Unexplained sinus tachycardia may be caused by physiologic factors, pathologic factors, and inappropriate sinus tachycardia. 1. Physiological factors: Strenuous exercise, emotional excitement, smoking and other reasons lead to rapid heartbeat, do the examination shows sinus tachycardia. This is generally no need to worry about, daily attention to peace of mind, appropriate exercise, smoking cessation and so on can be effectively alleviated. 2. Pathological factors: hyperthyroidism, severe anemia and other disease factors can also trigger sinus tachycardia, arrhythmia, need to actively treat the primary disease. 3. Inappropriate sinus tachycardia: refers to the persistent increase in heart rate at rest, the pathogenesis is unknown, need to take medication under the guidance of a doctor to regulate. Pathological and inappropriate sinus tachycardia should be timely to the hospital, under the guidance of professional doctors for proper treatment.