This ladder diagram is from the following publication Atrioventricular Block with Narrow and Wide QRS: The Pause That Refreshes. The full article can be accessed here:
https://www.ahajournals.org/doi/full/10.1161/CIRCULATIONAHA.121.055990
The authors present the following differential diagnoses:
1. Sinus Rhythm with PVC's
2. Sinus Rhythm with equal His conduction delay
3. Sinus Rhythm with resolution of LBB refractoriness
Here is another great ladder diagram from Chou's Electrocardiography in Clinical Practice (6 ed), Chapter 19: Atrioventricular Block; Concealed Conduction; Gap Phenomenon.
Incidentally, this hypothesis was constructed before the Kosowsky, et al, publication Multilevel Atrioventricular Block (Circulation, Vol 54, No 6, 1976).
I wonder if we can further extrapolate the original diagram by subdividing the AV junction (or, AV node) into upper and lower level components. It may look something like this:
The basic idea is that there is Wenckebach conduction in the upper level (UL), and fixed ratio conduction in the lower level (LL). This can be tricky to appreciate, so the repeating pattern has been colorized for enhanced optics.
The first cycle of the 4:3 Wenckebach (WB) is green, then repeats itself in yellow. I assume this pattern would continue to manifest had the telemetry been longer.
The (assumed) LL fixed conduction ratio of 3:2 is demarcated in red and purple.
The opposite of this pattern (that is, fixed ratio in the UL and Wenckebach in the LL) is hypothesized here:
https://ecgladder.blogspot.com/2023/09/atrial-flutter-with-variable-block.html
This diagram is from Chou's Electrocardiography in Clinical Practice (6 ed), Chapter 19: Atrioventricular Block; Concealed Conduction; Gap Phenomenon.
(Please excuse the yellow highlighter.)
Notice how this masquerades as Mobitz II. The first clue to some other mechanism is the changing PR-interval related to QRS 2-4.
Another great case from Dave Richley, @DaveRichley
My hypothesis:
Orange arrows: Sinus P waves (mostly stable PP CL)
Solid black line: Fast Pathway (FP). Dashed black line: Slow Pathway (SP)
Fundamentally, dual AVN conduction. The basic, recurring them (demonstrated in QRS 2 and 3) Sinus conduction down FP. Then, preferential utilization of SP because FP is refractory to antegrade travels, however subsequently recovers enough to permit momentary retrograde conduction into the Atria (blue upright arrow). This would otherwise reset the PP CL, but the assumption here is that the SN is protected via entrance block. Thus, it fires, and the surrounding Atrial tissue is receptive to its impulse, however fails to effectively enter the AVN.
QRS 9 is ventricular extrasystole that invades the AVN and stifles what should have been SP conduction at this predictable moment in time. I initially considered the very next PR-interval (associated with QRS 10) to be the consequence of concealed conduction into FP. –And this remains a possibility. However, given that the PR-interval here shares similar distance to all previous SP conduction, I think it might be preferential use of SP because FP remains refractory from the extrastystolic penetration.
From Dave Richley:
Beat 2: conducts down fast AVN p/way
Beat 3: block in fast p/w. Conducts down slow p/w, then retrograde conduction up fast p/w & thru atria causing pseudo r’ and scooped ST seg.
Retrograde concealed conduction from PVC blocks conduction in both p/ws.
ECG from Arron Pearce, @Arron_Pearce_
He asks:
Interesting rhythm case which I think is an atrial flutter with multilevel wenckebach block. I've never seen a baseline in lead II like it. I think it looks strange because of the way that the flutter waves are merging with the T waves Thoughts?
Dave Richley submitted this hypothesis:
Here's another depiction of multilevel AVN block:
https://ecgladder.blogspot.com/2023/09/atrial-flutter-with-variable-block.html
This ladder diagram is from the following publication Atrioventricular Block with Narrow and Wide QRS: The Pause That Refreshes . The full a...
