Risk factors of prosthetic valve endocarditis:: A case-control study

Background. Prosthetic valve endocarditis is an important cause of the morbidity and mortality associated with heart valve replacement surgery. The objective of this study was to assess risk factors of prosthetic valve endocarditis related to patients, perioperative events, and postoperative complications. Methods. This was a retrospective case-control study conducted in a tertiary care hospital in Santander, Spain, from January 1986 to January 1998. Cases were patients with "definite" and "possible" infective endocarditis defined according to the Durack criteria. Controls were patients undergoing prosthetic valve replacement who at the time of the study had not developed infective endocarditis. Information was abstracted from medical records. Cases and controls (1:2) were matched by sex, age at operation (+/- 5 years), surgery of one or more valves in the same anatomic position, and date of operation (+/- 6 months). Results. There were 81 cases and 162 controls. In the multivariate analysis, risk factors significantly associated with prosthetic valve endocarditis were functional class III or IV (New York Heart Association), alcohol consumption, prior history of endocarditis, fever in the intensive care unit, and gastrointestinal bleeding. Functional class III or IV and complications of the surgical wound were independent predictors of early infective endocarditis, whereas fever in the intensive care unit and gastrointestinal bleeding were predictors of prosthetic valve endocarditis late after operation. Conclusions. Patients with prosthetic valve endocarditis differ from people without infective endocarditis with regard to intrinsic and postoperative risk factors but not regarding perioperative-related variables.