Identifying Common ECG Artifacts and Troubleshooting

What Is an ECG Artifact?

An artifact is any mark on an electrocardiogram tracing that does not originate from the heart's electrical activity. Artifacts distort or mimic cardiac waveforms and can lead to misinterpretation—a serious patient safety concern. Your job as a medical assistant is to recognize each type of artifact, find its cause, and correct the problem before handing a tracing to the provider for interpretation. Never submit a tracing you know is artifactual without flagging it.

The Four Major Artifact Types

1. Somatic Tremor (Muscle Artifact)

Somatic tremor appears as a jagged, irregular baseline that varies in amplitude and frequency. It is caused by skeletal muscle activity—shivering, Parkinson's tremor, anxiety, pain, or simple voluntary movement during recording. Because the muscle generates its own small electrical signal, the ECG machine picks it up alongside the heart signal.

Correction:

• Ask the patient to lie still, breathe normally, and relax their arms and legs flat on the table.
• Provide a blanket if the patient is cold.
• Reposition limb electrodes onto the fleshy part of the limb, away from bony prominences.
• If tremor is unavoidable (e.g., neurological condition), document it on the tracing and notify the provider.

2. AC Interference (60-Hz Interference)

AC interference appears as a thick, fuzzy, uniform baseline with fine rapid oscillations—typically 60 tiny spikes per second matching the frequency of standard US electrical current. It looks like a wide, blurry line rather than a thin crisp one.

Causes: Poor skin preparation, dried or loose electrodes, electrodes touching or near electrical equipment, patient contact with metal table rails, lead wires lying across power cords, or a malfunctioning machine.

Correction:

• Check all electrodes for firm contact; replace any that are loose or dried out.
• Prep the skin: clean with an alcohol pad, let it dry, and apply a new electrode.
• Route lead wires along the body and away from power cords or electrical equipment.
• Confirm the patient is not touching metal parts of the table.
• Most modern ECG machines have a 60-Hz filter; ensure it is enabled (per your facility's protocol).

3. Wandering Baseline

Wandering baseline appears as the entire baseline slowly drifting up and down across the paper in a wave-like motion. Unlike somatic tremor, the oscillation is slow and smooth.

Causes: Breathing movement (the chest rises and falls, pulling on electrode cables), poor electrode adhesion, improper electrode placement on areas that move with respiration, or electrode gel drying out.

Correction:

• Confirm electrodes are firmly adhered to clean, dry skin.
• Reposition precordial electrodes if placed where skin moves significantly with breathing.
• Ask the patient to breathe normally and avoid deep breaths during acquisition.
• Replace electrodes that have lost adhesion.
• Allow alcohol used for skin prep to dry fully before applying the new electrode.

4. Lead Reversal

Lead reversal is not a random signal—it is a systematic error in which wires are connected to the wrong electrodes. The most common reversal is the right arm (RA) and left arm (LA) leads.

How it appears: Lead I will show an inverted (negative) deflection where a positive deflection is expected. A classic sign of RA–LA reversal is a negative P wave in lead I combined with an inverted QRS, which can mimic dextrocardia or other serious conditions. Lead reversal can cause a tracing to be misread as a life-threatening arrhythmia or infarction.

Correction:

• Stop the acquisition immediately.
• Visually trace each lead wire from the machine connector to the correct electrode color and anatomical placement before re-acquiring.
• Follow your facility's color-coding standard (in the US: white = RA, black = LA, red = LL, green = RL for limb leads; precordial leads V1–V6 by anatomical landmark).
• Re-acquire the tracing with correct lead placement.

Skin Preparation: The Foundation of a Clean Tracing

Most artifacts can be prevented at the preparation step. Follow these steps every time:

1. Select the correct anatomical sites.

2. If the site is hairy, clip—do not shave—excess hair.

3. Clean the site with an alcohol pad.

4. Allow it to dry completely.

5. Apply a fresh, within-expiration-date electrode.

6. Press firmly around the entire adhesive ring.

Patient Safety and Scope of Practice

• Never interpret the ECG for the patient or provider. Your role is acquisition and artifact identification, not diagnosis.
• If a tracing shows a pattern that concerns you regardless of artifact, alert the provider immediately rather than repeating the tracing without notification.
• Document every artifact noted and every corrective action taken in the patient record per your facility's policy.
• Dispose of single-use electrodes according to standard precautions; they contact intact skin but should still be treated as potentially contaminated.

A Systematic Troubleshooting Approach

When you encounter a poor-quality tracing, work through this sequence:

1. Look at the pattern — Is the artifact uniform (AC) or irregular (somatic)? Fast oscillations or slow drift (wandering)? Inverted expected waveforms (reversal)?

2. Identify which leads are affected — All leads equally suggests a systemic cause (AC power, patient movement). One or two leads suggest a local electrode or wire problem.

3. Check the patient first — Is the patient comfortable, warm, and still?

4. Check the equipment second — Electrodes, wires, connections, machine settings.

5. Correct, then re-acquire — Document what you found and what you did.

Following this sequence protects both the patient and the integrity of the clinical record.