The present study is aimed to compare the safety and efficacy of Ticagrelor with low-dose Aspirin versus standard dual anti-platelet therapy (DAPT) in patients with acute coronary syndrome (ACS) at high risk for ischemic events after percutaneous coronary intervention (PCI) and stent implantation.

This is a prospective, randomized, open-label, blinded-endpoint evaluation, single-center Study. There will be 1220 ACS patients at high risk for ischemic events after successful PCI with implantation of at least one drug eluting stent who will be enrolled in Fuwai Hospital, China. Then those included subjects will be randomized to either Ticagrelor plus low-dose Aspirin (50mg daily, LD group) or Ticagrelor plus regular dose Aspirin (75mg daily, control group) for 12 months. The primary endpoint of the current study is to determine the impact of low-dose Aspirin plus Ticagrelor versus standard DAPT for 12 months on major adverse cardiac and cerebral events (MACCEs), and the secondary endpoint is to determine whether the protocol of low dose Aspirin plus Ticagrelor reduces bleeding events, sufficiently inhibits platelet function, and increases the medication adherence among the included patients. In summary, the present study is to provide new evidence and strategy about the anti-platelet protocol for ACS patients at high risk for ischemia.

Inclusion Criteria:

• ACS patients at high risk for ischemic events after successful PCI with implantation of at least one drug eluting stent
• Able and willing to provide informed consent and participate in 12 months follow-up period
• Able to receive DAPT treatment
• Enrollment into the study will require meeting at least one angiographic or clinical inclusion and none of the exclusion criteria.

Clinical inclusion criteria:

1. Family history of premature coronary heart disease (Coronary heart disease in first-degree male relative <55 years old or in first-degree female relative <65 years old)
2. Repeated myocardial infarction
3. Positive serum cardiac troponin I/T
4. Combined with at least one organ/system with atherosclerotic disease (e.g. intracranial or peripheral arteries)
5. Type 2 diabetes mellitus under medication
6. Chronic kidney disease (eGFR<60 mL/min/1.73 m2 or CrCl<60ml/min)

Angiographic Inclusion Criteria:

1. LM lesion requiring stents
2. Proximal LAD lesion(s) requiring stents
3. Bypass grafts lesion(s) requiring stents
4. Overall stent length ≥60 mm
5. History of in-stent thrombosis
6. Bifurcation lesions requiring at least 2 stents
7. Over two vessels lesions requiring stents
8. Calcified target lesion(s) requiring atherectomy
9. The intraoperative occurrence of no-reflow or slow-flow
10. Compressed branch vessels with a diameter of at least 2.0 mm failing to reach flow restoration (at least TIMI 3)

Exclusion Criteria:

• Need for chronic oral anticoagulation
• With cardiomyopathy（HCM/DCM/RCM）
• With severe ventricular arrhythmia requiring ICD implantation
• With chronic respiratory disease (COPD, asthma, chronic bronchitis, pulmonary heart disease)
• With severe infectious disease（active hepatitis B, active hepatitis C, AIDS）
• With hematological disorders（thrombocytopenia, severe anemia, leukaemia）
• With severe liver disease or kidney failure
• With malignant tumor
• With cognitive impairment
• Unable or unwilling to provide informed consent or undergo follow-up