Eight-hour electrocardiogram: technique and clinical application.

The standard electrocardiogram is a sampling of but a small portion of the daily cardiac activity, and is only standardized for the supine position and the basal state. Such technique is not likely to reveal transient disturbances of cardiac rhythm and ST-T segment configuration. Accordingly, interest has been directed towards obtaining prolonged electrocardiographic recordings in ambulatory patients. A small, portable, battery-operated tape recorder capable of recording for 8-10 hours has been in use for several years (Holter, 1961; Gilson, Holter, and Glasscock, 1964). The complete system consists of three separate instruments: the tape recorder itself, called the Electrocardiocorder; a rapid playback unit, called the Arrhythmiagraph-AVSEP; and a slow playback unit called the Electrocardiocharter. The Arrhythmiagraph-AVSEP has two display screens, one superimposing all complexes on the same portion of the screen in rapid succession, and the other displaying successive R-R intervals in a bar graph array. The first reveals changes in configuration and the second changes in heart rate. A further aid is an audible tone which changes in pitch when the rate or rhythm changes. The Electrocardiocharter allows reproduction of portions of the recording in standard electrocardiographic format. In a recent clinical evaluation of this system, it was found to be most useful in evaluating obscure cerebral and cardiac symptomatology (Corday et al., 1965; Norland and Semler, 1964). In our laboratory, we were able to avoid the expense of this entire system and indeed move it one step closer to automation, by utilizing an inexpensive oscilloscope and building a simple rapid playback system.