Definition

• Your child’s heart rate (HR) sometimes speeds up. It seems too fast.
• The medical name for this is tachycardia.
• Most of the time, your child’s HR seems normal.

Health Information

Normal Causes of Transient Fast Heart Rates

• Normal: Fast heart rates (HR) for a short time are almost always normal in healthy children. The younger the child, the more the heart rate can normally jump around.
• Exercise: Exercise and physical work are the most common cause of rapid heart rates. Even more common during exercise in hot weather.
• Feeding or Crying: Both of these are equal to exercise for babies.
• Fear or Stress: Sudden fear or stress can cause a fast heart rate. Even the thought of something scary can speed up the heart in anxious children.
• Dreams: The heart rate decreases during sleep. This is normal. However, during intense dreams, bursts of fast heart beat can occur.
• Pain: Pain even from a minor injury can cause an increased heart rate.
• Fever: Fever helps fight infections. A rapid HR delivers more blood and immune cells to where they are needed.
• Dehydration: Even mild dehydration increases the heart rate. Drinking some fluids quickly brings it down.
• Stimulants: Caffeine is the most common one. Others include nicotine, ADHD medicines (such as Ritalin) and illegal drugs (such as cocaine).

Fast Heart Rates and Fever

• Fever increases the heart rate a lot.
• Fever only increases the breathing rate a little.
• Each degree Fahrenheit above normal causes the heart rate to increase by 10 beats per minute.
• Each degree Celsius above normal causes the heart rate to increase by 20 beats per minute.

Recurrent Fast Heart Rates: How to Diagnose the Cause

• A fast heart rate has many causes. Most are harmless or even normal. A few of them are serious.
• Any child with bouts of fast HR needs a complete exam by their doctor.
• If your child has not been seen about their bouts of fast HR, make an appointment.

Care Advice

1. Fast Heart Rate From Exercise - Overview:
   • The heart rate (HR) increases with exercise, sports, or physical work. This is normal. Reason: the muscles need more blood flow.
   • Exercise in a hot setting makes the HR go even higher.
   • Drink enough fluids to stay well hydrated during exercise. Reason: mild dehydration causes a higher HR.
   • Start with 2 cups (480 ml) of water for teens.
   • Then keep drinking 1 cup (240 ml) every 15 minutes until done(teens).
   • What to Expect. The heart rate should return to normal after 30 minutes of rest.
2. Fast Heart Rate From Stress - Overview:
   • Being frightened, surprised, or anxious can increase the heart rate. This is normal. Any stressful event can cause the heart to race. This is due to the normal release of adrenaline (a hormone).
   • During intense dreams or nightmares the heart rate can become very fast.
   • The HR also goes up with crying. This is also normal.
   • Try to calm your child. Use a soothing voice. Tell them they are safe and you will protect them. Help them talk about what has happened.
   • If being anxious is a chronic problem, teach your child how to relax.
   • What to Expect. The heart rate should return to normal after your child has calmed down.
3. Fast Heart Rate From a Stimulant - Overview:
   • Stimulants are a common cause of a fast heart rate.
   • Caffeine is the most common one.
   • Another is nicotine from smoking or chewing tobacco.
   • Some medicines can cause fast heart rates. Examples are asthma rescue meds (e.g., albuterol) and ADHD meds (such as Ritalin). Others are nasal decongestants (e.g., sudafed), diet pills, or herbal stimulants. Check the dosage if the medicine is essential. Stop the medicine if it is not needed.
   • See care advice #4 and 5 about caffeine and nicotine.
4. Reduce Caffeine Intake:
   • Some people are more sensitive to caffeine than others.
   • Try to reduce or avoid caffeine in the diet.
   • At least, limit caffeine drinks to 1 or 2 servings per day.
5. Avoid Nicotine:
   • Try to stop smoking and chewing tobacco.
   • Reason: Protect yourself from chronic lung disease and lung cancer.
   • Caution: Nicotine can quickly become an addiction.
   • Smoking cessation resources are available in every community. Find them on the Internet.
6. Fast Heart Rate From Fever - Overview:
   • The heart rate increases with fever. This is normal.
   • It also beats more strongly with fever.
   • What to Expect. The heart rate should return to normal once the fever comes down.
   • Details on treating fever are in the Fever handout.

Call Your Doctor If

• Heart rate does not come down to normal after treating the cause
• You think your child needs to be seen
• You have other questions or concerns

Author: Barton Schmitt MD, FAAP