Mitral Regurgitation (MR) is a common heart condition where the mitral valve, located between the heart’s upper and lower left chambers, does not close completely. This malfunction causes a portion of blood to leak backward into the left atrium with each heartbeat instead of flowing forward to the body. The seriousness of this condition varies considerably, ranging from a mild, often unnoticed finding to a severe state that significantly impairs heart function and can be life-threatening.
Understanding the Severity Scale
The seriousness of mitral regurgitation is determined by a clinical grading system that quantifies the volume of blood leaking backward. This classification moves from mild, through moderate, to severe MR, and guides the approach to monitoring and treatment. The distinction between primary and secondary MR is also important, as it speaks to the underlying cause of the leak.
Primary, or degenerative, MR occurs when the valve leaflets or their supporting structures are structurally defective, such as in cases of mitral valve prolapse or chordal rupture. Secondary, or functional, MR happens when the valve structure is normal, but the leak results from other heart issues, like a weakened or enlarged left ventricle due to a heart attack or heart failure.
In severe MR, the substantial backward flow leads to volume overload, forcing the left atrium and ventricle to handle excessive blood. A severe diagnosis is confirmed when the Effective Regurgitant Orifice Area (EROA)—the size of the opening through which blood leaks—measures \(40 \text{ mm}^2\) or greater, or the Regurgitant Volume (RVol) is \(60 \text{ mL}\) or more per beat. This chronic strain causes the left-sided chambers to enlarge and weaken the heart muscle, leading to heart failure.
Mild MR, conversely, involves a small EROA of less than \(20 \text{ mm}^2\) and RVol below \(30 \text{ mL}\). These cases often remain stable for many years and require regular surveillance.
Recognizing the Warning Signs
Patients with mild or moderate mitral regurgitation frequently experience no noticeable symptoms because the heart compensates for the extra workload. As the leak progresses to a severe level, the backward flow of blood elevates pressure within the left atrium and the veins leading to the lungs, causing physical changes.
One of the most common signs is shortness of breath (dyspnea), which initially occurs only during physical exertion. As the condition worsens, breathlessness may happen even at rest or when lying flat (orthopnea), often forcing individuals to sleep propped up. The heart’s inefficiency also manifests as chronic fatigue, as tissues do not receive adequate oxygen supply.
Fluid retention, often appearing as swelling (edema) in the feet, ankles, and legs, is another sign of significant MR. The constant strain on the left atrium can trigger an irregular heart rhythm, such as atrial fibrillation. Patients may feel this as heart palpitations, signaling that the heart’s capacity to cope has been surpassed.
Diagnostic Procedures and Monitoring
The diagnosis and ongoing assessment of mitral regurgitation rely on cardiac imaging to confirm and quantify its severity. The primary diagnostic tool is the echocardiogram, which uses sound waves to create a real-time image of the heart’s structure and function. This test visualizes the mitral valve leaflets, identifies the leak mechanism, and uses Doppler technology to measure the speed and volume of the backward blood flow.
The transthoracic echocardiogram (TTE) is the first test performed, providing detailed measurements of the EROA and RVol to determine the severity grade. Other tests include an electrocardiogram (EKG) to check for irregular heart rhythms, and a chest X-ray to look for an enlarged heart or fluid build-up in the lungs. Cardiac magnetic resonance imaging (MRI) may be used if echocardiogram results are inconclusive, offering a precise method for quantifying the leak and assessing heart muscle health.
For patients with mild or stable moderate MR, the standard approach is “watchful waiting,” or active surveillance. This involves regular, scheduled follow-up echocardiograms to monitor the size and function of the heart chambers and detect any progression of the leak. Close monitoring ensures that any deterioration is caught early, before irreversible damage occurs to the heart muscle.
Current Treatment and Management Options
The management strategy for mitral regurgitation is tailored to the severity of the leak, symptoms, and overall heart health. For patients with mild or moderate MR who are asymptomatic and have normal heart function, management involves regular monitoring. Medical management addresses the consequences of the leak, such as using diuretics to reduce fluid retention or prescribing medications to manage high blood pressure or heart failure.
Definitive treatment for severe MR focuses on repairing or replacing the damaged valve to stop the backward flow of blood. Repair is often preferred over replacement, as it preserves the native valve and results in better long-term heart function. Surgical repair involves open-heart surgery, typically indicated for primary MR patients who are healthy enough for the procedure.
For patients deemed too high-risk for open-heart surgery, transcatheter interventions offer a minimally invasive alternative. The MitraClip procedure (transcatheter edge-to-edge repair, or TEER) involves guiding a small clip through a vein to the heart, where it grasps the edges of the mitral valve leaflets to reduce the leak. This approach is valuable for severe secondary MR patients who remain symptomatic despite optimal medical therapy, improving quality of life and reducing hospitalizations.