1. A method for detecting signal artifact in a signal waveform acquired by an implantable physiological sensor, the method comprising: sensing a signal in a patient using the implantable physiological sensor and separating the signal into a plurality of waveforms; extracting a plurality of features from individual waveforms of the plurality of waveforms; classifying the individual waveforms according to expert observation, the individual waveforms classified into at least two classes comprising an artifact class; determining a distribution range for the plurality of features for each of the classes; establishing waveform classification criteria in response to the determined distribution ranges; acquiring unknown waveforms from an implantable physiological sensor; extracting the plurality of features from the unknown waveforms; classifying the unknown waveforms according to the established waveform classification criteria; and detecting signal artifact in response to a waveform being classified in the artifact class.