Aspirin Resistance in Children with Heart Disease at Risk for Thromboembolism: Prevalence and Possible Mechanisms

Aspirin is used to prevent thromboembolism in children with heart disease without evidence supporting its efficacy. Studies in adults report a 5%–51% prevalence of aspirin resistance, yet the mechanisms involved are poorly understood. Our aims were to determine its prevalence in these children and to explore its possible mechanisms. One hundred twenty-three cardiac patients routinely receiving aspirin were prospectively enrolled. Platelet function was measured by Platelet Function Analyzer (PFA)-100 using epinephrine and adenosine diphosphate (ADP) agonists. Aspirin resistance was defined as failure to prolong the epinephrine closure time following aspirin administration. Urine levels of 11-dehydro-thromboxane B 2 (11-dTXB 2 ) were measured to determine inhibition of the cyclo-oxygenase pathway. The prevalence of aspirin resistance was 26%. Median ADP closure time was shorter for aspirin-resistant (79.60–115 s) than for aspirin-sensitive (100.60–240 s) patients ( p