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.

Aspirin resistance has been reported in up to 80% of children with cardiovascular defects undergoing surgery. Because of a patient who had embolic stroke while on therapeutic aspirin dose but in whom aspirin resistance was present on his thromboelastography platelet mapping, we chose to obtain thromboelastography platelet mapping on cardiac patients on aspirin to assess their risk.

This study evaluates aspirin resistance noted in these patients and their characteristics.

This is a retrospective study of 25 patients taking aspirin for a month at therapeutic dose. In total, 11 female patients were enrolled. Ages in all subjects were 5 months to 27 years. A total of 19 patients had a Fontan surgery. Three had a cavopulomanary anastomosis, one had a hybrid procedure, and two had coronary anomalies. Compliance was assessed at the time of the clinic visit. Aspirin resistance was defined as platelet inhibition below 50%. Variables evaluated were level of platelet inhibition, age, body mass index, and gender.

Shunt thrombosis after implantation of systemic-to-pulmonary shunts in paediatric patients is common. Acetyl salicylic acid is used for anti-thrombotic treatment; however, the effect is rarely monitored, although it is known that the response varies. The aim was to determine the effects of acetyl salicylic acid medication on platelet aggregation in children with systemic-to-pulmonary shunts.

A total of 14 children – median age 12 days; ranging from 3 to 100 days – were included in a prospective observational longitudinal study. All children were treated with oral acetyl salicylic acid (3–5 milligrams per kilogram once daily) after shunt implantation. Acetyl salicylic acid-dependent platelet aggregation in whole blood was analysed with impedance aggregometry (Multiplate®) after addition of arachidonic acid. Analyses were carried out before the primary operation, before and 5 and 24 hours after the first acetyl salicylic acid dose, and after 3–6 months of treatment. The therapeutic range for acetyl salicylic acid was defined as a test result less than 60 units.

Acetyl salicylic acid reduced the arachidonic acid-induced platelet aggregation in all but one patient. Of the patients, 93% were in the therapeutic range 5 hours after acetyl salicylic acid intake, 86% were in the range after 24 hours, and 64% after 3–6 months.

Acetyl salicylic acid reduces platelet aggregation after shunt implantation in paediatric patients, but a considerable percentage of the children are outside the therapeutic range. Monitoring of platelet aggregation has the potential to improve anti-platelet treatment after shunt implantation by identifying children with impaired acetyl salicylic acid response.