Aortic Stenosis

Aortic valve stenosis is a condition in which the valve loses its flexibility, accompanied by a reduction in its opening.

To understand this condition, it’s important to know how the heart and its valves function.

The Heart and Its Valves

The heart, the engine of life, has four valves that ensure the one-way flow of blood from one heart chamber to another, preventing any backflow into the previous chamber.

Among the heart valves, two are called tricuspid valves, while the other two are known as atrioventricular valves.

 

Tricuspid valves

The tricuspid valves, which include the pulmonary valve and the aortic valve, are named for their three leaflets, called cusps.

The pulmonary valve separates the right ventricle from the pulmonary artery, while the aortic valve separates the left ventricle from the aorta.

The Aortic Valve

These very thin leaflets of the aortic valve give it great flexibility. They are shaped like a ladle, which is why they are also called cusps.

They are attached to the aortic annulus, located at the base of the aorta. The rest of the leaflet is free and moves according to the pressure variations on either side of the valve. Thus, the valve opens when the pressure inside the heart exceeds that in the aorta.

Opening and Closing the Aortic Valve

Each heartbeat represents a cycle divided into two phases: contraction and relaxation. The heart fills with blood during its relaxation phase.

When the heart contracts and the pressure inside the heart becomes higher than that in the aorta, the aortic valve opens, allowing blood to be ejected into the aorta.

After this effort, the heart relaxes to enter its resting phase. During this time, the blood expelled into the aorta tries to return to the ventricle, driven by the suction effect caused by the heart’s relaxation as it returns to its initial shape.

This attempt to return to the ventricle causes the cusps of the aortic valve to close. A useful image to visualize this is like inverted parachutes opening, blocking the blood from flowing back into the left ventricle.

Where the Narrowing Comes From

Aortic stenosis is, in most cases, the result of a degenerative process of the aortic valve, leading to its calcification and subsequent narrowing.

This degeneration usually begins with sclerosis of the aortic valve, which then progresses to stenosis. The process can be accelerated in the presence of a bicuspid aortic valve. We will discuss this further later.

Valve Degeneration

It was long believed that this condition was primarily caused by the mechanical pressure exerted on the valve with each ventricular contraction—in other words, by the wear and tear of time.
 
While this stress can indeed initiate the aging of the valve, it is now proven that the biological process at work in the aortic valve closely resembles that of atherosclerosis, the arterial disease that causes blockages.

An Inflammatory Process Marks the Beginning.

This process of sclerosis begins with the deposition of fats on the valve leaflets. The presence of this fat triggers a cascade of inflammatory events, leading to a loss of flexibility, thickening, and even the formation of calcifications on the leaflets.

This sclerosis reduces the mobility of the leaflets, and as the disease progresses, it can lead to a narrowing of the opening through which the blood is ejected. At this advanced stage, it is referred to as aortic stenosis.

Bicuspid Aortic Valve

In the case of a bicuspid aortic valve, two of the three leaflets of the aortic valve are fused from birth, resulting in a valve that is effectively made up of only two leaflets.

The opening of the valve, which normally takes the shape of a triangle, instead forms the shape of a football.

The passage of blood ejected from the heart is often suboptimal, and the increased turbulence at the valve usually leads to degenerative changes more quickly than would be expected in a valve that was initially normal.

Consequences on the Heart

As the narrowing of the valve progresses, it becomes increasingly difficult for the heart to eject blood into the aorta. To compensate, the heart must work harder, sometimes up to twice as hard with each beat in very severe cases.

To better understand this impact, imagine this diseased valve as an obstruction that gradually slows the emptying of blood from the ventricle into the aorta. The heart muscle must contract more forcefully to ensure the same amount of blood is circulated. As a result, the systolic pressure generated in the left ventricle can rise to over 200 mmHg with each beat, while the blood pressure measured on the other side of the obstruction is 120 mmHg (the top number on the blood pressure monitor).

Since the heart is a muscle, this increased contraction leads to thickening of the heart muscle, making it more muscular, much like the body muscles of a bodybuilder who trains with weights.

However, over time, this constant effort can fatigue the heart and cause it to lose the strength it had gained. At this stage, the heart may enlarge, become more voluminous, and in more advanced cases, weaken.

Risk Factors

The factors that contribute to the sclerosis, and thus the stenosis, of the aortic valve are very similar to those of coronary artery disease.

