BACKGROUND: The addiction crisis is widespread, and unsafe injection practices among people who inject drugs (PWID) can lead to infective endocarditis.

METHODS: A retrospective analysis of adult patients with definite or possible infective endocarditis admitted to a tertiary care center in Portland, Maine was performed over three-year period. Our primary objective was to examine differences in demographics, health characteristics, and health service utilization between injection drug use (IDU)-associated infective endocarditis and non-IDU infective endocarditis. The association between IDU and mortality, morbidity (defined as emergency department visits within 3 months of discharge), and cardiac surgery was examined. Bivariate and multivariate analyses were performed. A subgroup descriptive analysis of PWID was also performed to better examine substance use disorder (SUD) characteristics, treatment with medication for opioid use disorder (MOUD) and health service utilization.

RESULTS: One-hundred and seven patients were included in the study, of which 39.2% (n = 42) had IDU-associated infective endocarditis. PWID were more likely to be homeless, uninsured, and lack a primary care provider. PWID were notably younger and had less documented comorbidities, however had similar in-hospital mortality rates (10% vs. 14%, p = 0.30), ED visits (50% vs. 54%, p = 0.70) and cardiac surgery (33% vs. 26%, p = 0.42) compared to those with non-IDU infective endocarditis. Ninety-day mortality was less among PWID (19.0% vs. 36.9%, p = 0.05). IDU was not associated with morbidity (adjusted odds ratio (AOR) 0.73, 95% CI 0.18-3.36), 90-day mortality (AOR 0.72, 95% CI 0.17-3.01), or cardiac surgery (AOR 0.15, 95% CI 0.03-0.69). Ninety-day mortality among PWID who received MOUD was lower (3% vs 15%, p = 0.45), as were ED visits (10% vs. 41%, p = 0.42) compared to those who did not receive MOUD.

CONCLUSIONS: Our results highlight existing differences in health characteristics and social determinants of health in people with IDU-associated versus non-IDU infective endocarditis. PWID had less comorbidities and were significantly younger than those with non-IDU infective endocarditis and yet still had similar rates of cardiac surgery, ED visits, and in-hospital mortality. These findings emphasize the need to deliver comprehensive health services, particularly MOUD and other harm reduction services, to this marginalized population.