Abstract Body: Introduction - Thrombosis can lead to increased morbidity and mortality in pediatric Moyamoya disease (MMD). Antiplatelets are commonly used as adjuvant therapy after surgical revascularization. Therapeutic dosing and efficacy of antiplatelet medication, commonly aspirin, is not well studied in pediatric MMD. In patients with underlying cardiac disease, aspirin resistance was studied and found to be greater in children. We sought to determine efficacy and dosing of aspirin in pediatric patients with MMD.
Methods- We reviewed all patients in our cerebrovascular database from 2005-2023. All patients who were taking antiplatelet agents were included. The clinical and radiographic information was reviewed. Patients with follow-up antiplatelet efficacy testing were included. Patients with incomplete history or follow-up were excluded. Platelet efficacy was determined by VerifyNow system. Values less than 550 aspirin reaction units (ARU) indicate impaired platelet aggregation in response to aspirin and correlate with platelet inhibition; ARU greater than 550 indicated subtherapeutic levels.
Results- A total of 179 patients met inclusion criteria. Nearly all patients had an underlying diagnosis of moyamoya disease (N=169, 94%) requiring antiplatelet anticoagulation. Other associated diagnoses included trisomy 21 (9%), neurofibromatosis 1 (9%), sickle cell disease (6%) and cerebral aneurysms (3%). The majority of patients were female (N=102, 56%), and the average age was 7 (range 0.25-30 years old). 95% of patients were on Aspirin (ASA) for anticoagulation, and 86% were found to be therapeutic on standard weight-based dosing. Average age for the therapeutic cohort was 7.5 years old, average age for the subtherapeutic group was 9 years old (p= 0.4). Adjustments were made to increase dosing or add additional antiplatelet medication due to subtherapeutic levels in 36% of patients. No significant adverse effects were found on follow-up to antiplatelet use.
Discussion
In our study we found the rates of ASA resistance were lower in pediatric MMD patients compared to existing literature in pediatric cardiovascular patients. Further, we found no difference in ASA response rates based on age. Aspirin resistance in this study is defined by a laboratory result and this is distinctly different from treatment failure as a clinical outcome. There is still significant value to surveillance of ASA responsiveness to guide therapeutic dosage in pediatric MMD to minimize stroke risk.