Evolving epidemiology of injecting drug use-associated infective endocarditis: A regional centre experience MATTHEW K.Y. TUNG 1 , MELANIE LIGHT 1 , RINKY GIRI 2 , STEPHEN LANE 3,4 , ALAN APPELBE 5 , CRAIG HARVEY 5 & EUGENE ATHAN 4,5 1 MonashHEART, Monash Health, Melbourne, Australia, 2 Department of Medicine, St Vincent’s Hospital Melbourne, Melbourne, Australia, 3 Biostatistics Unit, Barwon Health, Geelong, Australia, 4 School of Medicine, Deakin University, Geelong, Australia, and 5 The Geelong Hospital, Barwon Health, Geelong, Australia Abstract Introduction and Aims. Injecting drug use (IDU) is a major risk factor for infective endocarditis (IE). An understanding of the epidemiology of IE and IDU is vital for delivery of health care for this disease. Our aim was to examine the rates of IDU-associated IE (IDU-IE) in a single centre over the last 12 years. Design and Methods. Retrospective analysis of two cohorts of consecutive patients (n = 226) admitted with IE from 2002 to 2013. Numbers of cases and rates of IE were compared between two cohorts (2002–2006 and 2009–2013). Rate ratios were calculated using Poisson distributions. Poisson regression was used to examine relationship over time. Results. One hundred thirty cases of endocarditis were seen in the first observation period (6 IDU-IE) and 96 in the second observation period (15 IDU-IE).The estimated incidence rate of IE had fallen from 10.1 to 6.45 per 100 000 person-years [rate ratio 0.64, 95% confidence interval (CI) 0.48, 0.85]. In contrast, the estimated incidence rate of IDU-E has risen from 0.48 to 0.79 per 100 000 person-years (rate ratio 1.65, 95% CI 0.59, 4.57). Incidence rate regression suggests that the number of IDU-IE cases is expected to increase by a factor of 1.25 (95%CI 1.09–1.44) for each increase of 1 year. Discussion and Conclusions. Over the last decade, there has been a decrease in incidence rate and total number of cases of IE but a rise in rate and number of cases of IDU-IE.This may indicate increasing IDU or increased rates of endocarditis in this region.This finding may inform health-care planning in the area. [Tung MKY, Light M, Giri R, Lane S, Appelbe A, Harvey C, Athan E. Evolving epidemiology of injecting drug use-associated infective endocarditis: A regional centre experience. Drug Alcohol Rev 2014] Key words: endocarditis, intravenous substance abuse, heart valve, Staphylococcus aureus, needle-exchange programs. Introduction Infective endocarditis (IE) is a common clinical problem with significant associated morbidity and mor- tality. Contemporary multicentre assessments of out- comes in IE have estimated inpatient mortality between 14% and 18% [1,2]. In developed countries, rheumatic heart disease is no longer the leading cause for predisposing valvular heart conditions, being surpassed by the presence of degen- erative or prosthetic valve disease [2]. Injecting drug use (IDU) and health care-associated IE have emerged as increasingly important aetiologic factors. The inci- dence of IE in injecting drug users is estimated to be 1.5–3.3 cases per 1000 injecting drug users per year [3,4]. The current model of the pathogenesis of IE suggests that damage from a variety of sources, including repeated intravenous injection of solid particles, dis- rupts the normally microbiologically resistant intact valvular endothelium predisposing to colonisation [5]. IDU is an established predisposing risk factor for IE and recognised as a minor criteria in the Duke defini- tions of definite and possible IE [6]. Estimates of the proportion of cases of IE associated with IDU range from 8.5% in multicentre studies [2] to The work for this manuscript was carried out at The Geelong Hospital (Department of Cardiology and Department of Infectious Diseases) and at the Deakin University School of Medicine, Geelong. Matthew K.Y.Tung MBBS, FRACP, Cardiac Rhythm Management Fellow, Melanie Light MBBS, Medical Intern, Rinky Giri MBBS, Medical Intern, Stephen Lane B.Sci (HONS), PhD, Research Fellow,Alan Appelbe MBBS, FRACP, Cardiologist, Craig Harvey Post Grad AOD Studies, Pharmacotherapy Outreach Worker. Eugene Athan MBBS, FRACP, MPH, Director. Correspondence to Associate Professor Eugene Athan, The Geelong Hospital, Barwon Health, PO Box 281, Geelong,Vic. 3220, Australia. Tel: 03 4215 2374; Fax: 03 4215 2385; E-mail: eugene@barwonhealth.org.au Received 21 July 2014; accepted for publication 5 October 2014. REVIEW Drug and Alcohol Review (2014) DOI: 10.1111/dar.12228 © 2014 Australasian Professional Society on Alcohol and other Drugs