The Impact of Medical Therapy on Short- and Long-Term Outcomes of Surgical Therapy for Culture-Positive Infective Endocarditis

BACKGROUND: Valve surgery is recommended for a limited number of patients with infective endocarditis (IE) meeting complicated, often anecdotal, criteria. Up to half of patients receiving medical therapy for culture-positive IE are prescribed inappropriate antibiotics for the etiologic microorganism. The impact of medical therapy on surgical outcomes is not well defined by existing literature. Design and Setting: Retrospective, observational cohort study conducted from 1990 to 2013. Data were collected from patient charts. Antibiotic therapy was graded as appropriate or inappropriate according to the most recent guidelines of the American Heart Association. Participants: 286 consecutive patients with culture-positive IE by the Duke Modified Criteria undergoing therapeutic valve surgery. 177 (62%) received appropriate antibiotic therapy and 93 (33%) received inappropriate antibiotic therapy. Antibiotic regimens of the 16 (5%) remaining patients could not be assessed. RESULTS: Kaplan-Meier survival analysis showed no statistical difference in survival between the appropriate and inappropriate therapy groups (p=0.795). Intraoperative deaths occurred in 3.4% of the appropriate therapy group and 3.2% of the inappropriate therapy group. All-cause mortality within 30 days of operation was 15% (95%CI: 10,20) in the appropriate group and 12% (5,20) in the inappropriate group. Two-year and five-year survival rates were 62% (55,70) and 48% (40,58) in the appropriate group and 63% (54,75) and 52% (42,65) in the inappropriate group. Contingency analysis of potentially confounding variables revealed the two cohorts had few statistically significant differences in frequencies of etiologic microorganism and comorbidities. There were no statistically significant differences between the groups in their gender composition, racial composition, mean age, or frequencies of affected valves. CONCLUSION: Although appropriate antibiotics are clearly superior for patients receiving medical therapy alone to treat IE, it appears that short-term and long-term survival of patients undergoing valve surgery are not affected by the appropriateness of prior medical therapy. This suggests that among the many variables physicians must weigh when considering surgical therapy for IE, the patients' antibiotic therapy regimen may not be an important factor. Further analysis may reveal other variables predictive of short or long-term mortality in these patients. Acknowledgment: Supported in part by an Alpha Omega Alpha Carolyn L. Kuckein Student Research Fellowship