Monitoring electrocardiographic data in ambulatory patients

Sustained periods of extremely rapid or slow heart rate or initiation of the heartbeat from an ectopic focus can lead to serious clinical impairment or even death. Because disturbances of cardiac rhythm are ofter intermittent and evanescent, the development of systems for recording electrocardiograms in ambulatory patients for later analysis has been of clinical utility in diverse forms of heart disease. The basic components of such systems include a compact portable tape recorder for recording electrocardiographic data and a playback system with facilities for data analysis. Recently, semi-automated, computer-assisted analysis of this electrocardiographic data and quantitative analysis of the frequency of abnormal rhythms have become possible. In addition to widespread application for diagnostic purposes, ambulatory electrocardiographic techniques are now being used to evaluate new drugs for the treatment of cardiac rhythm disturbances and to define subsets of cardiac patients in whom treatment of rhythm disturbances may be desirable.