ADAS1000 Pacemaker Detection PACE LEVEL Threshold clarification

Hi subbu ,

We will look into this. I will contact the product owner and get back to you.

Regards,

JC

Hi Subbash,

What are you using to generate the pace pulse here? Can you try to use a pace simulator if possible? 

regards,

Mark

Hi Mark, 

I am using ECG Simulator which provides pace pulses too.

We have defibrillator protection circuitry, filter circuit in the ECG path.

Without the defib circuit elements pace detection is happening properly. 

With defib circuit protection elements, pace detection is not working.

Can you let me know any means of sending you front end schematics through email. It will help you to suggest the solution better.

Can you also, clarify about knowing the minimum and maximum LEVEL thresholds computation from the waveform. 

Thanks and Regards, 

Subbash

Hi Mark, 

We were using 4k/10nF filter in our front end. After removing the 10nF capacitor. The pace detection is working with the defib proof cable and circuitry configuration. 

I have following observations which I need your inputs.

1. What is the relation between removal of capacitor and the pacemaker detection. I had probed the Waveforms before and after the filter circuit, There was not much difference in waveform. 

2. After removing capacitor, I am observing that, Pace pulse detected location is shifted with respect to Pace pulse peak (See image below). Datasheet mentions about pace latency. However, When capacitor was mounted. I was not observing this shift in pace peak. Pace pulse detected location was exactly same as the peak. Can you explain about this behavior.

3. If I remove the defib protection resistors and related circuitry and use ECG Cable with 0 ohm resistance. I am observing noise in the ECG data captured. However, When I use ECG Cable with Defib protection resistors and circuitry. Noise is not observed in the ECG data.

I am capturing data in Common electrode mode with Gain of 4.2 and pace is detected on Lead 2.

Thanks and Regards,

Subbash

Hi Subbash,

10nF is a big capacitor for this application. This is probably why you are not detecting the PACE. Can you try the 10kOhm and 200pF combination? 

Do you have more details about the defib-proof cable? Does it have an internal resistor or circuit? 

Some comments on your questions above:

1. The RC circuit will act as a low-pass filter, and if your cutoff frequency is too low then you may be filtering the Pace signal as well. If you remove the capacitor, you will only have the resistive component, which will attenuate your signal. 

2. I thought you were not detecting the pace when there is a capacitor? The pace detection is delayed vs. the actual pace pulse because the ADAS1000 will still have to run the internal pace detection algorithm to decide if there is a valid pace pulse. 

3. This is normal. Defib and ESIS filters help in attenuating/filtering out the noise from the line.

regards,

Mark

Hi Mark, 

1. Regarding the Shift in the Location of Pace detected Location and Pace Peak: 

When We were testing with the Capacitor placed. The Pace Peak location and Pace peaks were aligning properly. 

However, After removing the capacitor, There is a shift in the Pace peak location with respect to Pace detected Location.

I have messaged you the front end details. Please check.

Hi Subbash,

I replied to your message. We can continue communicating there.