ECG Artifact
An ECG artifact refers to a distortion or interference that appears in an ECG (electrocardiogram) signal, typically caused by external factors rather than the electrical activity of the heart. These artifacts can obscure or distort the actual heart rhythm and can make the interpretation of the ECG more challenging.
The most common form of ECG artifact is related to muscle contractions or other movement-related disturbances, and they are often time-locked to the QRS complex—the part of the ECG that represents the depolarization of the ventricles. This means that the artifact's occurrence is directly tied to the heart’s electrical activity, making it distinguishable from other artifacts that occur independently of the heart’s cycle.
In terms of location, these artifacts are typically more prominent on the left side of the chest, which is where the heart is located. They tend to be relatively low in amplitude, although they can sometimes become more prominent. This prominence could be misleading if mistaken for other kinds of signals that are not time-locked to the QRS complex.
It is critical not to confuse ECG artifacts with other phenomena, such as posterior discharges or POSTs (Post-auricular or post-auricular stimuli). Unlike ECG artifacts, which are time-locked to the QRS complex, POSTs or posterior discharges are not linked to the heart's electrical signals and may present differently in the ECG tracing. They are typically caused by external electrical sources or muscle activity and do not follow the same rhythm as the heart’s cycles.
Cardioballistic Artifact
A much less commonly observed type of cardiac artifact is the cardioballistic artifact. This artifact is generated when the EEG (electroencephalogram) electrode is placed near a pulsating artery. The pulsations of the artery, due to each heartbeat, create a motion artifact that is recorded by the EEG.
The pulsation of the artery is picked up by the electrode as motion artifact, causing fluctuations in the EEG signal that are synchronous with the patient’s heartbeat. This type of artifact is generally easy to distinguish because it is also time-locked to the heart's cycle and is linked to arterial pulsation, not neural activity.
Cardioballistic artifacts can be problematic in cases where accurate EEG recordings are necessary for diagnosing neurological conditions. The motion artifacts caused by the arterial pulse can obscure the brain’s electrical signals, making it difficult to identify abnormalities or track the brain's activity effectively.