Aortic valve stenosis is a medical condition affecting one of the heart’s valves. If the heart’s valves are not working as they should, then the ability of the heart to pump blood around the body can be reduced.
The Aortic valve is one of the heart’s four main valves; the Mitral valve, Pulmonary valve and Tricuspid valve being the other three. The Aortic Valve has 3 leaflets, that is it is made up of three ‘flaps’ of opening and closing tissue but in roughly 2 % of the population the valve has 2 leaflets, a common congenital heart defect.
Three Leaflet Valve Closed and Open
These valves control the flow of blood around the body by opening and closing as the heart contracts, controlling the flow of blood.
Positioned at the ‘exit’ of the Left Ventricle, every drop of blood being pumped around the body has to pass through the Aortic Valve.
A multitude of health conditions can lead to the valve not functioning as it should, either not opening properly, not closing properly or a combination of both.
Aortic stenosis is a condition where the valve does not open fully. This means that the pathway from the heart to the rest of the body is narrowed and blood cannot flow as freely as it should. If this narrowing (stenosis) is mild, then the patient will probably have no symptoms. If the stenosis becomes more severe it is possible that the patient may start to feel light headed and even faint as the blood flow to the head becomes restricted. Chest pain and palpitations are less common symptoms of more severe aortic stenosis.
Valves Level of Opening
Causes of Aortic Stenosis
Age Related Calcification
Calcium is a mineral found in the blood. As we get older the Aortic valve can start to accumulate deposits of calcium as the blood repeatedly passes through the valve. Some people’s valves accumulate a larger amount of calcium and this can start to stiffen and solidify the valve. This process is said to be apparent in roughly 1 in 20 adults over 65 years of age and can cause moderate to severe aortic stenosis.
Bicuspid and Unicuspid Aortic Valves
As mentioned earlier, roughly 2 % of people are born with Aortic valves that only have 2 leaflets, an even smaller percentage are born with unicuspid Aortic valves – those with 1 leaflet. These conditions are more susceptible to stiffening as a result of calcification, the affects of which tend to occur earlier in life.
Rheumatic Fever has the nasty ability to damage one or many of the heart valves. This scar tissue alone can hamper the opening and closing of the valve. The scar tissue also provides a a rougher surface that accelerates calcium deposits. As a result, extensive calcification can be triggered.
Rare Causes of Aortic Stenosis
Rare causes of aortic stenosis include Fabry disease, systemic Lupus Erythematosus, Paget disease, Hyperuricemia, and infection
Diagnosing Aortic Stenosis
Incidental finding of Aortic Stenosis are not uncommon in asymptomatic patients, this is because Aortic stenosis is often accompanied by a few typical traits.
– A murmur that can be detected by a physician listening to the patients chest with a stethoscope.
– Left Ventricular Hypertrophy that can be seen on an ECG.
Left Ventricular Hypertrophy is a thickening of the heart muscle. In Aortic stenosis the heart is often having to work harder to supply the body with blood, because the blood flow has increased resistance at the narrowing. Like any muscle the heart will increase in mass when it works harder!
Echocardiogram and Aortic Stenosis
It either of these are detected then an Echocardiogram will be used to confirm the diagnosis. An Echocardiogram is still the gold standard for finding and recognising the extent of Aortic stenosis. The echocardiogram can measure blood flow through the valve and can actually ‘SEE’ the movement and calcification of the Aortic valve. In the video below look at the structure labelled AV (Aortic Valve), it is brighter and whiter because Calcium deposits show up like this on an Echocardiogram. You can also see that it does not open and close freely like the Mitral Valve (labelled MV).
For a truly accurate assessment of the extent of Aortic stenosis, Cardiac Catheterisation is used. In this procedure catheters are fed along blood vessels into the heart, once in place accurate images can be acquired and blood pressures either side of the valve recorded.
In symptomatic patients an echocardiogram is still the most common tool to diagnose Aortic stenosis.
Treatment of Aortic Stenosis
If the narrowing is not severe and the patient is not symptomatic then often no treatment is required. If the patient is symptomatic then they may be prescribed medication to relieve symptoms, this is just a short term solution. Once symptomatic the treatment of choice is Aortic Valve repair/replacement surgery. Surgery gives the patient an excellent prognosis but without surgery the average survival is 2-3 years.
Aortic Valve Replacement
Aortic Valve Replacement is an open heart surgery carried out under general anaesthetic. To access the heart an incision is made along the chest. The heart is then stopped and the patient is put on a heart and lung bypass machine whilst the heart is operated on. The faulty valve is then removed and replaced with a prosthetic valve. The new valve is either a mechanical or biological.
Referred to as a ‘metal’ valve, the mechanical valve is commonly made from strong materials such as carbon or titanium. The benefits of such a valve are that it will last longer than the person it has been put in ever will. The downside of these valves are that they can be audible, i.e. when they open and close you can hear a clicking noise. Patients with these valves are also required to take anticoagulation medication for the rest of their lives, namely warfarin.
Biological Valve These valves come from Pigs or Cows. Whilst the ‘Pig’ valve is literally the pig’s Aortic valve, the ‘Cow’ valve is manufactured from heart tissue of the Cow. The pros and cons are the same regardless of which animal they are harvested from. Anticoagulation is not required and the valves are not audible, they do not make a clicking noise when they close. The downside is that they last a maximum of 15-20 years before further intervention may be required. For this reason they are the valve of preference in older patients. If the patient does outlive their ‘biological’ valve then a TAVI may be suitable at this point. You can see the different types of valves in this video.
TAVI – Transcatheter Aortic Valve Implantation A TAVI is a relatively new method of Aortic valve replacement. Instead of open heart surgery catheters are used to guide equipment through your network of blood vessels and in to your heart. Firstly a ‘balloon’ is placed inside the diseased Aortic valve and then inflated, this pushes the old diseased valve to the sides. The new prosthetic valve is then fed along your network of blood vessels deployed within the diseased and widened Aortic valve.
Aortic Valve Repair
Aortic valve repair is not at all common, usually because valves that have met the criteria for surgical intervention, are usually too diseased to repair. The most common repair is a balloon valvuloplasty, a procedure where a balloon catheter is inserted inside the valve and inflated forcing the valve to open wide. Once forced open the valve should have improved opening capability once the balloon has been removed. If you were to put your clenched fist in wax (do not do this) and let it dry, the first time you open your hand will be quite difficult. Once it has been fully opened, you can then make a fist and open it with a lot less resistance.