Clinical characteristics and prognostic determinants of infective endocarditis in adult intravenous drug users

Background and Purpose: Infective endocarditis (IE), one of the most serious complications of intravenous (IV) drug use, has been increasing in incidence in the past decade in Taiwan. The difference in prognostic determinants for IE between patients with and without IV drug use is poorly understood. This study investigated the clinical profile and prognostic determinants of IE in IV drug users. Methods: The medical records for 157 episodes (30 episodes in IV drug users and 127 episodes in non-drug users) of IE in 143 consecutively hospitalized patients were retrospectively evaluated. Independent prognostic determinants were identified by multiple Cox proportional hazards regression analysis. Results: IV drug users were younger with a predominance of males. They also had a higher frequency of right-sided IE, underlying disease, and had a larger area of vegetation than non-drug users. Staphylococci were the most common causative microorganisms in IV drug users while streptococci were more common in non-drug users. Septic pulmonary embolism and septic complications were more frequent in IV drug users. In-hospital mortality was similar between the 2 groups. Non-cardiac shock was the only significant prognostic determinant in IV drug users (odds ratio [OR] 15.5; 95% confidence interval [CI] 3.0 to 81.5); however, in non-drug users, non-cardiac shock (OR, 4.4; 95% CI, 2.0 to 9.8), older age (≥50 years), and neurological complications were independent predictors of in-hospital mortality. Conclusions: The clinical characteristics and prognostic determinants of IE in IV drug users were significantly different from those of non-drug users. IV drug users were less likely to have a benign clinical course and had a higher frequency of septic complications. These findings indicate the importance of risk stratification and modified treatment strategy in IV drug users who develop IE.