Introduction

Mitral valve disease is a common heart condition, especially in developing countries.^1,2 It occurs when the valve between the two left chambers of your heart doesn't work properly. It can be due to either stenosis, where the valve becomes too narrow, or regurgitation, where it becomes leaky.³ Both of these conditions put extra pressure on the upper left chamber of your heart, called the left atrium, causing it to enlarge over time. To understand how and why this happens, it may be helpful to know about the structure of your heart and how blood flows through it.

So, in this article, you will explore how mitral valve disease leads to left atrial enlargement, what symptoms you might notice, what its complications are and what treatment options are available.

Understanding the structure of the heart

Your heart is made up of four chambers, two on the left side and two on the right. The heart’s top two chambers are known as atria (singular: atrium), while the bottom two are called ventricles. Blood flows through them in a very specific order. The right chambers of the heart take in blood lacking oxygen from the body and direct it to the lungs to receive oxygen. After this, the oxygen-rich blood moves into the left side of your heart, which then distributes it throughout your body.

Your heart contains four valves that ensure blood flows in the correct direction and prevent it from moving backwards. Each valve is made up of thin flaps called cusps or leaflets. The mitral valve, or bicuspid valve sits between the heart’s left atrium and left ventricle. When this valve doesn’t function properly, it disrupts the normal flow of blood within your heart and puts extra stress on it.

How your left atrium enlarges

In mitral valve stenosis

Mitral valve stenosis means the opening of your valve becomes too narrow, which reduces the amount of blood flowing into your left ventricle. Your valve leaflets might become thickened and possibly fuse with one another.

As a result, blood begins to pool in the left atrium, leading to increased pressure inside it. To cope with this high pressure and to push the blood in the forward direction, your left atrium has to work harder. As a result, its muscular walls stretch and thicken, leading to enlargement of the chamber.

In mitral valve regurgitation

Mitral valve regurgitation, also called mitral insufficiency or mitral incompetence happens when the valve’s leaflets fail to close fully, allowing blood to leak backward.

It causes some of the blood to move backwards from the left ventricle into the left atrium each time your heart beats. Because of this, the volume of blood in the left atrium increases, causing its walls to stretch and enlarge over time.

Studies reported that mitral regurgitation occurs more frequently as compared to mitral stenosis.³

Causes of mitral valve disease

Causes of mitral valve disease include:³

Congenital heart defects

In some people, it occurs due to congenital heart defects, which means that they are born with a damaged or abnormal heart.⁴

Rheumatic fever

There are many other causes which are not related to birth. The most common among them is rheumatic fever, which is a complication of untreated bacterial infection (streptococcal infection) of your throat.¹ In rheumatic fever, the immune system mistakenly attacks your heart valves, causing their inflammation and scarring. Thus, it leads to mitral stenosis.

Age-related degeneration 

Age is also an important factor in causing mitral valve disease. As people grow old, their mitral valve becomes weak or it becomes calcified. This can lead to both stenosis and regurgitation, depending upon the changes.¹

People with chronic kidney disease (CKD) are at risk of developing mitral stenosis 10 to 20 years earlier than the general population through calcium deposition around their valve.⁵

Mitral valve prolapse

Mitral valve prolapse can cause mitral regurgitation.⁶ It occurs when the valve flaps are floppy and may bulge backward into the left atrium during heart contractions.

Thus, it causes the blood to move backwards.⁶

Endocarditis

Bacterial infections of the inner lining of your heart and its valves can damage the valve tissue. This may lead to either stenosis or regurgitation.⁶

Radiation therapy

It is commonly used to treat cancer. People with radiation therapy applied to the chest may present with mitral valve disease after several years. That is why it can often be confused with age-related changes in the mitral valve.⁷

Damage to the heart muscle

Sometimes, there is damage to the structures that support your mitral valve. This can make the valve leaky, resulting in mitral regurgitation, referred to as acute mitral regurgitation in such cases.⁶

Symptoms of mitral valve disease

Mitral valve disease often progresses gradually over several years.

