Bicuspid aortic valve

Article written and reviewed by Dr Luca Moretti

Bicuspid aortic valve is a congenital heart disease in which the valve has two functional cusps instead of the three cusps of the normal semilunar valve. It is the most common congenital cardiac abnormality, with an estimated prevalence of about 0.5-2% and a higher frequency in males; it is not, however, a single morphology, because orientation, raphe, commissural symmetry, tissue quality and root characteristics define different phenotypes.

Bicuspid disease involves both valve and aorta. Some patients develop early calcific aortic stenosis; others develop aortic regurgitation because of prolapse or root dilation; still others retain good valve function but develop aortopathy. Diagnosis therefore initiates lifelong surveillance, even after valve replacement.

In most patients no monogenic syndrome can be identified, but familial clustering of bicuspid valve, aortic dilation or both is well documented. In most families, transmission does not follow a simple Mendelian pattern: incomplete penetrance, variable expressivity and contributions from multiple genes and hemodynamic factors explain why relatives in the same family may present different phenotypes.

Embryology, nomenclature and genetics

The aortic valve and outflow tract derive from a complex developmental process involving endocardial cushions, conotruncal ridges, neural crest cells and matrix remodeling. Abnormalities in separation and sculpting of the cusps may therefore produce two functional leaflets: bicuspid valve is not simply a normal tricuspid valve that has become "fused," but the result of a different organization of valvular development.

The international consensus distinguishes three major types. The fused type has two functional cusps, one of which derives from fusion of two components and may contain a raphe. The two-sinus type has two cusps and two sinuses without evident fusion. The partial-fusion type appears nearly tricuspid in diastole but shows a small commissural fusion and a bicuspid systolic opening.

In the fused type, the fused cusps are specified: right-left, right-noncoronary or, rarely, left-noncoronary. Presence and calcification of the raphe, cusp symmetry and commissural angle are reported. This description provides more useful information for repair and TAVI than the historical numerical label alone.

Classification of aortopathy distinguishes the root phenotype, with predominant dilation of the sinuses, the ascending phenotype, and forms extending to the arch. The root phenotype is more often associated with regurgitation and may represent more aggressive biology in some individuals; the ascending phenotype is the most common. The description should include each segment, not simply state that the "aorta is dilated."

NOTCH1 variants have been identified in a minority of families and are also associated with calcification; other genes involved in developmental and matrix pathways contribute. A pathogenic variant cannot be demonstrated in most isolated cases. The absence of a positive genetic test does not negate familial clustering or the need for screening.

Genetic counseling is particularly appropriate when bicuspid valve and aneurysm are associated with familial dissection, young age, syndromic features, arterial tortuosity or other congenital heart disease. The panel should be directed toward heritable aortic disease because the result can modify surgical thresholds and extracardiac screening.

Bicuspid valve is associated with aortic coarctation, interrupted aortic arch, septal defects and Turner syndrome. Coarctation may be subtle and requires examination of femoral pulses, lower-limb blood pressure and imaging of the arch. Persistent hypertension after correction continues to increase aortic wall stress.

Echocardiography is recommended for first-degree relatives. Screening assesses valve morphology, function and the diameters of the root and ascending aorta; auscultation alone is insufficient. If imaging is nondiagnostic, CT or magnetic resonance may be necessary in relatives with suspected aortic disease.

Family findings may be discordant: a parent with a dilated aorta may have a tricuspid valve, while a child may have a bicuspid valve without dilation. This variability supports assessment of both phenotypes. In families with multiple cases or dissections, an apparently unaffected relative may still require evaluation through a heritable aortopathy pathway.

Prenatal diagnosis is possible when anatomy is visible, but subtle forms may be missed and function may evolve after birth. Fetal bicuspid valve does not necessarily imply critical stenosis. In familial cases or when associated with coarctation, fetal echocardiography and postnatal follow-up are planned with congenital cardiology.

