Valve involvement in infective endocarditis among intravenous drug users: a systematic review and meta-analysis

Abstract Background Intravenous drug use (IVDU) is a major risk factor for infective endocarditis (IE), with right-sided infective endocarditis (RSIE) most frequently observed. However, precise estimates of valve involvement and the relative risk (RR) of RSIE within the IVDU population remain unclear. This systematic review and meta-analysis aimed to quantify the prevalence of RSIE, left-sided IE (LSIE), both-sided IE, and valve-specific involvement in IVDUs while assessing the relative risk of right-sided versus left-sided IE within the IVDU population. Methods A systematic search was conducted in PubMed, Embase, and Web of Science to identify studies reporting IE in IVDUs. Inclusion criteria followed the PICO framework, ensuring clear definitions of IVDU status and valve involvement. A random-effects model was used to calculate pooled prevalence estimates and RR ratios with 95% confidence intervals (CIs). Heterogeneity was assessed using the I² statistic, and sensitivity analyses were performed. Results A total of 14 studies involving 1,783 patients met the inclusion criteria. The pooled prevalence of right-sided infective endocarditis (RSIE) was 59% (95% CI: 54%–65%), left-sided infective endocarditis (LSIE) was 39% (95% CI: 33%–46%), and both-sided infective endocarditis was 8% (95% CI: 6%–12%). Among individual valves, the tricuspid valve was most commonly affected (59% (95% CI: 53%–64%)), followed by the mitral valve (21% (95% CI: 18%–26%)) and the aortic valve (16% (95% CI: 12%–20%)). Pulmonic valve involvement was rare (1% (95% CI: 0%–3%)). Overall, individuals who inject drugs (IVDUs) had a 1.49-fold increased risk of developing right-sided IE compared to left-sided IE (RR = 1.49 (95% CI: 1.15–1.95), p = 0.008). Conclusion This SRMA confirms the predominance of right-sided IE, particularly tricuspid valve involvement, in IVDUs, with a significantly higher risk compared to left-sided IE. The findings underscore the need for targeted screening, early intervention, and IVDU-specific management strategies in IE care. Future research should focus on regional variations, microbiological patterns, and long-term outcomes in this high-risk population. Clinical trial number Not applicable.