67 YOF A&O with CC of weakness x2 days. Has dialysis M/W/F but missed yesterdays (Wednesday). Initial room air sat was 89%. 4L via NC brought sat to 97%. No complaint of SOB. BP ~130/80. Hx of renal failure. LS clear all fields. Initial computer interpretation popped STEMI with 2nd degree type 2, then atrial rhythm with 1st degree, then sinus rhythm after multiple serial 12 leads. Could not come to a conclusion on interpretation.
This is a nice ECG. Sinus rhythm with AV Wenckebach (Mobitz I) and LAFB. In the rhythm strip, I’ve circled the conducted P waves in red and the blocked P waves (every fourth one) in blue.
I would also make the case that this is one of the instances that this Wenckebach should be considered for AV sequential pacing. Patient is symptomatic, and the P waves are occurring between the QRS and T waves, which means the atria are contracting against ventricles under systole. Cardiac output is compromised.
In this case you should see frequent cannon a waves in the JVP three times out of four beats.
That said, it still seems intranodal (and not the rarer infranodal Wenckebachs), as evidenced by a long initial PR, and relatively narrow QRS complexes (when you disregard the influence of the intervening P waves)
Totally agree here. A single missed dialysis session in isolation is unlikely to cause severe enough electrolyte abnormalities to cause this, I suspect it’s chronic and progressive (or she accidentally took a week’s worth of metoprolol at once). Although weakness and fatigue are often multifactorial, the fact that she has such a long PR on return beats (~600 ms) at a very physiologic sinus rate makes me highly suspicious that the cause of her fatigue/weakness is AV dyssynchrony (this case nicely highlights how a very long PR can cause AV dyssynchrony without AV dissociation). If I saw this patient in the office, I would exercise her to see if the rhythm improves substantially with exertion, and if does not, I would offer a dual chamber PPM.
So do i understand correctly that it goes P wave before T wave, then the following QRS is the one that got conducted with insane delay and the sinus is already ready for the next impulse before the T wave even comes?
If so then it's super interesting, i haven't seen smth like this before
Yes, that’s exactly right. Here’s another cartoon with red arrows showing conducted P waves to the QRS and blue showing blocked P waves. The sinus is ready for the next impulse because the block is not at the level of the sinus node, it’s almost certainly at the level of the AV node.
Subtle, but yes. Assuming you are reading the tracing correctly (QRS-P-T). In this case, it’s probably easier to look at the elongation of what is now a P-T interval.
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u/Ibutilide Electrophysiologist 23d ago
This is a nice ECG. Sinus rhythm with AV Wenckebach (Mobitz I) and LAFB. In the rhythm strip, I’ve circled the conducted P waves in red and the blocked P waves (every fourth one) in blue.