Determine the long-term efficacy of clopidogrel compared with aspirin in reducing heart or brain attacks in patients with stable heart disease

Inclusion Criteria:

1. Age ≥18 years.
2. Significant coronary artery disease (coronary angiogram documentation of Left Main artery lesion ≥50% and/or lesion(s) ≥70% in other coronary arteries, and/or FFR<0.8 or iFR<0.9).
3. Completed at least 6 months post ACS (regardless of the bleeding risk, anti-platelet strategy, revascularization strategy "PCI, CABG, or conservative medical management only", before randomization).
4. Agreement to give written informed consent.

Exclusion Criteria:

1. History of hypersensitivity to aspirin or clopidogrel.
2. Presence of non-cardiac comorbidity with life expectancy ≤2 years from randomization.
3. Plan for surgery or intervention which requires stopping antiplatelet agents ≥3 months.
4. Females with childbearing potential or breast-feeding.
5. Co-administration of contraindicated medications as follows: anticoagulants (warfarin, direct oral anticoagulants (DOACs), or chronic therapy of heparin); cytochrome P450 2C19 inhibitors (fluoxetine, moclobemid or voriconazole); probenecid; high dose of methotrexate (≥15 mg/week); lithium.
6. Inability to have a complete follow-up for up to 5 years from randomization (e.g: high possibility of travelling outside the country).
7. Inability to afford paying for Clopidogrel out-of-pocket up to 5 years from randomization (in case not being covered by the health care system).