Artefact

Getting the electrodes well positioned is critical for recording a good quality ECG. Here are some common problems that you might encounter when you are recording a 12-lead ECG.

The Evil Bunny Ears: V1/2 Too High

It is very common to place the first two chest electrodes too high. If this has happened, the QRS complex may have developed ‘evil bunny ears’ that can be easily mistaken for an incomplete right bundle branch block. The T waves in these leads may also become inverted and mimic a heart attack. This will all go back to normal if the ECG is repeated with the V1 and V2 electrodes in the 4th intercostal space.

Shave That Hairy Chest: Poor Skin Contact

If the patient is sweaty, hairy or moving around, the electrodes may not be in good contact with the skin. If you see artefact like this, check the electrodes are in good contact with the skin. This is even more likely if only some of the leads are affected as some electrodes may be in better contact than others.

The Mirror Image: Switched Arm Leads

Some electrode swaps are hard to pick, but if you notice that Lead I has become a complete upside-down mirror image of normal then check the left and right arm electrodes. This pattern can be caused by accidentally putting the left arm electrode (LA) on the right arm, and vice versa. If in doubt, repeat the ECG and double check that RA is on the right arm and LA on the left arm.

Electrical interference

If the baseline looks like it has become a thick marker pen, it may be due to interference from electrical devices. Nerve stimulators can also create a similar artefact with lots of spikes close together. If possible, eliminate the source of the artefact, or adjust the filters on your ECG machine.

Oops, he flatlined: Electrodes falling off

If you see a flatline on the ECG it is more likely to be an electrode falling off (or a faulty wire) than a cardiac arrest – especially if only some leads are affected. If in doubt, check the patient!

Electrodes on Limbs vs Torso: Does it Matter?

Traditionally the limb electrodes are placed on the arms and legs. There is some evidence that placing these electrodes more proximally (i.e. on the trunk) can affect the ECG and can even obscure some signs of infarction. However, it might also reduce artefact from limb tremors. Consider marking the electrode placement the ECG if you do use a non-standard position.

Wandering Baseline

A wandering baseline can be a frustrating occurrence that makes interpreting the ST segments very difficult. Try to get the patient to relax (stop moving around), breathe calmly (if possible) and check the electrodes are in good contact with the skin. Sweaty patients are a challenge!

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ECG Library (72)

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In the ECGquest archives, this ECG has been tagged with: - 12-Lead Electrical interference artefact Dr Smith's ECG Blog CC BY-NC
What are all these little spikes?

This ECG is from an elderly woman who presented after a fall.

This ECG shows frequent artefact spikes due to a bladder stimulator implanted for her neurogenic bladder.

In the ECGquest archives, this ECG has been tagged with: - 12-Lead Nonspecific baseline artefact Dr Smith's ECG Blog CC BY-NC
A Text Message in the Middle of the night. Do you give thrombolytics? Repeat ECG

This ECG is from a man in his 60s who presented with chest pain.

This ECG shows baseline artefact obscuring most features of the ECG.

In the ECGquest archives, this ECG has been tagged with: - 12-Lead Nonspecific baseline artefact Atrial fibrillation Ventricular pacemaker Dr Smith's ECG Blog CC BY-NC
Computer often fails to diagnose atrial fibrillation in ventricular paced rhythm, and that can be catastrophic

This ECG is from an elderly patient who presented with a massive hemiplegic ischemic stroke due to MCA thrombus.

This ECG shows atrial fibrillation with ventricular pacemaker and significant artefact. The AF went undiagnosed.

In the ECGquest archives, this ECG has been tagged with: - Hypotension 12-Lead Nonspecific baseline artefact Bradycardia Extra P waves Irregular Peaked T waves Wide QRS Second degree AV block Hyperkalemia Dr Smith's ECG Blog CC BY-NC
What will you do for this altered and bradycardic patient?

This ECG is from a woman in her 60s who presented from a nursing home with altered mental status, hypotension, hypoxia and bradycardia.

This ECG shows an irregular rhythm due to second degree AV block with wide QRS and peaked T waves. The cause was hyperkalemia.

In the ECGquest archives, this ECG has been tagged with: - Chest pain 12-Lead Nonspecific baseline artefact Biphasic T waves Normal Axis Dr Smith's ECG Blog CC BY-NC
Dynamic, Reversible, Ischemic T-wave inversion mimics Wellens’. All trops negative.

This ECG is from a middle aged man who presented with intermittent chest tightness and nausea on walking that resolved with rest. This had happened twice over the past two days. He was likely pain free at the time that this ECG was recorded.

This ECG shows terminal T wave inversion in V2-4, resembling Wellens' waves. There was no wall motion abnormality on echo and troponins were negative (so it was not a true Wellens' syndrome), but a stress echo was markedly positive. Angiogram showed a 95% LAD stenosis and 70% first diagonal stenosis. The cause of the T wave changes was likely ischemia without infarction, ie. unstable angina.

In the ECGquest archives, this ECG has been tagged with: - Chest pain Dyspnoea 12-Lead Wandering baseline Excessive discordant ST depression. Excessive discordant ST elevation Pacemaker spikes Regular Tachycardia Wide QRS Ventricular pacemaker Multi-vessel disease Dr Smith's ECG Blog CC BY-NC
Can you see through this wide complex rhythm?

This ECG is from a man in his 70s who presented with intermittent dyspnoea and chest pain over the past 2 weeks. He had a history of a pacemaker, heart failure, aortic stenosis, diabetes, hypertension, stroke, ischemic heart disease, chronic kidney disease and peripheral vascular disease. This was his initial ECG.

This ECG shows a wide complex tachycardia with ventricular pacing. The excessively discordant ST changes in V4-6 and aVR suggested diffuse subendocardial ischemia. He was found to have severe three vessel disease and a proximal left circumflex stenosis was stented.

In the ECGquest archives, this ECG has been tagged with: - Chest pain 12-Lead Movement artefact Normal Sinus Rhythm ECG of the Week CC-BY-NC-SA
ECG of the Week – 10th December 2018 – Interpretation

This ECG is from a man in his 80s who presented with chest pain. He had a history of Parkinson's disease.

This ECG shows significant baseline artefact due to a Parkinsonian tremor.

In the ECGquest archives, this ECG has been tagged with: - 12-Lead Nonspecific baseline artefact Anterior ST depression Inferior ST depression Inverted T waves R in V1 Regular Right Axis Deviation Tall P waves Normal Sinus Rhythm Right atrial enlargement ECG Interpretation CC-BY-NC-SA
ECG Blog #156 (LVH – RVH – LAA – RAA – Strain – Ischemia)
In the ECGquest archives, this ECG has been tagged with: - 12-Lead Wandering baseline Bradycardia Extra P waves Third degree AV block ECG of the Week CC-BY-NC-SA
ECG of the Week – 12th November 2018 – Interpretation

This ECG is from a woman in her 70s who presented following a fall at home.

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