If the heart beats very fast, very slowly or irregularly, it is called cardiac arrhythmia or arrhythmia. Irregular heartbeat is common. Almost all people have extra heartbeats.
Here you can read about various diseases and disorders that have to do with the heart rhythm.
Heart palpitations in the form of extra beats, hard heartbeats or short-term heart murmurs are common and occur at all ages. Usually, there is nothing to worry about, especially if the trouble comes in connection with stress or worry. But if you get heartache and at the same time feel sick, get chest pain or difficulty breathing, you should seek treatment immediately.
Atrial fibrillation means that the heart beats irregularly and often even faster. This means that the heart cannot pump around the blood in the body as efficiently as it usually does. Permanent atrial fibrillation is the most common cause of stroke. This is because the flicker degrades blood circulation in the atrium of the heart, making blood clots more easily formed.
Although it is very uncommon, sports children and adolescents may suddenly experience unexpected cardiac arrest. This is usually because the child has had some disease of the heart muscle or the duct system that you have not previously known about.