Diagnostic value of intraoperative swabs of heart valves in infective endocarditis

Background ann aim of the study: Intraoperative swabs of heart valves are o btained regularly from patients undergoing heart valve surgery for infectiv e endocarditis (IE) in order to confirm the preoperative diagnosis and to a djust the antibiotic regimen. The study aim was to assess the diagnostic va lue of intraoperative swabs of heart valves in IE. Methods: A total of 83 patients was referred for surgical treatment of acti ve IE between October 1994 and May 1999. Preoperatively, microorganisms wer e isolated using a minimum of two positive blood cultures; results were com pared with those obtained from intraoperative heart valve swab cultures. Results: Preoperatively, 73 patients (88%) had a positive blood culture, an d 10 (12%) had culture-negative endocarditis. The intraoperative swab confi rmed the preoperative diagnosis in 31 cases (37%). Bacteria were isolated i n three of the ten patients with preoperative culture-negative IE. Despite positive histopathological findings in seven patients, no microorganisms we re cultured either pre- or intraoperatively. Among the remaining 42 patient s (51%) with active IE, 25 valve cultures were sterile and 17 valve swabs w ere presumed to be contaminated. Conclusion: In patients with active IE in whom the causative agent could be isolated and identified before surgery, intraoperative valve swabs did not contribute further to patient management. In isolating contaminants, the r isk of inappropriate modification of the antibiotic regimen is imminent. Th e diagnostic validity in culture-negative IE appears negligible.