Patent ID: 7248921

Claim:
A method of signal detection enhancement for a cardiac rhythm device comprising: receiving a signal from electrodes implanted for cardiac observation; observing characteristic features of the signal; counting the characteristic features; comparing the number of characteristic features to a threshold to: certify the signal for use in characterizing a cardiac complex; or determine the signal is unsuitable for use in characterizing a cardiac complex; wherein: the step of observing characteristic features includes identifying a number of points in the signal where the signal slope reaches a local maximum magnitude; the step of identifying a number of points in the signal includes identifying zero crossings of the second derivative of the signal; the step of observing characteristic features includes: (a) selecting a first zero crossing as a significant maximum slope point; (b) characterizing subsequent zero crossings as either significant maximum slope points or not significant maximum slope points; and (c) the significant maximum slope points are observed to be the characteristic features; the step of characterizing subsequent zero crossings includes application of a rule related to the signal shape between two points in the signal; and the rule calls for determining whether the path length from a most recent significant maximum slope point to the zero crossing under consideration exceeds the magnitude of the difference in amplitude between: the signal at the time of the most recent significant maximum slope point; and the signal at the time of the zero crossing under consideration.