The risk of PVE is greatest during the initial 6 months after valve surgery (particularly during the initial 5 to 6 weeks) and thereafter declines to a lower but persistent risk (0.2 to 0.35 per cent per year) PVE has been called "early" when symptoms begin within 60 days of valve surgery and "late" with onset thereafter. These terms were established to distinguish early PVE that arose as a complication of valve surgery from late infection that was more likely community acquired. In fact, many cases with onset between 60 days and 1 year after surgery are likely to be nosocomial and, despite their delayed presentation, derive from events during the surgical admission. Data suggest that during the initial months after valve implantation, mechanical prostheses are at greater risk of infection than bioprosthetic valves but that after 12 months the risk of infection of bioprostheses exceeds that of mechanical valves.
The intracardiac pathology of PVE differs notably from the largely leaflet-confined pathology of NVE. Infection on mechanical prostheses commonly extends beyond the valve ring into the annulus and periannular tissue as well as the mitral-aortic intravalvular fibrosa, resulting in ring abscesses, septal abscesses, fistulous tracts, and dehiscence of the prosthesis with hemodynamically significant paravalvular regurgitation.