Why Does My ECG Show Artefacts? Gel, Electrodes, Cables Diagnosed
Most ECG artefacts trace back to one of four sources: dry or degraded electrode gel, aged electrodes, damaged or poorly grounded cables, or inadequate skin preparation — and each leaves a distinctive signature on the trace.
When a 12-lead suddenly shows wandering baseline, fuzz, or sharp spikes, the temptation is to repeat the test. The faster fix is to read the artefact pattern, isolate the cause in under a minute, and correct it at the source. The four causes below cover the vast majority of preventable artefacts in routine clinical use.
Cause 1: Dry, expired or low-conductivity electrode gel
The hydrogel pad on a pre-gelled electrode dries out from the moment the foil pouch is opened. Once dry, contact impedance climbs, signal amplitude drops, and 50 Hz mains noise dominates the trace.
How to identify: open the foil pouch and press a fingertip into the centre of the gel. Fresh gel is tacky and slightly cool; dried gel feels rubbery or crusty. On the trace, suspect dry gel when all 12 leads share a fine, even fuzz that worsens when the patient relaxes.
Fix: discard the strip of electrodes and open a new pouch. Check the expiry on the foil — pre-gelled electrodes generally have a 12–24 month shelf life from manufacture, shorter once the pouch is opened. For wet-gel ECG, confirm the gel tube has not separated; reseal between cases and store cool. Switching to a fresh batch from a verified ECG-gel manufacturer (see our guide to what makes a good ECG gel) usually clears the fuzz.
Cause 2: Aged or partially detached electrodes
Foam-backed Ag/AgCl electrodes lose adhesion in humid storage, and partial lift-off — even a half-millimetre at one edge — introduces motion artefact and high-frequency noise.
How to identify: look at the electrode after the run. If the adhesive edge has curled, lifted from a hairy area, or pulled at the conductor stud, that lead's trace will show baseline wander synchronised with respiration or a sharp deflection on patient movement. Compare the suspect lead with its neighbours; a single noisy lead with calm neighbours almost always points to an electrode-contact problem rather than the cable or gel.
Fix: clip body hair (do not shave aggressively), abrade the skin lightly with a prep pad, and replace the electrode. Press firmly around the entire adhesive ring for ten seconds. The standard target is a skin-electrode contact impedance under about 10 kΩ for diagnostic-quality traces; severely lifted electrodes can exceed 50 kΩ.
Cause 3: Damaged cables, broken lead wires or poor grounding
Lead wires fail near the strain-relief at the patient connector and at the trunk connector. A partial wire fracture intermittently opens the circuit, producing a saw-tooth or square-wave artefact unique to one lead.
How to identify: the artefact follows the lead, not the patient. Move a clip lead to a different electrode position — if the noise moves with the clip, the cable is the problem, not the electrode. Pinch and flex the cable along its length while watching the trace; a sudden jump confirms a hidden wire break.
Fix: swap the suspect cable for a known-good one and re-run. Replace any cable older than the manufacturer's recommended service life (typically two to three years for trolley-mounted ECG, less for ambulance use). Ensure the patient-cable shield is intact and the equipotential ground is connected to the room's medical earth — floating grounds amplify 50 Hz pickup across all leads simultaneously.
Cause 4: Skin preparation and patient factors
Sebum, lotion, sweat or thick keratin block conductive contact even with fresh gel and fresh electrodes. Shivering, talking, or a tense patient adds muscle artefact that mimics electrical interference.
How to identify: muscle artefact is irregular, high-frequency, and changes with patient breathing or movement. Skin-prep issues usually affect only the electrodes placed on oily, sweaty or moisturised areas — chest leads in summer, limb leads after exercise.
Fix: wipe each electrode site with an isopropyl alcohol prep pad (70% IPA is standard) and allow ten seconds to dry. Lightly abrade with a gauze or commercial abrasive prep tape. Warm the room, drape the patient, ask them to relax their shoulders and breathe normally. For tremor patients, low-pass filtering (40 Hz) on the recorder reduces but does not cure the artefact — the underlying contact must still be good.
When to escalate beyond troubleshooting
If the artefact persists across multiple patients, fresh electrodes, a new gel batch and a swapped cable, the issue is the recorder or the room. Document the pattern (photograph the strip, note the time, the leads affected, what was tried) and call biomedical engineering. Common machine-side causes include a degraded patient-isolation amplifier, a faulty internal calibration pulse, or mains interference from a nearby device installed in the same circuit.
For single-patient persistent artefact despite clean technique, consider clinical factors: pacemaker spikes, tremor disorders, very thin chest wall, or implanted electronics. These are not equipment problems and the report should flag the artefact rather than the team repeat the test indefinitely.
A quick checklist before reordering equipment
Open a fresh electrode pouch and a fresh tube of ECG gel.
Prep the skin: clip, wipe with 70% IPA, abrade lightly, dry.
Press the electrode firmly around the full ring; wait thirty seconds before recording.
Check the cable: flex along its length while watching the trace.
Verify the room ground and that no high-current device shares the circuit.
Most "the ECG machine is broken" calls resolve at step 1 or step 2.
Pioma Chemtech, a specialty chemical manufacturer based in India, supplies ECG and electrode gel in bulk to distributors and procurement teams. Contact us for commercial availability and product datasheets.
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