What is this rhythm? Back to basics.

 Submitted by Dr. Arjun J V in India,

An elderly patient presented to the ED with multiple complaints.

An ECG was recorded in triage:

What do you think? Classic for those who have seen it before.

The ECG shows a regular narrow complex rhythm which is difficult to see amongst the very severe high voltage artifact which is occurring with a frequency of approximately 300 cycles per minute. 

Exam revealed significant upper extremity tremor as the cause of the artifact.

Another similar case from Dr. Arjun J V:

Learning Points:

Electrical artifact can be due to patient factors or external factors. 

Artifact can obscure the rhythm or cause misdiagnosis of rhythms such as atrial fibrillation, ventricular tachycardia, and ventricular fibrillation.

Searching for regular QRS complexes marching through potential artifact can help distinguish artifactual vs. actual ECG rhythms.

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MY Comment, by KEN GRAUER, MD (10/19/2022):

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Today’s case by Dr. Meyers (submitted by Dr. Arjun JV) — is important for recognizing what it is not. This is not VFib or polymorphic VT! 

For clarity — I’ve reproduced and labeled the initial ECG in today’s case in Figure-1. Recognition that this tracing represents artifact (and not VT/VFib) should be an interpretation that is made within 3-to-5 seconds. The process for making this rapid diagnosis always merits our periodic review.

• As worrisome as the initial recording in leads I and II look — a glance at lead III should immediately reassure us that defibrillation is not needed! Instead — lead III tells us that the underlying rhythm is sinus tachycardia at 100-105/minute.
• The other thing that we instantly learn from seeing that maximal artifact is present in standard leads I and II — but absent in lead III — is that “the problem” is in the RA ( = Right Arm) extremity. I thoroughly reviewed this concept (as well as other helpful clues to the presence of artifact) in My Comment — at the bottom of the page in the August 26, 2022 post in Dr. Smith’s ECG Blog.
• That the distribution of artifactual deflections in Figure-1 precisely follows the location and relative amount of amplitude distortion predicted by Einthoven’s Triangle — is confirmed by the finding of maximal artifact in lead aVR — with approximately 1/2 the amplitude of artifactual deflection in the other 2 augmented leads — and with approximately 1/3 the amplitude of artifactual deflection in the chest leads (Figures-2, 3, 4 and 5 in my August 26, 2022 Comment provide the source deriving these geometric relationships).
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• Confirmation of artifact in Figure-1 is further established by our ability to make out the underlying rhythm in each of the chest leads being undisturbed by artifactual deflections. Although the underlying rhythm is much less visible in the long lead II rhythm strip — vertical time lines in simultaneously-recorded leads V4,V5,V6 show that there is indication of normal QRS complexes even in the long lead II (RED lines that I’ve drawn for the last few beats in Figure-1).
• PINK lines in simultaneously-recorded leads V1,V2,V3 continue demonstration of the underlying rhythm in the long lead II rhythm strip.
• Now that we know what the underlying rhythm looks like in the artifact-laden long lead rhythm strip — we can more easily recognize that the underlying rhythm is present in lead aVF (dark BLUE lines). And even though we don’t see this nearly as clearly — the light-BLUE line in lead aVF shows where the next on-time underlying sinus beat almost certainly occurs. 
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• Last-But-NOT-Least — LOOK at the patient when you are suspicious of artifact. Doing so in today’s case confirmed significant right upper extremity tremor as the cause of the artifact.

Figure-1: I've labeled the initial ECG in today’s case to highlight how I instantly recognized artifact as the reason for the abnormalities in today’s case.