Friday, May 31, 2024

ECG Blog #432 — "Should I Shock this Patient?"

I was sent the ECG in Figure-1 — without the benefit of any history.
  • Is this VT?
  • What is the 1st thing — that YOU would do?

Figure-1: I was sent this ECG without any history. Is this VT?

MY Thoughts on Today’s CASE:
As tempting as it might be to reach for the defibrillator on seeing the ECG shown in Figure-1 — My initial reaction was different.
  • At 1st glance, my impression from seeing ECG #1 — was that the rhythm is very fast and irregular — with a highly variable QRS morphology — and, without atrial activity. These initial observations clearly suggested that the rhythm was either a coarse VFib (perhaps with the gain of the monitor turned way up) — or — PMVT (PolyMorphic Ventricular Tachycardia) vs Torsades de Pointes (depending on whether the baseline QTc was normal or wide). 

I then saw the additional deflections that I highlight
 in Figure-2 with RED arrows.
  • What to do next?

Figure-2: I've labeled the initial ECG in today's case.

The 1st Thing to Do . . . ?

RED arrows in Figure-2 highlight the surprisingly regular occurrence of what appears to be vertical lines that suggest possible QRS complexes ...
  • The 1st Thing to Do: — Check the patient! Is there a pulse?

The patient had a regular pulse and was stable. No shock was needed. RED arrows represent QRS complexes.
  • While true that there are some additional deflections in the limb leads that may be confused for QRS complexes (PINK arrows) — the perfect regularity of the deflections above the RED arrows in the chest leads is the "tip-off" that the rhythm in Figure-2 is not some form of PMVT — but rather artifact distortion.


Another Example:
I never learned about artifact in medical school. But considering that patients have been shocked for tracings resembling the ECG shown in Figure-1 — it may be worthwhile to present another example.
  • If you only looked at leads III, aVR, aVL and aVF — Wouldn't you think that the rhythm in Figure-3 was VFib?

  • PEARL #1: As I emphasize in ECG Blog #148 (from where I took the tracing I show in Figure-3) — 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. Therefore, despite close resemblance to VFib in leads III, aVR, aVL and aVF in this ECG — an underlying regular supraventricular (that is, narrow QRS) rhythm at a rate just under 100/minute can still be seen in other leads!
  • The vertical BLUE lines in the lower part of Figure-3 show that even in those leads that simulate VFib — we can still see indication of deflections that reveal the underlying supraventricular rhythm at ~100/minute!
  • PEARL #2: The simple step of going to the bedside to LOOK at the patient will often be revealing. Doing so will commonly show one or more electrode leads to be loose — OR — the patient to be shaking, trembling, shivering, having a seizure, scratching or other obvious cause of the bizarre deflections seen.

Figure-3: I've reproduced this tracing from ECG Blog #148 (See text).

Acknowledgment: My appreciation to Andreas Röschl (from Neumarkt, Germany) for the case and this tracing.

Related ECG Blog Posts to Today’s Case:

  • ECG Blog #185 — Reviews my System for Rhythm Interpretation, using the PsQs & 3R Approach.
  • ECG Blog #205 — Reviews my Systematic Approach to 12-lead ECG Interpretation.
Links to Examples of ARTIFACT:
What follows below is an expanding list of technical "misadventures" — many from Dr. Smith's ECG Blog (See My Comment at the bottom of these pages) — some from my ECG Blog and/or from other sources.

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