What causes EKG artifact in the EEG and EOG channels?

What causes EKG artifact in the EEG and EOG channels?

• A. M1 and M2 being placed directly on the auricular branch of the posterior auricular artery
• B. Improper EKG patch placement
• C. Incorrect filter settings on the EEG and EOG channels
• D. None of the above

Answer: (A)

Cardioelectric activity from the heart can be picked up by scalp electrodes when they sit over pulsatile vessels, causing EKG artifact. In this situation, placing the reference electrodes right on the auricular branch of the posterior auricular artery places sensing points directly over a strong pulsing source. The arterial pulsations generate small voltage changes with each heartbeat, and because these electrodes are on conductive scalp tissue, those pulsations are transmitted into the EEG and EOG channels. The result is a rhythm that mirrors the heart rate and can obscure or mimic brain activity. To reduce this artifact, move the reference electrodes away from arterial sites—position them on the mastoids or surrounding areas that aren’t directly over a pulsatile artery—and ensure good, balanced impedance. If needed, use a montage or referencing scheme that minimizes arterial pickup or record an EKG separately for correlation. The other options describe issues that would not fundamentally create a heartbeat-linked signal in EEG/EOG in the same way arterial placement does, and a simple filter change won’t generate a true cardioelectric artifact.

Cardioelectric activity from the heart can be picked up by scalp electrodes when they sit over pulsatile vessels, causing EKG artifact. In this situation, placing the reference electrodes right on the auricular branch of the posterior auricular artery places sensing points directly over a strong pulsing source. The arterial pulsations generate small voltage changes with each heartbeat, and because these electrodes are on conductive scalp tissue, those pulsations are transmitted into the EEG and EOG channels. The result is a rhythm that mirrors the heart rate and can obscure or mimic brain activity.

To reduce this artifact, move the reference electrodes away from arterial sites—position them on the mastoids or surrounding areas that aren’t directly over a pulsatile artery—and ensure good, balanced impedance. If needed, use a montage or referencing scheme that minimizes arterial pickup or record an EKG separately for correlation. The other options describe issues that would not fundamentally create a heartbeat-linked signal in EEG/EOG in the same way arterial placement does, and a simple filter change won’t generate a true cardioelectric artifact.