In infective endocarditis, infection may affect the lining of the heart, heart valves, and any areas with abnormal connections between the chambers of the heart or its blood vessels (birth defects of the heart). The top right panel shows a normal mitral valve, which prevents blow flow of blood from the left ventricle to the left atrium. The bottom right panel shows vegetations (bacteria combined with small blood clots) on the mitral valve leaflets, consistent with infective endocarditis. Vegetations and inflammation of the valve interfere with normal valve function and can allow abnormal backflow of blood from the left ventricle to the left atrium.