Bicuspid aortic valve
Bicuspid aortic valve
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The prevalence is 1.3% worldwide.
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Aortic stenosis and aortic regurgitation are the most common complication
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Bicuspid aortopathy is also found in approximately 50% of affected individuals, ranging from 20% to 84%.
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Occurring sporadically, most patients with BAV are not found to have a genetic variant; however, the modes of inheritance include autosomal dominant (with variable penetrance), X-linked, and familial.
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The abnormalities in the migration ability of neural crest cells may be a shared mechanism behind both valve and aortic pathologies.
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Certain types of heritable thoracic aortic diseases (HTAD) exhibit a high prevalence of BAV, such as Loeys-Dietz syndrome (TGFBT1, TGFBR2, SMAD3, TGFB2, and TGFB3 mutations) and variants involving the NOTCH1, ACTA2, MAT2A, SMAD6, and LOX genes.
Right coronary cusp
Non coronary cusp
Left coronary cusp
A normal aortic valve is composed of three cusps: the left, the right, and the non-coronary cusp. These cusps depend on their association with the respective coronary ostia to identify them.
The outer edges of each cusp connect to the aorta's wall, and the junction where the leaflets meet is known as a commissure.
Left coronary cusp
Fusion of the right and non-coronary cuspps
Bicuspid aortic valve RN fusion pattern
2-sinus BAV (5-7% of BAV) 2 phenotype
I
Latero-lateral
(most common)
2A
2B
Anteroposterior
(least common)
A bicuspid aortic valve usually consists of two unequal leaflets, entitled fused BAV (90-95% of cases).
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The most common RL fusion pattern (70-80% of cases) involves the right and left cusps.
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The second most common pattern is the RN fusion pattern(20-30% of cases), which involves the fusion of the right and non-coronary cusps.
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The least common pattern is the fusion of the left and non-coronary cusps.
The less common type (5–7% of cases), known as 2-sinus BAV, is characterized by two sinuses each with two cusps, generally of equal size, displaying symmetrical, with symmetrical nonfused commissural angles, and typically lacking raphae.
An example of 2-sinus BAV.
Aortopathy
Bicuspid aortopathy occurs in up to 50% of individuals with BAV. The debate continues about whether BAV aortopathy results from the below.
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Pathology in the vessel wall
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Abnormalities in the ability of neural crest cells to migrate.
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Changes in the architecture of vascular smooth muscle cells within the aortic media may lead to progressive cystic medial necrosis, resulting in dilatation and the formation of aneurysms.
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Aberrant matrix protein expression, a deficiency in fibrillin-1, and a surge in the local level of matrix metalloproteinases(MMPs) lead to a loss of integrity in the extracellular matrix.
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Altered hemodynamics, valve-related rheological changes, or both.
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BAV valve with or without stenosis or insufficiency is associated with changes in flow patterns across the valve. Flow pattern alteration due to valve pathology within the proximal aorta may promote asymmetric dilatation.
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BAV is associated with other lesions, including aortic coarctation, patent ductus arteriosus, and proximal coronary artery anomalies.
Type 1, the most common type, involves dilatation of the ascending aorta, usually asymmetrically along the convexity, with or without concomitant aortic root dilatation.
This type is often observed in the elderly with some degree of aortic stenosis and is associated with the RL fusion pattern.
Type 2 comprises isolated ascending aortic involvement (with minimal or no root dilation) and proximal or transverse arch involvement. It is frequently associated with RN fusion.
Type 3, the ‘root phenotype,’ involves isolated aortic root dilatation. It is seen in younger individuals and is associated with aortic regurgitation and higher rates of aortic complications.
Inherent defects in vessel wall integrity have been proposed in the pathogenesis of BAV aortopathy.
1
dilatation of the tubular ascending aorta (
along its convexity),
varying degrees of aortic-root dilatation
older age at diagnosis (>50 years)
valvular stenosis, and
the RL fusion pattern
2
isolated involvement of the tubular ascending aorta, sparing aortic root, extending into the transverse aortic arch
RN fusion pattern.
3
isolated
dilatation of the aortic root
younger age at diagnosis (<40 years)
male sex, and aortic regurgitation
most likely to be associated
with a genetic cause.
2022 ACC/AHA guideline for the diagnosis and management of aortic disease: a report of the American Heart Association/American College of Cardiology Joint Committee on Clinical Practice Guidelines.
Bicuspid Aortic valve
With indication for SAVR
Aortic root or ascending aorta < 4.5 cm.
AVR
Aortic root or ascending aorta ≥ 4.5 cm.
Concomittant
AVR and aortic root/ascending aorta replacement
Multidisciplinary team
Without indication for SAVR
< 4.0 cm.
Surveillance every 3-5 years
4.0-4.9 cm.
Yearly surveillance
5.0-5.4 cm.
without risk factor
Replacement of Aorta and/or aortic root (2B)
5.0-5.4 cm.
>1 risk factor*
Replacement of Aorta and/or aortic root (2A)
Aortic root or ascending aortic area to height ratio ≥ 10 cm/m2
Replacement of Aorta and/or aortic root (2A)
≥ 5.5 cm.
Replacement of Aorta and/or aortic root (1B)
>1 Risk Factor*
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Family history of aortic dissection/sudden death
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Growth ≥ 0.3 cm/year
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Coarctation
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Root phenotype
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Uncontrolled hypertension
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Predominant aortic insufficiency
Non-surgical management
Smoking Cessation
Antihypertensive therapies should be prescribed for a blood pressure of 130/80 mmHg (Class 1B).
Prefer beta-blockers (1B) and, if necessary, use them with angiotensin receptor antagonists (Class 2A). Angiotensin II receptor blockade improves matrix metalloproteinases/tissue inhibitor of matrix metalloproteinase-1 balance
High-intensity statins, particularly concomitant atherosclerosis (Class 2A).
References
Verma Subodh, Siu Samuel C. Aortic Dilatation in Patients with Bicuspid Aortic Valve. New England Journal of Medicine. 370(20):1920–9.
Verma R, Cohen G, Colbert J, Fedak PWM. Bicuspid aortic valve associated aortopathy: 2022 guideline update. Curr Opin Cardiol. 2023 Mar 1;38(2):61-67.
Isselbacher EM, Preventza O, Black JH III, et al. 2022 ACC/AHA guideline for the diagnosis and management of aortic disease: a report of the American Heart Association/American College of Cardiology Joint Committee on Clinical Practice Guidelines. Circulation 2022; 80:e223–e393.
Michelena HI, Della Corte A, Evangelista A, Maleszewski JJ, Edwards WD, Roman MJ, et al. Summary: International consensus statement on nomenclature and classification of the congenital bicuspid aortic valve and its aortopathy, for clinical, surgical, interventional, and research purposes. The Journal of Thoracic and Cardiovascular Surgery. 2021 Sep 1;162(3):781–97.