A computer readable program storage unit encoded with instructions that, when executed by a computer of a medical device, perform a method for indicating via a communication unit of the medical device an occurrence of an epileptic seizure, comprising: obtaining, using sensors coupled via sensor leads to the medical device, a time series of cardiac data from a patient; determining a reference heart rate parameter from the cardiac data; determining a heart rate derivative shape from the time series of cardiac data, wherein the heart rate derivative shape comprises at least one characteristic selected from a number of phases relative to the reference heart rate parameter, a number of extrema of a heart rate derivative, a number of directions of change of the heart rate derivative, an area under a curve of at least one phase, a number of positive phases, or a number of negative phases, in particular, wherein the heart rate derivative is selected from heart rate or heart rate variability; identifying the occurrence of the epileptic seizure based upon a determination that the heart rate derivative shape matches a state change template in at least one characteristic; characterised in that in response to the identifying, to validate the identifying: obtaining from said heart rate derivative shape data relating to at least a portion of a heart beat complex from said patient; comparing the at least portion of the heart beat complex with a corresponding portion of a first reference heart beat complex template of said patient; and indicating, via the communication unit, the occurrence of the epileptic seizure based upon a determination that the heart beat complex fails to match the first reference heart beat complex template. obtaining, using sensors coupled via sensor leads to the medical device, a time series of cardiac data from a patient; determining a reference heart rate parameter from the cardiac data; determining a heart rate derivative shape from the time series of cardiac data, wherein the heart rate derivative shape comprises at least one characteristic selected from a number of phases relative to the reference heart rate parameter, a number of extrema of a heart rate derivative, a number of directions of change of the heart rate derivative, an area under a curve of at least one phase, a number of positive phases, or a number of negative phases, in particular, wherein the heart rate derivative is selected from heart rate or heart rate variability; identifying the occurrence of the epileptic seizure based upon a determination that the heart rate derivative shape matches a state change template in at least one characteristic; characterised in that in response to the identifying, to validate the identifying: obtaining from said heart rate derivative shape data relating to at least a portion of a heart beat complex from said patient; comparing the at least portion of the heart beat complex with a corresponding portion of a first reference heart beat complex template of said patient; and indicating, via the communication unit, the occurrence of the epileptic seizure based upon a determination that the heart beat complex fails to match the first reference heart beat complex template.