EKG artifacts

Editor-in-Chief: Santosh Patel M.D., FRCA [mailto:santosh.patel@pat.nhs.uk]

Associate Editor-In-Chief:

Introduction
Electrocardiograph (EKG) artifacts are disturbances on EKG which is a measurement of cardiac potentials on the body surface. As a result of artifacts, normal components of the EKG can be distorted.

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.

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.