Mitral valve stenosis usually worsens slowly. You may not have any symptoms, or you may have mild ones for many years. Symptoms of mitral valve stenosis can occur at any age — even during childhood. Symptoms of mitral valve stenosis include: 
Shortness of breath, especially with activity or when you lie down
Fatigue, especially during increased activity
Swollen feet or legs
Sensations of a fast, fluttering or pounding heartbeat
Dizziness or fainting
Irregular heart sound, also called a heart murmur
Fluid buildup in the lungs
Irregular heart rhythms
Chest discomfort or chest pain
Coughing up blood
 Mitral valve stenosis symptoms may appear or get worse when the heart rate increases, such as during exercise. Anything that puts stress on the body, including pregnancy or infections, may trigger symptoms.