Patent ID: 8862210

Claim:
An application-specific integrated circuit for cardiac monitoring, the circuit comprising: an electrocardiogram readout channel having an input and an output, the input being arranged to receive a monitored signal and the output providing an electrocardiogram signal; an impedance readout channel configured to extract impedance information from the monitored signal; and an adaptive sampling unit configured to sample the electrocardiogram signal output by the electrocardiogram readout channel, the adaptive sampling unit comprising an adaptive threshold generation unit configured to generate a threshold value which is used to control the adaptive sampling unit, an activity detector which comprises a switched capacitor differentiator configured to sense the rate of change of the electrocardiogram signal and to provide an output indicative thereof, a comparator configured to compare the output from the switched capacitor differentiator with the threshold value, and a selector configured to select between a low sampling rate and a high sampling rate in accordance with the comparison.