Aspirin Nonresponsiveness in Congenital Heart Disease-Prevalence, Risk Factors, and Management

BackgroundAspirin is frequently utilized for antiplatelet therapy in children with congenital heart disease (CHD). Patients who are unresponsive to aspirin, as measured by aspirin reaction units (ARU), are at higher risk for thrombotic events. It is undetermined if dose modification of aspirin results in adequate responsiveness in these patients. This study evaluates the prevalence and risk factors for aspirin nonresponsiveness and the results of dose escalation in this population.MethodsThis is a retrospective review of patients cared for in the cardiac care unit at a quaternary care academic congenital heart center who received aspirin and had responsiveness evaluated between January 2018 and January 2023. Patient demographics and clinical characteristics were extracted from the medical record. Descriptive, parametric, and nonparametric univariate analysis were employed.ResultsA total of 142 patients (69 [49%] female, 45 [32%]Non-Hispanic White, and 63 [44%] Hispanic]) were identified. Median age at first aspirin responsiveness assessment was 54 [interquartile range, IQR: 23.3-411.5] days with a median weight of 5.2 [IQR: 3.64-9.29] kg. Of these, 32/142 (22.5%) were nonresponsive on their initial testing. Of these patients, 23/32 (72%) had follow-up testing with 19/23 (83%) subsequently becoming therapeutic. This was achieved with an increased dose in 12/19 (63%) patients and increased duration of therapy in 7/19 (37%) patients. Seventeen of 142 (12%) patients experienced a thrombotic event, 13/17 (77%) of which were therapeutic on initial responsiveness assessment.ConclusionsIt is common for CHD patients to be aspirin nonresponsive with initial weight-based dosing. If aspirin is used in this population, it is necessary to evaluate ARUs on all patients as underdosing is not uncommon with current weight-based dosing methods.