Thrombosis occurs in up to 15% of pediatric patients following cardiac surgery, and is associated with increased mortality. Although aspirin is commonly administered to pediatric patients after high-risk congenital cardiac surgery to reduce thrombosis risk, aspirin responsiveness is rarely assessed, according to Dr. Sirisha Emani and colleagues .
“In our observational study, aspirin unresponsiveness occurred in approximately 11% of patients undergoing specific high-risk cardiac procedures, and postoperative thrombosis was associated with aspirin unresponsiveness in this patient population,” said Dr. Emani.
In order to determine whether inadequate response to aspirin was associated with increased risk of thrombosis following high-risk procedures, the researchers performed a prospective analysis of 62 patients undergoing congenital cardiac surgical procedures involving placement of prosthetic material into the circulation or coronary artery manipulation who received aspirin.
Response to aspirin was determined using the Verify Now system at least 48 hours following administration. Patients were prospectively monitored for development of thrombosis events by imaging (echocardiogram, cardiac catheterization, MRI) and review of clinical events (shunt thrombosis, stroke, or limb ischemia) until the time of hospital discharge.
Aspirin responsiveness was tested a median of 2 days after initiation of therapy. The rate of aspirin unresponsiveness (Aspirin Responsive Unit, ARU greater than 550) was 7/62 (11.3%) in all patients and was highest in patients less than 5 kg who received 20.25 mg aspirin. Thrombosis events were demonstrated in 7 patients (11.3%). Thrombosis was observed in 6 (86%) of 7 patients who were unresponsive to aspirin as opposed to 1 (2%) of 54 patients who were responsive to aspirin, a significant difference. In two neonates who were unresponsive at 20.25 and 40.5 mg of aspirin, increase in dosage to 40.5 and 81 mg, respectively, resulted in an aspirin response, suggesting insufficiency rather than true unresponsiveness.
“Monitoring of aspirin therapy and consideration of dose adjustment or alternative agents for unresponsive patients may be justified and warrants further investigation in a prospective trial,” concluded Dr. Emani.