| abstract |
The present invention permits discrimination between evoked response signals and post-pace polarization signals sensed by an implantable medical device by noting the polarity of the positive or negative change in voltage in respect of time (or dv/dt) of the waveform incident on the lead electrodes during a short period of time immediately following a paced event. It has been discovered that the post-pace polarization signal exhibits a relatively constant polarity during the capture detect window, and that the evoked response signal may cause the polarity of post-pace polarization signal to reverse during the capture detect window. The sign of the post-pace polarization polarity, either positive or negative, is determined by the design of the specific output circuitry. The evoked response signal may, reverse the polarity of the sensed signal in either case, from positive to negative or from negative to positive, during the time window of interest. When the magnitude of the post-pace polarization is so great that the evoked response does not reverse the polarity of the waveform, discrimination of the evoked response can be achieved by comparing the sensed signal with a variable threshold for a defined duration. In another embodiment, if the amplitude of the sensed signal is not indicative of polarization, a constant sensing threshold for capture detection is employed. |