The main factors include:

  • Age,
  • Male sex,
  • Obesity,
  • Hypertension,
  • Diabetes,
  • Hypercholesterolemia,
  • Smoking.

 

Among these factors, age is by far the most significant. Aortic stenosis is present in 1 to 2% of people over 65 years old and in 12% of those over 75 years old. Among the latter, about 3% have severe narrowing.

Classic Symptoms of Severe Disease

Aortic stenosis, when not severe, is generally asymptomatic, much like sclerosis, meaning it causes no symptoms.

However, when the narrowing progresses to a level considered severe, according to echocardiography results, affected individuals may begin to experience the effects of the stenosis. The classic symptoms include angina, fainting during exertion, and shortness of breath.

An Insidious Disease

Since this narrowing develops over several years, individuals with aortic stenosis often tend to gradually reduce their physical activities, which masks the onset of symptoms.

This makes it an insidious disease, often unnoticed or ignored by the patients themselves.

Follow-Up

After a diagnosis of aortic stenosis, the follow-up is tailored according to the severity of the narrowing and the patient’s symptoms.

Control echocardiograms can be performed as frequently as every 6 months if the narrowing is severe or spaced up to 5 years apart if the narrowing is mild. Whenever possible, it is advisable to compare the latest exam with previous images to assess progression.

Other intervals may be set if symptoms evolve more rapidly than expected.

Prognosis

The prognosis is generally excellent for asymptomatic individuals. However, when symptoms appear or when the valve opening is severely reduced, the prognosis becomes less favorable, often requiring valve replacement.

The progression from mild stenosis to severe stenosis typically occurs over a period of about ten years, although this progression can vary significantly from one person to another.

Prevention

  • Adopting Healthy Lifestyle Habits: It’s important to remember that the process leading to aortic valve stenosis shares similarities with coronary artery disease. Therefore, adopting and practicing healthy lifestyle habits is essential.

 

This includes a balanced and nutritious diet, regular physical exercise, weight management, smoking cessation, monitoring blood pressure and cholesterol levels, and managing diabetes if applicable.

By adopting these preventive measures, it’s possible to reduce the risk of stenosis progression as well as the risk of developing other cardiovascular complications.

 

  • Antibiotic Prophylaxis and Endocarditis Prevention: It is not necessary to receive antibiotics for surgical procedures as part of the prevention of bacterial endocarditis, which is a secondary infection of the diseased valve.

 

However, if aortic valve stenosis is secondary to a previous infection, antibiotic prophylaxis is necessary.

Precautions

Individuals with mild to moderate aortic stenosis can lead a normal life without restrictions on physical activities.

However, as the stenosis becomes more severe, it is recommended to avoid intense efforts. This includes physical activities such as lifting heavy loads, digging in the ground, shoveling gravel, re-roofing a house, or pushing a car stuck in snow and ice. Your doctor will provide specific recommendations tailored to your situation.

Treatment

Even though the process leading to aortic stenosis is similar to that of atherosclerosis, treatments effective against coronary artery disease have not shown benefits for aortic stenosis.

When symptoms of this condition appear or when the narrowing becomes critical, it is generally necessary to replace the aortic valve.

For otherwise healthy individuals, surgery is usually the preferred method. However, for older patients or those with significant comorbidities, the valve can be replaced percutaneously using catheters, without the need for open-heart surgery.

In both cases, the heart no longer has to work against a narrowed valve, and symptoms can disappear completely.

Towards the Therapeutic Decision

When it is determined that an aortic valve replacement is necessary, a series of steps are initiated.

The first step is to obtain the patient’s consent to proceed with the aortic valve replacement. This discussion typically takes place well before reaching this critical point. If it hasn’t, there is never a need to make an immediate decision during the consultation with the doctor.

The patient will always receive medical guidance in either scenario.

The next step involves checking the coronary arteries to determine if they require unblocking at the time of the aortic stenosis correction.

In addition to coronary angiography, an angiography (a radiological dye test of the aorta and leg arteries) is performed. The results of this angiography indicate whether a catheter-based aortic valve replacement is feasible.

A thoraco-abdominal scan may also be requested for a more precise evaluation of the aorta and the main arteries in the legs.

Once all the information is gathered, including:

  • The echocardiogram,
  • The coronary angiography,
  • The aortography from the aorta to the legs,
  • The thoraco-abdominal scan,

all of this data, along with the patient’s medical history, is submitted to a team known as the “heart team.” This group, composed of various specialists, concludes the best approach for treating the aortic valve stenosis.