Valve disease and aortopathy

Bicuspid geometry creates an often elliptical orifice and eccentric jets, altering both stress on the cusps and forces exerted on the aortic wall. Helical flow tends to impinge asymmetrically on the ascending aorta and, together with intrinsic wall properties, contributes to calcification, prolapse and remodeling; hemodynamics alone, however, does not explain the entire spectrum of aortopathy.

Calcific stenosis develops on average earlier than in a tricuspid valve. The raphe often becomes a rigid calcific bar and calcium distribution is asymmetric. Velocity, gradients and area are interpreted according to the same hemodynamic principles as common aortic stenosis; bicuspid morphology, however, modifies planning and the choice between surgery and a transcatheter approach.

Regurgitation results from prolapse of the fused cusp, retraction, fenestrations, a coaptation defect or root dilation. It often affects younger adults and causes volume remodeling. Repairability depends on tissue quality, symmetry, effective height, the raphe and the ability to stabilize the annulus and sinotubular junction.

Stenosis and regurgitation may coexist and, when they do, a high gradient may result not only from reduced valve area but also from increased flow caused by regurgitation. To avoid overestimating the stenotic component, area, morphology and flow must therefore be integrated; in mixed disease the ventricle is simultaneously exposed to pressure and volume overload and may deteriorate along trajectories different from those of isolated lesions.

Bicuspid aortopathy results from the interaction between a predisposed wall and altered flow. Histologic studies show abnormalities of matrix, elastic fibers and smooth muscle cells; 4D-flow CMR links the fusion pattern to regions of increased wall shear stress. It is incorrect to reduce the disease to either pure genetics or pure jet-related injury.

The risk of dissection is higher than in the general population but much lower than in some syndromic aortopathies, especially at small diameters. It rises with diameter, growth, root phenotype, family history, coarctation and hypertension. Size remains the principal criterion, but not the only one.

Diameters should be interpreted in relation to body size, age and sex. In very short or very tall individuals, indices based on body surface area, height or cross-sectional area/height are useful. An index does not replace validated cutoffs, but prevents 50 mm from having the same automatic meaning in extremely different body sizes.

True growth requires comparable measurements. Differences of 1-2 mm may result from cardiac phase, imaging plane, edge convention or modality. Rapid growth should be confirmed with CT or magnetic resonance, ideally at the same center, before accelerating intervention unless an emergency is present.

Endocarditis is more frequent than with a normal valve and may cause acute regurgitation, abscesses and emboli. Native bicuspid valve alone is not a standard indication for antibiotic prophylaxis for dental procedures; oral hygiene, dental care and prompt assessment of persistent fever are essential.

The fusion pattern is associated with different flow directions, but does not allow deterministic prediction. Right-left fusion is often associated with dilation of the ascending aorta, whereas the root phenotype is more frequent with regurgitation and in some younger men. Follow-up is based on actual measurements, not morphology alone.

The aortic wall may continue to dilate even after normalization of flow with valve replacement. Average growth is often slow, but selected patients progress. The concept that SAVR automatically "cures" the aortopathy is therefore incorrect and may interrupt necessary surveillance.

Diagnosis and multimodality surveillance

Transthoracic echocardiography should visualize the valve in systole and diastole. In the short-axis view, the elliptical systolic "fish-mouth" opening is characteristic; in diastole, a raphe may simulate three closure lines. Diagnosis should not be based on a single suboptimal image, especially when calcification obscures the commissures.

The study describes type, orientation, raphe and function and measures the annulus, sinuses, sinotubular junction and ascending aorta. Continuous-wave Doppler from multiple windows quantifies stenosis; color Doppler, vena contracta, PISA, diastolic flow and volumes quantify regurgitation. The ventricle is assessed according to the predominant lesion.

2D and 3D TEE clarify anatomy when TTE is insufficient, in endocarditis and for repair planning. CT shows the number of commissures, raphe calcium, annular anatomy and aortic dimensions and is indispensable before TAVI. CMR measures valve function, regurgitation, ventricular volumes and aortic wall flow without radiation.

