Nonrheumatic mitral valve regurgitation is a leaky mitral valve caused by something other than rheumatic fever. The mitral valve sits between your heart’s two left chambers, and when it doesn’t close tightly, blood flows backward with each heartbeat. In developed countries, this is by far the most common form of mitral regurgitation, since rheumatic fever has become rare. The causes range from age-related wear on the valve to heart muscle problems that pull the valve out of shape.
Why the “Nonrheumatic” Label Matters
Rheumatic mitral regurgitation happens when a childhood strep throat triggers rheumatic fever, which scars and stiffens the valve leaflets over time. It remains the dominant cause of valve disease in parts of Africa and South Asia. In North America, Europe, and other high-income regions, mitral regurgitation is almost always degenerative, meaning it develops from structural changes in the valve tissue itself or from changes in the heart muscle around it. If you see “nonrheumatic” on a diagnosis code or medical report, it simply means your leak wasn’t caused by rheumatic fever.
Primary Causes: Problems With the Valve Itself
When the valve’s own tissue is the problem, doctors call it primary mitral regurgitation. The most common culprit is mitral valve prolapse, where one or both of the valve’s flaps become too stretchy and bulge backward into the upper chamber instead of sealing flat. Over time, the floppy tissue may allow progressively more blood to leak through. Prolapse affects roughly 2 to 3 percent of the general population and is the single leading reason people in Western countries need mitral valve surgery.
Other primary causes include connective tissue disorders like Marfan syndrome and Ehlers-Danlos syndrome, which weaken the structural proteins that keep valve tissue firm. Calcium buildup on the valve ring, a natural part of aging, can also prevent a clean seal. Congenital heart defects present from birth, infections of the heart lining (endocarditis), and prior chest radiation therapy round out the list.
Secondary Causes: A Normal Valve on a Struggling Heart
In about one-third of cases, the valve leaflets themselves are structurally normal. The leak happens because the heart muscle around the valve has changed shape. This is called functional or secondary mitral regurgitation.
The most common scenario involves a weakened, enlarged left ventricle, often from a heart attack or a condition called cardiomyopathy. As the ventricle stretches, the small muscles that anchor the valve’s cords (papillary muscles) get pulled apart. That displacement puts tension on the leaflets and prevents them from meeting in the middle. The heart becomes more spherical, the gap between the leaflets widens, and blood leaks backward. In rarer cases, the left atrium (upper chamber) itself enlarges enough to distort the valve ring and cause a leak.
Symptoms and How They Progress
Chronic nonrheumatic mitral regurgitation is often silent for years. Many people learn about it only when a doctor hears a heart murmur during a routine exam. Symptoms develop gradually as the upper left chamber enlarges, pressure builds in the blood vessels of the lungs, and the lower left chamber can no longer compensate for the extra workload.
When symptoms do appear, the most common are:
- Shortness of breath, especially during exertion or when lying flat
- Fatigue and weakness, because less blood is moving forward to the body
- Palpitations, often from an irregular heart rhythm called atrial fibrillation
- Swelling in the legs or feet as fluid backs up
Acute mitral regurgitation, which can result from a sudden event like a torn valve cord or a heart attack, is a different story. It causes rapid heart failure with severe breathlessness and can become a medical emergency.
Who Gets It
Age is the strongest risk factor. A 2021 global analysis of degenerative mitral valve disease found the prevalence nearly doubles with each five-year age bracket after 50. Among people aged 60 to 64, roughly 385 per 100,000 had the condition. By ages 75 to 79, that number jumped to about 2,255 per 100,000, and it continued climbing past age 90. Men are affected about twice as often as women, with an overall age-standardized rate of about 258 per 100,000 for men compared to 121 per 100,000 for women.
How It’s Diagnosed
An echocardiogram, essentially an ultrasound of the heart, is the primary tool. It shows doctors how well the valve closes, how much blood leaks backward, and whether the heart chambers have started to enlarge. Severity is graded from mild to severe based on several measurements. In general terms, the leak is considered severe when more than half the blood pumped into the ventricle flows backward, or when the opening through which blood escapes reaches a certain size threshold. Once moderate or severe regurgitation is identified, repeat echocardiograms every 3 to 6 months help track whether the heart is handling the extra load or starting to weaken.
Long-Term Risks if Untreated
Left unchecked, a significant leak forces the heart to work harder with every beat. The left atrium stretches to accommodate the extra blood sloshing back into it, and that enlargement raises the risk of atrial fibrillation, an irregular rhythm that itself increases stroke risk. Meanwhile, rising pressure in the lung’s blood vessels can lead to pulmonary hypertension, making breathlessness worse and eventually straining the right side of the heart as well. Over years, the left ventricle loses its ability to pump effectively, progressing toward heart failure.
Treatment Options
Mild regurgitation usually requires only monitoring. Treatment becomes relevant when the leak is severe, symptoms appear, or the heart shows early signs of weakening, specifically when the pumping strength of the left ventricle drops toward 60 percent or the chamber enlarges beyond a certain size.
Valve Repair
Surgeons strongly prefer repairing the existing valve over replacing it. Repair carries a lower operative mortality rate and avoids the lifelong complications that come with a prosthetic valve, such as blood-thinning medication or the limited lifespan of a biological replacement. A common repair technique involves trimming excess tissue on the floppy leaflet and implanting an artificial ring around the valve’s base to restore its shape and support a tight seal. This can be done through traditional open-heart surgery or through smaller incisions using robotic-assisted instruments.
Catheter-Based Procedures
For people who are too high-risk for open surgery, a catheter-based approach offers an alternative. A thin tube is threaded through a blood vessel to the heart, and a small clip is placed on the valve leaflets to reduce the leak. This is less invasive and has a shorter recovery time, though it typically reduces regurgitation rather than eliminating it entirely. Transcatheter valve replacement, where a new valve is delivered through a catheter, is also an emerging option for select patients.
Valve Replacement
When the valve is too damaged to repair, replacement with a mechanical or biological prosthetic valve is necessary. Mechanical valves are durable but require lifelong blood-thinning medication. Biological valves, made from animal tissue, avoid that requirement but wear out over 10 to 20 years and may eventually need a second procedure.
Timing of Surgery
One of the trickiest decisions is when to operate on someone who feels fine. Current guidelines recommend intervening before the heart muscle weakens, not after. The ideal window is when the ventricle is approaching, but hasn’t yet crossed, the thresholds that signal dysfunction. Waiting until symptoms are obvious or the heart has already stretched significantly leads to worse long-term outcomes. For this reason, people with severe but asymptomatic regurgitation are typically followed at specialized valve centers where surgical timing can be closely optimized.