Hydrogel coils are associated with reduced post-embolisation fever and inflammation in paediatric aortopulmonary collateral embolisation

Background: In patients with cyanotic congenital heart disease (CHD), aortopulmonary collateral arteries (APCAs) commonly develop as a compensatory source of pulmonary blood flow. However, APCAs increase pulmonary vascular resistance and ventricular preload, potentially complicating the establishment of Fontan circulation. Coil embolisation of APCAs is routinely performed before Fontan completion, but post-procedural fever is frequently observed and may delay subsequent surgery. This study aimed to identify factors associated with post-embolisation fever, with a particular focus on the influence of coil type. Methods and Results: We retrospectively reviewed 97 paediatric patients who underwent APCA coil embolisation between 2007 and 2023. Patients were categorised according to coil type: platinum coils only (P group, n = 52), both platinum and hydrogel coils (P-H group, n = 29), or hydrogel coils only (H group, n = 16). The incidence of post-embolisation fever (≥38°C) and inflammatory markers were compared among groups. Histopathological characteristics of embolised vessels were also assessed. Overall, post-embolisation fever occurred in 64% of patients. The incidence of fever was significantly lower in the H group (25.0%) than in the P group (73.0%) and P-H group (68.9%) (p < 0.01). C-reactive protein levels increased significantly after fever onset, whereas white blood cell counts showed no meaningful change. Histopathological evaluation demonstrated prominent fibrin deposition and inflammatory cell infiltration in vessels embolised with platinum coils, while vessels treated with hydrogel coils exhibited only mild inflammatory changes. Conclusions: Hydrogel coils were associated with a lower incidence of post-embolisation fever and a milder inflammatory response than platinum coils. These findings suggest that coil selection may play an important role in minimising post-procedural inflammation and facilitating perioperative management in children preparing for the Fontan procedure.