The goal of this clinical trial is to compare short-term Triple Antithrombotic Therapy (DAPT + Rivaroxaban) followed by DAPT with standard DAPT in selected ACS patients with high ischemic risk. The main questions it aims to answer are:

• Whether the intervention is effective in reducing ischemic events
• Whether the intervention is safe from increasing bleeding events, especially severe or fatal ones

Participants will be randomized to receive standard DAPT therapy for the entire study duration or low-dose rivaroxaban+DAPT for 3 months, followed by standard DAPT for the rest of the study duration. Patients enrolled should complete 5 follow-ups in the form of clinic visit or telephone call.

Inclusion Criteria:

• Diagnosed with Acute Coronary Syndrome 1-7 days after initial symptom stabilization,
• Aged 18-65 years old,
• Elevated D-dimer levels (≥0.28 μg/ml) on admission or PARIS coronary thrombosis risk score ≥ 3 points,
• Received Percutaneous Coronary Intervention and not on non-oral anticoagulants,
• Indicated for dual antiplatelet medication

Exclusion Criteria:

• Platelet level below 90 x10^6
• Hemoglobin level is less than 11g/dL
• History of severe bleeding
• History of stroke/TIA
• Severe hepatic/renal insufficiency
• Indicated for anticoagulation

This is an open-label study. But while the study is in progress, the grouping information is masked from outcome assessors (CEC).