Patients with heart rhythm irregularities (palpitations) or slow (bradycardia) or rapid (tachycardia) heart rhythms, which are not documented on the routine electrocardiogram (ECG), will usually require some type of home (ambulatory) documentation. The holter monitor is a small compact magnetic tape electrocardiographic recorder. Electrodes are placed on the skin of the chest beneath the patient's clothing and an ECG record is obtained over a 24 hour period. The recorder is returned the following day and the total ECG record is retrieved from the magnetic tape and interpreted by the physician. This technology is helpful in the diagnosis of paroxysmal (intermittent) rhythm disturbances and essential for selecting proper treatment and at times for evaluating the subsequent outcome on treatment.