Aim: Pre-procedural platelet reactivity (PR) in Korean patients may be greater because the CYP2C19*2 and *3 variant alleles are more common in Korean patients than in Caucasians. We investigated the level of PR and the prevalence of high post-clopidogrel platelet reactivity (HPPR) after a routine loading dose (LD) of clopidogrel in Korean patients.
Methods: We assessed the PR level at 12 to 24 hours after a 300-mg LD of clopidogrel in 215 patients undergoing scheduled percutaneous coronary intervention (PCI) (available CYP2C19 genotyping: n =176). PR was measured by conventional aggregometry and VerifyNow. Based on a previous study, HPPR was defined as a 5 µmol/L ADP-induced maximal PR >50%.
Results: With 5 and 20 µmol/L ADP stimuli, maximal PR were 48.7 ± 17.1% and 62.1 ± 15.7%, respectively, and the prevalence of HPPR reached 52.1%. The highest quartile cut-offs of 5 and 20 µmol/L ADP-induced PR(max) were 64% and 75%, respectively. P2Y₁₂ reaction unit (PRU) was 274 ± 76, and 69.8% (n =150) showed PRU ≥240. A carrier of at least one CYP2C19 variant allele showed higher PRs than non-carriers. In multivariate regression analysis, carriage of the CYP2C19 variant allele (*2 or *3) was determined to be a significant predictor of HPPR (odds ratio 4.202, 95% confidence interval 1.996 to 8.850, p< 0.001).
Conclusions: Korean patients undergoing scheduled PCI cannot achieve adequate pre-procedural platelet inhibition from a 300-mg LD of clopidogrel, which is related with a higher prevalence of the CYP2C19 mutant allele.