About 3% of patients will develop PVE by the end of the first year after valve replacement; thereafter, the incidence is lower. PVE is classified into two groups:
• Early:occurring within 2 months of surgery. It develops as a result of intra-operative contamination of the prosthetic valve or as a consequence of a post-operative nosocomial infection, such as sternotomy infection, postoperative pneumonia, urinary tract infection or intravenous cathether-related insertion. The clinical features may be masked by the ordinary events in the postoperative course or by another infection. Cutaneous signs are not common.
• Late PVE: develops more than 2 months after valve surgery. It can occur after transient bacteraemia as in minor skin or upper respiratory tract infections or following dental or urinary manipulations. The non-cardiac manifestations resemble those of native valve infective endocarditis. Although this classification is convenient, the high prevalence of Staph. epidermidis and diphtheroids among patients suggests that this division is not absolute.