An arrhythmia is simply an abnormality of the rhythm of the heart. More specifically, it is an abnormality of cardiac impulse formation or conduction. That means that the areas of the heart that produce impulse may not function correctly leading to heart rhythms being too fast, too slow, or even cease. Additionally, an arrhythmia may affect the conduction of the electrical impulse. This too may cause abnormal heartbeats or rhythms that are too fast, or too slow. Some arrhythmias are insignificant whereas other arrhythmias are very serious and life-threatening. People with arrhythmias may feel palpitations. Arrhythmias are diagnosed using electrocardiograms (ECG), heart monitors, or on home rhythm monitoring devices.