Dual antiplatelet therapy in ACS: time-dependent variability in platelet aggregation during the first week.

AIMS AND OBJECTIVES: Platelets play an important role in the pathogenesis of Acute Coronary Syndrome (ACS). Most of the complications of ACS occur during the initial hours of presentation. We tried to gain an insight into the platelet function during the initial phase of ACS in patients on dual antiplatelet therapy. MATERIALS AND METHODS: Platelet aggregation study was performed by light transmittance aggregometry in 64 ACS patients 48 hour and 7 days after initiation of dual antiplatelet therapy with aspirin and clopidogrel. RESULTS: Epinephrine, ADP and collagen induced platelet aggregation was significantly higher at 48 hours, following initiation of dual antiplatelet therapy, in comparison to the profile observed on the 7th day. Diabetics demonstrated a significantly higher aggregation at both the time points and aggregation was also somewhat higher in smokers though it did not reach statistical significance. CONCLUSION: This study conceptualizes the hypothetical role of alpha-2 adrenoreceptor blockers during the early hours following ACS and also warrants further investigations exploring the optimum loading dose of antiplatelet agents, especially clopidogrel in patients with ACS.

Antiplatelet drug resistance in patients with recurrent acute coronary syndrome undergoing conservative management.

AIMS AND OBJECTIVES: Recurrent ischemic events continue to occur despite combination anti-platelet therapy. Currently aspirin, clopidogrel and dual resistance are increasingly recognized entities. The relationship of such resistance to recurrent ischemic events is largely unknown. In this study, we tried to gain an insight into the role of antiplatelet drug resistance with recurrent Acute Coronary Syndrome (ACS). MATERIALS AND METHODS: The antiplatelet effect of aspirin and clopidogrel was studied in 40 recurrent ACS patients and 170 patients with first episode of ACS, after > or = 7 days of dual antiplatelet therapy. Platelet aggregation study was done with optical aggregometer. Resistance to aspirin and clopidogrel was defined as > or = 50% aggregation with collagen and ADP respectively. RESULTS: Aspirin, clopidogrel and dual drug resistance were encountered respectively in 35%, 72.5% and 32.5% patients with recurrent ACS. The corresponding figures for the patients with first episode of ACS were 25.3%, 42.3% and 18.8% respectively. P values for the comparisons were 0.237 for aspirin, 0.0007 for clopidogrel and 0.084 for dual drugs. Patients with recurrent ACS were relatively younger and had a higher prevalence of conventional risk factors like hypertension, diabetes and elevated LDL. CONCLUSION: Antiplatelet drug resistance is likely to play an important role in recurrent ACS alongside other conventional risk factors. Further research is required in this field to have a definitive conclusion.