Mitral stenosis: what is it, symptoms, treatment, prognosis and complications

What is mitral stenosis?

Mitral stenosis (also called mitral stenosis, narrowing of the left atrioventricular foramen) is a narrowing of the mitral valve opening that blocks (obstructs) blood flow from the left atrium to the left ventricle.

• Mitral stenosis is usually a complication rheumatic fever, but it can also be congenital.
• Mitral stenosis causes symptoms only when it is significant.
• Doctors diagnose a characteristic heart murmur heard with a stethoscope placed over the heart, and echocardiography is used to establish a more detailed diagnosis.
• Treatment begins with diuretics and beta-blockers or calcium channel blockers.
• The valve can be stretched with a catheter, but sometimes the valve needs to be replaced, which requires open heart surgery.

The mitral valve is located in the opening between the left atrium and the left ventricle. The mitral valve opens, allowing blood to flow from the left atrium into the left ventricle, and closes when the left ventricle contracts, pushing blood into the aorta. If the disease leads to thickening and reduced flexibility of the valve cusps, the valve opening narrows. Sometimes the hardened valve also cannot close completely, and then it develops 

mitral regurgitation.

In the case of mitral stenosis, blood flow through the narrowed valve opening is reduced. As a result, the volume and pressure of blood in the left atrium increases, and this atrium itself increases in size. The rhythm of contractions of an enlarged left atrium often takes the form of frequent irregular beats (a violation is called atrial fibrillation). As a result, the efficiency of the heart is reduced, because with atrial fibrillation, the atrium trembles and vibrates, rather than pumping blood. As a result, there is no rapid exchange of blood in the atrium, the blood stagnates, and blood clots can form inside the chamber. If the clot breaks off (becomes an embolus), it is pushed out of the heart and can block an artery, which can lead to stroke or other damage.

In the case of severe mitral stenosis, the pressure in the blood vessels of the lungs increases, leading to heart failure with an accumulation of fluid in the lungs and a decrease in the level of oxygen in the blood. When pregnancy occurs, a woman with severe mitral stenosis may develop rapidly heart failure.

Causes and risk factors

Mitral stenosis is almost always a complication rheumatic fever - childhood illness that develops in some cases after an untreated acute streptococcal upper respiratory infection, or scarlet fever. Today, rheumatic fever is rare in Russia and Western Europe because antibiotics are widely used to treat infections in these countries. In this regard, in these regions, mitral stenosis occurs mainly in elderly people with a history of rheumatic fever, who could not take advantage of all the benefits of antibiotic therapy during their youth, as well as among people who have moved from regions where there is no practice of widespread use of antibacterial drugs. In such regions, rheumatic fever is common and leads to the development of mitral stenosis in adults, adolescents, and sometimes even children. As a rule, if rheumatic fever is the cause of mitral stenosis, the leaflets of the mitral valve partially weld (stick together).

Rarely, some older people develop valve degeneration, where calcium is deposited in the walls. In this case, mitral stenosis is less pronounced.

Mitral stenosis may rarely be present at birth (congenital malformation). Newborns with this disorder rarely live to 2 years of age without surgery.

Signs and symptoms

Mild mitral stenosis is usually asymptomatic. Eventually the disease progresses and patients develop symptoms such as dyspnea and easy fatigue. Patients with atrial fibrillation may experience heart palpitations (heart beat sensation).

It usually takes 7–9 years from the onset of symptoms to the development of severe disability. Shortness of breath can occur even during rest. Some patients can only breathe comfortably while reclining in pillows or sitting. These patients with low blood oxygen levels and high blood pressure in the lungs may develop an unnatural plum-colored blush on their cheeks (called a mitral butterfly).

Such persons may have coughing up blood (hemoptysis) if veins or capillaries in the lungs begin to burst under the action of high pressure. The hemorrhages in the lungs caused by this are usually minor, but when hemoptysis occurs, the patient should be evaluated immediately by a physician as it indicates severe mitral stenosis or other serious problem.

Diagnostics

Diagnostics include:

• physical examination;
• echocardiography.

With the help of a stethoscope, doctors can hear the characteristic heart murmur during the passage of blood through the narrowed valve opening from the left atrium to the left ventricle. Unlike a normal valve, which works silently, the affected valve often makes a clicking sound when it opens to allow blood flow to the left ventricle. The diagnosis is usually confirmed with echocardiographyin which ultrasonic waves are used to obtain an image of a narrowed valve and the flow of blood through it. Electrocardiography (ECG) and chest x-ray can also provide valuable information.

Standard treatments

Mitral stenosis will not occur if rheumatic fever is prevented by early treatment of acute pharyngitis using antibacterial drugs.

People without symptoms do not need treatment.

If treatment is needed, diuretics and beta-blockers or calcium channel blockers are prescribed. Diuretics that stimulate the production of urine can lower blood pressure in the lungs by reducing blood volume. Beta blockers, digoxin, and calcium channel blockers help reduce the increased heart rate that can develop from atrial fibrillation. Patients with atrial fibrillation require anticoagulants to prevent blood clot formation.

In case of insufficient effectiveness of drug therapy, the possibility of valve repair or replacement may be considered.

Often, the valve can be stretched and opened using a procedure called balloon valvotomy. During this procedure, a special catheter is inserted through a vein with a balloon at the tip, which is then advanced to the heart (cardiac catheterization). Having reached the level of the valve, the balloon is inflated, thus separating the valve flaps. Or, heart surgery may be performed to separate the fused valve leaflets. If the valve is significantly damaged, it can be replaced with a prosthesis during surgery.

Patients with valve replacement are given antibiotics before surgical, dental, or medical procedures to reduce the existing small risk of developing an infection of the heart valve (infectious endocarditis).

Forecast

The natural course of mitral stenosis may vary, but the time interval between the onset of symptoms and severe functional impairment is 7–9 years. The result of treatment depends on the patient's age, functional status, degree of pulmonary hypertension and the level of regurgitation in case of mitral valve insufficiency. The results of balloon or surgical commissurotomy in patients without valve calcification are the same. However, over time, most patients develop restenosis and valve replacement is usually necessary. Factors that increase the risk of death - atrial fibrillation and pulmonary hypertension. Common causes of death are heart failure and pulmonary or cerebrovascular embolism.

Prevention

Disease prevention involves measures such as:

• anti-relapse prevention rheumatism;
• sanitation of foci of chronic streptococcal infection;
• regular observation by a cardiologist and rheumatologist to exclude the progression of mitral stenosis.