Mitral Regurgitation (Leaky Mitral Valve)

What is mitral regurgitation?

The mitral valve has two flaps (leaflets) held by fine cords (chordae tendineae) attached to small muscles in the left ventricle. When the ventricle squeezes, the leaflets close so blood goes forward into the aorta. In mitral regurgitation (MR), the leaflets do not meet properly, so part of each heartbeat leaks back into the left atrium.

Over time, a large leak causes:

• The left atrium to stretch, which triggers atrial fibrillation
• The left ventricle to enlarge and eventually weaken
• Pressure to back up into the lungs, causing breathlessness and pulmonary hypertension

Primary vs secondary mitral regurgitation

Acute vs chronic

Acute MR appears suddenly, for example when a cord ruptures or a papillary muscle tears after a heart attack, or when endocarditis destroys a leaflet. It causes sudden severe breathlessness and is a surgical emergency.

Chronic MR develops slowly over years, and the heart adapts, so many people have no symptoms for a long time.

Symptoms

Mild and moderate MR usually cause no symptoms. With severe MR, symptoms include:

• Shortness of breath, first on exertion, later at rest
• Breathlessness lying flat, or waking at night gasping
• Fatigue and reduced exercise capacity
• Palpitations, often from atrial fibrillation
• Swollen ankles and legs
• Cough, especially at night

A doctor may hear a blowing heart murmur throughout each heartbeat, loudest at the apex of the heart and often spreading toward the left armpit.

Severity: mild vs severe mitral regurgitation

An echocardiogram grades MR using measurements of the leaking jet, the regurgitant volume and the size of the leak opening.

The ACC/AHA guideline also uses stages A (at risk) to D (severe with symptoms).

Diagnosis

• Echocardiogram (echo): the key test. It shows the valve's structure, cause, severity and heart function.
• Transesophageal echo (TEE): a probe passed down the throat gives detailed images for surgical planning.
• ECG: checks for atrial fibrillation and signs of a past heart attack.
• Chest X-ray: heart size and fluid in the lungs.
• Cardiac MRI: measures the leak precisely when echo is unclear.
• Exercise testing: reveals hidden symptoms or pressure rises.
• Coronary angiogram: before surgery, or when blocked arteries are suspected.

Treatment

Watchful waiting

Mild to moderate MR without symptoms needs regular echocardiograms and good control of blood pressure.

Medicines

Medicines do not fix a leaky valve, but they help symptoms and the heart:

• Diuretics (water pills) for fluid buildup
• Heart failure medicines (such as beta-blockers, ACE inhibitors or ARNIs, SGLT2 inhibitors), especially in secondary MR
• Blood thinners and rate or rhythm control for atrial fibrillation

Surgery

For severe primary MR, surgery is recommended when there are symptoms, or even without symptoms if the left ventricle starts to enlarge or weaken (ejection fraction 60% or less), atrial fibrillation develops or lung pressures rise. Operating before the ventricle is damaged gives the best results.

• Mitral valve repair is preferred whenever possible. Surgeons reshape the leaflets, replace torn cords and add a ring to support the valve. Repairs last well and avoid lifelong blood thinners. Many are done through small incisions or robotically at specialist centers.
• Mitral valve replacement with a mechanical valve (needs lifelong warfarin) or tissue valve (may wear out after 10 to 20 years).

Catheter procedures

Transcatheter edge-to-edge repair (TEER), such as the MitraClip, uses a tube from a leg vein to clip the two leaflets together, reducing the leak. It is used for:

• Severe primary MR in people too high-risk for surgery
• Severe secondary MR with heart failure symptoms despite optimal medicines, where it can reduce hospitalizations and improve survival in selected patients

Transcatheter mitral valve replacement is a newer option at some centers.

Complications

• Atrial fibrillation and stroke
• Heart failure
• Pulmonary hypertension
• Infective endocarditis
• Sudden cardiac death (rare, mostly with severe untreated MR and weak heart muscle)

Living with mitral regurgitation

• Keep regular cardiology and echo follow-up.
• Report new breathlessness, palpitations or swelling promptly.
• Control blood pressure, as high pressure increases the leak.
• Keep teeth and gums healthy and see a dentist regularly.
• Most people with mild to moderate MR can exercise normally. Ask your cardiologist about competitive or heavy weight training with severe MR.
• Antibiotics before dental work are only recommended for people with a previous valve repair using prosthetic material, a valve replacement, or past endocarditis.

Frequently asked questions

Is mild mitral regurgitation serious?

Usually not. Trace or mild mitral regurgitation is common, often found on echoes in healthy people, and rarely causes problems. It may need an echo every few years to check that it is not getting worse, especially if caused by mitral valve prolapse. Most people need no treatment.

What are the symptoms of mitral regurgitation?

Mild cases cause no symptoms. Severe mitral regurgitation causes shortness of breath on exertion or when lying flat, tiredness, palpitations, swollen ankles and a night-time cough. Sudden severe regurgitation, such as after a heart attack, causes rapid breathlessness and is an emergency.

Can mitral regurgitation get better on its own?

Primary mitral regurgitation from a damaged valve usually stays the same or slowly worsens. Secondary mitral regurgitation can improve when the underlying heart problem is treated, for example with heart failure medicines, controlling atrial fibrillation or reopening blocked arteries.

What is the difference between mitral regurgitation and mitral valve prolapse?

Mitral valve prolapse is a structural problem where the leaflets bulge back into the left atrium. It is the most common cause of primary mitral regurgitation, which is the leak itself. Many people with prolapse have little or no leak, while others develop significant regurgitation over time.

What is MitraClip?

MitraClip is a catheter-based device used in transcatheter edge-to-edge repair. A doctor guides it through a vein in the leg to the heart and clips the two mitral leaflets together, reducing the leak. It is mainly used for people who are too high-risk for open surgery or have secondary regurgitation with heart failure.