A cardiac dysrhythmia, better known as arrhythmia, is an irregular heartbeat, according to the National Heart, Lung and Blood Institute. There are many different types of arrhythmias.
Bradycardia is the medical term for a heart rate that is too slow, as stated by the National Heart, Lung and Blood Institute. Tachycardia is a heart rate that is too fast. Other types of cardiac arrhythmias include atrial fibrillation, paroxysmal supraventricular tachycardia, ventricular tachycardia and ventricular fibrillation. Although most cardiac arrhythmias are harmless, some types of arrhythmias can impact the pumping action of the heart, which diminishes oxygen delivery to body tissues.