AORTIC VALVE STENOSIS
 

What is aortic valve stenosis?
 

Aortic valve stenosis describes a condition that causes narrowing of the aortic valve. The aortic valve is an outlet valve that is located in the outlet from the left sided chamber of the heart towards the body artery (aorta) and the body circulation. An aortic valve is made of three leaflets, which open widely to allow blood to flow to the lungs when the heart pumps, and closes to prevent any blood from returning back through it when the heart relaxes. When the valve is abnormal, either the edges of the leaflets are stuck or thickened or both, or there is a smaller size and structure of the valve. The valve often has only 2 leaflets (bicuspid aortic valve) and in severe condition only one. It may be associated with narrowing above the valve (supravalvar aortic stenosis).

 

 

What causes aortic valve stenosis?
 

The cause is not known in most cases. It can be associated with other heart conditions such as hole in the heart or more complex condition. Aortic valve stenosis caused by bicuspid aortic valve can occur in families and there seems to be genetic basis with different genes identified. It can be associated with abnormalities of other structures on the left side of heart (mitral stenosis, coarctation of aorta). The most severe form involves underdevelopment of almost all left sided structures – Hypoplastic Left Heart Syndome (HLHS).

 

 

What are the symptoms?
 

Babies born with very severe narrowing of aortic valve tend to get sick soon after birth (heart failure) and need urgent treatment. They need a special medication called prostaglandin that keeps the patent ductus arteriosus open and supports the circulation by bypassing the obstruction. After stabilisation, they need further definitive treatment by keyhole procedures (catheterization) or open heart surgery. Most infants and children with less severe forms are diagnosed with a heart murmur picked up during routine baby checks or assessment of non-cardiac problems. Generally, they do not have symptoms. When the valve stenosis is progressive and goes undetected, it could lead to symptoms of poor feeding, irritability, breathlessness and failure to gain weight in infancy and chest pain, poor exercise ability, palpitations or even fainting (syncope) in older children. 

 

 

How is it diagnosed?

 

Dr Khambadkone will make the diagnosis by clinical examination and confirm it by echocardiography. Echocardiography helps in assessing the severity of aortic valve stenosis and its effect on the heart muscle to determine whether it needs immediate treatment. An ECG will also be performed to judge the thickness and strain on the heart muscle from narrowing of the valve. With the advent of fetal echocardiography, it can be diagnosed before birth, particularly when moderate or severe, and a care plan can be made to avoid babies from becoming too sick. Babies are then treated soon after birth with prostaglandin medications to prevent them from deteriorating and transferred to a specialist centre where it can be treated.
 

 

How is it treated?
 

When treatment is necessary, Dr Khambadkone will perform a keyhole procedure by cardiac catheterization, balloon aortic valvotomy, stretching the valve with a balloon catheter. Although it does not change the valve, the balloon valvotomy improves its function by relieving the narrowing. It often causes the valve to be leaky to varying degrees. Reassuringly, this is very well tolerated in most patients and they can lead a normal active life. Mild to moderate aortic valve stenosis may only need regular monitoring and meticulous dental, skin and personal hygiene to reduce the burden of infection of the valve called endocarditis.

 

In some severe cases, the valve itself is underdeveloped and may need surgery to replace it with a larger valve. Valve replacement is generally not performed in small children as one can only put in small valves in small hearts. Small valves implanted in young growing children need replacing as children grow, and hence avoided if possible. The most common valve used is a tissue valve from their own lung artery (pulmonary valve) which is removed from the right side of the heart and inserted into the left sided outlet, an operation called the Ross procedure. The lung artery valve is then replaced with a donor tissue heart valve (pulmonary homograft).

 

In older patients and adults, artificial or mechanical heart valve may be used. This is longer lasting but needs daily medication to thin the blood (anticoagulation) with regular monitoring and a change in lifestyle. Aortic valve replacement by keyhole procedures (transcatheter aortic valve implantation TAVI) is a novel technique that has been used in elderly over the last two decades. It is not yet available in children and young adults.

 

The replaced valves that are not one’s own tissue are more prone to infection called endocarditis. Once infected, sadly, these valves almost always need to be removed to control the infection.
 

 

What is the prognosis?

Aortic valve stenosis needs life time monitoring. The prognosis depends on the size and structural abnormality causing aortic valve stenosis. A normal sized valve with three leaflets that are not thick but stuck at the edges improve the best after a balloon valvotomy rarely needing further procedures. They can lead a normal active life with regular meticulous follow-up. A smallish valve, with less number of leaflets that are thick and lumpy will most likely need multiple procedures until eventual valve replacement. At present, none of the valves available for replacement can last a life time and patients need constant monitoring. Meticulous dental, skin and personal hygiene and avoidance of tattooes and piercings help in reducing the burden of endocarditis.