High infective endocarditis rates found among women who inject drugs

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Rates of infective endocarditis (IE) are significantly increased among women who inject drugs (WWID), according to a recent study published in JAMA Network Open.¹

IE, defined as an infection of the endocardium and heart valves, has been linked to the opioid epidemic. Over 44,000 opioid-related deaths were reported in Canada between 2016 and 2024, highlighting the significant morbidity and mortality rates from injection drug use.²

A 5-fold increase in the number of people who inject drugs (PWID) was reported in the United States between 2011 and 2018.¹ Approximately 33% of non-PWID IE cases have been linked to women, vs 45% to 55% of IE cases among PWID.

To determine whether PWID with IE are disproportionately women, investigators conducted a retrospective cohort study. Participants included patients aged at least 18 years with a study hospital admission between April 5, 2007, and March 15, 2018.

IE was determined based on 2023 Duke–International Society for Cardiovascular Infectious Diseases (ISCVID) criteria. Case data was reviewed by infectious disease specialists to ensure ISCVID criteria was met.

Data was obtained from a study of bloodstream infections among patients receiving therapy for IE with a 5-year follow-up that included patients from Regina. Five-year mortality was reported as the primary outcome, determined using medical records and obituaries.

Definite IE based on 2023 Duke-ISCVID criteria was reported among 764 patients, 321 of whom were women and 441 were men. Of patients, 56% overall were PWID, with rates of 51.2% among women vs 48.8% among men.

The proportion of women comprising PWID was higher than men, at 51.2% vs 30.4%, respectively. Women were also on average younger than men and more often experienced tricuspid valve vegetation, right-sided infection, septic pulmonary emboli, and substance use disorder referral.

These rates were 76.2%, 71.8%, 69.3%, and 47%, respectively, among women vs 58.1%, 53.8%, 57.1%, and 31.6%, respectively, among men. However, differences in recurrent IE rates were not observed between women and men.

Mortality data during 1 year of follow-up was available for 415 patients. Death during this period was reported in 49 of 211 women and 67 of 204 men. Five-year follow-up data was reported in 347 patients, with 80 of 175 women and 89 of 172 men experiencing death. The overall 5-year mortality rate was 48.7%.

Province was linked to SUD counseling referral, indicating residence in London decreased the 5-year mortality rate when compared to Regina and surrounding areas. The adjusted hazard ratio (aHR) for this association was 0.29. However, this survival benefit was not reported among patients without referral to SUD counseling.

The hazard of 5-year mortality was reduced for right-side infection vs left-sided, bilateral, echo-negative infection, only within 90 days after index hospitalization, with an aHR of 0.24. The hazard of 5-year mortality was increased by congestive heart failure, with an aHR of 1.79. Similar mortality outcomes were reported when restricting the analysis to WWID.

Poorer fetal outcomes were observed among women with IE. This included a neonatal intensive care unit rate of 33% and a pregnancy termination rate of 46%.

Approximately half of patients with IE were women, despite this population comprising only one-third of PWID. Investigators recommended additional research about the underlying mechanisms behind the high IE incidence among WWID.

References

1. Adams JA, Spence C, Shojaei E, et al. Infective endocarditis among women who inject drugs. JAMA Netw Open. 2024;7(10):e2437861. doi:10.1001/jamanetworkopen.2024.37861
2. Government of Canada. Federal actions on the overdose crisis. June 2024. Accessed October 7, 2024. https://www.canada.ca/en/health-canada/services/opioids/federal-actions/overview.html