BICUSPID AORTIC VALVE

 

What is bicuspid aortic valve?
 

A normal aortic valve has three flaps – also called leaflets or cusps. They open and close to let blood out of the left pumping chamber of the heart – the left ventricle, that pumps blood to the body. The leaflets open fully when the heart pumps and close tightly to prevent any blood that is pumped out from returning back into the heart thus maintaining a forward flow. In some children or adults, instead of three leaflets, the aortic valve has only two, and hence called bicuspid aortic valve. Often, there are three leaflets of which two are stuck together at their edge forming a single leaflet and hence forming a two leaflet valve.

 

 

How common is a bicuspid aortic valve ?
 

It is thought to be one of the commonest congenital heart defect. 1 to 2 in a 100 may have it. It is certainly more commonly associated with other congenital heart defects, particularly those where there is narrowing of other structures in the left side of the heart (mitral stenosis, coarctation of aorta).
 

 

Can it run in families?
 

Bicuspid aortic valve is inherited and has many genes that are identified linked to its presence. This increases risk to the immediate family – parents or siblings. Often, children are referred for screening after one parent has heart surgery or a sudden cardiac problem involving the aortic valve or the main body artery- the aorta. Screening of immediate family is recommended with echocardiography to assess their aortic valve.
 

 

How is it diagnosed?
 

The diagnosis is made by clinical examination and confirmed by echocardiography. The abnormal structure of the valve creates a distinct sound called “ejection click”. Often, the abnormal flow pattern through the valve causes a heart murmur. If there is narrowing (stenosis) or leakage (regurgitation) of blood, there are associated characteristic murmurs. Echocardiography is a very important investigation to diagnose and assess the function of a bicuspid aortic valve. It identifies the three leaflets of a normal valve that appear like an inverted Y or a Mercedes Benz sign. However, a bicuspid aortic valve appears like a fish mouth when open and a straight line when closed. It also helps to assess the function of the aortic valve, size of the aorta and detects associated heart defects.
 

 

What are the symptoms of bicuspid aortic valve?

 

Most often there are no symptoms and it is diagnosed after a GP or Paediatrician picks up a heart murmur or abnormal heart sounds. It is however extremely important to have regular assessment once bicuspid aortic valve has been diagnosed. There are certain changes such as enlargement or dilatation of the aorta, that can only be detected by echocardiography. When the aortic valve has abnormal function, such as narrowing (stenosis; aortic valve stenosis) or leakage (regurgitation) then the symptoms related to aortic valve dysfunction may manifest. When associated congenital heart defects are present such as ventricular septal defect or coarctation of aorta, the symptoms related to these condition may lead to medical attention and the bicuspid aortic valve is diagnosed as an associated finding and monitored.
 

 

What is the long term burden of bicuspid aortic valve?
 

A bicuspid aortic valve needs lifelong monitoring, even in absence of associated defects or aortic valve dysfunction. There is a strong association of bicuspid aortic valve and weakness of the aortic wall that causes it to stretch and increase in size. This could happen gradually over time or suddenly related to certain events such as pregnancy or strenuous activity as lifting of heavy weights. A sudden weakening can create a defect within the wall with blood entering the wall and compromising the space available for blood to flow (dissection of aorta). Rarely, a stretched enlarged aorta may rupture with catastrophic consequences. It is important to monitor the size of the aorta to try and reduce these consequences.

 

The bicuspid aortic valve is at risk of infection due to its abnormal structure and flow characteristics, more so if the valve has stenosis or regurgitation. This event is called endocarditis and the risk increases with age and is more common in males. Once infected, there is a high risk of the valve function being compromised. Aortic valve endocarditis is a serious infection and can lead to septicaemia, heart failure, involvement of other valves in heart, multi-organ failure (kidney or liver), or stroke. Treatment has to be prompt with initial blood tests and intravenous antibiotics for a period of at least 6 weeks. If the infection is difficult to control or the aortic valve dysfunction causes heart failure or stroke, urgent surgery may be needed. Surgery often requires removal of the infected valve and replacement. Bicuspid aortic valve are at a high risk of hardening due to deposition of calcium. This is probably related to accelerated aging and could affect the function of the valve needing keyhole procedures or surgery.
 

 

How is bicuspid aortic valve treated?
 

A normally functioning bicuspid valve does not need any treatment but regular monitoring and follow-up. The need to reduce the risk of endocarditis cannot be overemphasized. Maintaining meticulous dental, oral, skin and personal hygiene is of utmost importance to reduce the risk of introducing bacteria or bugs into the circulation, an event called bacteraemia, which precedes endocarditis.

 

The aortic valve function further determines need for treatment and Dr Khambadkone will discuss all options available. If there is moderate to severe stenosis or regurgitation, the valve dysfunction is treated by keyhole procedure or surgery as indicated. If there is enlargement of the aorta (aortic dilatation or aneurysm), this may need regular monitoring. Progression could be reduced by medications. Control of blood pressure and certain lifestyle changes may help. If it enlarges to dangerous levels, surgery may be necessary to replace that segment of the aorta with a rigid tube. This is more common in teenagers or adults compared to infants and young children.