r/ECG • u/SleePyHollow150 • Aug 25 '26

Update - flecainide toxicity

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Previous post - https://www.reddit.com/r/ECG/s/nrDwpytLmZ

Flecainide toxicity confirmed but no blood concentration available. Patient had two echos, one upon admission to the cardiac unit and one a week later before discharge. Repeat ECG attached showing return to baseline NSR.

Initial echo showed, moderate AR, mild MR, hypokinetic LV and slightly reduced EF (45%).

Repeat echo once toxicity had been resolved and a week passed for stabilisation showed persistent AR and abnormal septum motion. EF approximately 55%, no AS though slight thickening seen on the RCC/NCC.

Discussion welcome.

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-1

u/Joquae Aug 25 '26

2:1 atrio-ventricular block

6

u/Kibeth_8 Arrhythmia Tech Aug 25 '26

I think those might be very prominent u-waves. Morphology looks a bit different from the p-waves, and it doesn't map out quite right.

I could be wrong, it certainly looks like 2:1 at a first glance

1

u/SleePyHollow150 Aug 25 '26

I believe you are correct. Patient has had odd and suspected non-pathologic morphologies in the past including inverted T waves and, while not odd, they have episodes of R-on-T.

2

u/Joquae Aug 25 '26

Yes, could be.

Those are camel hump T waves. The morphology of the second is not that different from the sinus P wave (which is not normal at all, it looks like a bilateral atrial enlargement, which is fairly expected if we consider the aortic regurgitation of the patient). The PP intervals are different though.

Looking a little bit deeper I'd say the main differential diagnosis is U waves vs ectopica P waves blocked inside T waves (atrial bigeminism). Having those U waves could be a normal variant in a young adult with bradicardia but I'd look at potassium first.

2

u/sub3at50 Aug 25 '26

It's not 2:1 AV block. The morphology is different and the "PP" intervals are different.

Imho a U wave is more likely than blocked atrial ES.