1. A non-transitive computer readable program storage device encoded with instructions that, when executed by a computer, perform a method of detecting an epileptic seizure using an estimate of a percentile value of a patient's heart signal in a plurality of time windows, the method comprising the steps of: (a) receiving a heart signal from a patient; (b) determining a heart feature signal from said heart signal; (c) determining a first percentile tracking filter estimate from the heart feature signal in a foreground time window; (d) determining a second percentile tracking filter estimate from the heart feature signal in a background time window; (e) determining a ratio of the first percentile tracking filter estimate and the second percentile tracking filter estimate; (f) comparing the ratio to a threshold value; (g) detecting an epileptic seizure when the ratio crosses the threshold value; and (i) in response to the detecting, providing an output indicative of the detection of the seizure.