implantable active medical device, in particular a between sturgeon and kennsignalen discriminatory bedarfsherzschrittmacher

摘要

An analogue cardiac signal (SA) passes through a low pass filter (10) which eliminates all frequencies above for example 500 Hz taken as the upper limit for characteristic signals. The resultant signal (SAF) is digitised (12) to produce a signal (SN). Sampling then takes place at a frequency at least double that of the low pass filter cut off. The digitised signal (SN) is differentiated (14) by measuring the change in successive samples over the sampling period to produce an output of limited slope (SL). The latter is subtracted (16) from the digitised signal (SN) to give a processed signal (ST) which is compared with a threshold (SD) to yield a control signal (SC).