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Disclosures: One study author reports he received a personal research grant from the Institut d’Investigacions Biomèdiques August Pi i Sunyer. The other study authors and editorial authors report no relevant financial disclosures.
February 01, 2021
3 min read

In infective endocarditis, mortality lower among injected drug users vs. nonusers

Disclosures: One study author reports he received a personal research grant from the Institut d’Investigacions Biomèdiques August Pi i Sunyer. The other study authors and editorial authors report no relevant financial disclosures.
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Individuals with infective endocarditis who inject drugs may have better chances for survival compared with nonusers, according to research published in the Journal of the American College of Cardiology.

Researchers noted that among people with infective endocarditis, those who injected drugs were more likely to be younger men, and their cases were more likely to involve left-sided valves and prosthetic valves.

Person injecting drugs
Source: Adobe Stock

“People who inject drugs have traditionally been a group at higher risk of infective endocarditis due to the potential direct inoculation of microorganisms into the bloodstream through syringes, especially when hygienic conditions are poor and when nonsterile excipients are used, as well as the direct valve damage secondary to injection, especially for right-sided cases,” Juan M. Pericàs, MD, PhD, MPH, of the infectious diseases department at the Hospital Clinic-IDIBAPS of the University of Barcelona, Spain, and colleagues wrote. “The so-called ‘opioid crisis’ in the United States, Canada, and other countries such as Australia has led to a sharp increase in infective endocarditis cases in people who inject drugs.”

For this analysis, researchers included participants from the ICE-PCS and ICE-Plus cohorts, which included 8,112 cases of infective endocarditis. Researchers compared outcomes between people who injected drugs and those who did not and performed a logistic regression analyses to determine risk factors for 6-month mortality and relapses among those who inject drugs.

Infective endocarditis risk factors, mortality

Patients who injected drugs tended to be younger (median age, 37 vs. 63 years; P < .001) and were more often men (73% vs. 67%; P = .007) compared with those who did not and presented with lower rates of comorbidities apart from HIV (13.6% vs. 0.8%; P < .001), liver disease (8.9% vs. 3.8%; P < .001) and higher rates of prior infective endocarditis (19.7% vs. 9.4%; P < .001).

Among people who injected drugs, 53% of infective endocarditis cases involved left-side valves and 34.5% were purely left-sided.

According to the study, people who injected drugs represented the majority of patients with native infective endocarditis (90.2% vs. 64.4%; P < .001), whereas prosthetic-infective endocarditis (9.3% vs. 27%; P < .001) and implantable electronic device infection were more frequent among nonusers (0.5% vs. 8.6%; P < .001).

Researchers also observed that Staphylococcus aureus was the cause of 65.9% of infective endocarditis among injected drug users and 26.8% of cases among nonusers (P < .001).

Moreover, people who injected drugs presented with higher rates of systemic emboli (51.1% vs. 22.5%; P < .001) and persistent bacteremia (14.7% vs. 9.3%; P < .001) compared with nonusers.

In addition, cardiac surgery was less frequent in patients who injected drugs (39.5% vs. 47.8%; P < .001) and they experienced lower rates of in-hospital (10.8% vs. 18.2%; P < .001) and 6-month mortality (14.4% vs. 22.2%; P < .001) compared with nonusers; however, relapses were more common among injected drug users (9.5% vs. 2.8%; P < .001).

“Although relapses are more frequent in people who inject drugs, infective endocarditis in people who inject drugs is associated with better survival rates than infective endocarditis in non-people who inject drugs. Left-sided infective endocarditis, prosthetic valve endocarditis and non-S. aureus infective endocarditis are relatively common in people who inject drugs,” the researchers wrote. “Cardiac surgery is associated with improved survival and was found to be largely performed in people who inject drugs, especially among left-sided infective endocarditis cases. Approaching people who inject drugs with a respectful attitude and offering the possibility of cardiac surgery when indicated, together with the adequate harm reduction services and drug abuse disorder treatment, are crucial management elements.”

Impact of addiction medicine management

“Although cited as necessary, the ICE investigators did not evaluate the impact of addiction medicine management,” Larry M. Baddour, MD, professor of medicine in the division of infectious disease and the department of internal medicine at Mayo Clinic, and colleagues wrote in a related editorial. “We know that this is critical because consultation for this management during the index hospitalization for infective endocarditis can reduce the likelihood of readmission for serious infections and enhance completion of parenteral antimicrobial therapy.

“Infective endocarditis in people who inject drugs is a global problem and will require complex strategies to control this epidemic,” the editorial authors wrote. “Lifelong interventions will be needed to reduce injectable drug use recidivism in people who inject drugs who have developed infective endocarditis and survived, because they remain at high risk for subsequent bouts of infective endocarditis, regardless of whether they continue to inject drugs or not.”