A simple digital filter to remove line-frequency noise in implantable pulse generators

Area of Science:

• Biomedical Engineering
• Signal Processing
• Implantable Devices

Background:

• Line-frequency noise (50/60 Hz) poses a significant challenge in acquiring accurate electrograms from implantable devices.
• Existing filtering methods may be complex or power-intensive for miniaturized applications.

Purpose of the Study:

• To develop and evaluate a simple, low-power digital notch filter for removing 50/60-Hz noise in implantable devices.
• To assess the filter's ability to differentiate true biological signals from noise interference.

Main Methods:

• A digital notch filter was implemented using running subtraction of electrogram data.
• Simultaneous rejection of 50/60 Hz was achieved by combining two notch filter outputs.
• A noise-sensing algorithm classified events based on a 33% threshold of filter output versus raw data.
• Filter performance was validated through computer simulations and animal studies with injected noise.

Main Results:

• Computer simulations identified an optimal threshold of 33% for noise classification.
• Animal studies demonstrated effective exclusion of incorrect line-frequency-noise senses.
• The filter successfully distinguished true sense events from noise interference.

Conclusions:

• The developed digital notch filter is a simple and effective solution for mitigating line-frequency noise in implantable pulse generators.
• The power-saving strategy of intermittent filter operation is suitable for battery-powered devices.
• This approach enhances the reliability of signal acquisition in the presence of noise.