Patent ID: 8521276

Claim:
An apparatus comprising: a cardiac signal sensing circuit configured to provide a sensed electrical cardiac signal representative of cardiac activity of a subject; a sampling circuit coupled to the cardiac signal sensing circuit; a therapy circuit, configured to provide one or more of high-energy cardioversion shock therapy, high-energy defibrillation shock therapy, and anti-tachycardia pacing (ATP) to the heart; and a controller communicatively coupled to the sampling circuit and the therapy circuit, wherein the controller includes: a detection module configured to detect tachyarrhythmia using the cardiac signal; and a signal analysis module configured to: establish significant points (SPs) of the sampled cardiac signal, wherein an SP corresponds to a time of occurrence of a turn encountered in the cardiac signal; perform autocorrelation of the SPs in an SP domain; perform a second autocorrelation of the SP autocorrelation; calculate a number of SPs per heart beat from an SP shift that produces a peak in the second autocorrelation; and estimate heart rate during the tachyarrhythmia using the number of SPs per heart beat; and determine a likelihood of the presence of noise in the cardiac signal using the SPs, and wherein the controller is configured to select a therapy for delivery by the therapy circuit in response to the tachyarrhythmia detection and to modify the selected therapy according to the heart rate estimation and the determined likelihood of noise.