A method and medical device for detecting a cardiac event that includes sensing cardiac signals from a plurality of electrodes, the plurality of electrodes forming a first sensing vector and a second sensing vector, identifying the cardiac event as one of a shockable event and a non-shockable event in response to first processing of a first interval sensed along the first sensing vector during a predetermined sensing window and a second interval simultaneously sensed along the second sensing vector, performing second processing of the first interval and the second interval, different from the first processing, in response to the cardiac event being identified as a shockable event, and determining whether to delay identifying the cardiac event being shockable in response to the second processing of the first interval and the second interval.
