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ECG sagas of subtlety 2

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You may have noticed that I am an ECG geek – I love their simplicity and their complexity. I certainly don’t claim guru status, as I don’t possess expertise in the same way that Amal Mattu or Steve Smith do, but I do love ECGs.

I regularly arrive on the ED floor at morning handover, and go ECG-snooping. When I hear a handover mentioning chest pain in any shape or form and the phrase “but the ECG was OK/normal/no acute changes”…etc, I complete the handover, and go and review the ECGs myself. No doubt, the residents hate me for it.

For this reason I regularly unearth “missed” abnormal and instructive ECGs which could be considered subtle (although worryingly sometimes they are barn-door obvious) and hence the “ECG sagas of subtlety” series was born in an attempt to share the lessons learned. I don’t intend criticism of the doctors involved. These are often subtle and difficult ECG findings. The one I share here was discovered on one such snoop:

The case: Chronologically a 50 year old man with 70 year old physiology, who presented with central chest and back pain. He was centrally obese, a diabetic, and had a history of prior warfarinisation for DVT, recently ceased.

This is his time-zero ECG (apologies for reproduction quality, but click on it and it should be discernable):

with chest and back pain at time zero

The night crew spotted the ST depression in III and aVF, called it “ischaemia” and treated the patient as ACS. I came on in the morning, heard the story and heard that the ECG was “OK,” and went snooping.

[DDET What do you think about this ECG?]

  • Sinus rhythm, normal axis, etc…
  • There is indeed ST depression in III and aVF as previously noted
  • There is subtle saggy ST depression in V6
  • As frequently mentioned by Steve Smith, ST depression DOES NOT LOCALISE ischaemia. So this COULD represent subendocardial ischaemia BUT:

WHEN YOU SEE ST DEPRESSION YOU SHOULD ALWAYS LOOK FOR THE ST ELEVATION THAT IT MAY BE RECIPROCAL TO

[DDET Is there any here?]

  • Yes – aVL shows 0.5mm of ST elevation
  • There may be a hint (read retrospective “eye of faith” hint) of ST elevation in I
  • This is a high lateral STEMI, and is likely to represent occlusion of either the diagonal or circumflex coronary artery or branch thereof

Unfortunately this went unrecognised. The patient was given 300mg of aspirin and 2 sprays of GTN. He had some improvement in his anterior chest pain, however his back pain was more severe than the chest pain and was ongoing. The following ECG was recorded 2 hours later in the context of ongoing pain:

with ongoing back pain

[DDET What is your interpretation of this ECG?]

  • The ST depression has largely settled (there may be a smidge persisting in III)
  • The ST elevation is now barely perceptible in aVL which has also developed a Q-wave and T-wave inversion
  • The T-waves in I and V6 are MUCH flatter, but the T-waves in III and aVF are MUCH more peaked
  • This may reflect some reperfusion but in the context of ongoing pain with dynamic ST changes, the cath lab should be activated

I met this man about 2 hours after this second ECG, four hours into his presentation. He had ongoing back pain and looked uncomfortable. He was given further antiplatelet therapy and anticoagulated, then referred to cardiology. His troponin peaked at 3.5.

This man had a “missed” high lateral STEMI. Did missing this have adverse consquences? Hard to know really. We may have saved a bit more myocardium if he’d gotten to PCI earlier. There were further delays to PCI and the case was somewhat frustrating. If you are interested in reading further on high lateral STEMI, click on this link to the always enlightening Steve Smith’s take on the topic. To quote Steve:

“When there is inferior ST depression, one is tempted to diagnose “inferior ischemia”. However (paradoxically and mysteriously) there is no correlation between location of subendocardial ischemia on the ECG and the location of the ischemia in the heart. When there is subendocardial ischemia, the ST depression tends to be diffuse.

So what does “inferior” ST depression represent?

It is reciprocal to high (lateral) ST elevation until proven otherwise

[DDET The denouement is of course the cath result – click here to reveal it:]

  • diffuse CAD
  • obstruction of 1st LAD diagonal branch
  • anterior wall hypokinesis, mild-mod LV dysfunction

And there you have it. His discharge letter from the treating team is still calling this an NSTEMI. For me, it is a STEMI with the D1 vessel being the culprit lesion that correlates nicely with the ECG changes

[/DDET] [/DDET] [/DDET] [/DDET]

The post ECG sagas of subtlety 2 appeared first on Underneath EM.


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