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 (ie, 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.


6 comments:

  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!

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

      Delete
  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.

    ReplyDelete
    Replies
    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 — :)

      Delete