Cardiac artifacts
in EEG recordings refer to unwanted signals that originate from the electrical
or mechanical activity of the heart. These artifacts can interfere with the
accurate interpretation of brain activity captured by the EEG.
1. Electrical
Cardiac Artifacts:
o Description: Electrical
cardiac artifacts result from the electrical signals generated by the heart's
activity.
o Characteristics: These artifacts
are time-locked to cardiac events and can appear similar to ECG signals.
However, due to the distance from the heart and suboptimal visualization axis,
they may not always resemble typical ECG waveforms.
o Types:
§ Pacemaker
Artifact: This
type of artifact has high-frequency polyphasic potentials with a shorter
duration compared to ECG artifacts. It often shows a broader distribution
across the EEG channels.
§ ECG Artifact: Represents the
actual ECG signal recorded from head electrodes but may not always be easily
recognizable as ECG due to recording conditions.
2. Mechanical
Cardiac Artifacts:
o Description: Mechanical
cardiac artifacts arise from the physical movements associated with cardiac
contractions.
o Characteristics: These artifacts
may manifest as periodic slow waves following the ECG peak or exhibit saw-tooth
patterns or sharply contoured waveforms.
o Types:
§Pulse Artifact: Typically seen
as a slow wave following the ECG peak, commonly observed over frontal and temporal
regions. Pressure on the electrode can alter the appearance of this artifact.
§Ballistocardiographic
Artifact:
Results from slight head or body movements during cardiac contractions, with a
waveform similar to pulse artifact but more widespread.
3. Identification
and Differentiation:
oDistinguishing
Features:
Pacemaker artifacts have distinct high-frequency polyphasic potentials, while
pulse artifacts exhibit slow waves following the ECG peak.
o Location: Pulse artifacts
are often observed over frontal and temporal regions, while
ballistocardiographic artifacts may involve multiple electrodes due to head or
body movements.
Proper
recognition and differentiation of cardiac artifacts from genuine brain
activity are crucial for accurate EEG interpretation and diagnosis. Techniques
to minimize or eliminate these artifacts during EEG recording can help improve
the quality and reliability of EEG data for clinical analysis.
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