Diagnosis of mitral stenosis? Here's what's happening

By Cristiano Antonino On Jun 19, 2023

Mitral stenosis is a narrowing (stenosis) of the mitral valve of the heart, which impairs the regular blood flow through the orifice located between the left atrium and the left ventricle

The main cause of the narrowing is a rheumatic disease, caused by a bacterial infection

Patients suffering from mitral stenosis experience multiple symptoms such as dyspnoea, atrial fibrillation and/or chest pain.

The correct therapy is prescribed depending on the severity of the stenosis and, in more severe cases, surgery may sometimes be required. Find out everything you need to know about this pathological condition.

Mitral stenosis: What is it?

Mitral stenosis occurs when there is a narrowing of the mitral valve to such an extent that its proper activity is impaired.

The mitral valve, located at the orifice that connects the left atrium to the left ventricle of the heart, has the function of regulating the unidirectional flow of blood between the two cardiac cavities during diastole and systole.

Simply put, in the individual with mitral stenosis, the passage of blood from the left atrium to the left ventricle is obstructed.

In its normal condition, the mitral valve consists of two thin movable leaflets attached by cords of tendon to two muscles called papillaries which, by contracting together with the left ventricle in which they are located, prevent the mitral leaflets from prolapsing into the left atrium.

When the valve opens, the edges of the two leaflets separate, allowing blood to flow from the left atrium into the left ventricle, and they come together again when the valve closes, preventing blood from flowing back.

Under certain circumstances, however, it can happen that the mitral valve undergoes alterations that cause it to narrow.

This happens when:

There is the presence of a supramitral ring, i.e. when a ring of fibrous tissue above the mitral valve restricts the passage of blood within the valve.
The valve leaflets are elongated and connected to a single papillary muscle (‘parachute’ mitral valve).
The flaps thicken and fuse, no longer being able to move independently of each other.

During the passage of blood from the atrium to the left ventricle, in the presence of mitral stenosis, the pressure in the left atrium increases.

This compensation mechanism leads to increased pressure in the veins that carry blood from the lungs back to the heart.

This in turn causes a build-up of fluid in the lungs and an increase in pressure in the pulmonary arteries, which puts the right ventricle overworked, eventually leading to exhaustion and heart failure.

For these reasons, a neglected mitral stenosis can lead to serious health consequences.

Main causes of mitral stenosis

The main cause leading to mitral stenosis is a disease of rheumatic origin, an autoimmune syndrome that can be triggered by a bacterial (streptococcal) infection of the airways.

Although this condition is increasingly rare in industrialised countries, it is still very common in developing countries and can cause severe damage to the mitral valve leaflets, preventing them from functioning properly.

Usually, following an infection, the human body responds by producing antibodies to eradicate the bacteria without complications.

In some individuals, however, the defences produced against streptococcus also tend to recognise the valve cells as foreign, attacking them.

This creates an inflammatory state that leads to deformation of the mitral valve, leading to thickening or fusion of its two leaflets and thus preventing it, in the first case, from opening properly and, in the second, from opening and closing.

However, there are also other causes that may underlie mitral stenosis, including

Congenital heart problems, i.e. deformations of the valve that have been present since birth.
Valve calcification, an age-related degeneration due to the progressive deposition of calcium salts on the valve leaflets. It usually afflicts 50-60 year olds.
Valve infections caused by endocarditis, a bacterial infection typical of the internal cavities of the heart.

What are the symptoms and signs of mitral stenosis?

Mitral stenosis is not always accompanied by symptoms; in fact, some people may have this condition but still feel well or experience modest symptoms that do not impair or limit their normal lifestyle in any way.

However, symptoms may arise or worsen suddenly and include:

Tiredness and ease of fatigue
Dyspnoea on exertion, i.e. shortness of breath especially when under stress or lying down
Swelling of the feet or ankles
Palpitations, atrial fibrillation
Frequent respiratory infections (e.g. bronchitis)
Chest pain
Wheezing cough
Hemoftoe, so-called blood sputum

How is the diagnosis made?

To detect mitral stenosis, it is necessary to recall diagnostic tests such as:

Stethoscopy, through which a diastolic or presystolic murmur could be detected.
Electrocardiogram (ECG), which measures the heart’s electrical activity and can show any hypertrophy, left atrial overload and atrial fibrillation due to valve occlusion. This type of test can give an idea of the degree of severity of the pathology.
Dynamic ECG according to Holter, a prolonged monitoring that can document arrhythmias.
Transesophageal echocardiogram, performed by inserting a probe from the mouth into the oesophagus. This test allows a better view of the valves and paravalvular structures and is very important for planning a therapeutic strategy.
Chest X-ray, also useful for observing the condition of the lungs, checking for oedema.
Echocardiography, a diagnostic tool that allows the fundamental elements of the heart to be observed.
Cardiac catheterisation, an invasive technique that allows the clinical diagnosis to be confirmed, haemodynamic changes to be assessed, whether surgery is possible and the presence of other cardiac pathologies to be evaluated.
Transthoracic echocardiogram, an imaging test that makes it possible to visualise the structures of the heart and the functioning of its moving parts. This is considered the most important test because it allows the extent of mitral stenosis, the size of the left atrium and left ventricle and its contractile function and the possible presence of pulmonary hypertension to be assessed. Images can also be collected during the performance of a stress test, also known as stress echo. Its performance is particularly indicated when there is a discrepancy between the severity of symptoms and the extent of mitral stenosis at rest.

What are the possible therapies?

The type of therapy that will be prescribed to the patient will depend closely on the severity of the mitral stenosis.

A mild stenosis that does not give rise to symptoms simply requires measures to prevent worsening.

Individuals suffering from mild mitral stenosis are therefore advised to perform periodic medical check-ups and observe general rules of hygiene to avoid and prevent bacterial infections.

In the event that the subject experiences some typical symptoms of stenosis, it is necessary to resort to the use of certain medications:

Beta-blockers, digitalis and antiarrhythmics in cases of atrial fibrillation.
Diuretics, to decrease pulmonary hypertension.
Anticoagulants, to prevent the formation of thrombi and emboli due to chronic atrial fibrillation.
Antibiotics in the case of endocarditis.

In moderate or severe cases, however, the therapeutic approach is completely different. In cases like this, surgery is required, especially in situations where, after tests, the patient is diagnosed with hypertension or pulmonary oedema.

Possible surgical operations are:

Mitral commissurotomy, which consists of separating by incision the two mitral valve leaflets that have fused resulting in stenosis. It can be performed either via a balloon catheter or after a thoracotomy. However, this type of approach is not valid for patients with cusp calcifications.
Replacement of the mitral valve with a prosthesis, an operation indicated in individuals with severe anatomical abnormalities of the valve. The prosthesis inserted can be mechanical or biological. The operation is performed by placing the patient in extracorporeal circulation (ECC), which is carried out using a device that creates a cardiopulmonary pathway to replace the natural one, providing the patient with an artificial blood circulation.
Valvuloplasty, in which the stenosis is reduced through the use of balloon catheters, thereby regulating the altered atrial pressure and ensuring proper blood flow. This operation is indicated in cases where stenosis caused by calcifications or stiffened flaps is established.
Mitral valve repair, an approach indicated in cases where mitral stenosis is due to a modification or rupture of one of the chordae tendineae. These are replaced by the heart surgeon by placing the patient, again, in extracorporeal circulation. Such a solution is also very valuable in cases of valve ring abnormalities, however, it is not suitable for cases of mitral stenosis of rheumatic origin.

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