A normal resting heart rate for a 2-year-old child is between 80 and 130 beats per minute, according to the A.D.A.M. Medical Encyclopedia. The University of British Columbia lists normal heart rate for the same age as being between 89 and 151 beats, with 119 being the average.
Average heart rate tends to be lower with age, so older children of the same cohort should show an average heart rate that is lower than younger kids. An abnormally rapid heart rate is called tachycardia and may present as fussiness in young children. Bradycardia, as noted by WebMD, is an abnormally slow heart rate that is rarely a sign of cardiac or thyroid issues. It is more often asymptomatic or a sign of good cardiovascular health.