Patients with cyanotic heart disease are at an increased risk of developing thrombosis. Aspirin has been the mainstay of prophylactic anticoagulation for shunt-dependent patients with several reports of prevalent aspirin resistance, especially in neonates. We investigate the incidence of aspirin resistance and its relationship to thrombotic events and mortality in a cohort of infants with shunt-dependent physiology.

Aspirin resistance was assessed using the VerifyNow™ test on infants with single-ventricle physiology following shunt-dependent palliation operations. In-hospital thrombotic events and mortality data were collected. Statistical analysis was performed to evaluate the effect of aspirin resistance on in-hospital thrombotic events and mortality risk.

Forty-nine patients were included with 41 of these patients being neonates. Six patients (12%) were aspirin resistant. A birth weight < 2500 grams was a significant factor associated with aspirin resistance (p = 0.04). Following a dose increase or additional dose administration, all patients with initial aspirin resistance had a normal aspirin response. There was no statistically significant difference between aspirin resistance and non-resistance groups with respect to thrombotic events. However, a statistically significant incidence of in-hospital mortality in the presence of thrombotic events was observed amongst aspirin-resistant patients (p = 0.04) in this study.

Low birth weight was associated with a higher incidence of aspirin resistance. Inadequate initial dosing appears to be the primary reason for aspirin resistance. The presence of both thrombotic events and aspirin resistance was associated with significantly higher in-hospital mortality indicating that these patients warrant closer monitoring.