Many individuals have irregular heart rhythms (arrhythmias) on occasion. The significance and seriousness of an arrhythmia depends on the kind of arrhythmia, how often they occur, how long they last, and whether they occur in association with other symptoms such as dizziness or chest pain.
Because a standard electrocardiogram (EKG or ECG) is safe, inexpensive, and widely available and provides valuable information, it is often the first test used in evaluating patients with possible arrhythmias. However arrhythmias are often intermittent and become noticeable only during activity, such as exercise, stress, or bowel movements, or during sleeping. It may thus be difficult to document an arrhythmia with a resting ECG while in the physician's office. A longer recording or monitoring period using a continuous recorder may thus be necessary to demonstrate them. 
Ambulatory electrocardiograms are recordings of the hearts electrical activity while a patient is performing everyday activities. Unlike a regular ECG a continuous recorder generally has 5 leads and provides less complete information than a 12-lead EKG.
Ambulatory EKG monitoring is done to: Abraham Salacata, MD, FACC