A Retrospective Review: Significance of Vegetation Size in Injection Drug Users with Right-Sided Infective Endocarditis

BackgroundPreviously described prognostic markers in right-sided infective endocarditis (RSIE) include vegetation size ≥1cm, fever for more than three weeks, cardiac failure and severe sepsis. This study aimed to evaluate effectiveness of medical therapy for vegetations ≥1cm and explore determinants of outcome in a representative population of intravenous drug users (IDUs) at a metropolitan Australian health service.MethodsRetrospective review of consecutive IDUs presenting to our institution with native-valve RSIE (by modified Duke criteria) over seven years (2005-2011). Data recorded included echocardiographic estimation of maximal vegetation diameter (classified as < or ≥1cm). Relationships between vegetation size and specified outcomes of death, septic shock, recurrence and relapse were examined by Chi-squared testing.ResultsOf 49 episodes five (10%) were managed surgically and a further four (8%) were lost to follow-up and excluded from the analysis. Of the remaining 40 evaluable medically treated patients (median age 28, range 20-55), 37 (93%) cultured methicillin-sensitive S. aureus and all had tricuspid valve involvement. Of 24 with vegetations ≥1cm, three died (mortality 13%) compared with one (6%) in 16 medically treated patients with vegetations <1cm (p=0.63). A Pittsburgh (PITT) bacteraemia score of ≥4 at presentation was associated with a mortality of 24% (four of 17 patients died) compared with 0 in 23 patients with PITT scores <4 (p=0.026).ConclusionMedical therapy alone can be effective for RSIE when large vegetations are present. However a high sepsis score at presentation may increase risk of death. Larger studies are required to determine optimal indications for early surgical intervention.