Assessment of Clopidogrel Resistance in Post Myocardial Infarction Patients after 24 to 48 Hours of Initiation of Treatment: A Cross-sectional Study

Abstract

Introduction: Clopidogrel is an antiplatelet agent used to prevent platelet aggregation and further blockage of coronary arteries in Acute Coronary Syndrome (ACS) patients. Inadequate response to clopidogrel has been demonstrated in some patients that might lead to re-infarction even when receiving standard doses of clopidogrel. Aim: To demonstrate the presence of resistance to standard oral doses of clopidogrel in a tertiary care hospital located in eastern India. Materials and Methods: It was a descriptive cross-sectional study conducted from January 2015 to June 2016, in Medical College Kolkata, (previously known as Calcutta Medical College), India. Total 32 patients, previously not on any antiplatelet therapy, presenting with biomarker positive ACS were evaluated. The patients were given clopidogrel (300 mg) along with aspirin (325 mg) on presentation followed by clopidogrel (75 mg) and aspirin (75 mg) once daily. Blood samples were collected after 24-48 hours of administering the above mentioned doses orally. A 3.2% citrate was used as anti-coagulant. Platelet Rich Plasma (PRP) and Platelet Poor Plasma (PPP) were prepared from this blood samples by centrifugation. Platelet aggregation was studied by adding 10 μM Adenosine Diphosphate (ADP) in that PRP and it was compared with PPP in Light Transmittance Aggregometer (LTA). Platelet aggregation ≥50% in presence of 10 μM ADP was termed as Clopidogrel Resistance (CR). Differences between groups were assessed with Chi-square test and Fisher-exact test for categorical variables. The p-value of <0.05 was considered to be statistically significant. Results: Mean age of the study participants was 60.7 years, and 23 (71.8%) out of 32 patients were male while 9 (28.2%) were female. Total 7 (21.8%) of the patients were found to be resistant to standard doses of clopidogrel. A 3 (60%) out of 5 patients with positive family history of Cardiovascular Diseases (CVD) showed CR (p-value=0.025). Incidences of CR was higher among women 3 (33.3%) and in patients receiving thrombolysis 4 (28.5%). Though these percentages were high but not statistically significant. Conclusion: In this study, 21.8% ACS patients showed resistance to the antiplatelet effects of clopidogrel in the conventional dose. A long term prospective Randomised Controlled Trials (RCT) with larger sample size is required to give an insight into this problem.