger at the time of AS diagnosis. Despite this, patients with BAV appear to have a more favorable prognosis when AS develops, compared with those with TAV-AS. Registration URL: www.anzctr.org.au/; Unique identifier: ACTRN12617001387314.

Objective: Bicuspid aortic valve (BAV) has been associated with less atherosclerosis as compared with tricuspid aortic valve (TAV) patients. It, however, remains unclear whether this reflects the older age of TAV patients and/or accumulation of atherosclerotic risk factors or that the BAV phenotype is atheroprotective. Therefore, we compared the atherosclerotic disease burden of BAV and TAV patients, with that of the general (age-matched) population., Methods: The prevalence of coronary artery disease (CAD) and CAD risk factors in BAV and TAV patients who underwent aortic valve surgery were compared with the Dutch general practitioners registry data. BAV (n=454) and TAV (n=1101) patients were divided into four groups: BAV with aortic valve stenosis (BAV-AoS), BAV with aortic valve regurgitation (BAV-AR), TAV with AoS (TAV-AoS) and TAV with AR (TAV-AR). The atherosclerotic disease burden of each group was compared with that of the corresponding age cohort for the general population., Results: CAD risk factors hypertension and hypercholesterolaemia were more prevalent in the surgery groups than the age-matched general population (all p<0.001). All BAVs (BAV-AoS and BAV-AR) and TAV-AR had a similar incidence of CAD history as compared to the age-matched general populations (p=0.689, p=0.325 and p=0.617 respectively), whereas TAV-AoS had a higher incidence (21.6% versus 14.9% in the age-matched general population, p<0.001)., Conclusions: Stenotic TAV disease is part of the atherosclerotic disease spectrum, while regurgitant TAV and all BAVs are not. Although the prevalence of cardiovascular risk factors is higher in all BAV patients, the prevalence of CAD is similar to the general population., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2021. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Importance: Transcatheter aortic valve replacement (TAVR) failure is often managed by an urgent implantation of a supplementary valve during the procedure (2-valve TAVR [2V-TAVR]). Little is known about the factors associated with or sequelae of 2V-TAVR., Objective: To examine the incidence, causes, and outcomes of 2V-TAVR., Design, Setting, and Participants: A retrospective cohort study was performed using data from an international registry of 21 298 TAVR procedures performed from January 1, 2014, through February 28, 2019. Among the 21 298 patients undergoing TAVR, 223 patients (1.0%) undergoing 2V-TAVR were identified. Patient-level data were available for all the patients undergoing 2V-TAVR and for 12 052 patients (56.6%) undergoing 1V-TAVR. After excluding patients with missing 30-day follow-up or data inconsistencies, 213 2V-TAVR and 10 010 1V-TAVR patients were studied. The 2V-TAVR patients were compared against control TAVR patients undergoing a 1-valve TAVR (1V-TAVR) using 1:4 17 propensity score matching. Final analysis included 1065 (213:852) patients., Exposures: Urgent implantation of a supplementary valve during TAVR., Main Outcomes and Measures: Mortality at 30 days and 1 year., Results: The 213 patients undergoing 2V-TAVR had similar age (mean [SD], 81.3 [0.5] years) and sex (110 [51.6%] female) as the 10 010 patients undergoing 1V-TAVR (mean [SD] age, 81.2 [0.5] years; 110 [51.6%] female). The 2V-TAVR incidence decreased from 2.9% in 2014 to 1.0% in 2018 and was similar between repositionable and nonrepositionable valves. Bicuspid aortic valve (odds ratio [OR], 2.20; 95% CI, 1.17-4.15; P = .02), aortic regurgitation of moderate or greater severity (OR, 2.02; 95% CI, 1.49-2.73; P < .001), atrial fibrillation (OR, 1.43; 95% CI, 1.07-1.93; P = .02), alternative access (OR, 2.59; 95% CI, 1.72-3.89; P < .001), early-generation valve (OR, 2.32; 95% CI, 1.69-3.19; P < .001), and self-expandable valve (OR, 1.69; 95% CI, 1.17-2.43; P = .004) were associated with higher 2V-TAVR risk. In 165 patients (80%), the supplementary valve was implanted because of residual aortic regurgitation after primary valve malposition (94 [46.4%] too high and 71 [34.2%] too low). In the matched 2V-TAVR vs 1V-TAVR cohorts, the rate of device success was 147 (70.4%) vs 783 (92.2%) (P < .001), the rate of coronary obstruction was 5 (2.3%) vs 3 (0.4%) (P = .10), stroke rate was 9 (4.6%) vs 13 (1.6%) (P = .09), major bleeding rates were 25 (11.8%) vs 46 (5.5%) (P = .03) and annular rupture rate was 7 (3.3%) vs 3 (0.4%) (P = .03). The hazard ratios for mortality were 2.58 (95% CI, 1.04-6.45; P = .04) at 30 days, 1.45 (95% CI, 0.84-2.51; P = .18) at 1 year, and 1.20 (95% CI, 0.77-1.88; P = .42) at 2 years. Nontransfemoral access and certain periprocedural complications were independently associated with higher risk of death 1 year after 2V-TAVR., Conclusions and Relevance: In this cohort study, valve malposition was the most common indication for 2V-TAVR. Incidence decreased over time and was low overall, although patients with a bicuspid or regurgitant aortic valve, nontransfemoral access, and early-generation or self-expandable valve were at higher risk. These findings suggest that compared with 1V-TAVR, 2V-TAVR is associated with high burden of complications and mortality at 30 days but not at 1 year.

