The congenital bicuspid aortic valve (BAV) condition is a valvulo-aortopathy with substantial heterogeneity in its clinical expressions, associated disorders, complications, and prognosis. This international evidence-based nomenclature and classification consensus document is intended for universal use by clinicians, imaging specialists, interventional cardiologists, surgeons, pathologists, geneticists, and researchers. The following are key points to remember:

1. The BAV condition is broadly categorized into three subgroups based on clinical and prognostic factors:
   • Complex valvulo-aortopathy is categorized by concomitant or associated disorders that may be clinically or prognostically more significant than the BAV condition (including Loeys-Dietz syndrome, Shone complex, or severe aortic coarctation) and/or early or accelerated valve dysfunction or aortopathy. This presentation commonly is diagnosed in pediatric, adolescent, or young adult populations, and requires early invasive treatment and close surveillance.
   • Typical valvulo-aortopathy is characterized by progressive valvular dysfunction and/or aorta dilation without other major associated disorders. This presentation commonly is diagnosed in young adult and adult populations, requires long-term surveillance, and commonly requires invasive treatment.
   • An undiagnosed or uncomplicated BAV condition is characterized as a lifelong silent condition with mild or nonprogressing valvulo-aortopathy that is discovered at autopsy or as an incidental imaging finding rather than manifesting clinically.
2. Common complications of typical valvulo-aortopathy, in order of frequency, are aortic stenosis (AS) requiring intervention, ascending thoracic aorta dilation that may require repair, aortic regurgitation (AR) requiring intervention, mitral valve prolapse requiring intervention, infective endocarditis, and aortic dissection.
3. Imaging for BAV relies on transthoracic echocardiography (TTE), cardiac computed tomography (CT), and cardiac magnetic resonance (CMR) imaging.
   • TTE is instrumental for BAV diagnosis, valvular phenotyping, assessment of valve function, assessment of aorta size, exclusion of aortic coarctation and other congenital lesions, and assessment for complications including infective endocarditis.
   • CT and CMR can be helpful in phenotyping, and are the gold standards for assessment of thoracic aorta size.
   • After TTE, CT or CMR should be performed if any aortic segment cannot be visualized, if coarctation cannot be excluded, or if any aortic segment is ≥45 mm.
4. The authors cite as rationale for nomenclature and classification consensus communication among clinicians specific morphological, functional, and prognostic aspects of BAV; and a common language to advance clinical, biological, and genetic understanding of BAV.
5. BAV types are defined as fused BAV, two-sinus BAV, and partial-fusion (or forme fruste) BAV.
6. The fused BAV type is the most common type (~90-95% of BAV cases); and is characterized by two of three cusps appearing fused within three distinguishable sinuses of Valsalva; frequently but not always with a congenital fibrous ridge (raphe) between the fused cusps.
   • Right-left fusion is most common (70-80%). The right-left phenotype also is most common across all variations of aortic valve dysfunction (AS or AR) and aortic phenotypes (normal aorta, dilated root, dilated ascending aorta, dilated arch).
   • Right-nonfusion is second most common (20-30%), and in adults is associated with a higher prevalence of AS and of progressive AR.
   • Left-nonfusion is least common (3-6%).
7. The two-sinus BAV type is uncommon (~5-7% of BAV cases), with two cusps of roughly equal size within two sinuses of Valsalva.
   • Laterolateral (side-to-side) two-sinus BAV has one coronary artery arising from each sinus.
   • Anteroposterior (front and back) two-sinus BAV can have one coronary artery arising from each sinus or both coronaries arising from the anterior sinus.
8. The partial-fusion BAV (or forme fruste) type is more recently recognized and of unknown prevalence. The appearance is similar to a typical tricuspid aortic valve, but with <50% fusion between two cusps at the commissural base forming a mini-raphe.
9. The authors propose reference to aortic dilation rather than aortic aneurysm.
10. There are two major forms of BAV aortic dilation phenotypes.
• The ascending phenotype, with dilation preferentially in the tubular ascending aorta accounts for approximately 70% of BAV aortopathy cases.
• The root phenotype, with dilation preferentially within the aortic root, accounts for approximately 20% of BAV aortopathy cases.
• There are two patient phenotypes, but the associations are not unequivocal: 1) Older patients of either sex with BAV present more often with aortic valve sclerosis or AS, ascending aorta phenotype, and right-noncusp fusion; and 2) younger patients with BAV, usually male, who present with AR, aortic root phenotype, and right-left cusp fusion.
• In some cases, aortic dilation is not dominant at a single segment, and in some cases, localized aorta dilation can evolve during follow-up.

Clinical Topics: Cardiac Surgery, Congenital Heart Disease and Pediatric Cardiology, Invasive Cardiovascular Angiography and Intervention, Noninvasive Imaging, Valvular Heart Disease, Vascular Medicine, Aortic Surgery, Cardiac Surgery and CHD and Pediatrics, Cardiac Surgery and VHD, Congenital Heart Disease, CHD and Pediatrics and Imaging, CHD and Pediatrics and Interventions, Interventions and Imaging, Interventions and Structural Heart Disease, Interventions and Vascular Medicine, Computed Tomography, Echocardiography/Ultrasound, Magnetic Resonance Imaging, Nuclear Imaging

Keywords: Aortic Aneurysm, Aortic Coarctation, Aortic Valve Insufficiency, Aortic Valve Stenosis, Bicuspid Aortic Valve Disease, Cardiac Surgical Procedures, Diagnostic Imaging, Dilatation, Echocardiography, Endocarditis, Heart Valve Diseases, Heart Defects, Congenital, Loeys-Dietz Syndrome, Magnetic Resonance Imaging, Mitral Valve Prolapse, Pediatrics, Sinus of Valsalva, Tomography, X-Ray Computed

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