Evidence from the COLCOT Trial has shown that anti-inflammatory effect of colchicine reduced the risk of cardiovascular events in patients with recent myocardial infarction. We hypothesized that this might be due to the improvement of the coronary plaque stability by colchicine. Optical coherence tomography (OCT) is the most precise method to detect plaque stability in clinical practice. Thus, the purpose of this study is to evaluate the efficacy and safety of colchicine on improving the stability of coronary plaque in patients with acute coronary syndrome.

This is a single-center, randomized, double-blind, placebo-controlled clinical trial. OCT coronary images analyzed at an independent imaging core laboratory (Department of Cardiology, Second Affiliated Hospital of Harbin Medical University, Harbin, China) by blinded expert readers.

Inclusion Criteria:

1. Participants who understand and sign the informed consent form voluntarily.
2. Age ≥ 18 years old and ≤ 80 years old, regardless of sex.
3. hospitalized patients diagnosed with acute coronary syndrome within 1 month.
4. at least one non-culprit lesion with diameter stenosis percentage of 30% to 70% by visual estimation on coronary angiography (CAG) after completing any planned percutaneous revascularization.
5. the lesion shown by OCT was lipid-rich plaque (Lipid pool arc > 90 °).

Exclusion Criteria:

1. Allergic to colchicine.
2. Colchicine was taken within 10 days before randomization.
3. Abnormal liver function (ALT > 3 times the upper limit of normal value).
4. Abnormal renal function (creatinine clearance rate < 45 ml/min).
5. Thrombocytopenia (PLT < 100G/L).
6. Uncontrolled infectious diseases during the screening period.
7. Known immune diseases or immune-related diseases such as systemic lupus erythematosus, asthma, inflammatory bowel disease, gout, malignant tumor and so on.
8. Pre-existing or plan for the administration of systemic anti-inflammatory treatments such as non-steroidal anti-inflammatory drugs, hormones, immunomodulatory and chemotherapeutic drugs.
9. History of surgery or interventional therapy within 6 months prior to the screening period.
10. A history of coronary artery bypass grafting or a plan for coronary artery bypass grafting within 1 year.
11. Left main coronary disease (≥50% reduction in lumen diameter by angiographic visual estimation).
12. Significant coronary calcification or tortuosity deemed to preclude OCT evaluation.
13. Diagnosed with mental disorders such as anxiety or depression.
14. Pregnant women, lactating women or women of childbearing age who do not use effective contraceptive methods.
15. Participated in other clinical trials within 3 months before the screening period.
16. Do not receive standardized treatment after being diagnosed with coronary heart disease.
17. The life expectancy of the subjects is less than 1 year.
18. The researchers determined that other conditions in which the patient was not suitable to participate in the clinical trial.