what is fast heart rate called
An arrhythmia (also called dysrhythmia) refers to what is usually an irregular heartbeat. The heart rate can be fast, slow, or irregular, taking into consideration age and activity. For example, a newborn's heart beats much faster than a 5-year-old child's heart. A fast heart rate is called tachycardia. A slow heart rate is called bradycardia. Some irregular heartbeats are normal: Sinus arrhythmia is the normal variation in heart rate that accompanies breathing in and out.