November 27 – 28, 2015 Grand Hotel Salerno – Sala Cilento via Lungomare Tafuri, 1, 84127 Salerno
2015/02/20 Aula F. Ferro – Polo Universitario Azienda Ospedaliera – Universitaria “San Giovanni Di Dio e Ruggi D’Aragona”…
1. What is Bicuspid Aortic Valve?
The aortic valve is a one-way valve between the heart and the aorta, which is the main artery originating from the left ventricle that distributes oxygen-rich blood to the body. Normally, the aortic valve has three small leaflets that open when the heart beats allowing blood to flow from the heart to the aorta and the rest of the body, and close right after to prevent blood from going backwards into the heart.
The normal aortic valve is “tricuspid” that means it has three separate cusps or leaflets: the right coronary cusp that gives rise to the right coronary artery, the left coronary cusp that gives rise to the left coronary artery, and the noncoronary cusp.
In bicuspid aortic valve (BAV), the valve has only two leaflets rather than the normal three. Most commonly BAV is characterized by fusion of the valvar leaflets along a commissure resulting in a functionally bicuspid valvar structure with unequal-sized leaflets. The most common form is the result of fusion of the left coronary cusp and right coronary cusp (type 1 in 70% of patients). Fusion of the right coronary cusp with the noncoronary cusp (type 2) is present in 10–20% of patients, and fusion of left coronary cusp with noncoronary cusp (type 3) is more rare and reported in about 5–10% of the cases. Less frequently only two well-developed, equal-sized leaflets are present (also known as “true” bicuspid valve) or a single cusp with a single commissure (also known as unicommisural valve). (Figure 1)
Figure 1. Cartoon demonstrates BAV phenotypes. First cartoon on the left shows a type 1 BAV (fusion of the left coronary cusp and right coronary cusp along the commissure); second cartoon shows a type 2 BAV (fusion of the right coronary cusp with the noncoronary cusp along the commissure); third cartoon shows the fusion of left coronary cusp with noncoronary cusp along the commissure (type 3); last cartoon on the right shows a type 1 BAV with only two well-developed, equal-sized leaflets (“true” bicuspid valve).
With this deformity, the valve doesn’t function perfectly and it may cause symptoms or problems.
The disease is very common affecting about 1-2% of the population, and it is more common in males than in females with the ratio ranging from 2:1 to 4:1.
The clinical spectrum of the disease goes from asymptomatic patients whose defective valve can function for years without causing symptoms to infants who develops complications early in life. These are the two clinical extremes. In between are those patients who need aortic valve and ascending aorta repaired or replaced mostly in mid-life.
2. What causes Bicuspid Aortic Valve?
The causes of bicuspid aortic valve disease are not completely clear.
We do know that the defect is present at birth, but the actual events that lead to abnormal aortic leaflets formation in the early stages of the heart development are not known.
BAV is frequently present in genetic syndromes, is associated with other congenital heart disease, and is usually an inherited heart disease. It is estimated that 9-20% of first degree relatives of people with a bicuspid valve has the same cardiac anomaly. In addition, the incidence of BAV increases 4 times in relatives of patients with a congenital left-sided heart disease.
Despite all this evidences, we still do not understand the genetic cause(s) of BAV. Genetic studies are currently underway in various centers: up to now only few genetic mutations have been linked to the defect, but none of them has been demonstrated directly correlated with the disease.
3. Are there any complications related to Bicuspid Aortic Valve?
Yes, about 30% of people with bicuspid aortic valve disease develop complications. Most common problems include aortic valve dysfunction (aortic stenosis, aortic regurgitation), followed by increased risk of aortic root dilation/aneurysm formation that can lead to aortic dissection or rupture, infective endocarditis, and association with aortic coarctation.
A BAV may become stenotic (narrowed), making it harder for blood to pass through it, or it may start to leak letting blood to go backwards into the heart (regurgitant valve).
If the aortic valve is narrowed (aortic stenosis), the left ventricle has to work harder to force blood through the valve. This lead to left ventricular hypertrophy and enlargement.
When the valve doesn’t close tightly, blood leaks backward into the left heart (aortic regurgitatation). During each cardiac cycle the left ventricle holds more blood than usual and gain this lead to left ventricular hypertrophy and enlargement.
At first, the hypertrophy helps the left ventricle to pump blood with more force, but eventually it can lead to severe heart failure.
Aortic Dilation and Aneurysm formation
It is now recognized that BAV is frequently associated with dilation of the ascending thoracic aorta (the first part of the aorta arising from the heart and going up in the front of the chest). If this segment enlarges significantly the dilation is called aortic aneurysm. (figure 2)
Figure 2. Aortic dilation can occur at different site along the ascending aorta giving different phenotypes.
