Are histopathological findings of diagnostic value in native valve endocarditis?

BACKGROUND: Optimal management of infective endocarditis (IE) depends on the early detection of IE-causing pathogens and on appropriate antimicrobial and surgical therapy. The current guidelines of the European Society of Cardiology (ESC) recommend histopathological examination as the gold standard for diagnosing IE Habib et al. (Eur Heart J 30:2369-2413, 2005). We hypothesize that histopathological findings do not provide additional information relevant to clinical decision-making.
METHODS: We retrospectively reviewed a cohort of patients who had undergone surgery for native valve endocarditis (NVE) at the University Hospital Regensburg between September 1994 and February 2005. All episodes of intraoperatively confirmed endocarditis during this period were included in the study. Data were retrieved from surgical records, microbiological and histopathological reports, and medical files of the treating as well as admitting hospital. Pathogens were correlated with the site of manifestation of the affected heart valve and with clinical and histopathological findings.
RESULTS: A total of 163 episodes of NVE were recorded and entered into our study for analysis. The valves affected were the aortic valve (45 %), the mitral valve (28 %), the aortic and mitral valve (22 %), and other valves (5 %). IE-causing pathogens were Staphylococcus aureus (22 %), viridans streptococci (18 %), enterococci (10 %), streptococci other than Streptococcus viridans (9 %), coagulase-negative staphylococci (5 %), miscellaneous pathogens (4 %), and culture-negative endocarditis (33 %). Infection with S. aureus was associated with high rates of sepsis, septic foci, and embolic events, while patients with enterococcal IE showed the highest rate of abscesses. Mortality rate in all subgroups was low without significant differences. However, histopathological findings correlated poorly with the pathogen involved and showed only few significant associations that were without clinical relevance.
CONCLUSIONS: The clinical presentation of IE depends on the pathogen involved. Among the episodes of NVE examined, the histopathological examination of resected heart valves did not show any pathogen-specific morphological patterns and therefore did not provide any additional information of clinical value. Based on our findings, we recommend complementary cultures of the resected materials (valve tissue, thrombotic material, pacer wire) and implementation of molecular diagnostic methods (e.g., broad-range PCR amplification techniques) instead of histopathological analyses of resected valve tissue.