You may feel fine with mitral valve stenosis, or you may have minimal symptoms for decades. Mitral valve stenosis usually progresses slowly over time. See your doctor if you develop:

• Shortness of breath, especially with exertion or when you lie down
• Fatigue, especially during increased physical activity
• Swollen feet or legs
• Heart palpitations — sensations of a rapid, fluttering heartbeat
• Dizziness or fainting
• Coughing up blood
• Chest discomfort or chest pain

Mitral valve stenosis symptoms may appear or worsen anytime your heart rate increases, such as during exercise. An episode of rapid heartbeats may accompany these symptoms. Or they may be triggered by pregnancy or other body stress, such as an infection.

In mitral valve stenosis, pressure that builds up in the heart is then sent back to the lungs, resulting in fluid buildup (congestion) and shortness of breath.

Symptoms of mitral valve stenosis most often appear in between the ages of 15 and 40 in developed nations, but they can occur at any age — even during childhood.

Mitral valve stenosis may also produce signs that your doctor will find during your examination. These may include:

• Heart murmur
• Fluid buildup in the lungs
• Irregular heart rhythms (arrhythmias)

Causes of mitral valve stenosis include:

• Rheumatic fever. A complication of strep throat, rheumatic fever can damage the mitral valve. Rheumatic fever is the most common cause of mitral valve stenosis. It can damage the mitral valve by causing the flaps to thicken or fuse. Signs and symptoms of mitral valve stenosis might not show up for years.
• Calcium deposits. As you age, calcium deposits can build up around the ring around the mitral valve (annulus), which can occasionally cause mitral valve stenosis.
• Other causes. In rare cases, babies are born with a narrowed mitral valve (congenital defect) that causes problems over time. Other rare causes include radiation to the chest and some autoimmune diseases, such as lupus.

Mitral valve stenosis is less common today than it once was because the most common cause, rheumatic fever, is rare in the United States. However, rheumatic fever remains a problem in developing nations.

Risk factors for mitral valve stenosis include:

• History of rheumatic fever
• Untreated strep infections

Like other heart valve problems, mitral valve stenosis can strain your heart and decrease blood flow. Untreated, mitral valve stenosis can lead to complications such as:

• Pulmonary hypertension. This is a condition in which there's increased pressure in the arteries that carry blood from your heart to your lungs (pulmonary arteries), causing your heart to work harder.
• Heart failure. A narrowed mitral valve interferes with blood flow. This can cause pressure to build in your lungs, leading to fluid accumulation. The fluid buildup strains the right side of the heart, leading to right heart failure.

When blood and fluid back up into your lungs, it can cause a condition known as pulmonary edema. This can lead to shortness of breath and, sometimes, coughing up of blood-tinged sputum.

• Heart enlargement. The pressure buildup of mitral valve stenosis results in enlargement of your heart's upper left chamber (atrium).
• Atrial fibrillation. The stretching and enlargement of your heart's left atrium may lead to this heart rhythm irregularity in which the upper chambers of your heart beat chaotically and too quickly.
• Blood clots. Untreated atrial fibrillation can cause blood clots to form in the upper left chamber of your heart. Blood clots from your heart can break loose and travel to other parts of your body, causing serious problems, such as a stroke if a clot blocks a blood vessel in your brain.