Cardiac complications after haematopoietic cell transplantation in paediatric patients are significant yet under-recognised. Pericardial effusion has been associated with worse outcomes and transplant-related mortality.

We aimed to evaluate the incidence, risk factors, and clinical course of pericardial effusion after paediatric allogeneic haematopoietic cell transplantation. We identified transplantation recipients “at risk” for clinically significant pericardial effusion based on our definition, described our clinical experience and provided recommendations for screening and management.

Clinical data of children who underwent allogeneic haematopoietic cell transplantation at Texas Children’s Hospital from January 2010 to April 2021 were analyzed retrospectively. Factors potentially contributing to time to pericardial effusion, time to pericardial effusion resolution, and overall survival were evaluated.

We included 629 haematopoietic cell transplantation recipients with a median age at transplantation of 8.5 years (0.1–24.3). Seventy-three patients (11.6%) developed pericardial effusion within a median time of 102 days (1–403) post-haematopoietic cell transplantation, and 50 (68.5%) had resolution of pericardial effusion at the time of last evaluation. Older age at the time of haematopoietic cell transplantation, transplant-associated thrombotic microangiopathy, and cytomegalovirus diagnoses independently increased the risk of pericardial effusion development, while cytomegalovirus diagnosis decreased the likelihood of pericardial effusion resolution. Both non-significant pericardial effusion development and clinically significant effusion development were significantly associated with post-haematopoietic cell transplantation mortality, compared to no pericardial effusion development.

Paediatric haematopoietic cell transplantation recipients with malignant diseases, older age at the time of transplantation, cytomegalovirus infection, or transplant-associated thrombotic microangiopathy are at higher risk for pericardial effusion development, which in turn predicts worse outcomes with increased risk of death. We propose a model for improved detection, evaluation, and management of pericardial effusion post-haematopoietic cell transplantation.