The goal of this observational cohort study is to establish a risk prediction model for adverse events in Chinese individuals under 45 years old with premature coronary artery disease. The main questions it aims to answer are:

• What are the major risk factors for poor prognosis in Chinese patients with premature coronary artery disease?
• What is the difference in the prognosis of patients with premature coronary heart disease with different phenotypes? Participants taking no mandatory intervention will be followed up for 2 year, with blood tests at 1 year and outpatient or telephone interviews at other timepoints.

Inclusion Criteria:

• Age 18-45 years;
• Clinically confirmed CAD with ≥50% luminal stenosis in at least one major coronary artery or significant branch, verified by coronary angiography;
• For acute coronary syndrome (ACS) or percutaneous coronary intervention (PCI) patients: clinical stability meeting discharge criteria post-treatment;
• Voluntary participation with signed informed consent.

Exclusion Criteria:

• Heart transplant recipients;
• Severe systemic comorbidities with life expectancy <1 year;
• Previous enrollment in other drug/device clinical trials without completing the primary endpoint observation period;
• Inability to comply with follow-up (e.g., dementia, severe psychiatric disorders).

Eligible participants are CAD patients aged 18-45 years confirmed by coronary angiography or other imaging modalities, including those with stable/unstable angina or myocardial infarction.