The risk of development of aortic dilation in patients with BAV is much higher than in the normal population. In BAV patient the aortic wall has intrinsic defects in the connective tissue and enzymatic activity that predispose the tissue to degeneration. As the tissue layers degenerate, the aortic wall loses its strength and dilates or forms aneurysms. Whether these histological changes are congenital or acquired due to hemodynamic changes caused by BAV is still unknown. Probably both contribute to the clinical picture. A higher gradient across a stenotic BAV and more severe aortic regurgitation are reported to be associated with faster increase in aortic dimensions. In contrast, severe dilation can also occur in the absence of stenosis or regurgitation, especially in young adults.
Aortic Dissection and Rupture
The dilated aorta can rupture or dissect (the inner and outer tissue layers of the aorta shred apart). The risk of dissection and rupture increases with the diameter of the aorta. Aortic rupture and dissection are life-threatening emergencies.
Aortic coarctation is a congenital narrowing of a short segment of the thoracic aorta. It is most commonly associated with the left coronary cusp-right coronary cusp type of BAV (type 1 – figure 1). Data on the prevalence of aortic coarctation in BAV are scarce: one report states 7%. In contrast, among patients with a coarctation, 50–75% have a BAV. In patients with coarctation and BAV, the risk of developing aortic dilation and dissection is much higher than in the population with BAV only.
Endocarditis is an inflammation of the heart that occurs when germs from another part of your body, such as your mouth, spread through your bloodstream and attach to damaged areas in your heart. A stenotic or regurgitant BAV is an ideal spot for germs to settle providing them the roughened surface they need to attach and multiply.
4. What are the symptoms of Bicuspid Aortic Valve?
Although BAV is present at birth, it usually is not diagnosed until adulthood because the defective valve can function for years without causing symptoms. Rarely, the disease is so severe at birth that the baby develops symptoms early in life. More commonly, patients will have a history childhood murmur and symptoms develop later in adulthood as the valve progressively degenerates.
BAV, either stenotic or regurgitant, can give rise to characteristic heart murmurs and clinical complaints that can be detected on clinical examination.
A dilating aorta is rarely symptomatic. Chronic chest, neck, and back pain can be atypical signs of a dilated aorta. Dyspnea, inspiratory stridor, and recurrent airway infection may indicate compression of airways due to a dilated aorta. The first clinical manifestation of untreated progressive aortic dilation associated with BAV is often aortic rupture or dissection.
A small subset of patients with BAV (<15%), almost exclusively young men, presents predominantly with aortic root dilation without substantial valvular stenosis or regurgitation, with very few or no clinical symptoms.
5. How is Bicuspid Aortic Valve diagnosed?
Patients experiencing symptoms typically go to their family doctor, who performs a physical examination and in case of suspicion of BAV referrers the patient to a cardiologist.
Cardiologists can use echocardiography (heart ultrasound), transesophageal echocardiography (an heart ultrasound performed through and esophagus), CT scans, and magnetic resonance imaging of the heart to evaluate the aortic valve and the aorta.
Echocardiography is often the first test done that identifies a BAV. The ascending aorta may also be imaged this way and any enlargement noted. Echocardiography does not always detect a bicuspid aortic valve, especially in older patient in whom images may not be very good in quality. In this case, MRI or CT can give more accurate images of the valve and aorta.
Because of BAV’s strong familial association, when a BAV is found in a family member, it is important to consider screening the entire family for the disease.
6. How is Bicuspid Aortic Valve treated?
Although there are no studies that provide evidence that medical treatment of a dilated aorta has any effect on the enlargement of the ascending aorta or of the aortic root in BAV, it is common clinical practice to advise beta-blocker therapy when the aorta is dilated.
About 80% of people with BAV will require surgical treatment to repair or replace the valve and part of the aorta during their life span. Most of the patients become symptomatic when mid-age. In the most severe cases, symptoms are present at birth or in early infancy and surgical repair of the valve must be performed in childhood.
For the patient who has valve stenosis or regurgitation that causes symptoms, the preferred treatment is to replace the valve or repair it if feasible.
When surgery is indicated for valve stenosis or regurgitation, aortic root replacement should be always considered if the aortic root is larger than 45 mm in diameter, because it is associated with an elevated risk of aortic dissection or rupture in the years following surgery.
An aorta that is enlarged and forms an aneurysm can be repaired or replaced with a section of plastic tubing that is sewn to replace the damaged part of the aorta.
7. What happens if I have Bicuspid Aortic Valve?
Every patient diagnosed with BAV must be seen regularly by a cardiologist. In fact, over time the abnormal valve can leak or become narrowed, and the aorta tends to enlarge. Rapid growth of the aorta is associated with increased risk aortic dissection or rupture.
8. What is BAVCon?
The International Bicuspid Aortic Valve Consortium (BAVCon) is a partnership of Investigators in the USA, Canada, Europe and other countries who work together to find the causes of BAV disease and its complications. Investigators collect data of patients with BAV and share them with others to establish a robust data bank and facilitate clinical research through use of these resources. The ultimate goal is to improve the diagnosis and management of patients affected by the disease in order to reduce cardiovascular complications which represent the primary cause of morbidity and premature death in persons with BAV.