The danger of sinus bradycardia with arrhythmia depends mainly on its severity. If the heartbeat is slow, 40 beats/minute or less, it cannot supply the whole body with the normal heart output and can cause many symptoms such as hypoperfusion of the trachea or chest tightness and dizziness. However, if sinus bradycardia is not too slow or without symptoms of cardiac insufficiency and the heartbeat is 50 beats/min or 45 beats/min or more, it is less likely to cause related symptoms. If the rhythm of sinus arrhythmia is within a certain range, it is normal and does not require any intervention, only regular follow-up to observe its changes.