Electrocardiograms, or ECGs, are commonly used as a diagnostic tool to assess heart health. They record the electrical activity of the heart over a period, providing valuable insights into its rhythm and overall function. However, these readings are not always perfectly clear due to “artifacts,” which are unwanted signals or disturbances that appear on the ECG tracing. Understanding these interferences helps in accurate interpretation and distinguishes them from actual cardiac activity.
What Are ECG Artifacts?
ECG artifacts are electrical signals or physical movements detected by the ECG machine that do not originate from the heart’s own electrical impulses. These disturbances are not indicative of an underlying heart problem, but they can significantly obscure or even mimic genuine cardiac signals, making the ECG difficult to interpret. Artifacts can lead to misdiagnoses if not properly recognized and addressed.
These unwanted signals can broadly be categorized by their source: patient-related, equipment-related, or environmental factors. Patient-related artifacts stem from the individual undergoing the test, such as muscle activity or movement. Equipment-related artifacts involve issues with the ECG machine itself, including its leads or electrodes. Environmental artifacts arise from external electrical interference in the testing area.
Common Sources of ECG Artifacts
Patient-Related Factors
Patient-related factors are a frequent source, including involuntary muscle tremors from shivering, anxiety, or neurological conditions like Parkinson’s disease. General patient movement, such as coughing, talking, or repositioning during the test, can also create distortions on the tracing. Respiration, particularly deep or irregular breathing, can also lead to interference. Poor skin preparation, where oils, lotions, dirt, or excessive hair interfere with electrode contact, is another common patient-related cause. Loose or improperly attached electrodes also fall into this category, as they prevent a stable connection.
Equipment-Related Issues
Equipment-related issues also contribute to artifact presence. These include faulty or damaged electrode wires, which can cause erratic signals or even a flat line on the tracing. Loose connections between the leads and the electrodes, or between the lead wires and the ECG machine, can disrupt signal transmission. Worn-out or expired electrodes with dried-out gel can also compromise conductivity, leading to poor signal quality. Machine malfunctions or low battery power in portable ECG devices can also produce unreliable readings.
Environmental Factors
Environmental factors contribute significantly to ECG artifacts, primarily through electrical interference. Nearby electronic devices, such as cell phones, electrical beds, surgical lamps, or fluorescent lights, can generate electromagnetic fields that interfere with the ECG signal. In the United States, this often presents as 60 Hz interference. Improper grounding of the ECG machine or other electrical equipment in the room can also introduce unwanted electrical noise into the tracing.
How to Identify ECG Artifacts
Recognizing the visual characteristics of artifacts on an ECG tracing is important for distinguishing them from actual cardiac rhythms. A “wandering baseline” appears as a slow, undulating, or wavy movement of the baseline, shifting up and down across the tracing. This pattern is often associated with patient movement, such as breathing, or poor electrode contact.
“Somatic tremor” presents as irregular, jagged, or fuzzy deflections throughout the ECG tracing. This type of artifact results from muscle activity, whether voluntary or involuntary, like shivering, anxiety-induced tremors, or movements related to neurological conditions such as Parkinson’s disease.
“AC interference,” also known as 60-cycle interference in regions with 60 Hz electrical grids, manifests as uniform, regular, small spikes that create a “sawtooth” pattern or a thick, fuzzy line on the ECG. This consistent, high-frequency noise is caused by electrical interference from external sources like power outlets, fluorescent lights, or other electronic equipment nearby.
A “loose electrode” or “electrode pop” artifact can result in sudden, erratic deflections, or even a flat line, indicating a temporary loss of contact between the electrode and the skin. This can resemble arrhythmias or cause brief signal loss, making accurate interpretation challenging.
Strategies for Clearer ECG Readings
Achieving clear ECG readings involves careful patient preparation and equipment management.
Patient Preparation
Patients should be made comfortable and warm to prevent shivering, as muscle tremors can obscure the tracing. Encouraging the patient to relax, remain still, and breathe normally throughout the procedure can reduce motion artifacts and baseline wandering. Explaining the procedure can help alleviate anxiety, which might otherwise cause muscle tension.
Proper skin preparation is also important for good electrode contact. This involves cleaning the skin to remove oils, lotions, or dirt with alcohol wipes or soap and water. If the patient has excessive hair in the electrode placement areas, shaving or clipping the hair ensures better adhesion and conductivity.
Equipment Management
Regarding equipment, ensure that electrodes are fresh, have adequate conductive gel, and are not expired. Electrodes should be applied firmly to the skin, with secure placement in the correct anatomical positions. Inspect lead wires for any damage, such as breaks or cracks, and confirm all connections are secure and free from defects. Regularly cleaning electrode clips prevents gel buildup that can affect conductivity.
Environmental Control
Environmental control also plays a role in minimizing interference. Turn off any unnecessary electronic devices, such as cell phones or other medical equipment, that are close to the ECG machine. Ensuring the ECG machine is properly grounded helps reduce electrical noise. If interference persists, consider moving the patient or equipment to a different location to minimize exposure to strong electromagnetic fields.