Aortic stenosis

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The aortic valve is a valve that separates the aorta from the left ventricle. It has three leaflets and allows for blood flow from the left ventricle through to the aorta to the rest of the body.

Under certain circumstances, the aortic valve may become thickened and a rather narrow. This condition is known as aortic stenosis. Here we take a closer look at aortic stenosis.

What is aortic stenosis?
Aortic stenosis is a condition where the aortic valve becomes thickened and narrow. This narrowing obstructs the flow of blood from the left ventricle into the aorta and onward to the rest of the body.

This narrowing of the aortic valve can place the heart under a great deal of stress. This is because the heart needs to work harder in order to pump more blood to the body. Due to this stress, the heart muscle may become weak and patients may develop clinical symptoms due to this.

Patients who have aortic stenosis require regular follow-up by a cardiologist.

What causes aortic stenosis?
Narrowing of the aortic valve may occur due to a number of different reasons. The common causes of aortic stenosis are listed below –

1. Advancing age

In India, the most common cause of aortic stenosis is advancing age. As we get older, calcium deposits on the valves leading to them becoming thicker and narrow. In the initial stages, this does not cause any problems but as the calcium deposition advances further, the narrowed wild begins to restrict the flow of blood through it.

Narrowing of the aortic valve is usually seen after the age of 65 years.

It is important to note that this deposition of calcium onto the valves is not linked in any way to the intake of calcium in our diet or from taking calcium supplements.
In certain cases, calcium can deposit on the valves at a younger age as well. This is usually seen in patients who already have some abnormalities of the heart valves. These abnormalities typically occur from birth.

2. Congenital aortic stenosis

This refers to narrowing of the aortic valve that has commenced at a very young age. This occurs because there is some abnormality in the aortic valve.

We have already discussed the normal anatomy of the aortic valve elsewhere. The aortic valve has three leaflets normally. However, in a small number of patients, the aortic valve may have only one leaflet (called unicuspid aortic valve), two leaflets (called bicuspid aortic valve) and sometimes even four leaflets (called quadricuspid aortic valve).

3. Rheumatic fever

Rheumatic fever is a well recognised cause of valvular heart disease. With respect to the aortic valve, it can cause scarring of the aortic valve leading to it becoming narrowed. Scarring can in turn lead to calcium sticking to the valves making it a rigid and extremely thick.

Typically, patients who have suffered from the rheumatic fever end up having multiple valves affected.

Are there any risk factors that increase the chances of developing aortic stenosis?
There are certain common risk factors between all kinds of heart disease.

High blood pressure, type II diabetes, smoking and the presence of high cholesterol levels are all risk factors for the development of aortic stenosis.

As already seen, advancing age, birth defects and rheumatic fever are also risk factors for the development of this condition.

What are the symptoms of aortic stenosis?
There are a variety of symptoms that patients with aortic stenosis can experience. The degree to which they experience these symptoms depends upon the severity of the condition. The common symptoms include the following –

1. Chest pain or heaviness on exertion
2. Giddiness or dizziness
3. Difficulty breathing especially up on exertion
4. Tiredness when exerting oneself
5. Palpitations or a feeling that the heart is racing
6. An audible heart murmur – this is a sound that is heard by the doctor when they stethoscope is placed on the chest over the aortic valve.

In early stages of aortic stenosis, patients may not experience any symptoms whatsoever. Usually, aortic stenosis is picked up on routine clinical examination.

In patients with advanced aortic stenosis, the heart muscle can become rather weak and can lead to heart failure. Patients with heart failure may experience a great deal of breathlessness and tiredness.

What are the tests needed to diagnoses aortic stenosis?
Many a times, aortic stenosis is suspected following clinical examination of a patient. In order to confirm the diagnosis, the best test is an echocardiogram.

An echocardiogram can help determine the structure of the aortic valve along with its function. It also helps to determine how narrow the heart valve is and what the effect of this narrowed valve is on the heart. A weak heart can be detected on echocardiography as well.

Changes seen on echocardiography include

  • Thickened aortic valve leaflets
  • Thickened heart muscle
  • Bright calcium deposition on the valve leaflets
  • Restricted opening of the leaflets
  • Increased velocity of blood flow across the valve due to a large amount of blood flowing through a narrow valve.

You can read more about echocardiography here.

Additional tests may be performed once a diagnosis of aortic stenosis has been made. For example, an electrocardiogram and a chest x-ray may be performed to assess the effect of aortic stenosis on the electrical conduction of the heart and the lungs.

In patients who have advanced aortic stenosis, there may be a need for surgery. In such patients, a coronary angiogram may be performed prior to the surgery in order to determine if a bypass operation needs to be performed along with the aortic valve surgery.

Other special tests that may be done include a CT scan or MRI scan of the heart. This can help determine the size of the aortic and can guide the surgeon and cardiologist regarding additional treatment if needed.

It is not essential that all patients with aortic stenosis have these tests. In the early stages, an echocardiogram is often sufficient. Patients who have very mild aortic stenosis may only require repeat echocardiogram is once every two years. In those who have moderate aortic stenosis, they may require echocardiography slightly more frequently every year. On the other hand, in those who have severe to critical aortic stenosis, very frequent echocardiograms may be performed or patients may be referred across to a surgeon for further management.

