Fast, Slow or Irregular Heart Rate in a Child

Most fast or slow heart rates in children have harmless causes — play, fever, crying or sleep. A few patterns point to a heart rhythm problem. This guide explains the difference and the signs that need a doctor.

Normal heart rates in children

Source: NIH MedlinePlus; awake and calm. Check any reading with our heart rate checker (choose "Child").

* Newborns: MedlinePlus lists 70–190 bpm. We use 100 as the lower limit, because in a newborn a heart rate below 100 needs prompt medical assessment (newborn resuscitation guidance treats under 100 as bradycardia).

Fast heart rate (tachycardia)

Usually harmless: sinus tachycardia

The heart's natural pacemaker simply speeds up in response to fever (roughly 10 bpm more per degree Celsius), activity, crying, pain, excitement or anxiety, dehydration, or medicines such as asthma inhalers and decongestants. The rate rises and falls gradually and settles when the cause goes away.

Needs a doctor: supraventricular tachycardia (SVT)

SVT is the most common abnormal fast rhythm in children. An extra electrical pathway lets the heart race — typically above 220 bpm in babies and above 180 bpm in older children. Typical features:

• It starts and stops suddenly, like a switch.
• The rate is very regular and does not change with activity or calming down.
• Older children describe a pounding or "too fast" heart, chest discomfort, dizziness or nausea. Babies become pale, sweaty, irritable, feed poorly or breathe fast.

Episodes are often stopped by doctors with vagal maneuvers (for example applying ice water to the face in infants) or medication; recurring SVT can be cured with catheter ablation. If your child is known to have SVT, follow the plan your cardiologist gave you.

Rare: ventricular tachycardia

A fast rhythm from the heart's lower chambers. Rare in children and usually linked to heart disease — it can cause fainting and is an emergency.

Slow heart rate (bradycardia)

Children's heart rates drop during sleep, and fit teenagers can rest in the 50s — both normal. Medical causes of a slow heart rate include low body temperature, low oxygen levels, an underactive thyroid, eating disorders, certain medications and raised pressure in the head after injury. A few children have a problem with the heart's conduction system (heart block), sometimes from birth.

A slow heart rate together with poor color, floppiness or difficulty breathing is an emergency, especially in babies.

Irregular heartbeat (arrhythmia)

Many parents notice that their child's pulse speeds up when breathing in and slows when breathing out. This is called sinus arrhythmia — it is normal and a sign of a healthy nervous system. Occasional "extra" or skipped beats (premature beats) are also common and usually harmless in an otherwise healthy child. Persistent irregularity, or irregular beats with fainting, chest pain or reduced exercise tolerance, should be checked with an ECG.

When to get help

• Call 911 (US) or your local emergency number: fainting during or right after exercise, fainting with a fast or slow heartbeat, chest pain with exertion, difficulty breathing, blue or grey color, or a baby who is floppy or hard to wake.
• Urgent care / same day: a resting heart rate above 220 (baby) or 180 (child) that started suddenly; a fast heart rate that does not settle with rest and fever control; a newborn whose heart rate is below 100 when calm.
• See your pediatrician: repeated resting rates outside the age range, palpitations, dizziness, or a family history of sudden cardiac death at a young age.

More: How to Measure a Baby's Heart Rate · Why Infants Have a Faster Heart Rate Than Adults