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Other Hospital Equipment Causing Electrocardiographic Interference.
Poor performance of conventional electrocardiographic or arrhythmia monitoring has been described due to radiated and conducted interference from a wide variety of sources, such as isolated power supply line isolation monitors, power distribution system components, televisions, radio, elevator motors, fluorescent lights, light dimmers, and smoke detectors. Arthroscopic shavers (used in orthopedic tissue resection) have been reported as causing pseudo–ventricular fibrillation.
Recognition and Identification
The development of artifacts during electrocardiographic monitoring is common, and often of no clinical significance. Most of the time, artifacts may be easily recognizable, and therefore are neglected. However, startling and unexpected appearance of some artifacts can be confusing and deceiving. Knowledge of the characteristics of artifacts may lead to their correct diagnosis, exclusion as causes of concern, and elimination from the environment.
Information from Other Monitored Parameters
Correlation with other monitored parameters may provide clues allowing the exclusion of genuine changes. Other waveforms providing rate and rhythm may not be consistent with the artifactual rhythm, e.g., plethysmographic, direct arterial blood pressure, and central venous pressure. Pulse rate from plethysmograph and direct arterial blood pressure trace will indicate true heart rate in case of pseudo–atrial fibrillation or –ventricular tachycardia. Conversely in case of true atrial fibrillation, these monitors may underestimate heart rate. In case of pseudo–atrial fibrillation, a waves on central venous pressure trace still may be seen. If this seemingly obvious comparison is missed, it can lead to inappropriate management. However, based on our personal observations, SSEP monitoring can also induce rate changes in the pulse oximeter waveform and value, confusing diagnostic resolution of arrhythmia. The use of electrocautery may be associated with loss of the pulse oximeter waveform, removing it as a source of comparison to electrocardiographic changes.
Appearance and Disappearance in Relation to Use of Equipment
Transcutaneous electrical nerve stimulator and other electrostimulator-induced artifacts have frequently disappeared once deactivated, whereas the sudden appearance of new “supraventricular arrhythmias” on the electrocardiogram, coincident with the start of SSEP monitoring and hemodialysis, are highly suggestive that the changes are artifactual. Communication with the neurotechnician during SSEP monitoring can confirm the diagnosis of pseudo-SVT. The “on–off test” is a simple method of eliminating medical devices from consideration as sources of artifact, e.g., cardiopulmonary bypass, dialysis unit, and intravenous infusion pumps. Intermittently appearing artifacts should be suspected and tested in this fashion. Random appearance is most likely due to either mechanical movement or loosening of electrodes. Unless recognized and rectified, these artifacts may occur and recur in many patients.
Other Environmental Factors
Artifacts arising from static electricity may be affected by temperature and relative humidity. Artifacts will not respond to administration of antiarrhythmic drugs or other therapeutic measures, and the lack of any response to intervention should at least raise the suspicion of an extrinsic source of pseudoarrhythmia. Changes on the electrocardiographic tracing may also be reproducible within simulated scenarios. It has been suggested that a baseline electrocardiogram be recorded after the placement of a spinal cord stimulator. It may define artifacts possible with that device and can be used for future reference.
