Mitral valve incompetence, also known as mitral regurgitation, is one of the most common heart valve problems affecting millions of people worldwide. When the mitral valve doesn’t close properly, blood leaks backward in the heart, which can range from a minor issue causing no symptoms to a serious condition requiring medical intervention.

Understanding Mitral Valve Incompetence

Mitral valve incompetence happens when the mitral valve, which sits between the two left chambers of your heart, fails to close completely. The mitral valve works like a one-way door that allows blood to flow from the upper left chamber, called the left atrium, down into the lower left chamber, called the left ventricle. When this valve closes properly, it prevents blood from flowing backward. But when it doesn’t seal tightly, some blood leaks back into the upper chamber instead of moving forward to supply the rest of your body.^[1]

This leaking can be mild or severe. Many people with mild leakage never know they have it because their heart compensates easily and they feel fine. However, when the leak becomes more severe, the heart must work harder to pump enough blood forward. Over time, this extra work can strain the heart and lead to symptoms and complications.^[4]

Epidemiology

Mitral valve regurgitation is the most common type of heart valve disease in the United States. It affects approximately 2% to 3% of the general population, though the exact numbers vary depending on the definition and measurement methods used. The condition becomes more common as people age, particularly affecting those over 65 years old.^[4][11]

In Europe, mitral regurgitation is the second most frequent reason people need valve surgery. The disease affects people across all age groups, from babies born with valve problems to elderly individuals whose valves have deteriorated over many years.^[2]

The patterns of who gets mitral valve incompetence differ based on the underlying cause. Mitral valve prolapse, one form of the condition, is more commonly diagnosed in women than men. However, men with prolapse are more likely to develop severe regurgitation that requires treatment. In developing countries, rheumatic heart disease—damage to the heart valves caused by untreated strep throat infections—remains the leading cause of mitral regurgitation. In developed countries, degenerative changes to the valve tissue, often called myxomatous degeneration, are the most common reason for mitral incompetence.^[3][20]

Causes

The causes of mitral valve incompetence fall into two main categories: problems with the valve itself, or problems with the heart chambers surrounding the valve. When the valve tissue itself is damaged or diseased, doctors call this primary mitral regurgitation. When changes in the heart’s structure affect how the valve works, it’s called secondary mitral regurgitation.^[4]

Primary mitral regurgitation happens when one or several parts of the mitral valve become damaged. The most frequent cause in developed countries is degenerative disease, where the valve tissue becomes too stretchy or develops weak spots. This includes conditions like mitral valve prolapse, where the valve flaps bulge backward, and situations where the cords that anchor the valve break or rupture.^[2]

Rheumatic heart disease, which results from inadequately treated streptococcal throat infections, can cause scarring and thickening of the valve tissue. Infections of the heart valve itself, called infective endocarditis, can destroy valve tissue or cause the supporting structures to rupture. Other causes include certain medications (particularly some older appetite suppressant drugs), injury from trauma or heart attacks, and connective tissue disorders like Marfan syndrome and Ehlers-Danlos syndrome.^[3][6]

Secondary mitral regurgitation occurs when the valve tissue is basically normal, but the heart chambers have changed shape due to other heart diseases. When the left ventricle becomes enlarged or weakened from conditions like cardiomyopathy (heart muscle disease) or coronary artery disease, it can pull the valve parts out of position. This prevents the valve flaps from meeting properly in the middle, creating a gap through which blood leaks backward.^[4]

Risk Factors

Several factors increase the likelihood of developing mitral valve incompetence. Age is a significant risk factor, as the valve tissue naturally weakens and degenerates over time. People with a history of rheumatic fever, which was once common but is now less frequent in developed countries, face higher risk because the infection can permanently damage heart valves.^[6]

Coronary heart disease and high blood pressure put stress on the heart and can lead to changes in the heart’s shape that affect valve function. Previous heart attacks can damage the muscles that support the mitral valve, causing it to leak. People with certain genetic conditions affecting connective tissue, such as Marfan syndrome, are at increased risk because their valve tissue may be abnormally stretchy or weak.^[3]

A past history of taking specific diet medications, particularly fenfluramine and phentermine (known as “Fen-Phen”) or dexfenfluramine, increases risk. These drugs were removed from the market in 1997 due to safety concerns after causing heart valve problems in some users. Conditions that cause the left ventricle to swell, such as heart failure or certain types of heart muscle disease, also raise the risk of developing secondary mitral regurgitation.^[6]

People with other heart valve problems, particularly mitral valve prolapse, face increased risk of developing regurgitation. Family history also matters, as some forms of degenerative valve disease appear to run in families, suggesting a genetic component to the condition.^[3][20]

Symptoms

Many people with mild mitral valve incompetence experience no symptoms at all. The condition may be discovered only during a routine physical examination when a doctor hears an abnormal heart sound called a murmur. This lack of symptoms is particularly common when the valve leak is minor and develops slowly, giving the heart time to adjust.^[1]

When symptoms do appear, shortness of breath is often the most common complaint. This difficulty breathing, called dyspnea, may occur during physical activity at first, then progress to happening during rest or even while lying down. Some people find they need to prop themselves up with pillows to sleep comfortably because lying flat makes breathing harder.^[4]

