The mitral valve controls blood flow between the chambers on the left side of the heart, which pumps oxygenated blood to the body. There are two main problems that can occur with the mitral valve: it can become too narrow (stenosis), or it can leak (regurgitation). Abnormal blood flow through the valve will then cause the heart to work harder, and eventually lead to heart failure. Symptoms of this include shortness of breath, light-headedness, fatigue, chest pain or palpitations.