Bicuspid aortic stenosis

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Varun Kumar, M.B.B.S. [2]; Usama Talib, BSc, MD [3]

A normal aortic valve has three leafs (it is a tricuspid valve), but some patients are born with a congenital abnormality in which the aortic valve has two leaflets (a bicuspid aortic valve)^[1].

A congenital bicuspid aortic valve may be associated with the development of either progressive clacific stenosis or regurgitation. What differentiates the pathophysiology of bicuspid aortic stenosis from other forms of aortic stenosis such as the degenerative aortic stenosis is the presence of concomitant valve disease, aortic root disease, and an increased incidence of coarctation of the aorta.^[2]

In this condition, instead of three valve cusps, the aortic valve has two cusps which results from the fusing of one of the commissures. Bicuspid aortic stenosis is the most common congenital abnormality of the heart accounting for 5% of congenital heart defects and it occurs in 1-2% of the population. It can be manifested as a murmur and usually has no long term health consequences, but if it does, the manifestation of aortic stenosis occurs 10 years earlier.

Risk factors of bicuspid aortic valve to progress to stenosis are hypercholesterolaemia, hypertension and asymmetrical leaflets.^[3]

First degree relatives of patients with bicuspid aortic valves should be screened using echocardiogram for its presence as there are evidence of familial clustering with autosomal dominant inheritance pattern.^[4]

Typically, aortic stenosis due to calcification of a bicuspid valve appears earlier, at 40 to 50 years of age, whereas that due to calcification and degeneration of a tricuspid aortic valve appears later, at 70 to 80 years of age.

Below is the video of Dr. Lars Svensson, Cardiothoracic Surgeon and Director of the Aorta Center, at the Cleveland Clinic giving an overview of bicuspid aortic valve and its management. {{#ev:youtube|n5V6ISV3VuA}}

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Varun Kumar, M.B.B.S. [2]; Usama Talib, BSc, MD [3]

The Bicuspid Aortic Valve has two cusps: one larger than the other. It is considered unobstructive if the edges of the cusps are free. If the edges are fused or no free the aortic valve is considered obstructive developing a dome during systole.^[1]

Bicuspid aortic valve have two distinct anatomical configurations:^[2]

1. Antero-posterior orientation of the commissures resulting in right and left cusps. This occurs in approximately 53 percent of cases. The right coronary artery originates from the right cusp and the left coronary from the left cusp. The false raphe is present in right cusp.
2. 47 percent of patients have commissures on right and left sides of annulus resulting in anterior and posterior cusps. The ostia of both coronary arteries and the false raphe are present in anterior cusp.

There are five varieties of congenitally abnormal aortic valves based on the number and types of cusps and commisures:^[3][4][5]

1. Unicuspid:
   • Acommissural
   • Unicommissural
2. Bicuspid
3. Tricuspid:
   • Miniature (small aortic ring)
   • Dysplastic
   • Cuspal inequality
4. Quadricuspid
5. Six-cuspid

Here is a bicuspid aortic valve compared with a normal aortic valve:

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Usama Talib, BSc, MD [2]

In 1513, Leonardo da Vinci was the first artist who first sketched the bicuspid aortic valve and termed it “cuspal inquelity”. ^[1]

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor-In-Chief: Cafer Zorkun, M.D., Ph.D. [2]; Usama Talib, BSc, MD [3]

A congenital bicuspid aortic valve may be associated with the development of either progressive clacific stenosis or regurgitation. What differentiates the pathophysiology of bicuspid aortic stenosis from other forms of aortic stenosis such as the degenerative aortic stenosis is the presence of concomitant valve disease, aortic root disease, and an increased incidence of coarctation of the aorta.^[1]

The pathophysiology of aortic stenosis is described in the main chapter on the pathophysiology of aortic stenosis here. What differentiates the pathophysiology of bicuspid aortic stenosis from other forms of aortic stenosis such as the degenerative aortic stenosis is the presence of concomitant valve disease, aortic root disease, and an increased incidence of coarctation of the aorta.^[2]

• Only 25% of patients with congenital aortic stenosis (AS) have aortic insufficiency (AI) compared with 75% of cases with acquired AS.
• In 75% of those with acquired AS, there is associated mitral valve disease. This association is rare in congenital AS.

The aorta of patients with bicuspid aortic valve does not have the same histological characteristics of a normal aorta. The tensile strength is reduced. These patients are at a higher risk for aortic dissection and aneurysm formation of the ascending aorta. The size of the proximal aorta should be evaluated carefully during the evaluation of the patient for aortic stenosis surgery. The initial diameter of the aorta should be noted and periodic evaluation with CT scan (every year or sooner if there is a change in aortic diameter) should be recommended. Therefore, if the patient needs surgery, the size of the aorta will determine what type of surgery should be offered to the patient.^[3]

Patients with bicuspid aortic valve are also at higher risk of aortic coarctation, an abnormal narrowing of the thoracic aorta ^[4].

