Patent ID: 7742812

Claim:
A method of detecting a cardiac event, comprising: sensing cardiac signals from a plurality of electrodes, the plurality of electrodes forming a first sensing vector and a second sensing vector; determining a first low slope content of the cardiac signals sensed by the first sensing vector after taking a first derivative of the cardiac signals sensed by the first sensing vector in each of a first plurality of sub-segments of a first predetermined sensing window, wherein the first low slope content is defined as a number of sample points representative of the first derivative of the cardiac signals of the first vector having an absolute value less than or equal to a first predetermined slope threshold; determining a second low slope content of the cardiac signals sensed by the second sensing vector after taking a first derivative of the cardiac signals sensed by the second sensing vector in each of a second plurality of sub-segments of a second predetermined sensing window, wherein the second low slope content is defined as a number of sample points representative of the first derivative of the cardiac signals of the second vector having an absolute value less than or equal to a second predetermined slope threshold; determining a first spectral width of the cardiac signals sensed by the first sensing vector defined by a difference between a mean frequency and a fundamental frequency of the cardiac signals sensed by the first sensing vector over the first predetermined sensing window; determining a second spectral width of the cardiac signals sensed by the second sensing vector defined by a difference between a mean frequency and a fundamental frequency of the cardiac signals sensed by the second sensing vector over the second predetermined sensing window; identifying each of the first sensing vector and the second sensing vector as being one of shockable and not shockable in response to the first low slope content, the second low slope content, the first spectral width and the second spectral width; and delivering therapy in response to the identifying.