Bacteriological outcome after valve surgery for active infective endocarditis: Implications for duration of treatment after surgery

Background. There has been no systematic evaluation of outcome after surgery for infective endocarditis with respect to duration of antibiotic treatment. Methods. We performed a retrospective chart review of episodes of valve surgery for active infective endocarditis at Green Lane Hospital (Auckland, New Zealand) for 1963 - 1999. We recorded the duration of antibiotic treatment before and after valve surgery; the extent of infection at operation; Gram stain, culture, and histopathological testing results for valve samples; and the bacteriological outcome after surgery. The primary outcome measure was relapse, defined as endocarditis due to the same species within 1 year after surgery. Results. For the 358 patients in our study, the median duration of follow-up was 4.8 years. Thirty-two patients (9%) had 36 subsequent episodes of endocarditis. Relapse occurred after 3 (0.8%) of the operations (95% CI, 0.2% - 2.0%). Relapse of infection was unrelated to the duration of antibiotic treatment before or after surgery, positive valve culture results, positive Gram stain results, or perivalvular infection. Since 1994, we have reduced the duration of antibiotic treatment by similar to 7 days for those with positive valve culture results and by similar to 14 days for those with negative valve culture results, without any increase in the number of relapses. Conclusions. Relapse is an uncommon event following surgery for endocarditis. Commonly suggested indications for prolonging postoperative treatment are not associated with higher relapse rates, and their relevance is debatable. We conclude that it is unnecessary to continue treatment for patients with negative valve culture results for an arbitrary 4 - 6-week period after surgery. Two weeks of treatment appears to be sufficient, and, for those operated on near the end of the standard period of treatment, simply completing the planned course should suffice.