Mitral regurgitation is a common heart valve condition where the mitral valve does not close completely, allowing blood to flow backward within the heart. Functional mitral regurgitation (FMR) is a specific type of this condition where the valve itself is not primarily damaged. Instead, changes in the heart’s structure, particularly the left ventricle, lead to the valve’s improper closure and subsequent leakage. This condition is a frequent cardiac issue, often observed in individuals with underlying heart problems.
Understanding Functional Mitral Regurgitation
The mitral valve, situated between the left atrium and the left ventricle, plays a role in directing blood flow. It opens to permit oxygen-rich blood to move from the left atrium into the left ventricle and then closes to prevent blood from flowing backward into the left atrium when the left ventricle contracts to pump blood to the body.
In functional mitral regurgitation, the valve leaflets and their supporting structures, such as the annulus (the ring around the valve) and papillary muscles, are not primarily damaged. However, their ability to function correctly is impaired because the left ventricle changes its shape and size. This alteration in ventricular geometry pulls the valve leaflets apart, preventing them from meeting properly during contraction. This distinguishes FMR from primary mitral regurgitation, where the valve leaflets themselves are damaged or diseased.
Underlying Causes
Functional mitral regurgitation primarily arises from conditions that cause the left ventricle to undergo structural changes, a process known as remodeling. Dilated cardiomyopathy, a condition where the heart muscle becomes weakened and enlarged, is a common cause. In such cases, the ventricular dilation leads to an enlargement of the mitral annulus and a displacement of the papillary muscles, which are small muscles that anchor the valve leaflets. This displacement pulls on the valve leaflets, preventing them from coapting effectively.
Ischemic heart disease, which involves damage to the heart muscle due to reduced blood flow, often from coronary artery disease, is another significant cause. Myocardial infarction, a severe form of ischemic heart disease, frequently leads to left ventricular remodeling. The changes in ventricular shape, including an apical and lateral displacement of the papillary muscles, increase the tethering forces on the mitral valve leaflets, restricting their motion and causing them to “tent” into the left ventricle.
Other conditions contributing to left ventricular remodeling can also lead to FMR. The imbalance between the forces that close the valve leaflets and the tethering forces that pull them open results in incomplete closure.
Recognizing the Symptoms
Individuals experiencing functional mitral regurgitation may present with a variety of signs and symptoms, which often stem from the heart’s reduced efficiency in pumping blood and the subsequent buildup of fluid. A common symptom is shortness of breath, medically known as dyspnea, which can be particularly noticeable during physical exertion or when lying flat. This occurs because the backward flow of blood into the left atrium can lead to increased pressure and fluid accumulation in the lungs.
Fatigue is another frequently reported symptom, as the heart works harder to compensate for the leaky valve, leading to insufficient blood flow and oxygen delivery to the body’s tissues. Patients may also experience swelling in their legs, ankles, and sometimes the abdomen, a condition called edema, due to fluid retention. Heart palpitations, described as a fluttering, pounding, or skipped beat sensation in the chest, can also occur. The severity of these symptoms can vary widely among individuals and often progresses as the condition worsens.
Diagnostic Methods
Diagnosing functional mitral regurgitation involves a series of tests to assess heart structure and function. Echocardiography is typically the primary diagnostic method, providing detailed images of the heart and its valves using sound waves. Both transthoracic echocardiography (TTE), where the transducer is placed on the chest, and transesophageal echocardiography (TEE), which involves a probe inserted into the esophagus for clearer images, are used to visualize the mitral valve’s structure, blood flow patterns, and the extent of leakage. Echocardiography can also reveal the size and function of the left ventricle and left atrium.
A chest X-ray may be performed to check for signs of an enlarged heart or fluid accumulation in the lungs, both of which can be indicators of heart failure related to mitral regurgitation. An electrocardiogram (ECG or EKG) records the heart’s electrical activity and can detect abnormal heart rhythms or signs of strain on the heart chambers. While not specific to FMR, these findings can support a diagnosis and help assess the overall cardiac impact. Blood tests might also be conducted to assess for underlying conditions, such as markers of heart failure like natriuretic peptides.
Treatment and Management Strategies
Treatment for functional mitral regurgitation primarily focuses on managing the underlying heart condition that is causing the ventricular remodeling and subsequent valve leakage. Medical therapies are often the first line of approach. Diuretics, sometimes called “water pills,” are prescribed to help reduce fluid buildup in the lungs and extremities, thereby alleviating symptoms like shortness of breath and swelling. Angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs) are used to help reduce the workload on the heart and can contribute to reversing some of the left ventricular remodeling. Beta-blockers are also commonly prescribed to improve heart function and control heart rate. These medications work to optimize the heart’s performance and can lead to a reduction in the severity of FMR by promoting left ventricular reverse remodeling.
For patients with specific heart rhythm issues, such as left bundle branch block, device-based therapies like cardiac resynchronization therapy (CRT) may be considered. CRT involves implanting a device that helps the heart’s ventricles pump in a more coordinated manner, which can improve left ventricular function and reduce the degree of mitral regurgitation. This therapy aims to address the dyssynchrony in ventricular contraction that often contributes to FMR.
When medical and device therapies are insufficient, surgical options may be explored. Mitral valve repair, which often involves tightening or reinforcing the ring around the valve (annuloplasty), is generally preferred over valve replacement when feasible, as it preserves the patient’s own valve and can lead to better long-term outcomes. In cases where ischemic heart disease is the cause, coronary artery bypass grafting (CABG) may be performed alongside valve surgery to improve blood flow to the heart muscle. Newer, less invasive transcatheter procedures, such as transcatheter edge-to-edge repair (TEER) using devices like the MitraClip, are also available for select patients who may be at high surgical risk. These procedures involve delivering a clip through a catheter to bring the mitral valve leaflets closer together, reducing the backward blood flow. Lifestyle modifications, including a heart-healthy diet, regular physical activity, managing blood pressure, and limiting sodium intake, also play a role in supporting overall heart health and managing the condition.