Effects of 600 mg versus 300 mg Loading Dose of Clopidogrel in Asian Patients with ST-Segment Elevation Myocardial Infarction Undergoing Primary Percutaneous Coronary Intervention: Long-Term Follow-Up Study

Purpose: The optimum loading dose of clopidogrel has not been established in Asian patients with ST-segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI). Our aim was to evaluate the impact of different clopidogrel loading doses on short- and long-term clinical outcomes in Asian STEMI patients undergoing primary PCI. Materials and Methods: We studied 691 STEMI patients undergoing primary PCI, loaded with 600 mg (n=381) or 300 mg (n=310) of clopidogrel. The primary outcome was major adverse cardiac events (MACEs), defined as a composite of all-cause death, reinfarction, or target vessel revascularization (TVR). Results: Baseline clinical and peri-procedural characteristics were mostly comparable between the 600 mg and 300 mg groups. There were no differences in 1 month MACEs as well as all-cause death, reinfarction, TVR, and stent thrombosis between the two groups. After a median follow-up of 921 days, MACEs [adjusted hazard ratio (HR) for the 600 mg group 1.79, 95% confidence interval (CI): 0.80-3.97, p=0.153], all-cause death (adjusted HR for the 600 mg group 0.97, 95% CI: 0.50-1.88, p=0.928), reinfarction (adjusted HR for the 600 mg group 1.03, 95% CI: 0.55-1.91, p=0.937), and TVR (adjusted HR for the 600 mg group 1.36, 95% CI: 0.68-2.69, p=0.388) did not differ between the two groups. These results were reliable even after analysis of propensity score-matched population, and were also constant among various subgroups. Conclusion: A 600 mg loading dose of clopidogrel did not result in better short- and long-term clinical outcomes in Asian STEMI patients undergoing primary PCI.