Objectives: The objective of this cohort study was to analyse long-term relative survival in patients with bicuspid aortic valve (BAV) who underwent aortic valve surgery., Methods: We studied 865 patients with BAVs who participated in three prospective cohort studies of elective, open-heart, aortic valve surgery at the Karolinska University Hospital, Stockholm, Sweden, between 2007 and 2020. The expected survival for the age, sex and calendar year-matched general Swedish population was obtained from the Human Mortality Database. The Ederer II method was used to calculate relative survival, which was used as an estimate of cause-specific survival., Results: No differences were found in the observed versus expected survival at 1, 5, 10 or 12 years: 99%, 94%, 83% and 76% vs 99%, 93%, 84% and 80%, respectively. The relative survival at 1, 5, 10 and 12 years was 100% (95% CI 99% to 100%), 101% (95% CI 99% to 103%), 99% (95% CI 95% to 103%) and 95% (95% CI 87% to 102%), respectively. The relative survival at the end of follow-up tended to be lower for women than men (86% vs 95%). The mean follow-up was 6.3 years (maximum 13.3 years)., Conclusions: The survival of patients with BAV following aortic valve surgery was excellent and similar to that of the general population. Our results suggest that the timing of surgery according to current guidelines is correct and provide robust long-term survival rates, as well as important information about the natural history of BAV in patients following aortic valve surgery., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2021. Re-use permitted under CC BY. Published by BMJ.)

Background Bicuspid aortic valve (BAV) is the most common congenital cardiac malformation, which is often complicated by aortic valve stenosis (AoS). In tricuspid aortic valve (TAV), AoS strongly associates with coronary artery disease (CAD) with common pathophysiological factors. Yet, it remains unclear whether AoS in patients with BAV is also associated with CAD. This study investigated the association between the aortic valve morphological features and the extent of CAD. Methods and Results A single-center study was performed, including all patients who underwent an aortic valve replacement attributable to AoS between 2006 and 2019. Coronary sclerosis was graded on preoperative coronary angiographies using the coronary artery greater even than scoring method, which divides the coronaries in 28 segments and scores nonobstructive (20%-49% sclerosis) and obstructive coronary sclerosis (>49% sclerosis) in each segment. Multivariate analyses were performed, controlling for age, sex, and CAD risk factors. A total of 1296 patients (931 TAV and 365 BAV) were included, resulting in 548 matched patients. Patients with TAV exhibited more CAD risk factors (odds ratio [OR], 2.66; 95% CI, 1.79-3.96; P <0.001). Patients with BAV had lower coronary artery greater even than 20 (1.61±2.35 versus 3.60±2.79) and coronary artery greater even than 50 (1.24±2.43 versus 3.37±3.49) scores ( P <0.001), even after correcting for CAD risk factors ( P <0.001). Patients with TAV more often needed concomitant coronary revascularization (OR, 3.50; 95% CI, 2.42-5.06; P <0.001). Conclusions Patients with BAV who are undergoing surgery for AoS carry a lower cardiovascular risk profile, correlating with less coronary sclerosis and a lower incidence of concomitant coronary revascularization compared with patients with TAV.

