High versus standard clopidogrel loading in patients undergoing carotid artery stenting prior to cardiac surgery to assess the number of microemboli detected with transcranial Doppler: Results of the randomized IMPACT trial

Aim. The aim of this study was to compare the effects of 300 mg or 600 mg clopidogrel loading dose, prior to carotid artery stenting (CAS) on the number of transcranial Doppler (TCD)-detected microembolic signals (MES) and to investigate the relationship between the magnitude of platelet reactivity and MES. Methods. In this prospective randomized, double-blind study, 35 consecutive asymptomatic patients (17.1% females), scheduled for CAS and cardiac surgery were included. The primary endpoint was the number of TCD-detected MES. The secondary endpoints were the absolute magnitude of on-treatment platelet reactivity and the adverse cerebral events. Negative binomial regression to find predictors for sum of single emboli, the student's t-test to assess the association between platelet function tests and randomized dose of 300 mg or 600 mg clopidogrel, and the R² calculation for the assessment of the association between platelet function tests and embolic load, were used. Results. No statistically significant difference in the number of TCD-detected MES, in the sum of all the single emboli or showers and platelet aggregation measurements between the two groups was observed (aggregometry: 21.7±18.3 versus 23+18%, P=0.8499 and 45.8±17.5 versus 46.5±14.5%, P=0.9003) (verifyNow P2Y12 assay: 231±293 PRU versus 222±86 PRU, P=0.7704). In one patient a transient ischemic attack occurred. Conclusion. A loading dose of 300 mg of clopidogrel in combination with aspirin is as effective as 600 mg of clopidogrel in achieving adequate platelet inhibition and preventing periprocedural events in asymptomatic patients undergoing CAS prior to cardiac surgery.