The mitral and tricuspid valves are both very important and both play different roles. Mitral valve: The mitral valve is the valve between the left atrium and the left ventricle, and is a one-way valve that prevents blood from flowing backwards. During diastole, the mitral valve opens, allowing blood to flow only from the left atrium into the left ventricle, ensuring that the ventricles fill; during systole, the mitral valve closes and the aortic valve opens, allowing blood from the left ventricle to be ejected into the aorta. Tricuspid valve: The tricuspid valve is the valve between the right atrium and the right ventricle, and is also a one-way valve, not allowing blood to flow back. During diastole, the tricuspid valve opens to allow blood to flow from the right atrium into the right ventricle only; during systole, the tricuspid valve closes and the pulmonary valve opens, allowing blood from the right ventricle to enter the pulmonary artery. Echocardiography plays an important role in the evaluation of heart valve disease, and if a patient discovers a valve problem, it must be treated promptly.