Monday, March 27, 2023

A 40-something with 100 minutes of chest pain

I was reading ECGs on the system, and saw this one:

What do you think?

I knew that, if the patient had presented with chest discomfort, that this ECG is diagnostic of inferior posterior OMI, even though it is not a STEMI.

However, it is difficult to recognize for an interpreter who is does not have special expertise in OMI ECG diagnosis. 

We taught an AI system from PM Cardio to recognize patterns of subtle OMI 
(beware: this version of the app is not available to the public yet).  
We named the AI app the "Queen of Hearts" 
This is what the Queen said about this ECG:
"OMI with High Confidence"

ECG explanation:
--There is STE in inferior leads with reciprocal STD and T-wave inversion in aVL.  There is additional ischemic ST depression from V2-V6.  
--The STD in V2-V6 might be interpreted as subendocardial ischemia, but with the inferior STE, it is far more likely to represent posterior OMI.

Here is the history:
A 40-something male had intermittent chest discomfort until 90 minutes prior to presentation, when it became constant.  At 100 minutes, the above ECG was recorded.  

In OMI, cath lab activation is indicated.  In subendocardial ischemia, cath lab is indicated if the pain persists in spite of medical therapy (aspirin, anticoagulant, IV nitro).

The first hs troponin I returned at 245 ng/L.  This is now further confirmation of ACS.

Another ECG was recorded at 160 minutes:
There is evolution, with worsening of ischemia.
There is no doubt that this is an inferior posterior OMI.  

The patient's nitro was dialed up to 100 mcg/min but the pain persisted.

The ACC/AHA guidelines mandate less than 2 hours cath for patients with ACS with refractory pain, pulmonary edema, or electrical or hemodynamic instability.  

Angiogram at 4 hours after ECG 1 (and approximately 6 hours after pain onset):

Culprit is 100% stenosis in the mid RCA.

After PCI

Peak trop I = 39,488 ng/L

Formal contrast echo

Normal estimated left ventricular ejection fraction .

No wall motion abnormality.  (Unusual and puzzling, as there was a large focal acute MI)

Final Diagnosis: Acute MI, Non ST Elevation Myocardial Infarction.

As we have discussed before, the diagnosis of "NSTEMI" is inadequate to describe the pathology of OMI.  NSTEMI is extremely heterogenous, from a very tiny Non-OMI to a massive OMI.  

The presence or absence of ST Elevation is a poor marker with which to describe a myocardial infarction.

My Comment by KEN GRAUER, MD (3/27/2023):
Today’s case is an important one, because as per Dr. Smith (in this patient with new chest pain) — “The initial ECG is diagnostic of infero-postero OMI.” Even after the 2nd ECG showed clear signs of evolution — a total of 220 minutes passed after ECG #1 until finally cardiac cath was performed.

Attention to a few KEY factors should be all that is needed for any emergency provider to be able to recognize acute OMI based solely on the history ( = new chest pain in a 40-something man) — and — the initial ECG.
  • Given the history in today’s case — there are ST-T wave abnormalities in all leads, except perhaps lead aVR ( = in 11/12 leads!) — that need to be assumed acute until proven otherwise! These ECG findings are subtle — but they are real (See ECG #1 — which I have reproduced in Figure-1).
  • As per Dr. Smith — there is ST elevation in the inferior leads (II,III,aVF) — with reciprocal ST depression in lead aVL (Note the mirror-image opposite picture of this subtle ST elevation from lead III in lead aVL — as shown in Figure-1).
  • In support of these reciprocal changes in lead aVL — is similar subtle-but-real ST segment depression in the other high-lateral lead ( = lead I).
  • (For more on the "magic" mirror-image relationship between leads III and aVL with acute inferior OMI — See My Comment at the bottom of the page in the October 6, 2018 post in Dr. Smith's ECG Blog).

  • Also (as per Dr. Smith) — there is subtle-but-real ST depression in chest leads V2-thru-V5. In view of limb lead evidence for acute inferior OMI — the shelf-like ST depression in lead V2 is diagnostic of acute posterior OMI until proven otherwise (ie, a positive "Mirror" Test — See My Comment at the bottom of the page in the September 21, 2022 post in Dr. Smith's ECG Blog).
  • Normally — there is a small amount of gradual upsloping ST elevation in leads V2 and V3. The fact that there is J-point ST depression in lead V3 (RED arrow in this lead) — supports our suspicion of acute posterior involvement.
  • Whether the result of posterior OMI or multi-vessel disease — the flattened ST depression in leads V4-to-V6 is additional evidence of ischemia.

  • Finally: — There is subtle-but-real ST elevation in lead V1. In the context of acute inferior OMI + posterior OMI — seeing any ST elevation at all in lead V1 is not normal. This supports acute RCA occlusion as the “culprit” artery — and is indication for right-sided leads to assess for associated RV infarction (See My Comment at the bottom of the page in the July 19, 2020 post in Dr. Smith's ECG Blog).

Bottom Line KEY POINT: The diagnosis of acute OMI in today’s case is not one to be made from any single finding. Instead, in view of the history of new chest pain — it is the sum total of 11/12 leads showing subtle-but-real ECG findings that have to be taken as acute until proven otherwise.
  • Emergency care providers should be able to recognize this overall picture in Figure-1, that in this patient with new chest pain — is diagnostic of acute OMI.
  • Delay of cardiac cath by the cardiology team for 220 minutes after ECG #1 was recorded — is a mistake that should have been avoided.

Figure-1: I've labeled the initial ECG in today's case (See text).

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