Importance: The prevalence and characteristics of bicuspid aortic valve (BAV) are mainly reported from selected cohorts. BAV is associated with aortopathy, but it is unclear if it represents a fetal developmental defect or is secondary to abnormal valve dynamics., Objective: To determine the prevalence of BAV and BAV subtypes and to describe the associated aortopathy in a large, population-based cohort of newborns., Design, Setting, and Participants: The Copenhagen Baby Heart Study was a cross-sectional, population-based study open to all newborns born in Copenhagen between April 1, 2016, and October 31, 2018. Newborns with BAV were matched 1:2 to newborns with a tricuspid aortic valve (non-BAV group) on sex, singleton/twin pregnancy, gestational age, weight, and age at time of examination., Exposures: Transthoracic echocardiography within 60 days after birth., Main Outcomes and Measures: Primary outcome was BAV prevalence and types, ie, number of raphes and spatial orientation of raphes or cusps (no raphes), according to the classification system of Sievers and Schmidtke (classified as type 0, 1, or 2, with numbers indicating the number of raphes). Secondary outcome was valve function and BAV-associated aortopathy, defined as aortic diameter z score of 3 or greater or coarctation., Results: In total, 25 556 newborns (51.7% male; mean age, 12 [SD, 8] days) underwent echocardiography. BAV was diagnosed in 196 newborns (prevalence, 0.77% [95% CI, 0.67%-0.88%]), with male-female ratio 2.1:1. BAV was classified as type 0 in 17 newborns (8.7% [95% CI, 5.5%-13.5%]), type 1 in 178 (90.8% [95% CI, 86.0%-94.1%]) (147 [75.0% {95% CI, 68.5%-80.5%}] right-left coronary raphe, 27 [13.8% {95% CI, 9.6%-19.3%}] right coronary-noncoronary raphe, 4 [2.0% {95% CI, 0.8%-5.1%}] left coronary-noncoronary raphe), and type 2 in 1 (0.5% [95% CI, 0.1%-2.8%]). Aortic regurgitation was more prevalent in newborns with BAV (n = 29 [14.7%]) than in those without BAV (1.3%) (absolute % difference, 13.4% [95% CI, 7.8%-18.9%]; P < .001). Newborns with BAV had higher flow velocities across the valve (0.67 [95% CI, 0.65-0.69] m/s vs 0.61 [95% CI, 0.60-0.62] m/s; mean difference, 0.06 m/s [95% CI, 0-0.1]) and larger aortic root and tubular ascending aortic diameters than those without BAV (10.7 [95% CI, 10.7-10.9] mm vs 10.3 [95% CI, 10.2-10.4] mm; mean difference, 0.43 mm [95% CI, 0.2-0.6 mm] and 9.8 [95% CI, 9.6-10.0] mm vs 9.4 [95% CI, 9.3-9.5] mm; mean difference, 0.46 mm [95% CI, 0.30-0.70], respectively) (P < .001 for all). Aortopathy was seen in 65 newborns (33.2%) with BAV (62 with aortic z score ≥3; 3 with coarctation)., Conclusions and Relevance: Among newborns in Copenhagen, the prevalence of BAV was 0.77%. Aortopathy was common in newborns with BAV, suggesting that it also represents a fetal malformation.

Bicuspid aortic valve (BAV) is the most common congenital heart disease. Since heritability is suspected, actual guidelines recommend to perform an echocardiographic assessment for first-degree relatives (FDR) of patient with BAV. This study aimed to assess the effectiveness and the feasibility of the current guidelines for the screening of FDR of patient with BAV in a pediatric cardiology daily practice. Consecutive patients with BAV and their FDR were prospectively included from January 2015 to March 2018 at Centre Hospitalier Universitaire de Laval, Quebec City (Canada). Data were retrospectively collected and analyzed. A total of 713 FDR of 213 consecutives index cases [median age: 11 (6-20) years] were studied. Up to 32 (6.6%) FDR had a BAV and 26 (5.4%) had an aortic valve dysfunction. A total of 14 (2.9%) FDR had an ascending aorta dilatation according to Z-score including 6 (1.2%) patients with an ascending aorta ≥ 45 mm. No statistically significant differences regarding BAV, aortic valve dysfunction and ascending aorta dilatation prevalence were identified between generations. Screening was done in 482 (67.6%), prescribed but not done in 134 (19%), not prescribed in 92 (13%) and declined in 5 (1%) FDR. The prevalence of BAV in FDR was similar to prospective adult studies and supports actual guidelines in pediatric cardiology practice. Ascending aorta dilatation was rare in our young population. Exhaustiveness and additional burden to implement current guidelines remain a challenge in daily practice.

