Cardiac analyzer with rem sleep detection

A compact, cardiac analyzer system (100) provides for monitoring physiological indicators of rapid eye movement (REM) sleep, autonomic fluctuations and ischemia. When any of these "indicators" is detected, a full complement of ECG data is recorded from a subject for subsequent analysis. In the absence of these indicators, only a minimal complement of ECG data is recorded. The system includes a first set of ECG electrode sets (110), from which the data are recorded only during REM sleep, extreme autonomic drive fluctuations, or ischemia, and a second set of ECG electrode sets (112), from which the data are constantly recorded. A set of electromagnetic interference sensors (116) is used to assess environmental noise levels so that corrupted data can be rejected or purified. During REM sleep, autonomic drive fluctuations provide a setting for assessing the variability of fractionated potentials in subjects susceptible to sudden cardiac death. In addition, the muscle atonia characterizing REM sleep provides exceedingly low muscle tremor noise levels. Accordingly, cardiac activity is most thoroughly monitored when fluctuating fractionated potentials are most likely to occur and when tremor noise levels are most favorable for their detection. Data recording is minimized in the absence of the indicators, allowing for up to a 5:1 data reduction during a typical sleep cycle.