Background Clopidogrel has become essential in managing coronary artery disease and other atherothrombotic diseases. It is an inactive prodrug that needs biotransformation in the liver by various cytochrome P (CYP) 450 isoenzymes for its active metabolite formation. However, 4-30% of patients on clopidogrel have shown no or decreased antiplatelet response. This condition is called 'clopidogrel non-responsiveness' or 'clopidogrel resistance.' This is attributed to genetic heterogeneity causing interindividual variation and increased risk of major adverse cardiac events (MACEs). This study aimed to assess MACEs and their association with CYP450 2C19 polymorphisms in post-coronary intervention patients on clopidogrel. Methods This prospective observational study was conducted on acute coronary syndrome patients, started on clopidogrel following coronary intervention. After considering inclusion and exclusion criteria, 72 patients were enrolled, and a genetic analysis was done. Based on genetic analysis, patients were divided into two groups, normal (CYP2C19*1) and abnormal phenotypes (CYP2C19*2 & *3). These patients were followed for two years, and the MACE during the first year and second year was compared between these two groups. Results Of 72 patients, 39 (54.1%) were normal, and 33 (45.8%) were abnormal genotypes. The mean age of patients is 67.71 ± 9.968. A total of 19 and 27 MACEs were seen during first- and second-year follow-ups. During the first-year follow-up, three (9.1%) patients with abnormal phenotypes developed ST-elevation myocardial infarction (STEMI), and none of the phenotypically normal patients developed STEMI (p-value = 0.183). Non-ST elevation myocardial infarction (NSTEMI) was seen in three (7.7%) normal and seven (21.2%) abnormal phenotype patients (p-value=0.19). Other events, such as thrombotic stroke, stent thrombosis, and cardiac death, were seen in two (6.1%) abnormal phenotypic patients (p-value=0.401). During the second-year follow-up, STEMI was seen in one (2.6%) normal and three (9.7%) abnormal phenotypic patients (p-value=0.183). NSTEMI was seen in four (10.3%) normal and nine (29%) abnormal phenotype patients (p=0.045). Comparison of total MACEs between normal and abnormal phenotypic groups at the end of the first year (p-value=0.011) and second year (p-value=<0.01) has statistical significance. Conclusion We can infer that the risk of developing a recurrent MACE in post-coronary intervention patients on clopidogrel is significantly high in the abnormal phenotypic group (CYP2C19*2 & *3) than in normal phenotypic patients.
Keywords: clopidogrel; coronary artery disease; genetic polymorphisms; major adverse cardiovascular event; post-coronary intervention.
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