An arrhythmia (ay-RITH-mee-uh) is an abnormal heart rhythm usually caused by an electrical "short circuit" in the heart. More to Know The heart normally beats in a consistent pattern, but an arrhythmia can make it beat too slowly, too quickly, or irregularly. This can cause the heart muscle's pumping function to work erratically, which can lead to a variety of symptoms, including fatigue, dizziness, and chest pain. Arrhythmias can be temporary or permanent. They can be caused by several things, but also can occur for no apparent reason. Congenital (present at birth) arrhythmias sometimes are due to a birth defect of the heart, but some happen even when the heart has formed normally. Keep in Mind Many arrhythmias don't require treatment; however, some can pose a health problem and need to be evaluated and treated by a doctor. 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 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 Coarctation of the Aorta When someone has coarctation of the aorta, that person's aorta (the major blood vessel that carries blood away from the heart to the body) is narrowed at some point. 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 Congenital Heart Defects Heart defects happen when there's a problem with a baby's heart development during pregnancy. Most heart defects can be treated during infancy. Read More Coarctation of the Aorta Coarctation of the aorta (COA) is a narrowing of the aorta, the major blood vessel that carries blood away from the heart to the body. 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 Cardiac Catheterization This minimally invasive procedure helps doctors perform diagnostic tests on the heart and even treat some heart conditions. 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.