The entire thoracic aorta should be visualized at least once if echocardiography is incomplete or dilation is present. CT and magnetic resonance measure the aorta using double-oblique planes perpendicular to the centerline; ECG gating improves assessment of the root and ascending aorta. Subsequent reports should explicitly state the method and segment measured.

Initial assessment includes:

• Valve morphology: type, orientation, raphe, symmetry and calcification.
• Function: severity of stenosis, regurgitation or mixed disease.
• Left ventricle: mass, volumes, LVEF and response to loading.
• Aorta: annulus, sinuses, sinotubular junction, ascending aorta and arch.
• Associated lesions: coarctation and other congenital heart disease.
• Family context: aneurysm, dissection, sudden death and bicuspid valve.

The follow-up interval depends on valve function and aortic diameter. A normally functioning valve and normal aorta may be checked every few years; stenosis or regurgitation follow lesion-specific intervals. Above 40 mm, the aorta requires regular surveillance, generally annually or every two years according to size, growth and risk.

Exercise testing is useful in apparently asymptomatic severe stenosis and for exercise prescription. Blood pressure should also be monitored outside the clinic. There is no biomarker that replaces imaging; Lp(a) may contribute to calcific risk but does not by itself determine follow-up or valve treatment.

Screening of relatives is not a perfect one-time test: a well-visualized normal valve excludes bicuspid morphology, but dilation may develop or progress later. If there is strong familial aortopathy, management follows heritable aortic disease guidance even in a relative with a tricuspid valve.

The report should avoid vague expressions such as "probable bicuspid valve." If calcification prevents a diagnosis, the limitation should be stated and the next imaging modality indicated. Before TAVI or repair, defining the number of commissures, raphe and symmetry is part of procedural planning, not an academic detail.

CT valve calcium scoring may confirm the severity of low-gradient stenosis, but thresholds derived from tricuspid valves require caution in bicuspid disease, especially in younger patients with a predominantly fibrotic component. Valve area, gradient, flow, calcium and morphology are integrated without forcing artificial concordance.

4D-flow CMR visualizes helical jets and quantifies wall shear stress. It is a research and advanced characterization tool, not a routine measurement that determines surgery. Its value lies in clarifying the relationship between valve and wall and in developing future individualized models.

Treatment of the valve and aorta

No medication corrects bicuspid anatomy or reliably prevents dilation. Hypertension should be treated according to guidelines; beta-blockers or angiotensin receptor blockers are reasonable in aortopathy according to the individual profile, but BAV-specific evidence is limited. Blood-pressure control reduces a modifiable stressor without eliminating anatomical risk.

Indications for replacement in stenosis and regurgitation follow lesion severity and ventricular response. Bicuspid disease adds the need to decide whether to treat the aorta and whether the valve can be preserved. A Heart Team including an aortic surgeon helps avoid an isolated valve procedure when a clinically relevant aneurysm is present.

Repair is particularly attractive in younger patients with regurgitation, mobile cusps and sufficient tissue. The surgeon corrects prolapse or the raphe, reconstructs the free margin and stabilizes the annulus and root. Calcification, retraction and tissue deficiency reduce durability; the result should be verified intraoperatively with TEE.

In calcific stenosis, SAVR often remains preferred in younger patients, in the presence of aortopathy, complex coronary artery disease or unfavorable anatomy. It allows calcium removal, prosthesis selection and simultaneous aortic replacement. Age alone does not determine the decision, but a lifetime strategy is crucial.

TAVI outcomes in bicuspid anatomy have improved with newer devices, but the major randomized trials excluded or underrepresented these patients. A calcified raphe, bulky calcium, an elliptical annulus, horizontal aorta and low coronary ostia increase the risks of leak, asymmetric expansion, rupture and obstruction. The 2025 ESC/EACTS guidelines allow TAVI in selected patients at increased risk after CT assessment and expert discussion.

For aortopathy, the 2024 European aortic guidelines generally recommend surgery at a maximum diameter of at least 55 mm; in the root phenotype the threshold is 50 mm. In low-risk patients with an ascending phenotype, surgery may be considered above 52 mm, or from 50 mm in the presence of modifiers such as rapid growth, family history of acute aortic syndrome, coarctation, resistant hypertension, young age or planned pregnancy.

