Definition and Overview

The mitral valve is one of the valves that help control blood flow through the heart. When the heart beats, the atria contract to push blood into the ventricles. The mitral valve then opens up, allowing blood to flow from the left atrium to the left ventricle.

Sometimes, the mitral valve can become stenotic or narrowed often due to rheumatic fever. When this happens, the blood flow to the left ventricle can be partially or totally blocked, causing the left atrium to enlarge. This results in a condition called atrial fibrillation in which the left atrium beats rapidly in an irregular pattern, decreasing the heart’s ability to effectively pump blood in the process.

Mitral valve stenosis increases the risk of blood clots, which can get dislodged and travel to other parts of the body through the bloodstream. If these clots get stuck and block an artery, the patient may suffer from a stroke. Severe mitral valve stenosis can also result in heart failure in which the heart is unable to pump enough blood to meet the body’s need for blood and oxygen.

Causes of Condition

The most common reason why the mitral valve narrows is rheumatic fever, an inflammatory disease that commonly develops in children aged between five and 15 years old. The condition, which can also sometimes develop in adults, is a common complication of scarlet fever or a rare strain of strep that triggers an immune response. In an attempt to fight the infection, the body releases antibodies, which mistakenly attack healthy cells including those of the heart muscle.

Rheumatic fever is now very rare in first-world countries because antibiotics that effectively treat the infection are widely available. However, it is still relatively common in underdeveloped and some developing nations.

In rare cases, the mitral valve narrows due to calcium buildup.

Key Symptoms

Many people with a stenotic mitral valve remain asymptomatic or symptom-free for years. However, as the condition progresses, they can develop the following:

  • Shortness of breath

  • Sudden inability to tolerate increased physical activity

  • Dizziness or fainting

  • Fatigue

  • Chest pain or discomfort

  • Severe headaches

  • Symptoms of stroke

  • Haemoptysis or coughing up blood

  • Mitral facies due to cyanosis or inadequate amount of oxygen in blood

Who to See and Types of Treatments Available

Mitral valve stenosis is usually asymptomatic in the early stages. Thus, it is often left undetected for several years or until complications arise. There are also cases where it is accidentally discovered when a person undergoes certain diagnostic tests for an unrelated disease.

The first sign of mitral valve stenosis is a heart murmur, an unusual sound between heartbeats that can be heard through a stethoscope. When this is detected, usually during a routine physical exam, doctors order additional tests and diagnostic procedures to identify its cause and rule out other heart disorders that also produce this symptom.

Patients suspected of mitral valve stenosis undergo a thorough physical exam where their blood pressure is taken and pulse checked. Their medical history and lifestyle are also discussed during which they are asked if they have had rheumatic fever in the past or suffering from heart conditions including endocarditis, congenital heart defects, or atrial fibrillation.

Diagnostic tests performed to make a diagnosis are:

  • Chest x-ray - A chest x-ray is an imaging test that produces pictures of the heart, lungs, blood vessels, and bones using small amounts of radiation. If a patient has a stenotic mitral valve, his upper atrium will appear swollen or enlarged in the pictures.

  • Echocardiogram - An ultrasound test that produces moving pictures of the heart using high-pitched sound waves. It is used to measure the area of the mitral valve and examine the left ventricle’s diastolic filling velocity and filling pressure. If the mitral valve is narrowed, it becomes difficult for the left ventricle to fill with blood and the lower atrium does not empty as quickly as normal.

  • Electrocardiogram - Checks the heart’s electrical activity using electrodes that are connected to an electrocardiogram machine. It is the most important tool for diagnosing mitral valve stenosis and determining the severity of the condition as well the optimal timing for intervention.

Treatment of mitral valve stenosis depends on whether it is mild, moderate, or severe.

Mild, asymptomatic cases are not treated with any type of medications or surgery because the risks or side effects of such treatment may outweigh their possible benefits. Instead, doctors advice watchful waiting in which the patient is monitored and advised to undergo periodic tests, including regular echocardiograms, to ensure that the condition is not worsening.

Patients who show symptoms are often prescribed with the following medications:

  • Anticoagulants or blood thinners, to prevent the formation of blood clots

  • Diuretics, to reduce fluid buildup

  • Beta blockers, to slow down heart rate

In severe cases, balloon valvuloplasty or mitral valve replacement is recommended. In balloon valvuloplasty, a thin catheter is threaded from a blood vessel in the arm or groin to the stenotic mitral valve. The balloon at the tip of the catheter is then inflated to widen the valve and restore normal blood flow. In many cases, this procedure offers immediate symptoms relief and adequately manages the condition.

However, in some cases, an open-heart surgery called commissurotomy becomes necessary to effectively remove calcium deposits and other scar tissue from the valve leaflets. If the mitral valve is damaged beyond repair, the last option is to replace it.

Mitral valve replacement can be performed through open-heart or endoscopic surgery. Depending on the method to be used, the heart surgeon may create a long incision or up to four smaller holes in the chest to remove the narrowed valve and replace it with either a tissue or mechanical valve. Tissue valves are obtained from a deceased human donor or from a cow or pig. Mechanical valves, on the other hand, are made from metal. Thus, they are very durable and typically do not need to be replaced. However, unlike tissue valves, mechanical valves require patients to take anticoagulant medications for the rest of their lives to avoid blood clots from forming.

References:

  • Roles of your four heart valves. American Heart Association. http://www.heart.org/HEARTORG/Conditions/More/HeartValveProblemsandDisease/Roles-of-Your-Four-Heart-Valves_UCM_450344_Article.jsp.

  • Otto CM, Bonow RO. Valvular heart disease. In: Mann DL, Zipes DP, Libby P, Bonow RO, Braunwald E, eds. Braunwald’s Heart Disease: A Textbook of Cardiovascular Medicine. 10th ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 63.

  • Webb JG, Carroll JD. Transcatheter therapies for structural heart disease in adults. In: Mann DL, Zipes DP, Libby P, Bonow RO, Braunwald E, eds. Braunwald’s Heart Disease: A Textbook of Cardiovascular Medicine. 10th ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 56.

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