Fatigue and feeling extremely tired are frequent symptoms. The heart isn’t pumping blood as efficiently as it should, so the body doesn’t get enough oxygen-rich blood to meet its needs during daily activities. This can make people feel exhausted even after minimal exertion. Some individuals experience a sensation of their heart beating irregularly or too fast, called palpitations. They might describe feeling their heart flip-flopping in their chest or skipping beats.^[1][4]

Additional symptoms can include coughing, particularly when lying down, as fluid backs up into the lungs. Swelling in the feet, ankles, or legs may develop as the heart’s pumping efficiency decreases and fluid accumulates in the body. Some people feel lightheaded or dizzy, though actually fainting is less common. Chest discomfort or pain can occur, though this is not always present.^[5][6]

When mitral valve incompetence develops suddenly due to a heart attack, infection, or rupture of valve structures, symptoms can appear rapidly and be severe. This acute situation often causes sudden, extreme shortness of breath and requires emergency medical care. In contrast, chronic mitral regurgitation that develops gradually may not cause noticeable symptoms for many years, even when the leak is quite significant.^[3]

Prevention

While not all cases of mitral valve incompetence can be prevented, several steps can reduce your risk or slow the progression of mild disease. Maintaining healthy blood pressure through lifestyle changes and medication when needed helps prevent damage to the heart that can lead to secondary mitral regurgitation. High blood pressure forces the heart to work harder, which can enlarge the left ventricle and affect valve function over time.^[18]

Eating a heart-healthy diet rich in fruits, vegetables, whole grains, and foods low in saturated fats supports overall cardiovascular health. This type of diet helps prevent coronary artery disease and other heart conditions that can contribute to valve problems. Limiting salt intake is particularly important if you already have mild mitral regurgitation, as sodium causes the body to retain fluid, which puts additional strain on the heart.^[18]

Staying physically active helps maintain a healthy weight and keeps the heart strong. Regular exercise, even moderate activities like walking, swimming, or biking, benefits heart health. However, if you have mitral valve disease, it’s important to discuss appropriate activity levels with your doctor to avoid overexertion while still maintaining muscle strength and fitness.^[18]

Preventing infections is crucial for protecting heart valves. Strep throat should always be properly treated with antibiotics to prevent rheumatic fever, which can permanently damage valves. People who have had valve replacement surgery may need to take antibiotics before dental procedures or certain medical treatments to prevent valve infections. Maintaining good dental hygiene and treating dental infections promptly also helps prevent bacteria from reaching the heart.^[6][18]

Avoiding smoking and limiting alcohol consumption supports heart health. Smoking damages blood vessels and contributes to coronary artery disease, while excessive alcohol can weaken the heart muscle. Managing other health conditions like diabetes, high cholesterol, and heart disease through proper treatment helps prevent complications that might affect the mitral valve.^[24]

Pathophysiology

The pathophysiology of mitral valve incompetence involves understanding how blood flow through the heart changes when the valve doesn’t close properly. Normally, the mitral valve opens during diastole (when the heart relaxes) to let blood flow from the left atrium into the left ventricle. Then it closes during systole (when the heart contracts) to prevent blood from flowing backward while the left ventricle pumps blood out through the aortic valve to the body.^[1]

When the mitral valve leaflets don’t seal completely, blood leaks backward from the left ventricle into the left atrium during systole. This backward flow is called regurgitant flow. The amount of blood that leaks backward can vary from a small amount to a large volume depending on how severe the valve defect is. The left atrium receives this extra blood on top of the normal blood returning from the lungs, causing it to stretch and enlarge over time.^[4]

To compensate for the blood that leaks backward, the left ventricle must pump harder and handle larger volumes of blood. Initially, the ventricle adapts by enlarging and developing stronger contractions to maintain adequate blood flow to the body. This compensation can work well for months or even years, which is why many people don’t have symptoms early on. However, this extra work eventually takes a toll on the heart muscle.^[14]

As the left atrium continues to receive excess blood with each heartbeat, the pressure inside it rises. This increased pressure transmits backward into the blood vessels of the lungs, called the pulmonary veins. When pressure in these vessels becomes too high, fluid can leak from the blood vessels into the air spaces of the lungs. This causes the shortness of breath and coughing that people with moderate to severe mitral regurgitation experience, particularly when lying down.^[6]

Over time, the constantly enlarged left atrium becomes more prone to developing abnormal heart rhythms, particularly atrial fibrillation, where the atrium quivers instead of contracting normally. The overworked left ventricle may eventually weaken and lose its ability to pump effectively, leading to heart failure. At this stage, the heart can no longer compensate for the valve leak, and symptoms become more severe. The right side of the heart can also become affected as back pressure from the lungs increases, potentially leading to swelling in the legs, liver enlargement, and fluid accumulation in the abdomen.^[1][3]

The severity of symptoms and complications depends largely on how quickly the regurgitation develops and how severe it is. Sudden, severe mitral regurgitation from causes like a ruptured valve structure gives the heart no time to adapt, causing immediate and dramatic symptoms. Chronic regurgitation that develops slowly allows the heart to compensate gradually, which is why people can sometimes have significant valve leakage yet feel relatively normal for extended periods.^[3]