The present invention relates to a medical device for analyzing cardiac related input signals. The device is capable of receiving an ECG-signal and a nerve activity signal, such as vagus nerve signal in order to detect a cardiac related neural activity, such as epilepsy. The device is programmed for detecting a trigger feature (e.g. the R-peak) in the signal and extracting a nerve activity signal segment from the nerve activity signal in response to detecting the trigger feature. An activity related feature is generated either based on a combined signal obtained from a number of nerve activity signal segments, or as a segment-based activity related feature obtained from a number of nerve activity signal segments. Moreover, the device is adapted for comparing the activity related feature to a predefine criterion in order to detect the cardiac related neural activity.