Underlying Conditions Over a Lifetime That Have the Highest Predisposition to the Acquisition of Endocarditis In Olmsted County, Minnesota, the incidence of IE in adults incidence has remained stable during the past 4 decades and is similar to that reported in other studies.100 103 Previously, RHD was the most common underlying condition predispos- ing to endocarditis, and RHD is still common in developing countries.99 In developed countries, the frequency of RHD has declined, and MVP is now the most common underlying condition in patients with endocarditis.104 Few published data quantitate the lifetime risk of acquisi- tion of IE associated with a specific underlying cardiac condition. Steckelberg and Wilson90 reported the lifetime risk of acquisition of IE, which ranged from 5 per 100 000 patient-years in the general population with no known cardiac conditions to 2160 per 100 000 patient-years in patients who underwent replacement of an infected prosthetic cardiac valve. In that study,90 the risk of IE per 100 000 patient-years was 4.6 in patients with MVP without an audible cardiac murmur and 52 in patients with MVP with an audible murmur of mitral regurgitation. Per 100 000 patient-years, the lifetime risk (380 to 440) for RHD was similar to that (308 to 383) for patients with a mechanical or bioprosthetic cardiac valve. The highest lifetime risks per 100 000 patient-years were as follows: cardiac valve replacement surgery for native valve IE, 630; previous IE, 740; and prosthetic valve replacement done in patients with prosthetic valve endocarditis, 2160. In a separate study, the risk of IE per 100 000 patient-years was 271 in patients with congenital aortic stenosis and 145 in patients with ventricular septal defect.105 In that same study, the risk of IE before closure of a ventricular septal defect was more than twice that after closure. 