Sinus bradycardia in neonates is considered if sinus rate is

Sinus bradycardia is a result of slow discharge of impulses from the sinus node, the hea's natural pacemaker. A sinus rate <90 beats/min in neonates and <60 beats/min in older children is considered to be sinus bradycardia. It is commonly seen in well-trained athletes; in healthy individuals, it is generally without significance. Sinus bradycardia may occur in systemic disease (hypothyroidism or anorexia nervosa), and it resolves when the disorder is under control. It may also be seen in association with conditions in which there is high vagal tone, such as gastrointestinal obstruction or intracranial processes. Reference: Nelson; 20th edition; Page no: 435