1. An implantable medical device comprising: an implantable sensing electrode; a variable gain sense amplifier in communication with the sensing electrode so as to receive signals sensed therefrom; and a controller in communication with the sensing electrode via the variable gain amplifier wherein the controller monitors the signals received from the sensing electrode and detects the occurrence of physiological processes based on the signals exceeding a programmable threshold value and wherein the device periodically performs an automatic sensing test by: evaluating the sensed signals; characterizing a pattern thereof; iteratively temporarily reprogramming sensing parameters to a more aggressive setting and recharacterizing the pattern of the sensed signal under the reprogrammed parameters until the characterized pattern changes; and reporting the parameters which caused a change in the pattern.