Risk Factors Of Infective Endocarditis In Persons Who Inject Drugs

Abstract

Background: The rising incidence of infective endocarditis (IE) among people who inject drugs (PWID) has been a major concern across North America. Details of injection practices leading to IE are not well characterized.Methods: A case-control study, using one-on-one interviews to understand risk factors and injection practices associated with IE among PWID was conducted. Eligible participants included those who had injected drugs within the last 3 months, were > 18 years old and either never had or were currently admitted for an IE episode. Cases were recruited from the tertiary care centers and controls were recruited from outpatient clinics in patients without IE and addiction clinics in London, Ontario. Results: 33 cases (PWID IE+) and 102 controls (PWID but IE-) were interviewed. Using clean injection equipment from the provincial distribution network was a protective factor against IE (p<0.001). Furthermore, using lighters during the injection process was also protective for IE (OR 2.5; 95% CI 1.11–5.63). Female sex (OR 3.63; 95% CI 1.58-8.36) and injection into multiple sites (OR 4.31; 95% CI 1.33-13.93) were associated with IE. Injection into the feet (57.6% cases; 36.6% control; p= 0.034) was also associated with IE. Discussion: Our pilot study highlights the importance of distributing clean injection materials for IE prevention. Injection into multiple areas may indicate a greater difficulty in accessing common and safer injection sites such as the arm, and thus multi-site injections may be a surrogate marker for injection-related venous damage in entrenched drug users. Moreover, the use of lighters may be correlated with the best practice of heating preparations of drugs prior to injection, which is known to reduce bacterial burden. Lastly, gender differences in injection techniques, which may place women at higher risk of IE, requires further study.