The diagnostic criteria for sick sinus syndrome, i.e., sick sinus node syndrome, include clinical symptoms, typical ECG manifestations, and correlation of ECG changes. Sick sinus syndrome is the manifestation of multiple arrhythmias due to sinus node pathology, which results in its reduced function. Patients may present with multiple arrhythmias at different times. 1. Clinical symptoms: including episodes of dizziness, fatigue, palpitations (rapid heartbeat, often accompanied by panic), decreased exercise tolerance, and in severe cases, transient blackouts, syncope or A.S. syndrome attacks. 2. Electrocardiogram (ECG): There may be persistent significant sinus bradycardia, sinus arrest or sinus standstill, sinus block. Bradycardia-tachycardia syndrome with alternating episodes of tachycardia and bradycardia may occur. Coexistence of sinus block and atrioventricular block may also occur. 3. Correlation of electrocardiographic changes: when clinical symptoms occur, the electrocardiogram shows corresponding changes. This may be manifested by syncopal episodes accompanied by marked bradycardia or cardiac arrest on the ECG. The diagnosis of sick sinus syndrome needs to be combined with symptoms and electrocardiogram, etc. It is recommended to consult a doctor for a clear diagnosis and standardized treatment under the guidance of a professional doctor.