Degenerative mitral valve disease (DMVD) is the most common form of heart valve disorder in developed countries, representing a slow, age-related deterioration of the heart’s inflow valve. This condition primarily affects the structural integrity of the mitral valve apparatus, causing a progressive failure to close properly. The defining characteristic of DMVD is a backflow of blood, known as mitral regurgitation, which places an increasing strain on the heart muscle over time. While the disease often remains silent for many years, its progression can eventually lead to significant changes in heart function and structure. The management of this condition centers on careful monitoring and determining the optimal timing for intervention to prevent irreversible damage to the heart muscle.
The Anatomical Failure of the Mitral Valve
The mitral valve functions as a one-way gateway between the heart’s upper left chamber, the left atrium, and the lower left chamber, the left ventricle. This valve is a complex structure composed of two fibrous flaps, called leaflets, which are tethered by thin, string-like attachments known as the chordae tendineae. When the left ventricle contracts to pump oxygenated blood out to the body, the leaflets must close tightly to prevent blood from leaking backward into the left atrium.
The root cause of DMVD is a structural breakdown of the valve tissue called myxomatous degeneration, where the connective tissue within the leaflets becomes excessively loose, thick, and floppy. This degeneration compromises the leaflet structure and often leads to an excess of tissue. The compromised leaflets consequently bulge backward into the left atrium during the heart’s contraction, a mechanical failure termed mitral valve prolapse (MVP).
Mitral valve prolapse (MVP) is the anatomical precursor to mitral regurgitation (MR), where the valve’s incomplete closure allows blood to leak backward. This mechanism is frequently categorized into two main phenotypes: diffuse myxomatous disease (Barlow’s disease), which involves significant excess and billowing of tissue, and fibroelastic deficiency, which is characterized by a more localized defect, often involving the rupture of one or more chordae tendineae. The resulting backflow of blood places a volume overload on the heart, forcing the left ventricle to pump the same blood multiple times to maintain adequate circulation.
Recognizing Symptoms and Diagnostic Confirmation
The earliest noticeable sign of DMVD may be a subtle change heard during a routine physical examination. A physician listening to the heart with a stethoscope may detect a characteristic heart murmur, which is the sound of blood leaking backward through the valve, often preceded by a distinct clicking sound associated with the prolapsing leaflet. Many individuals with mild or even moderate regurgitation remain entirely without symptoms for years, functioning normally without physical complaint.
When symptoms do emerge, they are typically related to the heart’s inability to cope with the increased workload and the backup of blood pressure into the lungs. Common complaints include shortness of breath, particularly during physical exertion or when lying flat, and excessive fatigue. Patients may also experience palpitations (a rapid or irregular heartbeat) or swelling in the ankles and legs due to fluid retention. These symptoms indicate the disease has progressed to a more advanced stage, warranting immediate clinical evaluation.
The gold standard for confirming the diagnosis and assessing the severity of DMVD is the echocardiogram, which uses ultrasound waves to create detailed images of the heart in motion. This test allows physicians to directly visualize the prolapse of the leaflets, quantify the volume of blood leaking backward, and measure the size and function of the heart’s chambers. A more detailed view, often used when considering intervention, is the transesophageal echocardiogram (TEE), where the ultrasound probe is guided down the esophagus for clearer images.
Monitoring Disease Progression and Risk Stratification
DMVD is a progressive condition that necessitates a structured surveillance strategy. Current guidelines categorize the disease into four main stages, ranging from Stage A (patients at risk) to Stage D (symptomatic severe disease). The disease’s severity is primarily determined by quantitative measurements from the echocardiogram, such as the size of the heart chambers and the degree of backflow.
Patients in Stage B have mild or moderate regurgitation but no symptoms, while Stage C involves severe regurgitation without symptoms. Surveillance for these asymptomatic stages relies on serial echocardiograms (typically every six to twelve months) to track the size of the left ventricle and the maintenance of its pumping strength. An increase in left ventricular size or a decrease in its ejection fraction suggests the heart is beginning to fail under the strain of the leaky valve.
Another important tool in risk stratification is the exercise stress test, which determines if a patient is truly asymptomatic or merely sedentary. This test can reveal subtle symptoms, such as shortness of breath or a drop in blood pressure during exertion, which might not be apparent at rest. Identifying these changes is a significant factor in determining the optimal timing for intervention, as operating before irreversible heart damage offers the best chance for recovery. The development of pulmonary hypertension (high blood pressure in the lungs) is another marker of advanced disease that strongly influences the decision to intervene.
Treatment Pathways and Interventional Options
Management ranges from conservative medical surveillance to definitive surgical or transcatheter intervention. For patients with mild disease or asymptomatic severe disease without ventricular strain, medical management focuses on addressing co-existing conditions, such as controlling blood pressure. Medications like diuretics may also be used to manage symptoms of fluid retention and congestion once they develop.
For patients with severe mitral regurgitation who show symptoms or evidence of heart strain, intervention is recommended to repair or replace the damaged valve. Mitral valve repair is the preferred approach for degenerative disease, as it is associated with lower operative mortality and better long-term survival rates compared to replacement. Repair procedures, such as annuloplasty (tightening the ring) and leaflet repair, aim to restore the valve’s natural function, eliminating the need for lifelong blood thinners.
If valve damage is too extensive for durable repair, the alternative is mitral valve replacement, involving removal of the native valve and implanting a mechanical or biological prosthetic valve. Mechanical valves are durable but require lifelong anticoagulation, while biological valves are less durable but avoid the need for long-term blood thinners. A less invasive option for patients at prohibitive risk for open-heart surgery is a transcatheter procedure, such as the MitraClip. A small clip is delivered via a catheter through a vein in the leg to grasp the leaflets and reduce backflow. This approach provides a significant reduction in regurgitation and improvement in symptoms for patients with limited therapeutic alternatives.