The goal of this observational study is to learn about The Atherogenic Index of Plasma(AIP) in patients with atrial fibrillation(AF). The main questions it aims to answer are: (1)To investigate the correlation between AIP and the occurrence rate of AF. (2) To investigate the correlation between AIP and the occurrence rate of cardiovascular outcome events (MACE events, heart failure, embolism events) in patients with AF. Patients's clinical data including medical history, laboratory tests, and imageological examination will be collected and further analysed.

Baseline demographic data: age, gender, height, weight, systolic blood pressure, diastolic blood pressure, smoking habit, drinking habit, physical activity, fasting blood glucose, medication use (statins, ACEI/ARB, anticoagulant related drugs), basic medical history (hypertension, diabetes mellitus, coronary heart disease).

Inclusion Criteria:

1. Atrial fibrillation was detected by electrocardiogram or 24-hour holter or portable electrocardiogram monitor;
2. age ≥18 years old;
3. "low-intermediate" risk group of AF cardioembolic stroke: male patients with CHA2DS2-VASc score 0-1 or female patients with CHA2DS2-VASc score 1-2

Exclusion Criteria:

1. patients with rheumatic heart disease, congenital heart disease, cardiomyopathy, hematological diseases, severe hepatic and renal insufficiency and connective tissue diseases;
2. Echocardiography showed valvular heart disease;
3. patients with transient atrial fibrillation secondary to reversible causes: hyperthyroidism, acute pulmonary embolism, recent surgery, acute myocardial infarction, etc.
4. severe carotid artery stenosis and intracranial artery stenosis;
5. AF patients with recent major surgery.
6. patients with serious lack of clinical data.

Patients diagnosed with AF during hospitalization in our hospital.