EKG of the Week – Week 6 ANSWERS

    This week’s write up comes from an EKG Dr. Sean Griffiths saw during his thrilling month on medicine.  He wrote up the case and sent it to me.  I’d encourage you to look at the EKGs first and then read his solution to each of them.  It’s really interesting case with a solution that I had never heard of before!  Enjoy!
-Lloyd

Had an interesting EKG case that I saw on the wards and thought it would be good to share with everyone. 

Brief Hx: 72 year old male PMHx of CVA with severe personality changes, dementia, AV pacer, HRrEF, aortic stenosis, and Afib who was admitted from the ED for possible pneumonia after infiltrate seen on CXR. To give you a better idea he was the patient screaming in B Pod a few days ago and had to be put down with Haldol, Ativan, and Benadryl. 

Overnight, the night float team was paged on him several times with strange rhythms on EKG and agitation requiring more haldol. In these rhythms he would go from paced left bundle pattern, to RBBB, then SVT and then convert back to regular pacing. In the morning, the tele tech and nurse paged me several times to come look at his monitor for “weird rhythms”. 

ECG 1: 30 Oct 0827 – irregular AV paced rhythm, with LBBB pattern no concerns for ischemia by Sgarbossa criteria

ECG 2: 0828 – irregular paced rhythm with RBBB pattern, PVCs – weird but not quite sure what to think. Machine saying ****ACUTE MI*****. Patient asymptomatic.

ECG 3: 0829 – irregular paced rhythm with what looks like paced beats of LBBB then PVCs that look RBBB to me. Again very weird, by this point I’ve already decided to call cards and have them come interrogate the pacer. No signs of acute ischemia and patient asymptomatic. Machine saying ****ACUTE MI**** but neg Sgarbossa

ECG 4: 0838 – at the end of the tracing he goes into SVT with what looks like a strain pattern at a rate of slightly less than 150. This stopped after a few seconds and patient remained asymptomatic. 

Ok all that was very weird, not sure what’s going on. I called the electrophysiology fellow and told him what’s up and he agreed to go check out the pacer and call me back; which of course he didn’t call after. A few hours later I get a page about his rhythm again so I have them do an ECG and go down there to check it out. 

ECG 5 (Rhythm Strip): on this ECG there are new T wave inversions in II, III, AvF, V3-V6. At this point now I am very concerned. The patient is asymptomatic but then I started thinking about Wellens Syndrome and T wave inversions in V2-V3 in a pain free patient could be indicative of proximal LAD lesion that is in imminent need for cath. I immediately walk down to the CCU work room and ask some people there who were useless and told me this is a fellow level ECG. So I went back upstairs, paged the cards fellow, and ordered a right sided ECG for the inferior changes I saw. 

Cards calls me back and I filled them in on the findings. So what happened? He informed me that he had adjusted settings on the patient’s pacemaker and that yes these findings would be concerning in a normal person but in this person they were not concerning. So what was going on?

They are called “memory T waves”

So what are memory T waves? According to the fellow, memory T waves are a phenomenon that result from a change in the electrical conduction of the heart that causes the heart to “remember” the old T waves and retain their morphology from the pre-changed state. Clear as mud? This case example is pretty similar to mine and it gives a good definition of “cardiac memory” as it applies to paced people:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4995449/

“Cardiac memory refers to persistent T-wave changes that develop after a period of abnormal ventricular activation (wide QRS complexes) once normal ventricular activation (with narrow QRS complexes) is restored. After normal ventricular activation is restored, the T wave “remembers” and mirrors the direction of the wide QRS complexes. Therefore, cardiac memory results in positive T waves in leads that had positive wide QRS complexes and negative T waves in leads that had negative wide QRS complexes. These T-wave changes can follow resolution of any condition that triggers transient QRS widening, including transient left bundle branch block, ventricular tachycardia, intermittent ventricular pre-excitation, and ventricular pacing. Cardiac memory can persist up to weeks after normal ventricular conduction is restored.”

So after all of the running back and forth to 3W, going to the CCU, paging cards fellows and a lot of worrying if I doing the right thing it ended up being sort of nothing. The EKGs were concerning enough for cards to mess with the pacer but the result of that tinkering was not actually Wellens or some terrible pattern just “cardiac memory/memory T waves”.

Take aways:

Interns: When shit looks weird and you’re concerned, go get help. I was nervous going to the CCU to ask for help in case they would have called me a jackass but I was more concerned something actually bad was happening. Trust yourself, but not too much.

Everyone: Someone with weird T wave inversions and pacer ask about recent changes made to their pacer by their cardiologist. A quick phone call with cards who will confirm these are memory T waves could prevent a hospitalization and large work up.

Thanks guys!

Sean Griffiths

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