ObjectiveTo determine the prevalence of aspirin (ASA) resistance in pediatric patients with congenital heart disease and evaluate whether postoperative thrombosis is associated with aspirin resistance.MethodsA total of 52 patients undergoing high-risk congenital cardiac surgery were recruited in a prospective cohort study at Fuwai Hospital from August 2016 to December 2017. There were 29 males and 23 females with a median age of 8 months (6 d to 13 years). The response to aspirin was determined using the thromboelastography with platelet mapping (TEG-PM) system several days after administration. According to the arachidonic acid (AA) inhibition< 50% or not, they were divided into an ASA resistance group (n=14) and an ASA sensitivity group (n=38). Risk factors of ASA resistance were identified using univariate and multivariate analysis. Patients were monitored prospectively for three months for the development of a thrombosis event. ResultsOf 52 children analyzed, 14 (26.9%) were ASA resistance. The prevalence of thrombosis after ASA antiplatelet therapy was 5.9%. Dose escalation based on aspirin testing was performed in 3 of 14 patients, and the ASA sensitivity was observed in 1 patient. No correlation was found between ASA resistance and postoperative thrombosis (r=0.04, P=0.80).ConclusionPostoperative thrombosis is not associated with aspirin resistance in these patients. Our findings also suggest that resistance may be due to lack of aspirin doses, monitoring of aspirin therapy and consideration of dose adjustment or alternative agents for unresponsive patients.