OBJECTIVES : Dual antiplatelet therapy (DAPT) as treatment for acute coronary syndrome (ACS) has been well-established. Considering the availability of P2Y12 receptor inhibitors, patient’s clinical characteristics and concurrent pharmacological therapy, there could be switching of P2Y12 receptor inhibitors between newer P2Y12 receptor inhibitors (prasugrel/ ticagrelor) and clopidogrel for DAPT. The study aimed to review clinical outcome of switching strategy of P2Y12 receptor inhibitor in DAPT to non-switching strategy.

METHODS : Clinical data was retrieved through Clinical Data Analysis and Reporting System from New Territories East Cluster, Hospital Authority Hong Kong. Patients who were diagnosed with ACS from 2008 to 2017 were included, with their clinical profile followed until 2018. Diagnosis and procedure information were identified using ICD-9-CM codes. Kaplan-Meier survival curve was used to illustrate post-discharge time to major cardiovascular events (MACE, including cardiovascular death, myocardial infarction (MI), stroke and stent thrombosis), all-cause mortality, cardiovascular mortality, MI and bleeding in propensity score matched cohorts. Clinical outcome comparison at 10-year post-discharge was made using Cox proportional hazard model.

RESULTS : There were 366 subjects in each matched cohort. The hazard ratio (HR) of MACE for switching strategy versus non-switching for the first two years was 0.26 (0.14-0.46, p<0.001), while the HR of MI was 0.31 (0.17-0.58, p<0.001) and the HR of bleeding was 0.04 (0.01-0.33, p=0.002). The HR of MACE, MI and bleeding for the subsequent eight years, as well as the HR of all-cause mortality and cardiovascular mortality, were statistically insignificant.

CONCLUSIONS : The study showed that switching of newer P2Y12 receptor inhibitors and clopidogrel in DAPT was associated with fewer MACE, fewer MI and fewer bleeding in first two years post-discharge, compared to non-switching strategy in East Asian ACS patients. There were no statistically significant differences for MACE, MI and bleeding in the subsequent eight years, nor for all-cause mortality and cardiovascular mortality.