Suspected arrhythmias sometimes may be documented by using a small, portable electrocardiogram (ECG) recorder called a Holter monitor (or continuous ambulatory electrocardiographic monitor). This can record 24 hours of continuous electrocardiographic signals. While an ECG is sort of a 12-second "snapshot" of the heart's electrical activity, the Holter monitor is more like a "movie." For suspected arrhythmias that occur less than daily, a patient can wear an event monitor. It has a continuously updated memory loop and can allow the heart to be monitored by telephone.
In Holter monitoring, electrodes are taped to the chest. The wires are connected to a portable, battery-operated recorder that can run for 24 to 48 hours. You can do most normal activities while being tested. The tape is then analyzed on a computer that rapidly identifies rhythm disturbances.