BACKGROUND:"Heterotaxy syndrome", best segregated as isomerism, is characterised by laterality defects of the thoraco-abdominal organs, causing functional impairment. In particular, the spleen is frequently affected, increasing susceptibility to bacteraemia. This study explored factors that may increase the risk of bacteraemia in patients with isomerism. METHODS:We identified patients with CHD and isomerism. Review of outpatient, inpatient, and surgical records was conducted to collect data and determine trends in the cohort. A Cox regression analysis was conducted to determine factors influencing freedom from bacteraemia (Fig 1). RESULTS:We identified 83 patients with CHD and isomerism - 17 (20%) who had documented episodes of bacteraemia with a total of 21 episodes. A majority (86%) were nosocomial. The median age at the time of bacteraemia was 4 months. Although splenic anatomy did appear to influence the risk of bacteraemia in univariate analysis, this significance was lost with multivariate analysis. None of the other factors was significantly associated in either univariate or multivariate analysis. CONCLUSION:Specific factors such as splenic anatomy, atrial appendage isomerism, and antibiotic prophylaxis status are not significantly associated with the risk of bacteraemia in patients with CHD and isomerism. Nosocomial infections represent a majority of bacteraemia in these patients.