Mitral stenosis is a condition affecting the heart’s mitral valve, located between the left atrium and the left ventricle. This valve normally functions like a one-way gate, opening to allow oxygen-rich blood to flow from the upper left chamber (left atrium) into the lower left chamber (left ventricle), and then closing tightly to prevent blood from flowing backward. When mitral stenosis occurs, this valve narrows, restricting the smooth flow of blood into the left ventricle, which is the heart’s main pumping chamber. This narrowing means the heart must work harder to push blood through the smaller opening, potentially leading to a buildup of pressure in the left atrium and a reduced amount of blood reaching the rest of the body.
The Most Common Cause
Globally, the most frequent cause of mitral stenosis is rheumatic fever. This inflammatory disease can arise as a complication of an untreated streptococcal throat infection caused by Group A Streptococcus bacteria. Rheumatic fever is considered an autoimmune reaction, where the body’s immune system mistakenly attacks its own healthy tissues after fighting the bacterial infection.
While rheumatic fever is now uncommon in many developed countries due to improved sanitation and access to antibiotics, it remains a significant health concern in developing regions worldwide. In these areas, it continues to be the primary reason for mitral valve damage, often leading to rheumatic heart disease. This condition accounts for a majority of mitral stenosis cases.
How Rheumatic Fever Leads to Mitral Stenosis
Rheumatic fever causes damage to the mitral valve through a complex immune response. The body’s defense system, in its effort to combat the strep infection, produces antibodies that also recognize and attack components of the heart valves. This leads to inflammation of the valve leaflets, which are the flaps that open and close to regulate blood flow.
Over time, this inflammation can cause the valve leaflets to thicken, stiffen, and fuse together, reducing the valve’s ability to open fully. The chordae tendineae, which are the small, cord-like structures that support the valve, can also become shortened and fused, further hindering valve movement. This progressive damage often takes years or even decades to manifest as noticeable symptoms of mitral stenosis, decades after the initial episode.
Recognizing Mitral Stenosis
Individuals with mitral stenosis may experience various symptoms as the condition progresses. Common complaints include shortness of breath, particularly during physical activity or when lying down, and persistent fatigue. These symptoms arise because the narrowed valve causes blood to back up in the left atrium and lungs, while simultaneously reducing the amount of oxygen-rich blood delivered to the body.
Other indicators can include heart palpitations, which are sensations of a rapid, fluttering, or skipped heartbeat, and chest discomfort or pain. Some individuals might also develop a cough or notice swelling in their ankles and feet. Mitral stenosis is often detected during a physical examination when a doctor listens for a characteristic heart murmur, an abnormal sound produced by turbulent blood flow through the narrowed valve. The primary diagnostic tool is an echocardiogram, which uses sound waves to create images of the heart’s structure and function.