The bicuspid valve, also known as the mitral valve, is located between the left atrium and left ventricle of the heart. Its purpose is to keep the flow of blood going in the right direction, into the ventricle from the atrium. When the left ventricle is filling, the bicuspid valve is open, allowing blood to flow from the atrium. When the left ventricle pumps, the bicuspid valve must be sealed to prevent the blood from backing up into the left atrium. This isolates the intense blood pressure of the left ventricle and systemic circulation from the much lower pressure of the pulmonary circulation.
When the bicuspid valve is not working correctly, blood may flow backwards through it when the heart beats in a pathology known as mitral valve regurgitation. This often can be detected externally by a stethoscope through a sound known as a murmur. This condition can be minor and asymptomatic; as much as 3 percent of the population may have some degree of mitral valve regurgitation and not know it. In more extreme cases, it can cause a sense of shortness of breath as it disrupts pulmonary circulation. In some cases it can lead to a general weakening of the systemic circulation.
Students often confuse the bicuspid and tricuspid valves. A useful memory technique is to remember that the tRicuspid valve is in the Right AtRium, which means the bicuspid valve is in the left.