Mitral regurgitation is a condition where the mitral valve in your heart doesn’t close completely, allowing blood to leak backward from the lower left chamber (the left ventricle) into the upper left chamber (the left atrium) each time the heart squeezes. It’s the most common type of heart valve disease, and it ranges from a trivial leak that never causes problems to a severe condition that can lead to heart failure if left untreated.
How the Mitral Valve Works
The mitral valve sits between the two left chambers of your heart. It has two thin flaps, called leaflets, that open to let oxygen-rich blood flow from the upper chamber down into the lower chamber, then snap shut to prevent blood from flowing back up when the heart contracts. Those leaflets are anchored by small cords (similar to the strings on a parachute) that connect them to muscles in the wall of the lower chamber. If any part of this system is damaged or distorted, the leaflets can’t seal properly, and blood slips backward with every heartbeat.
That backward leak means two things for your body. First, less blood gets pumped forward to your organs with each contraction, so the heart has to work harder to deliver the same output. Second, the upper chamber receives extra blood it wasn’t designed to hold, gradually stretching it out over time.
Primary vs. Secondary Causes
Doctors split mitral regurgitation into two broad categories based on what’s actually going wrong.
Primary mitral regurgitation means the valve itself is the problem. The most common cause is mitral valve prolapse, where one or both leaflets bulge back into the upper chamber during contraction instead of sealing flat. Over time, the cords holding the leaflets can stretch or tear, making the leak worse. Other primary causes include infection of the valve, rheumatic heart disease, and damage from radiation therapy.
Secondary (functional) mitral regurgitation means the valve’s structure is normal, but the heart around it has changed shape. When the left ventricle enlarges from conditions like dilated cardiomyopathy or damage after a heart attack, the ring surrounding the valve stretches and the anchoring muscles shift position. The leaflets get pulled apart and can no longer meet in the middle. In this case, fixing the leak also means addressing the underlying heart disease.
Symptoms to Recognize
Mild mitral regurgitation often causes no symptoms at all. Many people live with a small leak for years without knowing it, and it’s found incidentally during a routine physical when a doctor hears a heart murmur.
As the leak worsens, the heart compensates by pumping harder and the left atrium gradually expands. Eventually that compensation fails, and symptoms begin to appear. The most common are shortness of breath (particularly during exercise or when lying flat), fatigue that seems out of proportion to your activity level, and a fluttering or rapid heartbeat. Some people notice swelling in the ankles or feet. Because symptoms develop slowly, it’s easy to attribute them to aging or being out of shape, which is one reason moderate or severe cases sometimes go undiagnosed for years.
How It’s Diagnosed
An echocardiogram, which is an ultrasound of the heart, is the primary tool for diagnosing and grading mitral regurgitation. It shows the valve in motion, measures how much blood is leaking, and tracks changes in the size and pumping strength of both the left atrium and left ventricle over time.
Doctors look at several measurements to classify the leak as mild, moderate, or severe. The key ones include the size of the opening through which blood leaks, the volume of blood flowing backward per beat, and the proportion of each heartbeat’s output that goes the wrong direction. Severe mitral regurgitation is generally defined as a leak opening of 0.4 square centimeters or larger, a backward flow volume of 60 milliliters or more per beat, or more than half the stroke volume going backward. In practice, though, distinguishing mild from moderate can be tricky because measurements overlap, so doctors also track whether your heart chambers are enlarging over time as a sign that the leak is worsening.
Complications of Untreated Severe Leaks
Chronic mitral regurgitation puts a sustained volume load on the left side of the heart. The left atrium stretches to accommodate the extra blood, which raises the risk of atrial fibrillation, an irregular heart rhythm that itself increases the chance of stroke. Meanwhile, the left ventricle gradually weakens from years of overwork, eventually leading to heart failure.
The prognosis for untreated severe cases is sobering. In a study of 400 patients with severe secondary mitral regurgitation who did not undergo valve intervention (even though their overall heart pumping strength was still normal), roughly 1 in 5 died within one year and more than 1 in 4 died within three years. These numbers underscore why doctors monitor the condition closely and intervene before the heart sustains irreversible damage.
When Treatment Is Recommended
Not every leaky mitral valve needs treatment. Mild regurgitation typically just requires periodic monitoring with echocardiograms to make sure the leak isn’t progressing. For moderate cases, the frequency of follow-up increases.
Current guidelines from the American College of Cardiology and American Heart Association recommend considering surgery when the heart’s pumping strength begins to drop toward 60% (a normal heart ejects about 55 to 70% of its blood per beat) or when the left ventricle starts to enlarge beyond 40 millimeters at the end of a contraction. The goal is to intervene before those thresholds are crossed, because once the heart muscle weakens past that point, the damage may not fully reverse even after the valve is fixed.
Surgical Repair vs. Replacement
When surgery is needed, repair of the existing valve is strongly preferred over replacing it with a mechanical or tissue valve. A large international registry tracking patients for 20 years found dramatic differences between the two approaches for degenerative mitral regurgitation.
Operative mortality (death within 30 days of surgery) was 1.3% for repair compared to 4.7% for replacement. Twenty-year survival was roughly double after repair: 46% versus 23%. Freedom from valve-related complications like stroke, bleeding, and infection at 20 years was 83% after repair versus 50% after replacement. And the repairs held up well over time. At 20 years, 88% of repaired valves still showed no significant re-leaking.
Repair also avoids the lifelong need for blood thinners that comes with a mechanical replacement valve. For these reasons, if you’re told you need mitral valve surgery, it’s worth confirming that your surgeon has extensive experience with repair techniques, since success rates vary significantly between surgical centers.
Catheter-Based Options for High-Risk Patients
For people who are too sick or frail for open-heart surgery, a less invasive option called transcatheter edge-to-edge repair (TEER) offers an alternative. During this procedure, a catheter is threaded through a vein into the heart, and a small clip is placed on the mitral valve leaflets to reduce the leak. No chest incision or heart-lung machine is required.
Current guidelines recommend TEER for patients with severe mitral regurgitation who face high surgical risk or have conditions that make surgery unsafe. Acute procedural success, meaning the leak is reduced to moderate or less, is achieved in about 84 to 90% of cases depending on the patient population. In patients with advanced heart failure symptoms, roughly 73% improved to mild or no symptoms within a year of the procedure.
TEER is not suitable for everyone. Patients with rheumatic valve disease, heavy calcium buildup on the valve ring, or a very small valve opening are generally not candidates. The procedure also doesn’t eliminate the leak entirely in most cases; it reduces it to a level the heart can tolerate.
Living With Mitral Regurgitation
If you’ve been diagnosed with mild or moderate mitral regurgitation, the most important thing is consistent follow-up. Regular echocardiograms let your cardiologist spot changes in valve function or heart size before you develop symptoms. How often you need imaging depends on severity: mild cases might be checked every few years, while moderate cases are typically monitored annually.
Staying physically active is generally safe and encouraged for mild to moderate cases, though your doctor may recommend avoiding very intense or competitive sports if you have significant valve prolapse or enlargement of the heart. Managing blood pressure is particularly important because high blood pressure increases the workload on an already-stressed valve, potentially accelerating the leak. For secondary mitral regurgitation caused by an underlying heart condition, treating that condition (with medications to improve heart function, for example) can sometimes reduce the severity of the leak itself.