Burden of infective endocarditis in an Australian cohort of people who inject drugs

Background: Infective endocarditis (IE) results in substantial morbidity and mortality in people who inject drugs (PWID). Aims: To describe the burden of IE and its outcomes in PWID. Methods: Retrospective cohort study of adults admitted to a tertiary referral centre in Melbourne, Australia, with IE due to injection drug use from 1997 to 2015. Results: Ninety-seven PWID with 127 episodes of IE were identified with a median acute inpatient stay of 37 days (1-84). Admission to an intensive care unit was required in 67/127 (53%) episodes. Twenty-seven percent (34/127) of episodes occurred in patients with a previous episode of endocarditis. One third (43/127, 34%) of episodes involved left-sided cardiac valves. Antimicrobial treatment was completed in 88 (70%) episodes. Valve surgery was performed in 25/127 (20%) episodes. Predictors of surgery in univariable analysis were left-sided cardiac involvement (risk ratio (RR) 6.0), severe valvular regurgitation (RR 2.6) and cardiac failure (RR 2.2) (all P < 0.005). Twenty (16%) episodes resulted in death. Predictors of mortality on univariable analysis were left-sided cardiac involvement (RR 6.4), and not completing treatment (RR 0.12; both P < 0.001). The average estimated cost per episode was AU$74 168. Conclusions: IE causes a considerable burden of disease in PWID, with significant healthcare utilisation and cost. Surgery and death are not infrequent complications. In addition to ensuring completion of antimicrobial therapy, strategies such as opioid maintenance programmes may be useful in improving health outcomes for PWID.