Abstract 4356954: Causative Organism Predicts Diagnostic Utility of TTE in Bacteremia-Associated Endocarditis

Introduction: Transthoracic echocardiogram (TTE) is a critical diagnostic tool for detecting infective endocarditis (IE) in patients with bacteremia. Despite being a common sequela of disseminated infection and a source of morbidity and mortality, limited data exists on TTE yield by bacteriology. Research Question: This study compared the diagnostic yield of TTE in patients with atypical versus typical bacteremia. Typical organisms included Viridians group streptococci, Staphylococcus spp., and Enterococcus spp. Methods: A retrospective cohort analysis was conducted using the TriNetX database which included 143 healthcare organizations in the Global Health Collaborative Network. Two cohorts were analyzed: patients with atypical bacteremia ( n = 22,523) and patients with typical bacteremia ( n = 28,696). Inclusion criteria: patients ≥ 18 years with bacteremia diagnosed ≤ 1 month before TTE (index event). Propensity score matching adjusted for 35 potential confounders. The mean age was 64 years; the study population was approximately 53% male. Results/Data: The prevalence of endocarditis diagnosis was 5.54% in the typical bacteremia group and 2.19% in the atypical bacteremia group. This provided a number-needed-to-diagnose of 18 and 45 for typical and atypical bacteremia, respectively. The odds ratio (OR) for endocarditis diagnosis in atypical versus typical bacteremia was 0.382 (95% CI: 0.342 to 0.427, p<0.0001). The positive predictive value (PPV) of TTE was 37.9% for typical bacteremia and 19.4% for atypical bacteremia, while the negative predictive value (NPV) was 97.3% and 98.9%, respectively. TTE remains valuable for IE detection in bacteremia, but with 2.6 times greater diagnostic yield in typical bacteremia cases. Patients with atypical bacteremia were more likely to have TTE in the presence of rheumatic heart disease (13% vs 25%, p<0.0001). Conclusion(s): These findings highlight the role of the causative organism in bacteremia when interpreting TTE results. Although AHA/ACC guidelines recommend TTE for initial evaluation in patients with suspected IE, the lower odds ratio in atypical bacteremia supports a more selective approach to TTE use. Overall, this study establishes a need to develop or refine risk stratification tools to guide TTE utilization, optimizing resource allocation and improving diagnostic efficiency by reserving it for patients with additional risk factors or clinical signs suggestive of infective endocarditis.