Comparison of P2Y12 Inhibitors in Acute Coronary Syndromes in the Australian Population

Clopidogrel in combination with aspirin after acute coronary syndromes (ACS) reduces recurrent ischaemic events compared to aspirin alone. Further reductions in events have been demonstrated when clopidogrel is replaced by ticagrelor or prasugrel albeit with increases in bleeding. There are few studies documenting the patterns of use of P2Y12 inhibitors or their association with outcomes in the Australian population.

To describe the patterns of use of each P2Y12 inhibitor and to determine the associations between initial P2Y12 inhibitor use and outcomes.

Data were extracted from Cooperative National Registry of ACS, Guideline Adherence and Clinical Events (CONCORDANCE)-a prospective database of patients presenting to 43 sites across Australia with ACS. Patients were stratified based on first antiplatelet agent received. Baseline clinical characteristics were compared between these patient groups and hospital investigations, management as well as in-hospital and 12 months outcomes (death, a composite of cardiac-related death, myocardial infarction, and stroke, and major bleeding) were compared between the three treatment cohorts after adjustment for differences in baseline characteristics.

Mean ages of the clopidogrel (n=7,537), ticagrelor (n=1,878), and prasugrel (n=347) cohorts were 65, 63, and 58 yrs respectively (p<0.0001), the mean Global Registry of Acute Coronary Events (GRACE) risk scores were 107, 104, and 102 (p=0.0016). The ticagrelor and prasugrel cohorts were more likely to receive percutaneous coronary intervention (PCI) (clopidogrel 52%, ticagrelor 66%, prasugrel 88%, p<0.0001), and evidence based medications (≥4 guideline indicated medications: clopidogrel 76%, ticagrelor 82%, prasugrel 93%, p<0.0001). Patients treated with ticagrelor and prasugrel were less likely to experience in-hospital death (clopidogrel 2.5%, ticagrelor 1.4%, prasugrel 1.2%, p=0.05), major adverse cardiac events (MACE) (clopidogrel 5.1%, ticagrelor 3.0%, prasugrel 3.5% [p=0.01]), or bleeding (clopidogrel 8.4%, ticagrelor 4.6%, prasugrel 7.5% [p<0.001]) compared to clopidogrel. These differences were no longer apparent after multivariable adjustment. There was no difference in outcomes between cohorts at 12 months.

In Australia, ticagrelor and prasugrel are used in younger patients who are more likely to undergo percutaneous coronary intervention (PCI) and receive evidence based therapy. Patients receiving clopidogrel were more likely to experience in hospital ischaemic or bleeding events but this was explained by their higher baseline risk. Selection of therapy was not associated with any difference in outcomes at 12-month follow-up, but our findings suggest there is room for improvement towards guideline-driven usage of P2Y12 inhibitors.