Gross pathologic evaluation in patients with bicuspid aortic stenosis demonstrates fusion of one of the three commisures which results in two functional leaflets instead of the usual three aortic leaflets. Left ventricular hypertrophy is present in bicuspid aortic stenosis.^[5]

Images shown below are courtesy of Professor Peter Anderson DVM PhD^[6] and published with permission.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Usama Talib, BSc, MD [2]

In this condition, instead of three valve cusps, the aortic valve has two cusps which results from the fusing of one of the commissures. Bicuspid aortic stenosis is the most common congenital abnormality of the heart accounting for 5% of congenital heart defects and it occurs in 1-2% of the population. It can be manifested as a murmur and usually has no long term health consequences, but if it does, the manifestation of aortic stenosis occurs 10 years earlier.

Bicuspid aortic valve has been found to be an inheritable condition, with a demonstrated association with Notch 1.^[1] Familial clustering as well as isolated valve defects have been documented. The incidence of bicuspid aortic valve can be as high as 10% to 20% in families affected with the valve problem^[2]. Other congential heart defects are associated with bicuspid aortic valve at various frequencies.

This condition is often undiagnosed until later in life when the person develops symptomatic aortic stenosis. Aortic stenosis occurs in this condition usually in patients in their 40s or 50s, an average of 10 years earlier than can occur in people with congenitally normal aortic valves. 30% of cases are diagnosed in adolescence.

The congenital bicuspid aortic valve may become calcified, which may lead to half the cases of surgically important pure aortic stenosis in adults, with varying degrees of severity of aortic stenosis and aortic regurgitation.

Bicuspid aortic stenosis is more common in men than women (3:1 to 5:1).^[3]

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Varun Kumar, M.B.B.S. [2]; Usama Talib, BSc, MD [3]

Risk factors of bicuspid aortic valve to progress to stenosis are hypercholesterolaemia, hypertension and asymmetrical leaflets.

Factors affecting the rate of stenosis of bicuspid valves are not clearly defined.

• The rate of calcification of the bicuspid aortic valve depends on:^[1]
  • Total cholesterol
  • Hypertension
  • Asymmetrical leaflet sizes as there is more pronounced hemodynamic stress, resulting from straightening and stretching of the leaflets when they are open and close^[2]
• Sclerotic changes resulting in stenosis tend to occur at faster rate in patients with:^[3]
  • Anteroposteriorly located cusps than in those with right-left located cusps
  • Asymmetrical leaflet sizes

There are increasing evidences of heritability of bicuspid aortic valves which follows autosomal dominant inheritance pattern.^[4][5]

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Varun Kumar, M.B.B.S. [2]; Usama Talib, BSc, MD [3]

First degree relatives of patients with bicuspid aortic valves should be screened using echocardiogram for its presence as there are evidence of familial clustering with autosomal dominant inheritance pattern.^[1]

Template:WS Template:WH CME Category::Cardiology

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Varun Kumar, M.B.B.S. [2]; Usama Talib, BSc, MD [3]

• There is increasing evidence that occurrence of bicuspid aortic valve is heriditary with incidence as high as 10-17% in first-degree relatives of probands.^[1]
• Hypercholesterolemia accelerates the stenotic process via calcification.
• Other conditions associated with occurrence of bicuspid aortic valves include:
  • Turner’s syndrome^[2]
  • Williams syndrome^[3]
  • Coarctation of aorta^[4]
  • Patent ductus arteriosus^[5]

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Varun Kumar, M.B.B.S. [2]; Usama Talib, BSc, MD [3]

Bicuspid aortic valve, during childhood functions without any significant pressure gradient. However, the thickening and calcification of the valves may be detectable pathologically and on echocardiography by second decade^[1]. This progresses to aortic stenosis requiring operative correction in approximately 75% of cases.^[2][3]

Bicuspid aortic stenosis progressively leads to heart failure, arrythmias, angina and other symptoms which generally manifests between 40 to 60 years of age which is relatively younger to manifestation of aortic stenosis otherwise.^[2] However, children who develop early pathologic changes in bicuspid aortic valve are more likely to develop aortic insufficiency than stenosis.

Bicuspid aortic valve disease is associated with the following complications:

• Aortic stenosis in the majority (75%) of patients.^[2]
• Aortic insufficiency^[4][5]
• Endocarditis^[6]
• Aortic aneurysm^[3]
• Aortic dissection^[3]
• Sudden death can occur in children during and immediately after exertion especially among those with pressure gradient > 50 mmHg across the aortic valve.^[7]

For complications of aortic stenosis, click here

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