An arrhythmia is an irregular heartbeat – the heart may beat too fast (tachycardia), too slowly (bradycardia), too early (premature contraction) or too irregularly (fibrillation). Arrhythmias are heart-rhythm problems – they occur when the electrical impulses to the heart that coordinate heartbeats are not working properly, making the heart beat too fast/slow or inconsistently.
Many heart arrhythmias are harmless. We all occasionally experience irregular heartbeats, which may feel like a racing heart or fluttering. Some arrhythmias, however, especially if they veer too far from a normal heartbeat or result from a weak or damaged heart, may cause troublesome and even potentially fatal symptoms.