Prophylactic antibiotics to prevent infective endocarditis (IE)? Relative risks re-assessed

A case-control study was conducted in 54 Philadelphia-area hospitals, IQ88-1990, to quantify the risk of factors used as an indication for antibiotic prophylaxis to prevent IE. We enrolled 273 cases of community-acquired IE (no IV drug-use IE); diagnoses were confirmed by expert review of medical abstracts with risk factor data removed. Controls were recruited by random digit dialing, matched to the cases by 5 year age stratum, sex, and neighborhood. Structured interviews were conducted, and the results analyzed using conditional logistic regression. Cases were substantially more likely than controls to know of cardiac valvular abnormalities (adjusted odds ratio (OR) and 95% confidence interval (CI): J2.8 (6.1-27. In particular, cases were more likely to have a history of mitral valve prolapse (OR 24.3 (CI 6.4-91)); congenital heart disease (OR 4.1 (CI 1.2-13)); cardiac valvular surgery (OR 17.0 (CI 2.5-U7)); rheumatic fever with heart involvement (OR 5.1 (CI 0.5-50)); and heart murmur without other known cardiac abnormality (OR 8.2 (CI 3.5-19)). Overall, 112 (41%) of the 273 cases knew of predisposing cardiac lesions. However, data about dental treatment, the major indication for prophylaxis, showed that cases were no more likely than controls to receive dental treatment at any time in the preceding 60 days: OR 1.2 (CI 0.81.9). Results were similar when restricted to invasive dental procedures: OR 1.8 (CI 0.8-3.9). Among those with known cardiac lesions, the OR(CI) for dental treatment was 0.3 (0.03-3.2). Furthermore, this risk did not differ with or without prophylactic antibiotics: OR 0.5 (CI 0.01-9.6) and 0.0 (0.00-39), respectively. Among 155 cases infected with oral flora (49% of whom had known cardiac lesions), 33 (21.3%) had recent dental treatment, as did 23 (14%) of their matched controls. OR 1.6 (CI 0 9-2 9). Only 18(11.6%) of the cases infected with oral flora had both known cardiac lesions and recent dental treatment, 10 of whom had received prophylaxis. Given these findings about dental therapy as a risk factor for IE, the small proportion of cases with both known cardiac valvular abnormalities and dental treatment prior lo the inception of their disease, and the risks and costs associated with antibiotic use, the recommended practice of prophylactic antibiotic prescription for denta! patients with cardiac abnormalities should be reassessed.