Impact of prior antiplatelet therapy on risk of embolism in infective endocarditis

Background. Embolism is a dreaded complication of infective endocarditis (IE). Currently, antimicrobial therapy is the only medical intervention proven to decrease the risk of embolism associated with IE. We hypothesized that, because platelet aggregation is operative in the pathogenesis of vegetation formation, embolism associated with IE should occur less frequently among patients who have received prior, continuous daily antiplatelet therapy for noninfectious reasons. Methods. We studied a retrospective cohort of adult patients with a diagnosis of IE who presented to the Mayo Clinic ( Rochester, MN) during 1980 - 1998. The cohort was divided into 2 groups on the basis of whether they had received continuous daily antiplatelet therapy for at least 6 months prior to the time of hospitalization for IE. Antiplatelet therapy included aspirin, dipyridamole, clopidogrel, ticlopidine, or any of combination of these agents. The primary end point was a symptomatic embolic event that occurred prior to or during hospitalization. Multivariable logistic regression was used to assess the impact of continuous daily antiplatelet therapy on risk of symptomatic emboli associated with IE. Results. One hundred forty-seven (24.5%) of 600 patients experienced a symptomatic embolic event; the most common embolic manifestation was stroke ( in 48.2% of patients). Embolic events occurred significantly less often among those who had received prior, continuous daily antiplatelet therapy (12.0% of patients who had received therapy vs. 27.8% patients who had not receive therapy; P < .001). After adjustment for several covariates known to influence both risk of embolism and propensity for antiplatelet use, the adjusted odds ratio for a symptomatic embolic event was 0.36 (95% confidence interval, 0.19 - 0.68;) for patients receiving continuous daily P = .002 antiplatelet therapy. Conclusions. The risk of symptomatic emboli associated with IE was reduced in patients who received continuous daily antiplatelet therapy before onset of IE.