US Patent 7734347 Cardiac pacing response classification based on waveform feature variability

Methods and systems involve determining the cardiac response to pacing pulses. The variability cardiac signal features detected during initialization is used to establish a variability threshold. A cardiac signal associated with a pacing pulse is sensed and one or more features of the cardiac signal are detected. The variability of the one or more features is compared to the variability threshold. The cardiac response to the pacing pulse is determined based on the feature variability.