Objectives: Prenatal diagnosis of coarctation of the aorta (CoA) is associated with reduced mortality and morbidity, however, accurate prenatal prediction remains challenging. To date, studies have used retrospective measurements of the outflow tracts to evaluate their potential to predict CoA. Our primary objective was to evaluate prospectively acquired measurements of the outflow tracts in fetuses with prenatally suspected CoA. A secondary aim was to report the postnatal prevalence of bicuspid aortic valve in this cohort., Methods: Pregnancies with suspicion of isolated CoA and with a minimum of 6 months' postnatal follow-up available were identified from the cardiac database of a tertiary fetal cardiology center in the UK, between January 2002 and December 2017. Measurement of the aortic valve, pulmonary valve, distal transverse aortic arch (DTAA) and arterial duct (AD) diameters were undertaken routinely in fetuses with suspected CoA during the study period. Z-scores were computed using published reference ranges based on > 7000 fetuses from our own unit., Results: Of 149 pregnancies with prenatally suspected CoA included in the study, CoA was confirmed within 6 months after birth in 77/149 (51.7%) cases. DTAA diameter Z-score and the Z-score of second-trimester DTAA/AD diameter ratio were smaller in fetuses with postnatally confirmed CoA than those in false-positive cases (-2.8 vs -1.9; P = 0.039 and -3.13 vs -2.61; P = 0.005, respectively). Multiple regression analysis demonstrated that the Z-scores of DTAA and AD diameters were the only significant predictors of postnatal CoA (P = 0.001). Bicuspid aortic valve was identified in 30% of the false-positive cases., Conclusions: Measurement of DTAA and AD diameter Z-scores can be used to ascertain risk for postnatal CoA in a selected cohort. The high incidence of bicuspid aortic valve in false-positive cases merits further study with respect to both etiology and longer-term significance. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd., (Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.)

Background/aim: From a pathophysiological point of view, inflammation is thought to be more dominant in bicuspid aortic valve (BAV) stenosis than tricuspid aortic valve (TAV) stenosis. Our study aimed to determine the association between monocyte to high- density lipoprotein cholesterol (HDL-C) ratio (MHR), a new inflammatory marker, and the speed of progression of stenosis and pathophysiology of BAV stenosis., Materials and Methods: A total of 210 severe aortic stenosis patients (70 consecutive BAV patients, 140 matched TAV patients) were retrospectively enrolled in the study. Clinical and echocardiographic data and laboratory results related to our research were collected retrospectively from the patients’ records. MHR was measured as the ratio of the absolute monocyte count to the HDL-C value., Results: Seventy BAV (mean age: 72.0 ± 9.1 years, 42.9% female) and 140 TAV patients (mean age: 77.9 ± 8.3 years, 51.4% female) with severe aortic stenosis were enrolled in this study. There was no difference between the two groups in terms of another baseline demographic or clinic findings except age (P < 0.001). Monocyte count, hemoglobin level, mean platelet volume was significantly higher, and HDL-C level was significantly lower in the BAV group, while other lipid and CBC parameters were found to be similar. In the multivariate analysis, MHR (P = 0.005, 95% CI: 0.90–0.98) and, as expected, age (P = 0.001, 95% CI: 1.02–1.11) were found to be significant as the independent predictor of BAV, after adjusting for other risk factors., Conclusion: Our study showed a significant correlation between increased MHR and BAV. MHR was determined as a significant independent predictor for the speed of progression and diagnosis of severe BAV stenosis in multivariate analysis., Competing Interests: The authors declare that there is no conflict of interest., (This work is licensed under a Creative Commons Attribution 4.0 International License.)

