ECG Interpretation: ECG Blog #511 — A Patient with Chest Pain ...

The ECG in Figure-1 was obtained from an older man who presented to the ED (Emergency Department) for new CP (Chest Pain).

Thinking the rhythm is VFib (Ventricular Fibrillation) — the emergency team went to charge the defibrillator.

QUESTIONS:

Do YOU agree?

How certain are you about what to do?

Figure-1: The initial ECG in today's case — obtained from an older man who presented to the ED with new CP (To improve visualization — I've digitized the original ECG using PMcardio).

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ANSWER:

The rhythm in Figure-1 should not be shocked.

I was sent this case — and immediately responded with 100% certainty that the rhythm is not VFib.
The 1st thing to do is to go to the bedside to Check the patient! Although possible to maintain consciousness for a period of seconds at the onset of VFib — If your patient is alert and talking, then you have confirmed this is not VFib.
Check the Left Leg extremity. This is almost certain to be the principal source of the Artifact that we see in Figure-1 (ie, from a faulty LL electrode connection? — or from excessive tremor in the left leg?).
Repeat the ECG. Since this older man presented to the ED for new CP — We want to obtain a technically adequate 12-lead ECG to ensure that there is no sign of an acute cardiac event.
Stay at the bedside while the repeat ECG is recorded. If the same artifact distortion appears while the repeat ECG is recorded — you want to be there to problem solve the source of the artifact.

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How Do We Immediately Know this is Artifact?

If we simply looked at the 5 limb leads beginning with lead II — it would be easy to think this patient had just gone into VFib. However, the presence of a regular rhythm for the 5 simultaneously-recorded beats in lead I immediately tells us that the rhythm is not VFib.

Artifact is common. Potential sources of artifact include tremor, shivering, brief seizure activity or other body movement; loose or faulty lead connection; external devices that may produce various types of interference; and application of a monitoring lead in close contact with a pulsating artery, among others.
The clinical reality — is that recording an ECG on an acutely ill patient may sometimes result in unavoidable artifact. That said — a general interpretation of the ECG will usually still be possible despite a technically imperfect recording. The BEST way to prove artifact — is to recognize persistence of an underlying spontaneous rhythm that is unaffected by any erratic or suspicious deflections that are seen (as is shown in Figure-2).

Figure-2: I've labeled today's tracing to prove this is not VFib.

This is Not VFib:

The BLUE arrows in Figure-2 prove that the rhythm is not VFib.

Baseline artifact is seen in lead I. That said, even though we cannot be certain if there is (or is not) atrial activity in this lead — we can easily recognize that a regular rhythm with 5 fairly normal-appearing narrow QRS complexes is present.
The BLUE arrows that I've drawn under beat #2 — show that QRS complexes can also be seen to occer at the same moment in time in other leads. This is most easily appreciated in lead aVL — in which we can recognize 5 regular QRS complexes occurring simulaneously with the 5 regular beats that we see in lead I.
Specifically in lead aVL — the 3rd QRS complex is the most difficult to recognize, because it is preceded by high-amplitude artifact deflections. But the 1st, 2nd, 4th and 5th QRS complexes in lead aVL are clearly evident.
KEY Point: What makes it especially challenging to appreciate artifact in today's tracing — is the presence of baseline artifact undulations in each of the limb leads, even in lead I. But 5 regular QRS complexes are seen not only in lead I — but also in all 6 chest leads that display these same 5 supraventricular beats. Presumably this is a normal sinus rhythm at ~60/minute, albeit there is too much baseline artifact to make out P waves.

Identifying the "Culprit" Lead:

Einthoven's Triangle tells us to immediately look at the patient's Left Leg for the source of artifact. Note the following:

The relative amount of artifact distortion is approximately equal in 2 of the 3 standard limb leads (ie, leads II and III) — but is minimal in the 3rd limb lead (ie, other than the small amplitude baseline artifact in lead I — the high amplitude artifact deflections are not seen).
By Einthoven’s Triangle (See Figure-3 below) — the finding of equal artifact distortion in Lead II and Lead III, localizes the “culprit” extremity to the LL ( = Left Leg) electrode.
The absence of these high-amplitude artifact deflections in lead I is consistent with this — because, derivation of the standard bipolar limb lead I is determined by the electrical difference between the RA ( = Right Arm) and LA ( = Left Arm) electrodes, which will not be affected if the source of the artifact is the left leg.
As I discuss in detail in the Audio Pearl below — the finding of maximal amplitude artifact in unipolar lead aVF confirms that the left leg is the “culprit” extremity.

Click on this image to hear the Audio Pearl!

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ECG Media PEARL #18 (7:45 minutes Audio) — on recognizing artifact, and using Einthoven's Triangle to determine within seconds the "culprit" extremity causing the artifact on your ECG.

Figure-3: Using Einthoven's Triangle to identify the "culprit" extremity.

CASE Follow-Up:

Although providers brought the defibrillator to the bedside — they found the patient to be alert and oriented. The ECG monitor on the defibrillator showed sinus rhythm without artifact — at which point providers realized the problem was a loose electrode.

After fixing the loose connection — a normal ECG was recorded.

CHALLENGE:

Take a LOOK at ECG Blog #490.

Can you identify the problem? (The Answer on Blog #490).

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Acknowledgment: My appreciation for the anonymous submission of today's case.

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ADDENDUM (12/27/2025):

For More Material — I have added this Tab on Lead Reversals & Artifact — to the Menu at the top of every page in this ECG Blog:

— Where to find this LINK in the Top Menu! —

All-too-often lead reversals, unsuspected artifact, and other "technical misadventures" go unrecognized — with resultant erroneous diagnostic and therapeutic implications.

In the hope of facilitating recognition of these cases — I am developing an ongoing listing on this page with LINKS to examples that I’ve published in this ECG Blog, as well as in Dr. Smith’s ECG Blog where I frequently write commentaries.

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NOTE: I reproduce below in Figures 4, 5 and 6 — the 3-page article by Rowlands and Moore (J. Electrocardiology 40: 475-477, 2007) — which is the BEST review I’ve seen on the physiology explaining the relative size of artifact amplitude deflections when the cause of the artifact is a single extremity. These principles are illustrated above in today's case.

As noted by the equations on page 477 in the Rowlands and Moore article: i) The amplitude of the artifact is maximal in the unipolar augmented electrode of the “culprit” extremity — which is lead aVF in Figure-2; — and — ii) The amplitude of the artifact in the other 2 augmented leads (ie, leads aVR and aVL) is about 1/2 the amplitude of the artifact in lead aVF.
Similarly — the amplitude of the artifact deflections in the 6 unipolar chest leads that we saw in Figure-2 — is also significantly reduced from the maximal amplitude seen in leads II, III and aVF.

BOTTOM LINE: Artifact is common in real-life practice. With a little practice, you can immediately know that the bizarre deflections you see are the result of artifact — and, when a single extremity is responsible, you can identify within seconds the "culprit" extremity.

Nothing else shows the relative amount of artifact in the mathematical relationships described above, in which there is equal maximal artifact deflection in 2 of the 3 limb leads (with the 3rd limb lead being spared) — and in which maximal artifact in the unipolar augmented lead will be seen in the extremity electrode that shares the 2 limb leads that show maximal artifact (as according to Einthoven's Triangle).
In Other Words: When the cause of artifact originates from a single extremity — the relative amount of artifact will be:

Maximal in 2 of the 3 standard limb leads.
Absent in the 3rd standard limb lead — and ...
Maximal in the unipolar augmented electrode of the "culprit" extremity (which in today's case is lead aVF — which is a unipolar lead recorded from the left leg).