The following are key points to remember from a state-of-the-art review on mechanisms of aortic dilation in patients with bicuspid aortic valve (BAV):

1. BAV is the most common congenital heart anomaly, with a prevalence of 0.7-1.4% in the general population (2-3:1 male predominance). Patients with BAV are at risk for dilation of all aortic segments from the root to the mid-aortic arch. The age-adjusted risk of aortic aneurysm is 80 times higher in BAV patients than in the general population, and the age-adjusted risk of aortic dissection is 8.4 times higher.
2. Aortic root dilation occurs in approximately 20-30% of BAV patients, and ascending aortic dilation in 60-80%. The ascending aortic aneurysm phenotype is related to aortic stenosis and older age at diagnosis, while the aortic root aneurysm phenotype is associated with aortic regurgitation, male sex, and younger age at diagnosis. A recent study in the pediatric population showed that 50% of children with BAV presented with aortic root or ascending aortic dilation, more commonly the latter.
3. Protocols for follow-up aortic imaging in BAV patients are not well-standardized. The authors recommend imaging every 1-2 years, depending on aortic diameters and cardiovascular risk factors. If echocardiographic measurements correlate with those from computed tomography or cardiovascular magnetic resonance (CMR), echocardiography may be used for follow-up, but measurements should be confirmed with cross-sectional imaging; approximately 3 every 3 years. Cross-sectional imaging should also be performed to confirm any aortic diameter ≥45 mm by echocardiography, and to assess aortic root diameters when echocardiography suggests an asymmetric aortic root.
4. The two major etiologies of aortic dilation in BAV are: 1) genetically mediated intrinsic alterations of the aortic wall, and 2) altered blood flow dynamics related to valve dysfunction and aortic stiffness. Variants in genes such as NOTCH1 have been associated with BAV, but these account for only a small proportion of familial and sporadic BAV cases. Therefore, genetic testing in not recommended for most patients with BAV, though it is reasonable in patients <30 years old with the root phenotype (given the association with genetic syndromes such as Loeys-Dietz) and in patients with syndromic features or a family history of aortic dissection or unexplained sudden cardiac death.
5. BAV-associated flow disturbances may result in increased wall shear stress, which is associated with aortic wall elastic fiber thinning and extracellular matrix dysregulation. Patients with the right-noncoronary fusion (RN) phenotype have more severe flow alterations than those with the right-left fusion (RL) phenotype. In BAV with aortic stenosis, wall shear stress tends to be asymmetric, and aortic wall fiber thinning is most pronounced in regions where the jet impacts the wall. Conversely, in BAV with aortic regurgitation, the increase in regional wall shear stress is more homogeneous and correlates positively with stroke volume. The authors suggest that 4D flow CMR at BAV diagnosis may help identify patients at risk of progressive aortic dilation, so that they may be followed more closely.

Clinical Topics: Arrhythmias and Clinical EP, Cardiac Surgery, Congenital Heart Disease and Pediatric Cardiology, Invasive Cardiovascular Angiography and Intervention, Noninvasive Imaging, Prevention, Valvular Heart Disease, Vascular Medicine, SCD/Ventricular Arrhythmias, Aortic Surgery, Cardiac Surgery and Arrhythmias, Cardiac Surgery and CHD and Pediatrics, Cardiac Surgery and VHD, Congenital Heart Disease, CHD and Pediatrics and Arrhythmias, CHD and Pediatrics and Imaging, CHD and Pediatrics and Interventions, CHD and Pediatrics and Quality Improvement, Interventions and Imaging, Interventions and Structural Heart Disease, Interventions and Vascular Medicine, Echocardiography/Ultrasound, Magnetic Resonance Imaging

Keywords: Aortic Aneurysm, Aortic Valve Insufficiency, Aortic Valve Stenosis, Bicuspid Aortic Valve Disease, Cardiac Surgical Procedures, Death, Sudden, Cardiac, Diagnostic Imaging, Dilatation, Dilatation, Pathologic, Echocardiography, Genetic Testing, Heart Defects, Congenital, Heart Valve Diseases, Loeys-Dietz Syndrome, Magnetic Resonance Imaging, Pediatrics, Phenotype, Risk Factors, Secondary Prevention

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