What is a bicuspid aortic valve?

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Last updated: October 24, 2026 • View editorial policy

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What is a Bicuspid Aortic Valve?

A bicuspid aortic valve (BAV) is the most common congenital heart abnormality, occurring in 1-2% of the population, where the aortic valve has only two functional cusps and two commissures instead of the normal three, resulting from either fusion of two adjacent cusps or developmental absence of a third cusp 1, 2.

Anatomical Definition and Diagnosis

The diagnosis is established by identifying only 2 commissures delimiting only 2 valve cusps on imaging, most commonly via transthoracic echocardiography in the parasternal short-axis view at the base of the heart 2, 3. On long-axis imaging, you may observe systolic doming of the conjoined (fused) cusp, particularly with right-left coronary cusp fusion.

Classification System

The 2021 International Consensus recognizes three main types of BAV 2:

1. Fused Type (most common) - with three phenotypes:

  • Right-left cusp fusion (most frequent)
  • Right-non cusp fusion
  • Left-non cusp fusion

2. Two-Sinus Type - with two phenotypes:

  • Latero-lateral
  • Antero-posterior

3. Partial-Fusion (Forme Fruste)

Clinical Significance and Associated Conditions

BAV is not a benign condition despite potentially remaining silent for years 4. The condition encompasses both valve dysfunction and an intrinsic aortopathy affecting the ascending aorta wall, likely sharing a common embryological origin involving neurocrestal cells 4.

Major Complications (in order of frequency)

The most common complications of typical BAV valvulo-aortopathy are 2:

  1. Aortic stenosis requiring valve surgery (most common)
  2. Ascending thoracic aortic dilatation requiring surgical repair
  3. Aortic regurgitation requiring valve surgery
  4. Mitral valve prolapse (may involve anterior leaflet)
  5. Infective endocarditis
  6. Aortic dissection (rare in pediatrics and adults without aortic dilatation)

Associated Aortopathy

BAV patients develop intrinsic aortic wall disease characterized by elastic fiber fragmentation, smooth muscle cell death, and mucoid extracellular matrix accumulation, leading to progressive aneurysmal dilatation independent of hemodynamic factors alone 4. The consensus recognizes three aortopathy phenotypes 2:

  • Ascending phenotype (most common)
  • Root phenotype
  • Extended phenotypes

Genetic and Familial Aspects

BAV has significant genetic components with autosomal dominant inheritance patterns 1. First-degree relatives have up to a 50% risk of inheriting the predisposition, with 9% of BAV patients having affected family members 1.

Critical screening recommendation: First-degree relatives of BAV patients should undergo echocardiographic screening for both BAV and asymptomatic thoracic aortic disease 1, 4. This screening can prevent premature deaths through early detection and monitoring.

Clinical Presentations

BAV manifests across a spectrum 2:

  • Complex presentations: Associated with syndromes, left-sided obstructions, significant aortic coarctation, early valve dysfunction, or early aortopathy—typically diagnosed in childhood through young adulthood

  • Typical presentations: Usually diagnosed in young to middle-aged adults, featuring progressive valvular dysfunction with high cumulative incidence of aortopathy over time

  • Undiagnosed/uncomplicated: Never causes complications requiring treatment (retrospective definition only)

Essential Imaging Approach

Transthoracic echocardiography serves as the first-line modality for 2:

  • BAV diagnosis and phenotyping
  • Valvular function assessment
  • Thoracic aorta measurement
  • Exclusion of aortic coarctation and other congenital lesions

All patients with BAV must have both the aortic root and ascending thoracic aorta evaluated for dilatation 1. When thoracic aorta assessment is inadequate by TTE, ECG-gated CT angiography or MR angiography is required 2.

Distinguishing Congenital from Acquired Fusion

Important pitfall: Heavily calcified or rheumatic tricuspid valves can mimic BAV through acquired fusion. Distinguishing features of congenital BAV include 3:

  • Obtuse angle between fused cusps (vs. acute in acquired)
  • Absent cleavage plane on ventricular aspect (vs. present in acquired)
  • Lower pseudocommissure height at raphe attachment compared to true commissures

Long-term Prognosis

More than 50% of BAV patients will require aortic valve replacement during their lifetime, and over 25% will undergo aortic surgery for root or ascending aorta dilatation, often concurrent with valve replacement 5. The risk of aortic dissection is increased, particularly in patients with bicuspid valve, aortic coarctation, hypertension, or pregnancy 1. Notably, 15% of patients with acute aortic dissection have BAV, and 12.5% of BAV patients with aortic diameter <5 cm experienced dissection 1.

References

4
Research

Bicuspid aortic valve: The most frequent and not so benign congenital heart disease.

Cardiovascular pathology : the official journal of the Society for Cardiovascular Pathology, 2024

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This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.