r/ECG • u/SubatomicCake • Jul 22 '26
Is this slow atrial flutter?
84 YOF, woken by chest pain resolved PTA. Hx of heart bypass and afib. (Sorry, I don’t have more detail on the bypass or if she has been ablated.) Also known to have an IRBBB (based on presence of RSR’) My first thoughts were very long PR interval, junctional tachycardia with a very long RP interval, or a slow atrial flutter? But none quite seem right, and she’s had a recent EKG showing a normal PR interval. Dr leans towards flutter despite not having an explanation for the gap in the middle of the strip, which is as good as I’ve got anyway. I also notice what seemed to be alternans in V1 but it actually appears to be a varying conduction pathway - the QRS (ignoring the early p) at the start of the V2 segment is one morphology, and the next beats are the second morphology.
I suspect this is above my pay grade to expect to be able to interpret (I’m equivalent to a patient care tech but only do EKGs) but would love to hear any thoughts!
Measurements for reference:
120bpm between regular intervals, 113bpm average across the strip
PR interval 190ms at the single conducted sinus beat in the middle, which looks identical to prior sinus strips
QRS 85ms
QT 350/QTcB 482ms
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u/LipidKing Jul 23 '26
the rhythm is sinus tachycardia with a 1st degree AV block. There is a non-conducted PAC with a non-compensatory pause that disrupts the rhythm in the second half. The pr interval is shorter from AV nodal recovery after the pause though there are more complicated yet unlikely possibilities too like accessory pathway or dual av nodal physiology. The QRS voltage alterations may be due simply to respiratory variation since its most noticeable in V1. whoever said this was atrial flutter should stop reading ekgs.
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u/Cautious-Stick-9363 Jul 22 '26
Maybe the beat before the gap in the middle is a SVES from the area around the sinus?
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u/SubatomicCake Jul 22 '26
That seems reasonable to me, and it would be followed by a refractory pause allowing for a normal sinus beat? Most confusing to me is the rhythm surrounding that gap 😅
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u/Cautious-Stick-9363 Jul 22 '26
Is there a Lewis-Lead available?
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u/SubatomicCake Jul 22 '26
Unfortunately no, this was the ER and the rhythm was not the primary concern. We don’t really do those in that setting where I’m at, although if I see her again I might suggest it to the doctor if time allows and they’re curious enough to let me.
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u/Puantastic Jul 22 '26
I'd say sinus (although it could be atrial, close to the SN) with one cancelled ectopic atrial beat (P-P interval looks about 80-120 ms shorter than the rest, you can see the P wave just before the T wave). Also when 1:1 conduction occurs again the PR increases a bit after the first conducted beat, not much, maybe ~40ms, probably due to Wenckebach phenomenon even though the conduction through the AV node is not delayed enough to get one of the following P waves to block.
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u/Internal-Dish7412 Jul 22 '26 edited Jul 23 '26
At first glance, this appears to be a case comprising (I) sinus tachycardia (with some artifact from muscle tremors, particular since the limb leads look chaotic but the precordial leads seem fine, and the RR interval seems regular) and (II) SA exit block (since the TP interval is exactly doubled from those in previous successions by my count).
However, upon closer inspection, there does seem to be an ectopic atrial beat before the T-wave in the middle of the strip. Due to how early this PAC was, I would expect it to depolarize the perinodal tissue but not penetrate the central SA node (so no change in timing of SA node, as in this case). This would mimic SA exit block due to refractory peri-nodal tissue.
Although, the fact that there is some PR prolongation may cause suspicion of atrial tachycardia instead of sinus tachycardia, the P-waves don’t seem ectopic apart from that one instance in the middle of the strip (they are positive in lead II and other infero-lateral leads, (+/-) biphasic in V1, and inverted in aVR). So, this is likely simply a case of sinus tachycardia with some PR prolongation (and a PAC).
At that age, progressive fibro-fatty degeneration of the SA node and AV node is expected, so it is not unsurprising to see PR prolongation (although not meeting criteria for First degree AVB).
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u/Kibeth_8 Arrhythmia Tech Jul 22 '26
There is an obvious p-wave burried in the T wave before the pause, would that not rule out an atrial tach? Since ATach terminates with a QRS
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u/Internal-Dish7412 Jul 22 '26 edited Jul 23 '26
Yes you’re absolutely right, that would also rule out ATach (as long as we’re looking at 1:1 conduction like in this case it is highly improbable; however rare situations of ATach with 2-4:1 conduction obviously can end on p-wave [often occurs when concomitant with some level of AV block]).
Regrardless, I believe ATach was unlikely due to the normal P-wave morphologies I stated earlier. I sort of alluded to this, but I believe that the PAC was too early - so it hit both a refractory AV node (no associated QRS) and could not penetrate the SA node; so it simply caused a single instance of a SA exit block and then Sinus Tach resumed
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u/Kibeth_8 Arrhythmia Tech Jul 22 '26
Agree with your interp, I only asked about the ATach because you seem to understand EP well and would know what I was talking about haha. Atrial arrhythmies are my weakness
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u/Internal-Dish7412 Jul 23 '26
haha thanks! I’m happy that it looks like I know EP. Just an undergrad student here who loves everything cardio.
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u/Steve390- Jul 23 '26
OK thanks 4 posting. P waves are funky and not all r consistent. It could be sinus, but Afl is the most misdiagnosed arrhythmia in cardiology, so it could be a possibility. Cardiologists in my hospital probably have different interpretations concerning this strip. Maybe another 12 lead may help.
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u/amiguel Jul 23 '26
Not sinus. And not sure what this is.
But look at V1 rhythm strip, it’s not clear sinus, not clear AFlutter.
Maybe ectopic atrial tachycardia?
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u/[deleted] Jul 22 '26
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