Rheumatic heart disease was the predisposing cardiac lesion for IE in 20 to 25 per cent. In patients with rheumatic heart disease, endocarditis occurs most frequently on the mitral valve, a site at which women are more commonly infected. The aortic valve is the next most common site for IE; infection in this setting occurs more commonly in men.
Congenital heart disease is the substrate for IE in 10 to 20 per cent of younger adults and 8 per cent of older adults. Among adults, the common predisposing lesions are patent ductus arteriosus, ventricular septal defect, and bicuspid aortic value, the latter particularly found among older men (> 60 years).