3.3 Scenario Practice for EKG Acquisition

The Three Artifacts You Must Recognize

An artifact is any deflection on the EKG that is not generated by the heart. The CET must distinguish artifact from true pathology, find the cause, and re-run a clean strip. The three classically tested artifacts are:

The distinguishing clue for AC interference is its absolute regularity — 60 identical, evenly spaced spikes per second produce a thick, uniform band of constant height. Somatic tremor is irregular fuzz of varying height. Wandering baseline moves the whole tracing slowly up and down rather than thickening it.

Scenario 1: Wandering Baseline

Scenario: You run a 12-lead and the baseline slowly drifts up and down across the strip like gentle waves; P-QRS-T complexes are intact but ride the drift.

Diagnosis: Wandering baseline. First actions in order: (1) check that electrodes are fresh and not dried out — replace any expired ones; (2) re-prep the skin (clean, dry fully, abrade); (3) confirm electrodes adhere flat and lead wires are not pulling; (4) reassure the patient to breathe normally if respiration is the driver. Wandering baseline is overwhelmingly an electrode/skin-contact problem, so fresh electrodes and good prep solve most cases.

Scenario 2: Somatic (Muscle) Tremor

Scenario: A cold, anxious, or tremor-prone patient produces a tracing covered in fine, jittery fuzz that varies moment to moment.

Diagnosis: Somatic tremor. Fixes: warm the patient with a blanket, raise room temperature, and help them relax (explain the test, ensure limbs are supported and not dangling). For Parkinsonian or essential tremor, place limb electrodes on the torso (proximal limbs/trunk) or have the patient sit on their hands or fold them under the buttocks to dampen the tremor. Never tell a shivering patient to simply 'hold still' — address the cause.

Scenario 3: AC (60-Cycle) Interference

Scenario: The entire tracing is a thick, uniform, perfectly regular blur of identical small spikes, the same in every lead.

Diagnosis: AC / 60-cycle interference from electrical power (mains electricity in the US runs at 60 Hz). Troubleshooting steps: (1) unplug or move away nearby electrical equipment (IV pumps, warming devices, phones, fans); (2) verify the EKG machine is properly grounded and check for frayed or crossed cables; (3) ensure lead wires lie flat and are not crossing power cords; (4) confirm the patient is not touching metal bed rails; (5) confirm electrodes have good contact (high impedance worsens AC pickup).

Modern machines include a notch (AC) filter, but the filter masks the problem rather than curing it, so find and remove the electrical source first.

Decision rule for any artifact: identify the pattern (drift vs. irregular fuzz vs. regular blur) → infer the source (electrode/skin vs. patient/muscle vs. electrical) → apply the targeted fix → re-run and verify before handing off the tracing.

Scenario 4: A Single Bizarre Lead

Scenario: Eleven leads look clean, but one lead (say V3) shows wild, isolated noise or a flat line.

Diagnosis: A single noisy or flat lead points to that one electrode — a loose, dried, or disconnected electrode, or a broken lead wire — not a patient-wide problem. Fix: re-seat or replace that specific electrode and wire; if a single limb lead is dead, check that one cable connection. Because artifact in only one lead isolates the culprit, you rarely need to re-prep the whole patient.

Scenario 5: Distinguishing Artifact from True Pathology

Scenario: A jittery, irregular tracing could be ventricular tachycardia or could be muscle tremor.

Diagnosis approach: Look for 'marching' P waves or normal complexes hidden within the noise — if you can find regular underlying QRS complexes at a normal rate beneath the fuzz, the rhythm is sinus and the chaos is artifact, not a lethal arrhythmia. A true ventricular rhythm has no normal complexes peeking through. The CET's job is never to diagnose, but recognizing that artifact can mimic dangerous rhythms prevents a false alarm — always re-run a clean strip before the tracing reaches the physician, and report obvious emergencies immediately while you re-acquire.

A useful mental model is to treat every artifact as a clue pointing to one of four sources. Electrode and skin problems (dried gel, poor prep, oily or sweaty skin) cause wandering baseline and flat or noisy single leads. Patient and muscle sources (cold, anxiety, tremor, talking, movement) cause somatic-tremor fuzz. Electrical environment sources (ungrounded machine, nearby devices, crossed cables) cause regular 60-cycle interference. Equipment and cable faults (broken wire, loose connector) cause an isolated dead or wild lead.

Walking this short list in order — skin, patient, environment, equipment — lets you correct nearly any artifact methodically instead of guessing. Crucially, you fix the cause rather than hiding it with filters: turning on a muscle filter or AC notch filter can smooth the display, but an over-filtered tracing distorts the true waveform and can erase real findings, so filters are a last resort after the physical source has been addressed and the strip is still acceptable for the ordering provider.