1. A non-transitory computer readable program storage unit encoded with instructions that, when executed by a computer, perform a method for detecting a seizure, comprising: receiving a heart rate of a patient; calculating a change in said heart rate in reference to at least one of said patient's maximal heart rate, a reserve heart rate, an activity heart rate, or a resting heart rate; detecting a seizure if said change in said heart rate reaches a threshold value; and taking at least one responsive action selected from issuing a warning, delivering a therapy, determining a seizure severity, or logging at least one of a date and time of occurrence of said seizure, its severity, the type of therapy, or its effect, in response to said detection.