Data on arterial thromboembolism in children undergoing cardiac surgery are limited. We sought to characterise, and estimate rates of, incident and recurrent arterial thromboembolism, and describe antithrombotic therapies for treatment in a large multinational population of children with CHD undergoing cardiac surgery.

We queried the TriNetX global electronic health record (derived real-world data research platform) from 2017 to 2024 for patients less than 18 years of age and an index arterial thromboembolism within 1 year of congenital cardiac surgery. Data were descriptively analysed.

Of 20,102 children who underwent an index cardiac surgery for CHD, 206 (1.1%) developed an index arterial thromboembolism within 1 year of surgery: 111 (53.9%) had only arterial thromboembolism and 95 (46.1%) had concomitant venous thromboembolism. The most common anatomic site for arterial thromboembolism was the lower extremity (n = 141, 68.4%), and the most common surgery was the Glenn procedure (n = 35, 17%). Unfractionated heparin was utilised in 136 (67 %) and aspirin in 91 (44.2%) patients. Recurrent thromboembolism occurred in 36 (17.5%) patients within 1 year of the index thromboembolism.

Among children undergoing congenital cardiac surgery, arterial thromboembolism was rare (1% of patients), but the 1-year risk of recurrent thromboembolism was high, at 17.5%. Multicentre prospective cohort studies are warranted to further evaluate risk factors for recurrent thromboembolism, to facilitate future risk-stratified interventional trials designed to reduce the high thromboembolism recurrence risk in these children.

Thromboembolism is a complication in paediatric patients with CHD requiring cardiac surgery. Previous research has focused on post-operative thromboembolism. This study aimed to describe thromboembolism frequency before or after cardiac surgery in children with CHD.

We performed a single-centre retrospective study from October 2020 to June 2023 (inclusive). Patients were eligible for inclusion if they were <21 years of age and underwent cardiac surgery. Outcomes of interest included the occurrence and characteristics of thromboembolism in the 12 months before and after surgery, antithrombotic therapies, recurrent thromboembolism, and clinically significant bleeding.

Among 260 patients included, 35 (13.5%) developed an index thromboembolism. Twelve (34.3%) patients had an index thromboembolism <12 months before surgery and 23 (65.7%) had an index thromboembolism <12 months after surgery, including 8 (22.9%) patients who had thromboembolism during both exposure periods. The median interquartile range (IQR) time of thromboembolism relative to cardiac surgery was –26 (–4 to –140) days and 15 (4 to 41) days, respectively. Seven (20%) patients had arterial, 18 (51.4%) venous, and 3 (8.6%) had both arterial and venous thromboembolism. Median (IQR) antithrombotic therapy duration was 49 (24–84) days. Nine (25.7%) patients developed recurrent thromboembolism and five (14.3%) patients experienced clinically significant bleeding.

The risk of thromboembolism and recurrence is high both before and after cardiac surgery among paediatric patients with CHD. Prospective multi-centre studies should seek to identify risk factors for preoperative and postoperative thromboembolism to inform the design of future risk-stratified thromboembolism prevention trials in children with CHD.