Microbiological cultures of heart valves and valve tags are not valuable for patients without infective endocarditis who are undergoing valve replacement.

We evaluated the significance of the results of microbiological cultures of heart valves and identification tags from newly inserted prosthetic valves that were removed from patients with valvular heart disease; none of these patients had a preoperative diagnosis of endocarditis. We reviewed the charts of patients with positive cultures for evidence of infections before or after surgery. Cultures were positive for 11.9% of 219 valves (206 native valves and 13 prosthetic or bioprosthetic valves) and 11.6% of 224 tags. The most common isolates were coagulase-negative staphylococci. Typical agents of endocarditis--viridans streptococcus, Enterococcus faecalis, and Staphylococcus aureus--were cultured from five specimens, and Mycobacterium avium complex was identified in six valves. None of the patients with positive valve or tag cultures developed postsurgical endocarditis or wound infection. Findings on histopathologic examination of the valves were not consistent with endocarditis. We conclude that the results of cultures of valves from patients without preoperative diagnoses of endocarditis lack clinical significance, and positive tag cultures are not predictive of postsurgical infection. Positive cultures are most likely a result of contamination during surgery or thereafter.