A subcutaneously implantable cardiac medical device and a method of sensing a cardiac signal therein that includes a plurality of electrodes to sense a cardiac signal along a plurality of sensing vectors to detect a first interval and a second interval associated with a first detected event, and a processor configured to determine whether the first interval and the second interval are shorter than a predetermined threshold, determine whether the first interval and the second interval are similar, and determine, in response to the first interval and the second interval being similar, whether the sensed cardiac signal is either a noisy signal or a QRS signal.