When a patient is already a candidate for valve surgery, concomitant replacement of the root or ascending aorta is considered from about 45 mm in low-risk patients with suitable anatomy. The decision depends on the segment, wall thickness and quality, body size, type of operation and experience; not every 45-mm aorta should automatically be replaced.

The procedure varies: supracoronary replacement of the ascending aorta, root replacement with a valved conduit, or a valve-sparing procedure. In younger patients with suitable cusps and a dilated root, valve-sparing reimplantation avoids a prosthesis and stabilizes the annulus, but requires a center with documented outcomes.

After valve replacement, the residual aorta continues to require surveillance. Surgery does not eliminate the predisposition of untreated segments. After TAVI, aortic imaging and future coronary access should be included in the lifetime plan.

The Ross procedure may be discussed in highly selected young adults because it provides a living autologous valve and good hemodynamics without anticoagulation. It introduces, however, an autograft susceptible to dilation and a pulmonary prosthesis; bicuspid valve and aortopathy require stabilization and considerable expertise. It is not a standard choice based on age alone.

A mechanical prosthesis reduces the likelihood of structural reintervention but requires anticoagulation; a biological prosthesis facilitates a future valve-in-valve procedure but may leave high gradients in a small annulus. Annular size, the aorta and the possibility of surgical enlargement are part of the strategy for the first operation.

Complications, physical activity and pregnancy

Severe stenosis leads to hypertrophy, fibrosis, angina, syncope and heart failure; regurgitation leads to dilation, dysfunction and arrhythmias. The rate of progression is individual. A young patient with regurgitation and a dilated root has a different problem from an older patient with calcific stenosis and a normal ascending aorta.

An aneurysm is often asymptomatic and does not produce a murmur proportional to risk. Dissection presents with sudden pain, syncope or malperfusion, but may be atypical. Acute symptoms in a patient with a dilated aorta require urgent imaging, not a scheduled outpatient assessment.

Endocarditis may destroy a cusp and cause acute regurgitation, abscess or emboli. Good oral health reduces daily bacteremia. Prosthetic valves and previous endocarditis are indications for prophylaxis; isolated bicuspid valve is not, according to current recommendations.

Exercise prescription depends on both valve and aorta. With normal function and nondilated diameters, recreational sports are generally possible; aortopathy requires caution with heavy lifting, the Valsalva maneuver and sports with a high static component. Competitive participation requires dedicated assessment and follow-up.

Pregnancy increases cardiac output and aortic wall stress. Valve function, ventricular function, diameter, growth and associated syndromes should be assessed before conception. A markedly dilated bicuspid aorta may be an indication for preventive surgery; during pregnancy, coordinated surveillance and delivery planning are required.

People with Turner syndrome deserve particular attention because small body size makes absolute diameters inadequate and increases the relevance of the aortic size index. Coarctation, hypertension and assisted pregnancy add risk. A diagnosis of bicuspid valve in this context requires a congenital/aortic center.

After intervention, complications include prosthetic dysfunction, residual regurgitation after repair, aortic progression, endocarditis and need for reintervention. The optimal strategy considers durability, anticoagulation, valve-in-valve feasibility and coronary access from the outset.

With identification, family screening and appropriate surveillance, most patients maintain good quality and length of life. Risk arises mainly from unrecognized disease or fragmented follow-up. A precise anatomical description and a written plan transform a heterogeneous diagnosis into measurable management.

Occupations involving extreme lifting, diving, high altitude or inability to obtain rapid medical care require specific assessment. Indiscriminate restriction promotes sedentary behavior, whereas absence of limits with significant aortic disease exposes patients to pressure surges. A written, updated prescription is preferable to generic recommendations.

Transition from pediatric to adult care is a vulnerable point. An adolescent with a normally functioning valve may be lost to follow-up just before the age at which regurgitation and aortopathy begin to appear. A transition program should transfer morphology, measurements, family history and the interval to the next imaging study.