Sick sinus syndrome refers to a series of arrhythmias and clinical manifestations caused by lesions in the sinus node itself and its surrounding tissues that result in impaired excitation formation and/or conduction. I. Etiology The most common cause of sick sinus node syndrome is fibrotic degeneration, and because the cause is unknown, this pathologically altered sinus is also called idiopathic sinus. This is followed by ischemic heart disease, cardiomyopathy, rheumatic heart disease, hypertensive heart disease, and others have been reported to be caused by amyloidosis, hypothyroidism, certain infections (brucellosis, typhoid), etc. Clinical manifestations The clinical symptoms of sick sinus node syndrome are mainly caused by insufficient blood supply and insufficiency of major organs such as heart, brain, kidney and gastrointestinal tract caused by cardiac arrhythmia, such as episodes of dizziness, blackness and weakness. In addition, the disease can also be secondary to hypertension, coronary artery disease, myocarditis, chronic rheumatic heart valve lesions, and metabolic diseases. Therefore, in addition to the symptoms caused by arrhythmia, there are also various clinical manifestations of the primary disease. Electrocardiographic examination Electrocardiographic manifestations: (1) persistent and significant sinus bradycardia (less than 50 beats/min), not caused by drugs; (2) sinus atrial block or sinus arrest; (3) coexistence of sinus atrial block and atrioventricular block; (4) bradycardia-tachycardia syndrome (also called slow-fast syndrome), which refers to bradycardia and atrial tachyarrhythmia ( Atrial flutter, atrial fibrillation, or atrial tachycardia) alternating with episodes of bradycardia.