Patent ID: 7647095

Claim:
A medical device comprising: a plurality of sensors configured to sense cardiac signals; a physiologic sensor sensing physiologic signals configured to generate a plurality of oxygen (O 2 ) variation index samples corresponding to the sensed signals; and a microprocessor configured to: detect a cardiac event in response to the sensed cardiac signals; compute an O 2 variation index trend associated with a predetermined number of O 2 variation index samples of the plurality of O 2 variation index samples in response to the detected cardiac event; determine, in response to the O 2 variation index trend being less than a variation index trend threshold, whether a rate of change of the O 2 variation index trend is within a predetermined cardiac event zone defined by a first zone threshold having a first rate of change corresponding to the O 2 variation index trend becoming less than the variation index trend threshold in a first period of time and a second zone threshold having a second rate of change corresponding to the O 2 variation index trend becoming less than the variation index trend threshold in a second period of time greater than the first period of time; and confirm the determined detected cardiac event in response to both the computed O 2 variation index trend being less than the variation index trend threshold and the rate of change of the O 2 variation index trend being within the predetermined cardiac event zone.