Infective endocarditis in intravenous drug users from Italy: the increasing importance in HIV-infected patients

BACKGROUND: Intravenous drug users (IDUs) are at increased risk of infective endocarditis (IE). PATIENTS AND METHODS: Episodes of IE in IDUs were retrospectively analyzed in this multicenter study. Cases were collected between 1986 and 1999. Only definite diagnosis according to the Duke criteria were analyzed. RESULTS: Two hundred and sixty-three cases, including 100 cases in HIV-positive patients, were observed in IDUs. Any right-sided involvement was detected in 167 out of 263 cases (63.5%) and any left-sided involvement in 115 out of 263 cases (43.7%). The tricuspid valve (TV) alone was affected in 135 cases (51.3%), the mitral valve alone in 32 patients (12.1%), the aortic valve alone in 41 cases (15.6%) and the pulmonic valve alone in 3 cases. Staphylococcus aureus was isolated in 156 cases (59.3%) and Streptococcus spp. in 33 cases (12.5%). No major differences were observed between HIV-negative and HIV-positive patients. Any TV valve involvement was significantly associated with female rather than male gender (p = 0.02). There was a significant association between S. aureus etiology and TV involvement (p < 0.0001). The mortality rate was 16%. On multivariate analysis, only left-side IE (p = 0.0006; OR 5.2; 95% CI 2.0-13.5) and age greater than 35 years (p = 0.0068; OR 3.6; 95% CI 1.4-9.0) were independently associated with mortality. CONCLUSIONS: Infective endocarditis in IDUs is significantly associated with right-side localization (63.5% for any rightsided heart involvement vs 43.7% for any left-sided heart involvement; OR 2.24; 95% CI 1.55-3.23; p < 0.001). S. aureus is the microorganism most frequently isolated and is significantly associated with TV involvement. Any left-side involvement and age greater than 35 years are independently associated with mortality. HIV infection does not appear to have a significant effect on mortality.