Wednesday, January 11, 2023

ECG Blog #356 — Multiple Wavelets ...

The ECG in Figure-1 — was obtained from a patient with fatigue and an "irregular pulse". What is the rhythm?

Figure-1: 12-lead ECG and long lead II rhythm strip — obtained from a patient with fatigue and an "irregular pulse". (To improve visualization — I've digitized the original ECG using PMcardio).

MY Thoughts on the ECG in Figure-1:
I thought today's tracing would be interesting to share — in that I have never seen atrial activity looking quite like this.
  • My approach to this tracing is the same as always — which is to start by assessing the rhythm in the long lead II rhythm strip. The QRS is narrow. The ventricular rhythm is fast and irregularly irregular. Sinus P waves are absent. Therefore the rhythm is AFib (Atrial Fibrillation) with a rapid ventricular response.
  • Looking at the rest of the 12-lead ECG — overall QRS amplitude is reduced. The frontal plane axis appears to be leftward — but not enough to qualify as a hemiblock (ie, the QRS is not predominantly negative in lead II). There is no chamber enlargement. Although difficult to assess given baseline atrial activity — ST-T wave changes look nonspecific, and do not appear to be acute.

What About the Atrial Activity?
The aspect of this tracing that I had not seen before — regards the appearance of atrial activity. The leads are on correctly. The reason for the unusual-looking atrial activity is neither baseline artifact nor tremor. Instead — it is all atrial activity.
  • Atrial activity is multi-directional. An observer described this activity in Figure-1 as "atrial torsades" — in that atrial deflections are clearly all positive (ie, between beats #3-thru-6) — then all negative (between beats #8-9) — flat (beween beats #9-thru-11) — negative again (between beats #12-13) — and then all positive a final time toward the end of the tracing.
  • Although we think of AFib as a completely irregularly irregular rhythm without design — on occasion, AFib may temporarily organize into "wavelets" of electrical activity. When it does — the rhythm may resemble AFlutter in lead V1 (often only in this lead) — until the wavelets deteriorate, and clear AFib activity resumes.
  • An example of this temporarily "organized" atrial activity is seen in Figure-2. Although tempting to interpret this activity in lead V1 as AFlutter — the rhythm does not qualify as "atrial flutter" — because atrial activity is too fast (ie, well over 350/minute in parts); irregular; and not consistent in atrial morphology.
  • Descriptively — the term "AFib-Flutter" has sometimes been used to describe the atrial activity seen in Figure-2. The point to emphasize is that in the absence of consistent regular flutter activity throughout the rhythm strip — the rhythm  seen in Figure-2 behaves clinically as if it was AFib.

Why Today's Rhythm is Different:
The picture of transient "organization" of atrial activity seen in lead V1 of Figure-2 is common. 
  • What is different about today's rhythm in Figure-1 — is the distinctly directional atrial waves of similar morphology that so clearly alternate in direction.

Figure-2: AFib with temporary "organization" of atrial activity. The rhythm resembles atrial flutter.

Mechanisms that Maintain AFib:
Advances in our understanding of the pathophysiology responsible for maintaining AFib suggests a number of ways in which this arrhythmia may be sustained. These include: i) Local ectopic discharge from one or more atrial pacemakers; ii) A single localized reentry circuit; and/or, iii) The presence of multiple functional reentry circuits that alternate control of the arrhythmia (Iwasaki et alCirculation 124:2264-2274, 2011).
  • The most logical explanation for the distinctly directional atrial activity in Figure-1 — is the 3rd mechanism cited above, in which there are multiple functional reentry circuits that continually alternate control, with changing direction of atrial activity as they do.


Acknowledgment: My appreciation to Arron Pearce (from Manchester, UK) for the case and this tracing.


Related ECG Blog Posts to Today’s Case:

  • ECG Blog #205 — Reviews my systematic approach to 12-lead ECG Interpretation.
  • ECG Blog #185 — My systematic approach to Rhythm Interpretation.


  1. Amazing! "atrial torsades"! Apart from reading every word in your Posts, i peep at who sent you the ECG and the country he/she is residing in. You have fans or students or "tuti" from every corner of the world!

    1. THANKS for the kind words. It is gratifying to have international followers! — :)

  2. Unusual to flutter waves at 300+ but possible. Never seen Afib in sawtooth form although I'm sure you've seen more EKGs than I have. Either way a problematic EKG.

    1. THANKS for your comment! AFlutter can go faster than 300/minute (especially in patients with scar, after ablation, etc.). I bet you will begin to see occasional AFib "sawtooth patterns" in lead V1 now that you ARE aware. This DOES occur (due to transient "organization" of AFib wavelets — :)