Sinus bradycardia is clinically known as sinus bradycardia. Whether the heart rate of 55 beats/min is serious needs to be combined with the specific causes, if it is due to physiological factors such as sleep state and so on, it is not serious; if it is due to diseases such as hypothyroidism and so on, it is serious and needs to be actively treated. 1. Physiological factors: sinus bradycardia with a heart rate of 55 beats per minute is commonly seen in young people, athletes, or sleep, which is a physiological condition and is generally not serious and is not treated. 2. Pathological factors: common causes of hypothermia, hypothyroidism, etc., some acute myocardial infarction can also occur sinus bradycardia, the serious can even have dizziness, fatigue, chest tightness palpitations, etc., need to be timely for the treatment of the primary cause, such as warming, supplemental thyroid hormone, and even need to perform coronary stenting, etc., and actively correct the sinus bradycardia. Sinus bradycardia heart rate of 55 beats / min, in the exclusion of physiological factors, to find the cause, and actively follow the medical advice to avoid adverse consequences.