An irregular heartbeat, also known as an arrhythmia (10 letters) or palpitations (11 letters), is a condition in which the heart beats with an abnormal rhythm. This can cause the heart to beat too fast, too slow, or with an irregular pattern. Symptoms of an irregular heartbeat can include chest pain, shortness of breath, dizziness, and fatigue. Treatment for an irregular heartbeat may include lifestyle changes, medications, or medical procedures.