Portable heart monitor. Man holding a portable electrocardiograph that is worn on a strap around the neck. The wires lead to electrodes attached to his body. An electrocardiograph is used to monitor the electrical activity of the heart, allowing the diagnosis of abnormal heart rhythms (arrhythmias). This portable version, called a Holter monitor, records the heart's activity for 24 hours or more, leaving the patient free to continue normal activities. The recording is then analyzed by computer. This technique is useful for diagnosing sporadic heartbeat disturbances that could be missed by a short examination with a fixed monitor. This is a Vista Plus monitor from the French company Novacor.