Patients with hypoplastic left heart syndrome and its variants following palliation surgery are at risk for thrombosis. This study examines variability of antithrombotic practice, the incidence of interstage shunt thrombosis, and other adverse events following Stage I and Stage II palliation within the National Pediatric Cardiology Quality Improvement Collaborative registry.

We carried out a multicentre, retrospective review using the National Pediatric Cardiology Quality Improvement Collaborative registry including patients from 2008 to 2013 across 52 surgical sites. Antithrombotic medications used at Stage I and Stage II discharge were evaluated. Variability of antithrombotics use at the individual patient level and intersite variability, incidence of shunt thrombosis, and other adverse events such as cardiac arrest, seizure, stroke, and need for cardiac catheterisation intervention in the interstage period were identified. Antithrombotic strategies for hybrid Stage I patients were evaluated but they were excluded from the variability and outcomes analysis.

A total of 932 Stage I and 923 Stage II patients were included in the study: 93.8% of Stage I patients were discharged on aspirin and 4% were discharged on no antithrombotics, and 77% of Stage II patients were discharged on aspirin and 17.5% were discharged on no antithrombotics. Only three patients (0.2%) presented with interstage shunt thrombosis. The majority of patients who died during interstage or required shunt dilation and/or stenting were discharged home on aspirin.

Aspirin is the most commonly used antithrombotic following Stage I and Stage II palliation. There is more variability in the choice of antithrombotics following Stage II compared with Stage I. The incidence of interstage shunt thrombosis and associated adverse events was rare.