In fact, the damage to your valve can begin long before any noticeable symptoms appear. Even after the disease has fully developed, some people may not experience symptoms right away.⁸

When symptoms do appear, they may include:^6,1

• Shortness of breath (dyspnoea), particularly occurs when you lie down or during exercise 
• Fatigue and dizziness, when you perform any physical activity, such as exercise
• Rapid or pounding heartbeats, called palpitations
• Irregular heart rhythms, called arrhythmia
• Chest discomfort
• Swelling of feet or ankles
• Coughing up blood (hemoptysis), particularly in the case of mitral stenosis

If you are having any of these symptoms, it's important to consult your healthcare provider. When mitral valve disease is suspected, your doctor may refer you to a heart specialist, known as a cardiologist, for further evaluation.

Why left atrial enlargement matters

In the early stages of left atrial enlargement, you might not notice any clear symptoms. In such cases, treatment is usually not necessary, but regular monitoring is important.⁹

However, if the enlargement worsens over time, especially when it is associated with untreated or advanced mitral valve disease, it can lead to serious health problems. This progression usually takes several years, but without timely management, it increases the risk of complications such as:⁸

Atrial Fibrillation

Increased pressure and changes in the structure of your left atrium can overstimulate your heart’s electrical system, leading to irregular, often rapid heartbeats known as atrial fibrillation.¹ You might feel palpitations and fatigue, and it increases your chances of having a stroke. It mostly occurs due to mitral stenosis associated with rheumatic fever.^8,10

Formation of Blood Clots

During atrial fibrillation, your heart doesn’t pump blood as effectively as it should. This may result in blood collecting in the enlarged left atrium, which can increase the risk of clot formation.⁸

Stroke

If a blood clot moves from the heart to the brain, it can obstruct blood flow and lead to a stroke. This is one of the most serious risks associated with left atrial enlargement and atrial fibrillation.⁸

Pulmonary Hypertension

This term describes elevated blood pressure within the lung arteries. It occurs when blood cannot move efficiently into your left atrium, which is already overfilled. This, in turn, causes increased pressure in the lung’s blood vessels.

Infections

People with mitral stenosis are more prone to respiratory infections.⁸

Congestive Heart Failure

Over time, an enlarged left atrium can wear down your heart’s ability to pump effectively. This can lead to fluid building up in your lungs and other parts of your body, a condition known as congestive heart failure.

Diagnosis of mitral valve disease

Diagnosis of mitral valve disease is usually done by echocardiography and electrocardiography (ECG). Echocardiography  (or cardiac ultrasound), employs sound waves to produce images of the heart. It basically evaluates the structure and function of your heart. To assess its electrical activity, electrocardiography is done.

Some experienced doctors can diagnose mitral valve disease even by listening to your heart sounds through the stethoscope. This process is known as auscultation. Sometimes, cardiac MRI may also be used for detailed heart imaging. 

Treatment options

Treatment for mitral valve disease varies based on its severity. In mild cases, it may involve lifestyle adjustments and medication. You can lessen the strain on your heart by avoiding alcohol and smoking, maintaining a healthy and balanced diet and engaging in regular exercise. Medications such as blood thinners, beta-blockers, and calcium channel blockers are often prescribed to control symptoms, manage blood pressure, and prevent complications like blood clots or irregular heart rhythms.

When there is significant damage to your valve, surgery may be needed. Your mitral valve may need to be repaired or replaced in this case.³ Repair is usually preferred because it preserves your natural valve and tends to have fewer long-term complications.²

In mitral regurgitation, procedures like annuloplasty or the mitral valve clip (e.g., MitraClip) help tighten or reshape your valve to stop the backwards flow of blood. In cases of mitral stenosis, a procedure known as valvuloplasty can be performed, where a catheter with a balloon at the tip is used to expand the narrowed valve opening.²

If the valve cannot be repaired, valve replacement is done by removing the damaged valve and replacing it with a prosthetic valve. These can be either by:

• Mechanical valves, which are long-lasting but require lifelong use of blood thinners, or
• Tissue (biological) valves, which usually don’t need long-term anticoagulation therapy, but may wear out over time

Summary

Mitral valve disease involves the valve that separates the left atrium from the left ventricle of the heart. When the valve becomes too narrow or leaky, it places extra strain on your left atrium, which may enlarge over time. Many people don’t notice symptoms until the disease becomes more serious. It usually takes several years to develop and can lead to problems like irregular heartbeats, stroke, or heart failure. The treatment approach varies with disease severity and may involve medication, valve repair, or valve replacement. Early diagnosis and regular follow-up are important in managing the condition and avoiding serious complications.