A device for detecting a cardiac event is disclosed. Detection of an event is based on a test applied to a parameter whose value varies according to heart rate. Both the parameter value and heart rate (RR interval) are filtered with an exponential average filter. From these filtered values, the average change in the parameter and the RR interval are also computed with an exponential average filter. Before computing the average change in the parameter, large changes in the parameter over short times, which may be caused by body position shifts, are attenuated are removed, so that the average change represents an average of small/smooth changes in the parameters value that are characteristic of acute ischemia, one of the cardiac events that may be detected. The test to detect the cardiac event depends on the heart rate, the difference between the parameters value and its upper and lower normal values, and its average change over time, adjusted for heart rate changes. The upper and lower normal parameter values as a function of heart rate are determined from long term stored data of the filtered RR valuse and parameter values. Hysteeresis related data and transitory deviations from normal (e.g. vasospasm related data) are excluded from the computation of normal upper and lower parameter bounds.
