The aortic valve is the exit valve of the heart. When the heart contracts, it forces open this one-way valve to push the blood out into the main blood vessel, the aorta, from where the blood goes to the rest of the body. If there is a problem with this valve, then the heart may not be able to pump blood out as efficiently and this will impact on how much blood is delivered to the rest of the body.
Usually the valve is made up of 3 leaflets and hence when the valve is closed it resembles a Mercedes Benz sign. In patients with a bicuspid valve, there are only 2 functioning leaflets making up the valve. This may be because there were only 2 to start off with or because of the three leaflets, two have fused together and therefore you have only 2 functioning leaflets. The problem is that when the valve structure is abnormal, the blood flow through the valve will not be as efficient or stream-lined as normal and therefore the valve will be subjected to a lot more ‘wear and tear’. There are 2 consequences to more ‘wear and tear’. Firstly the valve is more likely to calcify , thicken and narrow to the point that it may impact on the blood coming out of the heart. Secondly the valve is more likely to degenerate and therefore leak more.
A bicuspid valve is a congenital/inherited problem. The patient is born with it. It is the most common inherited heart problem. It is estimated that perhaps more than 1% of the population have a bicuspid valve. One in every 100 people you meet on the street will have a bicuspid valve. Most of these people will not know that they have a bicuspid valve because until the valve is excessively narrowed or excessively leaky, it will not cause any symptoms and so it is usually an incidental discovery either when the doctor hears a heart murmur or if the patient happens to have an ultrasound scan. As it is inherited, it is also found more frequently in family members of a patient. The prevalence is 9-10% in 1st degree relatives. This means that if a patient has a bicuspid valve, 1 in every 10 first degree relatives will also have a bicuspid valve and therefore these days, we recommend that all 1st degree relatives also have an echocardiogram. If it is not there, it is not there as it is usually present from birth.
It is very important to understand that the aortic valve is made from the tissue of the aorta – the big blood vessel and therefore people who have a bicuspid aortic valve may have problems with their aorta or other blood vessels in the body. Patients with a bicuspid valve may also have other lesions such as:
- Coarctation of the aorta
- Dilation and aneurysms of the aorta
- Patent ductus arteriosus
- Ventricular septal defect
- Sinus of valsalva aneurysms
- Anomalous coronary arteries
- Intracranial aneurysms
Therefore in my own practice, if I find a patient with a bicuspid aortic valve I usually look carefully for any other associated lesions because they may in themselves have a bearing on the patient’s longevity.
What is the natural history of a bicuspid aortic valve?
There are some patients in whom the bicuspid valve may continue to function normally without any problems for the duration of the patient’s lifespan but at least a third and probably the majority will develop some sort of complication in their lifetime. If a patient is lucky enough not to develop a complication then their life expectancy is the same as that of the normal population.
- The valve becomes progressively leaky
- The valve becomes progressively narrowed
- The valve is more prone to getting more infected
- There may be a complication as a result of the associated lesions such as progressive dilation or even dissection/rupturing of the aorta
The treatment is usually surgery to replace the valve when a complication develops. Bicuspid valves in general will require surgery 5-10 years before trileaflet valves. In those patients, who require aortic valve surgery before the age of 50, at least ⅔ will have a bicuspid valve. Even patients who develop an infection of their bicuspid aortic valve are more likely to need surgery to replace the valve compared to those who have similar infection on a trileaflet valve. If there is an associated lesion such as dilation or aneurysm of the aorta then the surgeon will plan the operation in such a way that the aneurysm is also operated on at the same sitting. The good news is that the operative and post-operative risks of such daunting surgery are low. At 30 days post-op, mortality is between 0-2.5%. Another good bit of news is that there is now a keyhole method by which aortic valves can be fixed. This is called TAVI and this procedure is being performed in several centres worldwide and the results seem to be as good with this procedure as with open heart surgery provided the patients are selected carefully.
In summary the main points are
- I think it goes without saying that you should have regular surveillance of the valve by making sure you attend for regular echocardiography to allow careful monitoring of whether the valve is getting more leaky or narrowed and also to look for the associated lesions such as aortic aneurysm.
- I think looking after your lifestyle is very important. It makes you a healthier person. It will probably delay the onset of complications and the healthier you the lower the overall risk from operative intervention.
- Bicuspid aortic valves are more prone to getting infected and therefore in my own practice, I recommend that patients ask for prophylactic antibiotics when having dental procedures or operations. They are not considered a very high risk lesion and current guidelines don’t advocate it but i usually speak to my patients and if they are keen to take necessary precautions then i support their decision
- Finally if a complication does develop, then timely surgery will fix the problem and allow you to get back to a very acceptable level of functioning. The risks associated with an operation are generally very low.
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