The ADAS1000 has a very flexible digital pace detection algorithm with a lot of programmability for various thresholds used in the pace detect algorithm. Please consult this in conjunction with the ADAS1000 datasheet.
A good starting point for the pace thresholds is as follows:
Note these settings may need to be tweaked for each application depending on what filtering is present in the ecg line up between patient and the pace algorithm. There are two componets to this, firstly the ADAS1000 pace channel has some filtering internally as there's a low pass 13kHz filter after the ADC, before it goes to the pace algorithm, so the ECG channel will introduce some rounding in the pace signal before the pace algorithm can digest it.
The second area of filtering is external, between the patient and the ECG pin of the ADAS1000. As you design your system, assess what filtering you are placing in front of the ECG pins. Aggressive filtering in the line up from defib protection and ESIS (electro-surgical interference suppression) will change the shape of the signal at the ECG pins, so assess this first and choose bandwidths that allow the pace pulse through. To much filtering here might change the nature of the incoming pulse such that the pace algorithm can't detect as a valid pulse.
If you find that some pace amplitudes or widths are not being detected, then one method to assess what's going on is to see what the pace pulse signal looks like as presented to the Pace algorithm. Either by probing at the ecg pins or alternatively, digitally by using the 128kHz data rate mode and capture a few seconds of data, take a look at how the pulse looks versus what you expected.