Bicuspid aortic valve (BAV) is the most common congenital cardiac malformation. It is an aortopathy and is associated with other congenital heart disease. Although there is no mortality increase with BAV, the natural history increases the risk of aortic valve disease, aortic dilatation and infective endocarditis over the time frame of a full military career. Military service theoretically increases the risk of aortic dilatation and endocarditis in BAV. Conversely, there are some who have BAV who would not suffer any complications during their military career. Currently, potential UK Army recruits undergo personal/family history and physical examination plus an ECG and, although this goes beyond American Heart Association guidelines, it does not screen specifically for BAV. This would necessitate a transthoracic echo for each potential recruit but would be a considerable increase in resources-both time and financial. In addition to the recruitment medical, military personnel undergo frequent medicals, which could identify those who develop significant valvular disease. Those with mild valve disease are at lowest risk of complication. Those with aortic dilatation only remain a concern., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2020. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: Marfan syndrome is an autosomal dominant disorder of the connective tissue, whose cardinal features affect eyes, musculoskeletal, and cardiovascular system. Despite prevalence and natural history of cardiovascular manifestation are well known in adults, little is known about children and young adult patients. The aim of this study was to describe a well-characterised cohort of consecutive children and young patients with marfan syndrome, looking at the impact of family history and presence of bicuspid aortic valve on disease severity., Methods: A total of 30 consecutive children and young patients with Marfan syndrome were evaluated. All patients underwent a comprehensive clinical-instrumental-genetic evaluation. Particular attention was posed to identify differences in prevalence of cardiovascular abnormalities between patients with and without family history of Marfan syndrome or bicuspid aortic valve., Results: Of these 30 patients, family history of Marfan syndrome and bicuspid aortic valve were present in 76 and 13%, respectively. Compared to patients with family history of Marfan syndrome, those without showed higher prevalence of aortic sinus dilation (87 versus 32%, p-value = 0.009), greater aortic sinus diameters (4.2 ± 2.1 versus 1.9 ± 1.1 z score, p-value = 0.002), and higher rate of aortic surgery during follow-up (37 versus 0%, p-value = 0.002). Compared to patients with tricuspid aortic valve, those with bicuspid aortic valve were younger (3.2 ± 4.3 versus 10.7 ± 6.8 years old, p-value = 0.043), showed greater aortic sinus diameters (4.2 ± 0.9 versus 2.2 ± 1.6 z score, p-value = 0.033), and underwent more frequently aortic root replacement (50 versus 4%, p-value = 0.004)., Conclusions: In our cohort of patients with Marfan syndrome, the absence of family history and the presence of bicuspid aortic valve were associated to severe aortic phenotype and worse prognosis.

Objective: We aimed to investigate the combined effects of arterial hypertension, bicuspid aortic valve disease (BAVD) and age on the distensibility of the ascending and descending aortas in patients with aortic coarctation., Design: Cross-sectional study., Setting: The study was conducted at two university medical centres, located in Berlin and London., Participants: A total of 121 patients with aortic coarctation (ages 1-71 years) underwent cardiac MRI, echocardiography and blood pressure measurements., Outcome Measures: Cross-sectional diameters of the ascending and descending aortas were assessed to compute aortic area distensibility. Findings were compared with age-specific reference values. The study complied with the Strengthening the Reporting of Observational Studies in Epidemiology statement and reporting guidelines., Results: Impaired distensibility (below fifth percentile) was seen in 37% of all patients with coarctation in the ascending aorta and in 43% in the descending aorta. BAVD (43%) and arterial hypertension (72%) were present across all ages. In patients >10 years distensibility impairment of the ascending aorta was predominantly associated with BAVD (OR 3.1, 95% CI 1.33 to 7.22, p=0.009). Distensibility impairment of the descending aorta was predominantly associated with arterial hypertension (OR 2.8, 95% CI 1.08 to 7.2, p=0.033) and was most pronounced in patients with uncontrolled hypertension despite antihypertensive treatment., Conclusion: From early adolescence on, both arterial hypertension and BAVD have a major impact on aortic distensibility. Their specific effects differ in strength and localisation (descending vs ascending aorta). Moreover, adequate blood pressure control is associated with improved distensibility. These findings could contribute to the understanding of cardiovascular complications and the management of patients with aortic coarctation., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2020. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

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.