Patent ID: 7734333

Claim:
A method of detecting a cardiac event in a medical device, comprising: sensing a cardiac signal from a plurality of electrodes, the plurality of electrodes forming a first sensing vector and a second sensing vector different from the first sensing vector; determining first amplitudes of the sensed cardiac signal sensed along the first sensing vector during a predetermined sensing window; determining second amplitudes of the sensed cardiac signal sensed along the second sensing vector during the predetermined sensing window; determining a first noise to signal ratio corresponding to the determined first amplitudes; determining a second noise to signal ratio corresponding to the determined second amplitudes; comparing the first noise to signal ratio to a noise to signal ratio threshold; identifying the first sensing vector as noisy in response to the comparing the first noise to signal ratio to the noise to signal ratio threshold; comparing the second noise to signal ratio to the noise to signal threshold; identifying the second sensing vector as noisy in response to the comparing the second noise to signal ratio to the noise to signal threshold; and delivering therapy in response to the identifying.