The human heart rhythm is regulated by an electrical current in the heart muscle, and the normal controlling mechanism can occasionally malfunction, causing extra heart beats, fast heart rates, or very slow rhythms.  While frequently benign, these electrical abnormalities can sometimes cause significant symptoms or dangerous situations such as passing out, chest pain, dizziness, shortness of breath, or even sudden death.  In order to evaluate your rhythm, your doctor may order a Holter monitor, which records 24 hours of information.  For those patients with less frequent arrhythmias, more prolonged monitoring for weeks or even months is possible utilizing loop monitors, event monitors, or even a monitor implanted under the skin.