EKG artifacts
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Editor-in-Chief: Santosh Patel M.D., FRCA [1]; Associate Editor-In-Chief: Cafer Zorkun, M.D., Ph.D. [2]
Overview
Electrocardiograph (EKG) artifacts are defined as EKG abnormalities, which are a measurement of cardiac potentials on the body surface and are not related to electrical activity of the heart. As a result of artifacts, normal components of the EKG can be distorted. It is very important to recognize these artifacts, otherwise they can lead to unnecessary testing and therapeutic interventions. In this chapter, we will present the common causes and ways to characterize EKG artifacts.
Causes
Artifacts can be generated by patient's motion or other electrical devices attached to or implanted (e.g. deep brain stimulator) in the body. Tremors and shivering are good examples of motion induced artifacts. Simple movements such as brushing and combing the hair can cause EKG disturbances during ambulatory EKG monitoring. External sources of EKG artifacts mainly include power line electrical disturbances and radiofrequency based commercial (e.g. mobile phones) or medical devices. In operation theatres and intensive care unit various equipments can affect EKG measurement system (e.g. electrodes, leads, amplifier, filters). Examples of equipment which can cause EKG artifacts are - electrocautery, transcutaneus nerve stimulator (TENS), hemofiltration machines etc.
EKG artifacts can be generated by internal and external
| Type of equipment | Artifact | ||
|---|---|---|---|
| IVAC intravenous infusion controller | Atrial or ventricular extrasystoles, pseudowaves (QRS)
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Cardiopulmonary bypass pump | Uninterpretable tracing, non-specific |
| Transcutaneous electrical nerve stimulator | Atrial flutter | ||
| COBE Prisma System for continuous venovenous hemofiltration, Pressure-controlled irrigation pump, | Atrial flutter | ||
| Flexible bronchoscope | Atrial fibrillation | ||
| Deep brain stimulator | Uninterpretable tracing | ||
| Straight shot microdebrider (nasal endoscopy) | Ventricular tachycardia | ||
| Intra-aortic balloon pump | Pseudowaves (P), premature atrial contraction | ||
| Somatosensory evoked potential monitoring unitshigh-frequency oscillatory ventilation, | Supraventricular tachycardia | ||
| High-frequency oscillatory ventilation | Atrial flutter, atrial fibrillation, ventricular tachycardia | ||
| Intraoperative high-field MRI | Ventricular tachycardia, ventricular fibrillation, non-specific | ||
| Transcutaneous electrical nerve stimulator | Spikes, runaway pacemaker, ventricular fibrillation, non-specific | ||
| Peripheral nerve stimulator | Spikes, loss of pacemaker spikes |
The table was adapted from Am J Crit Care 2006;15:310-311 and includes data from references[1][2]
Charectristics
Artifacts on the EKG can distort individual or all components (P, QRS, T waves and PR and ST segments). Most of the time they are easily identifiable and neglected as they do not resemble any specific pattern. On occasions, changes may mimic specific arrhythmia like ventricular tachycardia and atrial flutter or fibrillation. It is important to differentiate these artifactual changes from genuine changes to prevent misdiagnosis. If ST segments are affected by artifacts, either ST segment depression or elevation can occur on the EKG. These changes can be misinterpreted as myocardial ischemia or infarction.
Consequences
Apart from the poor quality of EKG, artifacts can cause serious consequences particularly when they mimic like genuine changes. If EKG artifacts are not recognized by physician, anesthesiologist or intensivist unneccasry diagnostic and therapeutic measures could be taken. Such actions may subject patients to invasive investigations or they may receive unnecessary medications like antiarrythmics.
Correction
Attention to basic principles such as proper electrodes placement and lead connections is required during EKG measurement. Well designed and maintained EKG measurement devices can withstand routine internal or external electrical and motion-related disturbances. However, it is not always possible to eliminate artifacts completely. It is essential that physicians keep high vigilance and interpret EKG keeping EKG artifacts in differential diagnosis list.
Examples of Artifacts
The gallery of images below shows a variety of EKG artifacts that are due to tremor, movement, movement disorders and electrical interference. These artifacts should not be confused with an abnormality in the patient's electrocardiogram. Atrial fibrillation can be confused with these artifacts.
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Movement artifacts
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Increasing movement artifacts in a Parkinson patient.
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Baseline drift. The amplifier in the ECG machine has to re-find the 'mean'. This often occurs right after lead connection and after electric cardioversion.
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Cardioversion from atrial fibrillation to sinus rhythm, with clear baseline drift.
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Electrical interference from a nearby electrical appliance. A typical example is a 100 Hz background distortion from fluorescent lights. Not to be confused with atrial fibrillation.
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Another example of an artifact caused by an electrical appliance. The patients rhythm is regular. This strip shows 10 QRS complexes.
Video explaining ECG artifacts
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References
- Einthoven W. Le telecardiogramme. Arch Int de Physiol 1906;4:132-164
- Marquez PMID 12177632
- Hurst PMID 9799216
- Kligfield PMID 17322457
- Patel S, Souter M: PMID 18156892
- Patel S: PMID 19344913
- Patel S: PMID 16632773
- Patel S: PMID 19563573
- Patel S, Souter M: PMID 18648245
- Patel S: http://www.springerlink.com/content/w054881370x61802/
- ↑ Patel S (2006). "Electrocardiographic artifact mimicking ventricular tachycardia during high-frequency oscillatory ventilation: a case report". Am. J. Crit. Care. 15 (3): 310–1. PMID 16632773. Unknown parameter
|month=ignored (help) - ↑ Patel SI, Souter MJ (2008). "Equipment-related electrocardiographic artifacts: causes, characteristics, consequences, and correction". Anesthesiology. 108 (1): 138–48. doi:10.1097/01.anes.0000296537.62905.25. PMID 18156892. Unknown parameter
|month=ignored (help)