You can read about surgical treatment of aortic stenosis here.

Treatment of aortic stenosis
The treatment of aortic stenosis depends upon how bad the patient’s symptoms are. In those who are experiencing little or no symptoms whatsoever, no specific treatment is required. However, those who experience chest pain or any of the symptoms previously described, specific treatment options may need to be pursued.

Medical treatment

Unfortunately, there is no specific medical treatment that is available in the management of aortic stenosis. There are no drugs or no medicines that can help reverse this condition.
Medical therapy however can play a role in the management of complications of aortic stenosis such as heart failure and irregular heartbeats.

Some of the commonly prescribed drugs include beta-blockers, digoxin and diuretics.

Surgical treatment

Surgical treatment is offered to patients with aortic stenosis who are experiencing troublesome symptoms. There are numerous therapies currently available and much of research has been conducted in this area. Some of the treatments that are currently offered in India include –

1. Balloon valvuloplasty

Balloon valvuloplasty is a treatment where a soft balloon is guided through the blood vessels in the groin all the way to the heart. When the balloon is within the narrowed aortic valve, it is inflated and this can stretch the valve opening. This stretching increases the valve area and can improve the flow of blood through it.
Balloon valvuloplasty is often reserved for young patients such as infants and children with congenital aortic stenosis. In adults, aortic valve replacement is offered.

2. Aortic valve replacement

Aortic valve replacement is a type of surgery where the diseased aortic valve is removed and a new aortic valve is stitched in place. The new valve might either be a metallic (mechanical) valve or a tissue valve.

The choice of valve depends upon the age of the patient, the co-existing risk factors and the choice of the surgeon and patient. A detailed discussion will be held by the cardiac surgeon regarding the benefits and risks of aortic valve replacement before the procedure is performed.

Patients who have a metallic mechanical valve inserted have a higher risk of developing blood clots. Due to this reason, they require some form of blood thinning medication such as warfarin.

Tissue valves are harvested either from pigs, cows or from dead human donors (cadavers). They are usually offered to older patients as they can become narrowed (just like normal human valves) with advancing age.

Not everyone with aortic stenosis who requires surgery is a suitable candidate for aortic valve replacement. This is because aortic valve replacement is an open heart surgery and has inherent risks. In such patients, transcatheter aortic valve replacement may be performed.

3. Transcatheter aortic valve replacement

This is a relatively new procedure where a balloon that has a prosthetic aortic valve loaded on it is inserted through the groin blood vessels all the way up with a heart. When in position, the balloon is inflated and this pushes the new aortic valve into the old diseased aortic valve. Balloons may not necessarily be used and sometimes self inflating aortic valves may be inserted.

Transcatheter aortic valve replacement is still undergoing a lot of research but so far the procedure has had good outcomes. Much more research and new techniques are being looked into.

Follow-up

Patients who undergo aortic valve surgery required regular follow-up in clinic. Stable patients may undergo a once a year clinic review along with echocardiography.

What is the long-term prognosis?
Many patients who have aortic stenosis are worried about what the effect will be on their longevity. The good news is that patients who have critical aortic stenosis without having any symptoms rarely succumb to this condition. In fact, only 1 out of 100 patients die from asymptomatic critical aortic stenosis.

In patients with mild or moderate aortic stenosis, the rate at which the condition progresses is often dependent upon the age of the patient. In those patients who have some form of kidney disease or coronary artery disease, the degree of obstruction worsens more rapidly when compared to those who do not.

In those patients with moderate to severe aortic stenosis with accompanying symptoms, a quarter of them may succumb to the condition at one year and half of them at two years. Some of the deaths can be sudden.

Is there any way to prevent aortic stenosis?
There are no specific measures that can be taken to prevent age-related aortic stenosis. However, following a healthy diet and performing a regular exercise can help prevent risk factors such as high blood pressure and diabetes – both of which are linked to aortic valve stenosis.

Children who have a sore throat must promptly see their doctor in order to check for and treat rheumatic fever.

Valve infections can be prevented by maintaining a healthy oral cavity and brushing and flossing twice a day. Make sure you visit your dentist on a regular basis.

Aortic stenosis and pregnancy
Aortic stenosis is uncommon in pregnancy. However, the most common cause of aortic stenosis in pregnancy is the presence of a bicuspid aortic valve (congenital abnormality).

In pregnant women with mild to moderate aortic stenosis and a normal functioning left ventricle, there is often no significant problem associated and the condition is well tolerated.

On the other hand, in those patients with severe aortic stenosis, there is a one in 10 chance of symptoms developing during pregnancy. This is often seen in the second trimester or in the early third trimester. As time progresses, a large proportion of these patients will require surgery post pregnancy.

Women who are known to have aortic valve disease who wish to become pregnant must visit their cardiologist for a complete cardiovascular examination prior to conception. Those with severe aortic stenosis may require surgical correction first.

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