1. A medical device including a power source for detecting an epileptic seizure, the medical device configured to implement a method including: (a) receiving via one or more processors a heart signal from a patient; (b) determining via the one or more processors a heart signal feature from the heart signal; (c) determining via the one or more processors a first percentile tracking filter estimate from the heart signal feature in a foreground time window; (d) determining via the one or more processors a second percentile tracking filter estimate from the heart signal feature in a background time window; (e) comparing via the one or more processors a foreground data to a background data; (f) detecting via the one or more processors the epileptic seizure based on the comparison of the foreground data to the background data; and (g) in response to the detecting of the epileptic seizure, providing via the one or more processors an output indicative of the detection of the epileptic seizure; wherein at least one of the first percentile tracking filter estimate and the second percentile tracking filter estimate is updated using a difference equation, wherein the difference equation updates the at least one of the first percentile tracking filter estimate and the second percentile tracking filter estimate based on a comparison of a heart signal feature status versus a most recent percentile tracking filter estimate status where the comparison determines a first state, a second state, and a third state, wherein the difference equation updates the at least one of the first percentile tracking filter estimate and the second percentile tracking filter by incrementing the at least one of the first percentile tracking filter estimate and the second percentile tracking filter estimate by a first non-negative value based on the first state where the first state is that the heart signal feature is greater than a most recent percentile tracking filter estimate, wherein the difference equation updates the at least one of the first percentile tracking filter estimate and the second percentile tracking filter estimate by decrementing the at least one of the first percentile tracking filter estimate and the second percentile tracking filter estimate by a second non-negative value based on the second state where the second state is that the heart signal feature is below the most recent percentile tracking filter estimate; and wherein the difference equation updates the at least one of the first percentile tracking filter estimate and the second percentile tracking filter estimate by leaving the at least one of the first percentile tracking filter estimate and the second percentile tracking filter estimate unchanged based on the third state where the third state is that the heart signal feature value is equal to the most recent percentile tracking filter estimate; wherein the utilization of the first percentile tracking filter estimate and the second percentile tracking filter estimate extends a power source life of the power source based on a power consumption associated with a computational process relating to the first percentile tracking filter estimate and the second percentile tracking filter estimate.