May also be called: Rapid Heart Rate; Rapid Heartbeat Tachycardia (tak-ih-KAR-dee-uh) is an abnormally rapid heartbeat. More to Know The heart has its own electrical system that controls the heart rate and contraction of the heart, which pumps blood throughout the body. Normal heart rates vary based on a person's age. A rapid heart rate can be caused by many different factors. Sometimes tachycardia is the body's response to a trigger like fever, anxiety, exercise, or pain, just to name a few. It also can be due to an abnormal rhythm in the heart (called a dysrhythmia), such as supraventricular tachycardia (SVT). Congenital heart abnormalities, high blood pressure, medications, dehydration, caffeine, smoking, and recreational drug use also can cause tachycardia. Tachycardias can lead to dizziness, shortness of breath, chest pain, fainting, and heart palpitations (a sensation of feeling the heart beat fast or irregularly). Some tachycardias are life threatening and can lead to blood clots, causing a stroke, heart failure, and sudden death. Keep in Mind Most tachycardias resolve without causing any problems. However, some require immediate medical attention and can be life threatening if they're not treated. Be sure to talk to your doctor if you are concerned about tachycardia or its related symptoms. All A to Z dictionary entries are regularly reviewed by KidsHealth medical experts. Back to Articles Related Articles The Heart Your heart beats and sends oxygen throughout your entire body. Find out how it works and how heart problems can be fixed. Read More Arrhythmias Arrhythmias are abnormal heartbeats usually caused by an electrical "short circuit" in the heart. Many are minor and not a significant health threat, but others can indicate a more serious problem. Read More Words to Know (Heart Glossary) Your heart beats and sends blood all around your body. Find out more about the heart, from A to Z, in this glossary. Read More Your Heart & Circulatory System Your heart is a hard-working muscle. Find out more in this article for kids. Read More Heart Murmurs Everyone's heart makes sounds, but some people have hearts that make more noise than others. Usually, however, these heart murmurs don't mean anything is wrong. Find out more about these mysterious murmurs. Read More Heart Murmurs Heart murmurs are very common, and most are no cause for concern and won't affect a child's health. Read More Arrhythmia (Abnormal Heartbeat) An arrhythmia is an abnormal heartbeat usually caused by an electrical "short circuit" in the heart. Many are minor and not a health threat, but some can indicate a more serious problem. Read More Heart and Circulatory System The heart and circulatory system (also called the cardiovascular system) make up the network that delivers blood to the body's tissues. Read More Heart and Circulatory System The heart and circulatory system are our body's lifeline, delivering blood to the body's tissues. Brush up on your ticker with this body basics article. Read More Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor. © 1995-2021 KidsHealth®. All rights reserved. Images provided by The Nemours Foundation, iStock, Getty Images, Veer, Shutterstock, and Clipart.com.